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xMAP User`s Manual

1. 7 Sawtooth Function 3 0 7 Reset Level Preamp Sawtooth kfig 960923 T T T T 0 1 2 3 4 5 Time ms Figure 7 12 A sawtooth function having the same average slope as the preamp output is subtracted from it and the difference amplified and offset to match the input range of the ADC 7 4 Analog to Digital Converter Each DXP channel employs a 14 bit 5 0MHz ADC to digitize the conditioned input signal Unlike competing products the DXP directly digitizes the wideband preamplifier signal 11 19 2008 106 DXP XMAP xManager User Manual MAN XMAP 1 0 6 7 5 The Filter Pulse Detector amp Pile up Inspector FiPPI 11 19 2008 The FiPPI performs the various filtering pulse detection and pileup inspection tasks discussed in sections6 3 6 8 As described therein the FiPPI contains up to three digital trapezoidal filters A fast filter for pulse detection and pileup inspection and event rejection an intermediate filter for low energy i e soft x ray event detection and baseline acquisition a slow filter for pulse height energy measurement An output stream of accepted baseline subtracted 16 bit x ray event energies is stored in a FIFO pipeline that is periodically read out by the DSP The FiPPI also measures live time real time and the number of detected accepted and rejected input events In the DXP XMAP the FiPPI also takes on the tasks of ASC monitoring and control and baseline processing reducin
2. Table 5 2 A single buffer for a data acquisition run with Mapping Pixels Per Buffer j 5 3 3 1 Statistics Units Realtime and Livetime are expressed in 320ns units 5 3 3 2 Buffer Header For all timing applications that use the dual buffers the buffer header will have a fixed 256 word length the word size is 16 bits in this mode The contents of the header are defined below Mapping Mode 1 Full Spectrum 2 Multiple ROI 3 List Mode Sequential Buffer Number low word first BufferID 0 A 1 B 68 DXP XMAP xManager User Manual MAN XMAP 1 0 6 Det Element Ch3 Buffer errors Buffer overrun 0 No error gt 0 Number of extra pixels combined with last pixel in buffer Reserved set to 0 32 User words set in USER DSP array Reserved set to 0 Table 5 3 The buffer header contents 5 3 3 3 Mapping Mode 1 Full Spectrum Mapping The pixel header for full spectrum mapping mode is described below due to the constraint that the spectra sizes are a multiple of 256 and must start on an even multiple of 256 the size of the pixel header is 256 words in this mode The data block for full spectrum mapping mode contains four sections each section holds the spectrum from one of the four detector channels in the 11 19 2008 69 DXP XMAP xManager User Manual MAN XMAP 1 0 6 module The length of the spectra are constrained to be a multiple of 256 and must start on a memory location that is a mu
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4. If the hardware is identified as an XIA xMAP Digital Spectrometer select Install the software automatically Recommended and press Next and proceed to step 6 If not select Search for a suitable driver for my device recommended option and press Next to proceed to the Locate Driver Files page Select Specify a location and press Next Browse to or type C WINNT inf for Windows 2000 or C Windows inf for Windows XP or Vista and press OK Windows should find the file xmap9054 inf in the specified directory Press Next A warning may appear regarding Windows Logo testing Press the Continue Anyway button to complete the driver installation Repeat steps 1 6 for each xMAP module installed Note Driver selection can be changed at any time via the Windows Device Manager To open the Device Manager right click on the My Computer icon and select Manage Now click on Device Manager in the left pane of the Computer Management window DXP XMAP cards can be found under Other Devices 11 19 2008 14 DXP XMAP xManager User Manual MAN XMAP 1 0 6 3 System Configuration At this point the xManager software and drivers should have been installed and the DXP XMAP hardware should be powered on and identified by Windows This chapter will guide you in using the xManager Configuration Wizard utility 3 1 Initialization Files After power up the DXP XMAP s DSP and programmable logic a
5. e All runs can be synchronized between modules using the LBUS signal connecting all the modules together e Single spectrum mode provides for the acquisition of a single spectrum per DXP channel e Mapping modes offers time resolved data acquisition i e one spectrum or set of SCA windows per pixel or scan point DXP XMAP xManager User Manual MAN XMAP 1 0 6 1 2 Data Acquisition Modes 11 19 2008 The DXP XMAP currently supports two data acquisition modes static single spectrum Normal acquisition and time resolved multi spectrum Mapping acquisition Note The two data acquisition modes use different memory architectures and thus require different firmware code to be downloaded 1 2 1 MCA Mode In Multi Channel Analyzer MCA mode a data acquisition run produces a single energy spectrum and associated run statistics for each DXP processing channel Data acquisition runs can be started and stopped manually or can be stopped automatically according to a preset real time live time or number of input or output events Spectrum size ranges from 256 bins to 16384 bins Each spectral bin is stored as a 32 bit value allowing for up to 4 294 967 295 events per bin per run Data is stored in on board memory and can be read by the host at any time during or after the run The memory is normally cleared at the beginning of a run but can instead be preserved allowing for pause and resume functionality Data acquisition can be
6. For the latest documentation please refer to XIA s website at www xXia com DXP XMAP_Download html XIA values all of the feedback it receives from customers This feedback is an important component of the development cycle and XIA looks to use this feedback to improve the software All bug fixes and feature suggestions should be directed to software _support xia com Please be sure to include as much information as possible when submitting a bug report For further instructions please refer to section 1 5 DXP XMAP xManager User Manual MAN XMAP 1 0 6 2 3 Configuring the Analog Signal Conditioner The term jumper is used in this section Jumpers are placed on 3 pin headers connecting the center pin to one or the other peripheral pin similar to a single pole double throw SPDT switch Note Four equivalent DXP channels are present on a single DXP XMAP card Component references for each channel begin with a unique number All components in channel 0 are numbered 1 xx in channel are numbered 2xx etc For example the input attenuator for channel 0 is JP100 The equivalent attenuator for channel 1 is JP200 etc 2 3 1 Input Attenuation JP100 JP200 JP300 JP400 Attenuation may be necessary if the preamplifier gain or output voltage range is excessive and or high energy x rays are to be processed Pulses up to several hundred milliVolts in size and a voltage range of 5 Volts can be accommodated without attenuation
7. Place Cursor 1 immediately before the x ray pulse Similary place Cursor 2 immediately after the signal has settled following the pulse The dX field of the cursor data area in the upper right hand corner should now display the 0 100 preamplifier risetime in us 52 DXP XMAP xManager User Manual MAN XMAP 1 0 6 11 19 2008 Oct Trace rt E Senginghteva 0020 e Save Trace ao oan aa vune zl Geng 2 Sg Eent I 8 g t 0 100 5000 4900 4000 ADC Arb Units J J D J J KI KE y 3 2 wa we we xu GC Tine microseconds Figure 4 22 Use the zoom function and cursors to measure the preamplifier risetime The risetime is approximately 400ns 4 7 1 3 Measuring the RC Decay Time t RC Feedback Preamplifiers only The Trace panel is also useful for measuring the decay time for RC feedback preamplifiers Acquire an ADC trace that includes at least one well separated x ray event Use the zoom tool accessed via the right click menu or through the display controls at the graph s upper left if necessary to expand the horizontal axis about the selected event such that the entire decay time is displayed Place Cursor 1 by right clicking in the display area and selecting Place Cursor 1 at the peak value of the x ray pulse Similarly place Cursor 2 immediately before the x ray pulse such that a baseline value is selected Record the dY value from the cursor data display this is the pulse height No
8. The baseline is the output of the energy filter in the absence of x rays A running average of baseline samples acquired between x ray events is subtracted from the x ray peak samples to arrive at the true energy of incident x rays A perfect detector and preamplifier would produce a constant baseline however in the real world the actual baseline varies The number of Baseline Average Samples can strongly affect performance More samples improve noise reduction but slow the reaction time to actual changes in the baseline In most cases a value between 64 and 512 will produce the best results Please review section 6 4 for a detailed description of baseline acquisition and averaging Section 4 7 1 4 describes the empirical optimization of the number of samples in the baseline average 31 DXP XMAP xManager User Manual MAN XMAP 1 0 6 11 19 2008 4 3 4 Setting Regions of Interest ROIs A region of interest ROI is a user defined energy range of the MCA spectrum for which separate statistics are displayed in the ROI Table Typically an ROI corresponds to an energy peak ROIs are used for energy calibration and SCA acquisition 4 3 4 1 Adding ROIs The Region Of Interest table is located below the spectrum A single ROI is displayed by default If you cannot see the ROI table slide the panel separator up and or press the Add button The four leftmost columns in the table control the display of the ROIs The first column indica
9. Note that all channels have now been set to the new value Manager v0 7 Build 2 15 xj Channel Selection Preset Run Reatre 7930 601 seconde e kW Apply to Al KI ai 0 11 Update m Livetine 7851 511 seconds Seve SCA Save Run ng D input Rate 1897 cps Do Deto Outpt Rate ken Fiters l Reame W Continuous seconds Geste e oes Peaking Tino Zoom e Float X v ifios Y e HLoepee v Cursce 1 1 Everts 20 47 Ei CV 100000 10000 Everts Courts 8 9 2 4 6 6 10 12 HI 16 18 2 Energy evi Upper Everts OCRikcps Gaumean Gauri Jcap gei Name 3 53 9775 0 00 1 4280 0 2462 5898 ROG 254 269 21689 om 26210 01207 RO 2 0 1976 ROS 0 1225 RO A 000 3 6851 Sa s 10604263 is 504 Configuration SCA Charneets 0 wl M Ready Figure 4 8 A calibrated Ee spectrum with four regions of interest ROIs 11 19 2008 34 DXP XMAP xManager User Manual MAN XMAP 1 0 6 11 19 2008 4 3 6 System Wide Gain Calibration The GainMatch tool automates the gain calibration for all specified processing channels simultaneously according to user constraints Selected channels can be skipped The iterative routine acquires data for the user specified Acquisition Time looks for a peak within the Calibration Peak Range compares the measured peak centroid to the Calibration Energy and adjusts the gain as necessary The process repeats until to the Number of Interations has expired or the of Calibrat
10. The best value for each decimation should be determined empirically though the general trend illustrated in the table i e larger number to average for higher decimations should be followed 84 DXP XMAP xManager User Manual MAN XMAP 1 0 6 6 4 4 Why Use a Finite Averaging Length Physically the baseline is a measure of the instantaneous slope volts sec for a pulsed reset detector and a measure of the DC offset for an RC feedback preamplifier The variation in leakage current of the detector and offset drift and 1 f noise of the preamplifier often contribute to a baseline with significant low frequency i e relative to the energy filter cutoff noise These variations pass through the energy filter and thus should also pass through the baseline averaging stage to achieve good cancellation when the baseline average is subtracted from the energy filter sample The goal is to produce a baseline average that has a sufficient number of samples to average out the high frequency noise but which still reflects the local instantaneous baseline upon which the x ray step rides Generally speaking the number of baseline samples in the average is set to achieve the best energy resolution performance over the desired range of input count rate There are two considerations worth emphasizing 1 Excess detector preamplifier noise and pickup all decimations The values in the table above implicitly assume a flat noise spectrum from t
11. VCC2 5 DSP core supply V 3 3_ PX 85 00 V 5 analog supply V 12_PXI 12 100 10 5 100 83 00 V 10 analog supply 2 V 12_PXI 12 100 10 25 100 83 00 J V 10 analog supply 11 19 2008 115
12. content of the x ray beam striking the detector remained constant with varying intensity 95 DXP XMAP xManager User Manual MAN XMAP 1 0 6 NOTE The DXP s peaking time is twice as long as the analog system peaking time in this comparison and yet the throughput is nearly the same Output Count Rate kcps 200 L e DXP OCH d A DXPICR ae i E Analog ee BE l a Analog S Pe 150 F True ICR ER dl 100 F BS 50 F e ICR OCR Plot kfig 960922 0 50 100 150 200 Input Count Rate kcps Figure 6 12 Curves of ICRm and OCR for the DXP using 2 us peaking time compared to a common analog SCA system using 1 us peaking time Table 6 4 Comparing the deadtime per event for the DXP and an analog shaping amplifier Notice that that the DXP produces a comparable output count rate even though its peaking time is nearly twice as long 11 19 2008 Functionally the OCR in both cases is seen to initially rise with increasing ICR and then saturate at higher ICR levels The theoretical form from Poisson statistics for a channel which suffers from paralyzable extending dead time is given by OCR ICR Sept ICR ta Equation 6 12 where Tq is the dead time Both the DXP and analog systems OCRs are so describable with the slow channel dead times tq shown in Table 6 4 The measured ICRm values for both the DXP and analog systems are similarly describable with the fast cha
13. 72 DXP XMAP xManager User Manual MAN XMAP 1 0 6 5 3 3 5 Mapping Mode 3 List Mode Mapping The pixel header for list mode mapping is described below there is no constraint on the data alignment in the buffer so the header length is shorter than the 256 words required for full spectrum mapping Note that in list mode the data for all channels is mixed the channel number is embedded into the data word itself For the data block in list mode each word contains data for a single event The events are stored in the order they are processed and so the data are not separated according to channel The channel number information is embedded into the upper two bits of the data word itself the lower 14 bits are sued to store energy information typically MCA channel number Pixel Number low word first In the case of a mapping error where one pixel record combines data from several pixels this is the number of the last pixel recorded Total Pixel block size in words including header low word first Channel 0 Statistics 32 to 39 Realtime 2 words low word first Livetime 2 words 11 19 2008 73 DXP XMAP xManager User Manual MAN XMAP 1 0 6 Triggers 2 words Output events 2 words Table 5 6 The pixel data block for Mapping Mode 3 11 19 2008 74 DXP XMAP xManager User Manual MAN XMAP 1 0 6 6 Digital Filtering Theory of Operation and Implementation Methods This chapter provides an in depth di
14. DXP channel will then effectively count as rapidly as two analog channels 6 11 Dead Time Corrections 11 19 2008 The fact that both OCR and ICRy are describable by Equation 6 12 makes it possible to correct DXP spectra quite accurately for deadtime effects Because deadtime losses are energy independent the measured counts Nyyj in any spectral channel i are related to the true number N j which would have been collected in the same channel i in the absence of deadtime effects by Nti Nmi ICRYOCR Equation 6 14 Looking at Figure 6 12 it is clear that a first order correction can be made by using ICRm of Equation 6 11 instead of ICR particularly for OCR values less than about 50 of the maximum OCR value For a more accurate correction the fast channel deadtime tqf should be measured from a fit to the equation ICRm ICR exp ICRy taf Equation 6 15 Then for each recorded spectrum the associated value of ICRm is noted and Equation 6 15 inverted there are simple numerical routines to do this for transcendental equations to obtain ICR Then the spectrum can be corrected on a channel by channel basis using Equation 6 12 In experiments with a DXP prototype we found that for a 4 us peaking time for which the maximum ICR is 125 kcps we could correct the area of a reference peak to better than 0 5 between and 120 kcps 97 DXP XMAP xManager User Manual MAN XMAP 1 0 6 7 DXP XMAP Hardware Description
15. Interval to 1 000 us and press the Get Trace button to display a 4096 point raw ADC data set Select the Detector tab of the Settings panel The Polarity setting enables or disables a digital inverter depending on the signal polarity of the preamplifier The Reset Interval is the settling time in microseconds of the preamplifier reset The Preamp Gain is the gain in milli Volts per kilo electron Volt of the charge sensitive preamplifier The Apply button downloads the adjusted setting s to the DXP XMAP hardware The Save button saves adjusted setting s to the currently selected INI file For a thorough discussion of oscilloscope diagnostic tool please review section 4 7 1 4 2 1 Pre Amplifier Polarity Preamplifier polarity denotes the polarity of the raw preamplifier signal NOT the detector bias voltage polarity A positive polarity preamplifier produces a positive step defined as a voltage step with a rising edge response to an incident x ray The digital filters in the DXP XMAP expect an input signal with positive steps An optional input inverter is employed to correct the signal polarity for negative polarity preamplifiers If the polarity has been set correctly the ADC oscilloscope trace should display positive steps If the ADC trace displays positive steps as in Figure 4 2 the polarity has been set correctly If not change the Polarity setting and press the Apply button Acquire a new trace to verify that the polarity settin
16. Manual MAN XMAP 1 0 6 To Save or Load a spectrum e Press the Save MCA Data button in the MCA Window or e Select Save MCA Data or Open MCA Data from the File menu 11 19 2008 4 3 9 2 Running with SCAs Acquire data by starting and stopping an MCA run Notice that when the run is complete the SCA table is updated with the sum of events in the SCA window In xManager the SCA function is included for demonstration purposes The SCA data is redundant because xManager automatically reads out the entire spectrum in any case SCAs are intended for users building applications on Handel who desire very fast readout times Please refer to the Handel User Guide for help reading out SCAs directly via the Handel device driver 4 3 10 Saving and Loading Data All data is stored in ASCII format and are easily readable using a text editor The default format for MCA data includes bin scaling and other basic operating parameters and is date time stamped We would like to directly support as many formats as possible please let us know if your format is not supported 4 3 10 1 MCA Data Spectra can be saved for later display or for analysis in another program Acquire a spectrum then select Save MCA Data from the File menu Saved MCA data can be displayed at any time There are two methods of displaying saved MCA data gt Ifyou want to compare a saved spectrum to currently acquired spectrum the saved data can be displayed as a
17. Samples Clock Clock cycle Range averaged frequency interval in us 0 1 50 MHz 20 ns 0 08 0 50 2 12 5 MHz 80 ns 0 5 8 0 4 16 3 125 MHz 320 ns 8 32 6 64 781 25 kHz 1 28 us 32 128 Table 6 3 For decimation 0 the slow filter output is sampled a fixed time after the x ray is detected PEAKSAM must be set properly to achieve optimum performance For example consider a preamplifier with a pulse risetime of 260ns For decimations 4 and 6 SLOWGAP would be set to 3 or greater For decimation 2 SLOWGAP would be 4 or greater and for decimation 0 SLOWGAP would be set to 13 or greater xManager will select these values automatically if you enter a Gap Time of 260 ns SLOWGAP is independent of SLOWLEN thus all peaking times having a common decimation can share the same SLOWGAP value 6 6 2 Peak Sampling vs Peak Finding The figures below illustrate the two peak capture methods Under the peak finding method the slow filter output is monitored over a finite interval of time and the maximum value within that interval is selected The interval is set automatically solely based on the values of the DXP parameters SLOWLEN and PEAKINT SLOWLEN and PEAKINT are both automatically derived from the peaking time value selected in xManager and should normally not be adjusted by the user PEAKINT is also a pileup inspection parameter as will be discussed in further detail in section 6 8 87 DXP XMAP xManager User Manual MAN XMAP 1 0 6 Peak va
18. Some SiLi detectors show resolution improvements out to 80us or longer 29 DXP XMAP xManager User Manual MAN XMAP 1 0 6 Making a plot of energy resolution versus peaking time provides a useful future reference CAUTION In almost all cases the Energy Threshold should be set to zero An error term in the counting statistics is introduced when the Energy Threshold is enabled For this reason it should only be enabled at low data rates 11 19 2008 The Edit Filter Parameters button accesses additional filter parameters including the energy gap time the fast or trigger filter settings and pileup rejection parameters The default filter settings reflect a compromise between robustness and performance and typically do not need to be changed In some cases energy resolution for a given peaking time can be improved significantly if these settings are optimized as described in section 4 6 4 3 3 2 Trigger Threshold The trigger or fast filter threshold sets the low energy limit for the fast filter which is used primarily for pileup inspection If the baseline threshold is employed the detection of x rays actually extends to energies significantly below the trigger threshold see section 4 3 3 3 For this reason it is not necessary to set the trigger threshold aggressively i e setting the threshold as low as possible will derive little benefit If set too low the trigger threshold will introduce a zero energy noise peak int
19. Start run commands have been issued by the host to all XMAP modules The transition from LO to HI on LBUS indicates that all XMAP modules are ready and in fact have started simultaneously however data acquisition does not actually begin until the GATE signal is released 11 19 2008 100 DXP XMAP xManager User Manual MAN XMAP 1 0 6 All XMAP modules ready READY LBUS Dead gt lt Live gt Dead lt Live GATE Start Figure 7 4 The beginning of a data acquisition run in a system that employs LBUS and GATE Start Run commands have been issued to all modules LBUS goes HI indicating that all modules have been initialized however GATE disables data acquisition User then releases GATE resulting in a system wide synchronized start 7 2 3 GATE Function MCA Mode The GATE input allows realtime user control over data acquisition during a normal MCA data acquisition run Data acquisition is halted when the GATE signal is asserted i e incident events are not processed and the realtime and livetime counters are disabled The assert polarity of the GATE signal can be set via software The Realtime can be set to increment during GATE assertion via software The GATE signal can be ignored entirely via software 7 2 3 1 GATE Polarity The interpretation of the user provided GATE signal can be inverted in the hardware such that data acquisition is halted when the signal is HI or LO The GATE polarity correspo
20. and makes a correction of the form E k Sx kz Vx lt Sg kz Vg gt Equation 6 9 Here the quantities Sx and Vx are the step height and ADC amplitude measured for the step and the corresponding values with the B subscript are baseline values which are measured frequently at times when there is no trigger The brackets lt gt indicate that the baseline values are averaged over a large enough number of events to not introduce additional noise in the measurement The constant k the DSP parameter called RCFCOR is inversely proportional to the exponential decay time this correction factor is a constant for a detector channel at a fixed gain and shaping time The constant k is effectively a gain factor and is taken into account with a detector gain calibration The parameter RCFCOR is a function of the digital filter parameters SLOWLEN SLOWGAP and DECIMATION and the preamplifier decay time the DSP parameter RCTAU The decay time defined by RCTAU and fractional word RCTAUFRAC has 50 ns granularity and is measured and 91 DXP XMAP xManager User Manual MAN XMAP 1 0 6 entered by the user At the start of an acquisition run the DSP calculates RCFCOR using the following approximate expression RCFCOR 2 LEN GAP RCTAU LEN GAP 2 22 Equation 6 10 The above expression is valid for peaking times less than about RCTAU 2 Alternatively RCFCOR can be determined empirically in a special test run fr
21. caused by improper uses or inadequate care XIA LLC shall not be obligated to furnish service under this warranty a to repair damage resulting from attempts by personnel other than XIA LLC representatives to repair or service the product or b to repair damage resulting from improper use or connection to incompatible equipment THIS WARRANTY IS GIVEN BY XIA LLC WITH RESPECT TO THIS PRODUCT IN LIEU OF ANY OTHER WARRANTIES EXPRESSED OR IMPLIED XIA LLC AND ITS VENDORS DISCLAIM ANY IMPLIED WARRANTIES OF MERCHANTABILITYOR FITNESS FOR A PARTICULAR PURPOSE XIA S RESPONSIBILITY TO REPAIR OR REPLACE DEFECTIVE PRODUCTS IS THE SOLE AND EXCLUSIVE REMEDY PROVIDED TO THE CUSTOMER FOR BREACH OF THIS WARRANTY XIA LLC AND ITS VENDORS WILL NOT BE LIABLE FOR ANY INDIRECT SPECIAL INCIDENTAL OR CONSEQUENTIAL DAMAGES IRRESPECTIVE OF WHETHER XIA LLC OR THE VENDOR HAS ADVANCE NOTICE OF THE POSSIBILITY OF SUCH DAMAGES Contact Information 11 19 2008 XIA LLC 31057 Genstar Rd Hayward CA 94544 USA Telephone 510 401 5760 Downloads http xia com DXP XMAP_Download html Hardware Support support xia com Software Support software_support xia com viii DXP XMAP xManager User Manual MAN XMAP 1 0 6 1 Introduction The DXP XMAP includes four Digital X ray Processor DXP channels on a single 3U PXI CompactPCI card Each DXP channel is a high rate digitally based multi channel analysis spectrometer designed for energy dispersive x ray
22. correction to achieve good energy resolution without a pole zero stage Figure 6 9 and Figure 6 10 illustrate the method used The first shows the output voltage of a RC feedback preamplifier with a x ray or y ray step of amplitude A appearing at t 0 Ve is the voltage just before the step pulse arrives and Vo is the asymptotic value that the signal would decay to in the absence of steps D is the earliest time used in the slow filter L and G are the length and gap of the trapezoidal filter in clock units and At is the clock period In addition to the normal slow filter measurement of the step height the ADC amplitude Vp is made at time tp In the following discussion it is assumed that the signal rise time is negligible 90 DXP XMAP xManager User Manual MAN XMAP 1 0 6 11 19 2008 ICR 41 kcps 6000 sa rK 1 S H amp 4000 2000 0 2000 0 4000 8000 2000 Amplitude Figure 6 10 Correlation between step size and amplitude for Zr Ka x ray events measured with the DXP 4C As Figure 6 10 makes clear there is a linear correlation between the step height from the trapezoidal filter and the ADC amplitude for pulses of a given energy This is due to the fact that the exponential decay causes a deficit in the measured step height which grows linearly with the distance from the asymptotic ADC offset at zero count rate The DSP reads these two values for each event that passes the FiPPI s trigger criteria
23. corresponding to the first pixel from the buffer will be displayed When the total number of pixels processed exceeds the Total Number of Pixels setting the display will again refresh and the run will automatically end Alternatively the Stop Mapping button can be pressed at any time to end the run 5 3 Mapping Mode Data 11 19 2008 In mapping mode the DXP xMAP uses two completely separate memory buffers enabling the system to take data into one buffer while the other buffer can be read out by the host The capacity of each buffer is 2MB organized as 1Mword by 16 bits however the portion that is used can be significantly smaller depending on the Mapping Pixels Per Buffer setting see section 5 2 4 Dealing with all this data in real time is a challenge xManager streams the buffer data to a binary file for offline analysis For visual feedback the display is refreshed with data from the first pixel of each buffer that is read out 66 DXP XMAP xManager User Manual MAN XMAP 1 0 6 5 3 1 Mapping Data Options The name of the output file is automatically generated with the user specified File Prefix For diagnostic purposes the user can elect not to save output data If the Save Mapping Data checkbox is un checked the output data will be lost The default location of the output file is C Program Files xia xManager 0 x data To change the folder select Options from the Tools menu then select the Mapping Data tab to dis
24. data 1 4 2 Device Driver Handel XIA provides source code and documentation for the Handel driver layer to advanced users who wish to develop their own software interface XIA recommends using Handel for almost all advanced applications Handel is a high level device driver that provides an interface to the DXP hardware in spectroscopic units eV microseconds etc while still allowing for safe direct access to the DSP xManager uses the Handel driver and thus also serves as a development example Installation files and user manuals for Handel are available online at http www xia com DXP_Software html 1 4 3 Firmware and FDD Files Firmware refers to the DSP digital signal processor and FPGA Field Programmable Gate Array configuration code that is downloaded to the DXP XMAP itself Typically two System FPGA files one each for normal and mapping acquisition modes one DSP file and up to four FiPPI Filter Pulse Pileup Inspector FPGA files are necessary to acquire spectra across the full range of peaking times with a given detector preamplifier For simplicity XIA provides complete firmware sets in files of the form firmware _name fdd This file format is supported by Handel XIA s digital spectrometer device driver and is the standard firmware format used in xManager Two standard firmware files are available one for pulsed reset type preamplifiers and one for RC feedback type preamplifiers Updates to the firmware are
25. data was stored in DSP internal memory 4 The use ofa high speed interface The 32 bit PCI bus operates at 33MHz providing for transfers in excess of 130 MBytes second This readout speed is critical for supporting the continuous mapping data acquisition mode particularly in systems with multiple detector elements 7 2 Timing and Synchronization Logic The front panel LEMO connector provides external access to the backplane PXI trigger lines These lines shared across all slots in each PCI bus segment are used for timing and synchronization in multi module DXP XMAP systems For more information about PCI bus segments and the PXI bus see 11 19 2008 section 2 1 2 7 2 1 Connections Overview One external LEMO TTL CMOS connection is required for each trigger line used in each PCI bus segment The module that accepts the LEMO connection must be configured via software as a Master for that timing signal a Master drives the designated signal onto the backplane but also receives other backplane lines when applicable The front panel LED corresponding to the 99 DXP XMAP xManager User Manual MAN XMAP 1 0 6 chosen timing function is illuminated for each designated Master module Other modules are automatically configured as Slaves i e they receive all applicable backplane trigger lines ds a E E E E 8 Yg D ef O o amp ZZ e OC L Es Af cS o LFS KC LS d ES e d amp A d ES FESS TI 8 2 E E es
26. e g preamplifier type and polarity correct v Troubleshoot the signal using the Oscilloscope tool as described in section 4 7 1 Figure 4 3 An uncalibrated 55Fe spectrum Press the Refresh button to manually read out the MCA data or check the Continuous checkbox to automatically refresh the spectrum A horizontal line at zero on the y axis indicates that no output events have been acquired although the run is active This can result from a hardware setup problem e g x rays not hitting detector detector not powered etc Or it can result from incorrect configuration settings The most common problem is incorrect detector preamplifier settings To troubleshoot these settings please refer to the Diagnostics section 4 7 4 3 2 Skipping Channels The manual or automatic MCA data readout operates on all active processing channels i e though only one spectrum is displayed data from all channels is locally accessible via the Channel Selection control Processing channels can be disabled or skipped from the readout operation Select the System settings tab to display the Channel Selection Detail Click in the Skip Session column to de select individual channels Note Channel skipping also applies to system wide gain matching as described in section 4 3 6 11 19 2008 28 DXP XMAP xManager User Manual MAN XMAP 1 0 6 To change common acquisition settings select the Configuration tab of the settings panel Note Th
27. energies 11 19 2008 4 6 2 1 Maximum Width Constraint The DSP parameter MAXWIDTH sets the maximum acceptable time that the fast trigger output can stay above threshold for a single event Properly set this constraint detects fast pileup event separation on the order of 100ns See section 6 8 for more information The Max Width setting is accessible in the Edit Filter Parameters panel By default it is set to 400ns allowing for a preamplifier risetime up to 200ns MAXWIDTH should be at least twice the fast peaking time plus the preamplifier s 1 settling time Max Width gt 2 Fast Peaking Time Preamp Risetime 4 6 2 2 Peak Interval The DSP parameter PEAKINT sets the minimum acceptable time that the slow energy filter needs to process a single event i e the interval between peaks that can be properly sampled This constraint detects slow pileup event separation on the order of the energy peaking time See section 6 8 for more information The optimum peak interval is usually fixed relative to the sum of the peaking time and gap time The Peak Interval Offset is measured forwards in time from this sum i e measured forwards from the end of the flattop period see Figure 4 18 Peak Interval Peaking Time Gap Time Peak Interval Offset 47 DXP XMAP xManager User Manual MAN XMAP 1 0 6 At very high rates the fast filter peaking time may be reduced to maintain good pileup inspection 11 19 2008 The Peak Interv
28. filter length of 4 should be used Table 6 1 FiPPI decimation details In practice it is important to realize that implementing an energy filter in a Decimation N FiPPI sets certain limitations on the flat top lengths that can be obtained in trapezoidal filters Because the decimation process is uncorrelated with the arrival of x rays the gap G must be 3 or greater to assure that the filter s peak truly represents the x ray s energy Therefore the minimum Decimation N gap time is G 2N At where At is the ADC s sampling interval With the DXP XMAP s At 20 ns sampling interval for instance the smallest useful flat top in Decimation 6 is 3 1 28 us 3 84 us Given the significant overlap in peaking time ranges it is generally better to choose a lower decimation value such that a shorter gap time can be used Decimation 0 has other limitations i e no intermediate baseline filter and is thus an exception to this rule The FDD firmware file defines the actual i e non overlapping peaking time ranges used 6 3 3 Time Domain Benefits of Trapezoids One extremely important characteristic of a digitally shaped trapezoidal pulse is its extremely sharp termination on completion of the basewidth 2L G This may be compared to analog filtered pulses which have tails which may persist up to 40 of the peaking time a phenomenon due to the finite bandwidth of the analog filter As we shall see below this sharp termination gives the
29. important first to set the energy filter Gap so that SLOWGAP to at least one unit greater than the preamplifier risetime lt Key gt Angle brackets denote a lt W gt indicates the W key lt Shift Alt Delete gt key on the keybord not lt Ctrl W gt represents holding or lt Ctrl D gt case sensitive the control key while pressing A hyphen or plus the W key on the keyboard between two or more key names denotes that the keys should be pressed simultaneously not case sensitive Bold italic Warnings and CAUTION Improper cautionary text connections or settings can result in damage to system components CAPITALS CAPITALS denote SLOWLEN is the length of DSP parameter names the slow energy filter vii DXP XMAP xManager User Manual MAN XMAP 1 0 6 End Users Agreement XIA LLC warrants that this product will be free from defects in materials and workmanship for a period of one 1 year from the date of shipment If any such product proves defective during this warranty period XIA LLC at its option will either repair the defective products without charge for parts and labor or will provide a replacement in exchange for the defective product In order to obtain service under this warranty Customer must notify XIA LLC of the defect before the expiration of the warranty period and make suitable arrangements for the performance of the service This warranty shall not apply to any defect failure or damage
30. is started when all connected modules release this line indicating they are ready This wired OR line can be extended between PCI bus segments when the front panel LEMO connector is configured as an LBUS extension For now do not make any LEMO connections The Configuration Wizard utility will help you make decisions about which function s to use and how to make the proper LEMO connections See sections 3 2 and 7 2 for more details 2 6 Starting the System 11 19 2008 Make sure of the following before proceeding v Your system satisfies the requirements outlined in section 1 3 above v A PCI to optical interface card e g National Instruments MXI 3 or MXI 4 has been installed and communicates properly with the host computer 13 DXP XMAP xManager User Manual Ro KRIS MAN XMAP 1 0 6 The xManager software and drivers have been installed DXP XMAP modules have been installed Detectors and preamplifiers are connected A low to moderate intensity x ray source is available for calibration and system verification Turn on the crate detector HV and preamplifier power supplies and restart the host computer 2 6 1 DXP XMAP Driver Selection Windows should automatically find the new hardware and start the Found New Hardware Wizard 1 2 3 4 5 6 7 The welcome screen prompts Can Windows connect to Windows Update to search for software Select No not this time and press Next
31. larger x ray steps A slow energy filter averages out the most noise and can thus detect smaller x ray steps but has a response that is much slower An intermediate filter used in decimations 2 4 and 6 only is a derivative of the slow filter that provides a balance between the speed of the fast filter and the noise reduction of the slow filter The fast filter is used solely for x ray detection i e a threshold crossing initiates event processing Its short basewidth 2L G means that successive pulses that would pile up in the slow filter can be resolved in the fast filter and rejected from the spectrum see Figure 6 11 below Conversely little noise 85 DXP XMAP xManager User Manual MAN XMAP 1 0 6 reduction is achieved in the fast filter thus the fast threshold cannot be set to detect particularly low x ray energies The intermediate filter is used for reset type preamplifiers in decimations 2 4 and 6 only Its threshold is automatically set by the DSP and applied as part of the baseline acquisition circuitry i e baseline measurements are taken when the signal is below this threshold Intermediate threshold crossings by default also trigger event processing extending the detectable energy range significantly below the fast filter threshold After an x ray has been detected the step height is measured at the slow filter output The slow filter s excellent noise reduction also allows for detection of the very lowest ener
32. mouse enter the new value and press Return If you do not press Return the parameter will return to its unmodified value when another item is selected Changing parameters in this panel without a deep understanding of XIA s DSP processors may produce exotic and unpredictable results We recommend doing so only under the guidance of XIA support staff 4 7 4 Submitting a problem report XIA encourages customers to report any problems encountered using any of our software via email In most cases the XIA engineering team will need to review bug information and run tests on local hardware before being able to respond All software related bug reports should be e mailed to software_support xia com and should contain the following information which will be used by our technical support personnel to diagnose and solve the problem v Your name and organization 59 DXP XMAP xManager User Manual MAN XMAP 1 0 6 Ki Brief description of the application type of detector relevant experimental conditions etc XIA hardware name and serial number Version of the library if applicable OS Description of the problem steps taken to re create the bug XS NN NN Full Error Report see section 4 7 4 1 plus additional data o Saved MCA data if relevant see section 4 7 4 2 o Saved Baseline data if relevant see section 4 7 4 3 o Saved Trace data if relevant see section 4 7 4 4 Please compress the Error Report into a ZIP ar
33. of each buffer is 2MB organized as 1Mword by 16 bits The XMAP must periodically swap buffers The swap must occur after the host has completed reading the inactive buffer and before the active buffer becomes full The Mapping Pixels Per Buffer setting controls when the swap takes place The DSP also calculates the maximum number of pixels that can be stored in a memory buffer based upon the MCA Number of Bins If the Maximum Allowed checkbox is checked or if a greater number is entered the XMAP will override the Mapping Pixels Per Buffer and use this calculated maximum number instead The effects of this setting are generally qualitative gt Changes the structure but not the content of the data stream binary file see section 5 3 gt The xManager display updates after each buffer thus the number of pixels per buffer sets the visual refresh rate 5 2 5 Mapping Mode Data Acquisition Press the Start Mapping button to begin a data acquisition run If you are using GATE or SYNC for the pixel advance you should see the Progress Bar begin to fill If it does not please review sections 5 1 and 7 2 adjust your hardware and use the Configuration Wizard see section 3 2 3 to correct your settings if necessary Alternatively press the Next Pixel button to manually advance pixels When the incremental number of processed pixels exceeds the Mapping Pixels Per Buffer setting the buffer will be read and spectrum or SCA data and statistics
34. often takes several iterations Another approach to calibration is re interpreting the bins This is not difficult to do but may produce confusion for the novice user We are considering supporting this feature in future xManager releases 11 19 2008 9 DXP XMAP xManager User Manual MAN XMAP 1 0 6 2 Installation CAUTION Improper connections or settings can result in damage to system components Such damage is not covered under the DXP XMAP warranty Please carefully follow these instructions It is important that you follow the steps in order Install the PXI interface and identify the crate install xManager and drivers power off computer and crate install DXP XMAP hardware power on crate power on computer identify hardware drivers run xManager software 2 1 PXI Interface Installation XIA recommends using National Instruments PXI instrument crates and interface cards and this document assumes this recommendation has been followed In any case please follow the instructions provided with your crate and or controller 2 1 1 PXI System Configuration File PXISYS INI Make sure that your host computer properly communicates with the CompactPCI crate before continuing Specifically use the National Instruments Automation Explorer NIMAX EXE to identify your crate Doing so generates the PXI system intialization file PXISYS INI in your windows directory Please verify that the file exists in C WINNT directory for
35. positive Preamp Output V Figure 6 2 depicts the large signal sawtooth waveform that results from successive x ray steps followed by the reset Note that the units here are Volts and milliseconds vs millivolts and microseconds in the previous figure enlarged view 0 50 100 150 Time ms Figure 6 2 The large signal reset waveform for a reset type preamplifier with positive signal polarity as 11 19 2008 displayed on a real oscilloscope Note that the large signal character of the DXP XMAP diagnostic ADC readout used in xManager s Trace panel looks quite different because of the dynamic range reduction carried out in the ASC as described in section 0 6 1 2 RC Type Preamplifiers Figure 6 3a is a simplified schematic of an RC type preamplifier wherein Cf is discharged continuously through feedback resistor R The output of an RC type preamplifier following the absorption of an x ray of energy Ex in detector D is again a voltage step of amplitude Vx The continuous discharge of Cf through R results in an exponential voltage decay after the x ray step with decay constant t where 76 DXP XMAP xManager User Manual MAN XMAP 1 0 6 a Os Re Cr Equation 6 1 In practice the decay time may depend on subsequent circuitry i e if a pole zero cancellation circuit is used thus t may not be directly related to the feedback elements of the front end The point of this simplified model is that the resulting
36. rate at or above the point of maximum throughput U51 Status Indicators RUN Illuminated green when a run is in progress LO Illuminated yellow when a PCI transfer to or from the module is in progress ERR Illuminated when the module is in an error state U50 Front Panel Logic LEMO Mode Indicators Illuminated green when the modules is designated as a GATE Master Illuminated green when the modules is designated as a SYNC Master Illuminated green when the modules is designated as an LBUS Master These LEDs flash in a test pattern when firmware is being downloaded to the board 11 19 2008 114 DXP XMAP xManager User Manual MAN XMAP 1 0 6 A 3 Connectors Jx00 Signal Inputs 4 SMA connects preamplifier output to the XMAP Pasternack P N PE4545 J5 Logic Input Output LEMO configurable as GATE or SYNC input or LBUS input output LEMO P N EPL 00 250 NTN J1 Standard PCI Port High speed parallel communications port standard pinout Erni P N 064 176 J2 Standard PXI Port High speed parallel communications port standard pinout DDK P N HTC SEB110 R11A A 4 Power Consumption DXP XMAP Power Budget Power Source Name Source Per Efficiency Comment Current Channel 85 00 VCC main digital voltage supply 85 00 VCC1 8 FPGA core voltage supply 95 00 V 5 analog supply V 5_PXI 75 00
37. start synchronization is still available in this mode All XMAP modules ready READY LBUS Dead gt lt Live GATE Pixel 0 Pixel 1 Pixel 2 J J Start Pixel Advance Pixel Advance Figure 7 8 Mapping mode acquisition using the GATE input with default polarity and with the GATE Ignore option selected The pixel advance occurs on each falling edge of GATE but data acquisition runs continuously with no pause The above examples all use the same cable connections shown in Figure 7 3 above Only one connection each for LBUS and GATE are necessary for each PCI bus segment 7 2 5 SYNC Function Mapping Mode In Mapping mode multiple spectra are generated as an x ray beam is rastered across the sample Each spectrum corresponds to a pixel The so called 11 19 2008 103 DXP XMAP xManager User Manual MAN XMAP 1 0 6 pixel advance controls when the XMAP changes from one pixel spectrum to the next A more complex pixel advance is implemented using the SYNC input 7 2 5 1 Pixel Advance using SYNC Clock The user provides a clock signal to the SYNC input s Using this method the pixel will advance for every N LO to HI transitions on the SYNC line where N can be set from 1 to 65535 Note that the pulse widths must be greater than 40 ns in duration 7 2 5 2 Synchronous Starts with SYNC It is especially important to synchronize the beginning of a run when using the SYNC pixel advance Two methods are suppor
38. template such that some data entry steps below are skipped This is quite useful when creating multiple similar configurations 3 Firmware The firmware file contains all program code for the programmable devices on the DXP XMAP Press the FDD File button to browse or type C Program Files xia xManager 0 x firmware xmap_revb fdd and press Next If you have updated your firmware since xManager was installed be sure to select the new file Note that different firmware files are required for pulsed reset and RC feedback type preamplifiers Updates to the firmware are available online at www xla com DXP_Resources html 11 19 2008 16 DXP XMAP xManager User Manual MAN XMAP 1 0 6 Ba xMAP Configuration Wizard x Firmware Select a previously used firmware file C Program FilesixiaixManager 0 7 firmwarexmag D Select a new firmware file Cancel Back Le Finish Figure 3 2 The firmware file contains program code for the DXP XMAP s programmable devices 4 Detector Configuration Select the appropriate detector type For Reset type enter the Reset Interval This is the time in microseconds that the preamplifier takes to reset and settle and should be set conservatively to prevent associated voltage transients from entering the spectrum If you don t know the reset time enter 10 microseconds For RC Feedback enter the RC Decay Time in microseconds Press Next BeaxMap Configuration Wizard x Detector C
39. the Fast Trigger Filter output stays below threshold This measurement has units of 320ns and is used to calculate the input count rate 4 3 8 3 Energy Live Time This DSP level output is the computed live time of the Energy Filter This value is also accurate to 320 ns at end of run but is only computed at 8 ms intervals during the run 37 DXP XMAP xManager User Manual MAN XMAP 1 0 6 11 19 2008 4 3 8 4 Input Count Rate ICR The measured input count rate ICR is displayed in units of thousands of counts per second kcps The DSP applies internal correction procedures so that the measured ICR is very close to the true ICR especially for longer peaking time settings Please see section 0 for a discussion of this issue 4 3 8 5 Output Count Rate OCR The output count rate is also displayed in units of thousands of counts per second kcps The OCR is simply the total number of detected events that did not pile up divided by the real time elapsed Detected events that do not pile up but whose measured energy falls outside the spectrum upper and lower limits are called overflows and underflows respectively Both overflows and underflows are included in the OCR 4 3 8 6 Dead Time The Dead Time Percentage is calculated as the OCR divided by the ICR multiplied by the real time 4 3 8 7 ROI Statistics The peak centroid and width measurements are displayed in the ROI table The centroid can be displayed as the arithme
40. weighting values decrease with separation from the step then the equation produces cusp like filters When the weighting values are constant one obtains triangular if the gap is zero or trapezoidal filters The concept behind cusp like filters is that since the points nearest the step carry more information about its height they should be more strongly weighted in the averaging process How one chooses the filter lengths results in time variant the lengths vary from pulse to pulse or time invariant the lengths are the same for all pulses filters Traditional analog filters are time invariant The concept behind time variant filters is that since 11 19 2008 78 DXP XMAP xManager User Manual MAN XMAP 1 0 6 11 19 2008 the x rays arrive randomly and the lengths between them vary accordingly one can make maximum use of the available information by adjusting Length on a pulse by pulse basis In principal the very best filtering is accomplished by using cusp like weights and time variant filter length selection There are serious costs associated with this approach however both in terms of computational power required to evaluate the sums in real time and in the complexity of the electronics required to generate usually from stored coefficients normalized wi sets on a pulse by pulse basis A few such systems have been produced but typically cost about 13K per channel and are count rate limited to about 30 Kcps Even time i
41. 1 for a description of the mapping modes 12 Mapping Configuration If you want to use the DXP XMAP in mapping mode select Continue with mapping configuration and press Next Otherwise select Don t use mapping mode and press Next 13 Pixel Advance Mode The Pixel Advance triggers the change to a new spectrum in multiple spectrum data acquisition Typically the Pixel Advance is controlled by a user provided logic signal In GATE mode each leading edge transition generates a Pixel Advance instruction See section 7 2 4 for a description of this mode In SYNC mode a Pixel Advance instruction is generated every N LO to HI transitions See section 7 2 5 for a description of this mode In User mode the Pixel Advance is triggered by a command from the host computer 14 EA The next panel depends on the Pixel Advance Mode selection a GATE Pixel Advance Options As described in section 7 2 4 3 in GATE Pixel Advance mode the GATE signal by default also halts data acquisition If Pixel advance only is selected on this panel data will be written to the new spectrum immediately after each leading edge transition regardless of the pulse width Note The polarity selection made in step 11 above is used for both the normal and mapping modes e g if LO halt acquisition was selected the pixel advance occurs on the HI to LO transition 21 DXP XMAP xManager User Manual 15 wm MAN XMAP 1 0 6 b SYNC Pixel Advance Optio
42. 7 1 DXP XMAP Overview INPUT O INPUT 1 INPUT 2 INPUT 3 GATE SYNC Bus DXP CHANNEL 0 i DXP CHANNEL 1 y DXP CHANNEL 2 The DXP XMAP system shown in Figure 7 1 consists of four Digital Xray Processor DXP channels a Digital Signal Processor DSP a System FPGA SRAM memory and a PCI interface Each of the four DXP channels accepts a preamplified signal input and produces a 16 bit pipelined output stream of x ray energies DXP XMAP MODULE ARCHITECTURE CUSTOM PXI LINES Digital Signal System FPGA Processor DSP rot re Event processing FIPPI parameter control Memory access Trace capture DSP Access Run and mapping control GATE SYNC LBUS logit Run statistics LBUS Interface Event energy scaling PXI backplane logic snavivo asa PLX Interface DXP CHANNEL 3 5 PCI BUS PCI BUS lt gt LOCAL BUS 32 bit Interface Figure 7 1 Block diagram of the XMAP system architecture 11 19 2008 7 1 1 Four Independent DXP Channels The Digital X ray Processor DXP is a proprietary architecture see Figure 7 2 designed to rapidly measure the pulse heights of voltage steps Shown below are the three major DXP operating blocks the Analog Signal Conditioner ASC an analog to digital converter ADC and the Filter Peak Detector and Pileup Inspector FiPPD The DXP XMAP contains four independent DXP Digital Xray Processor DXP channels Each DXP channel accepts a detector preamplifier signal input and produces a FIF
43. A E EE yY O I i g e d af amp e w O a e oP H H soe TOC GATE READY ee ae ADPOOOOHOlOOOO ol o oo og o oe PCI BUS SEGMENT 1 _ pl BUS SEGMENT 2 _ pc BUS SEGMENT 2 Figure 5 6 The LEMO cable connections for SYNC pixel advance with LBUS and GATE used to synchronize the run start If LBUS is not used GATE connections would shift over one module to the left connecting to slots 2 7 and 13 5 1 4 Pixel Advance under Host Control It is also possible to advance the pixel using Handel Manually advancing the pixels is slower and unwieldy because the command must be issued separately to each module but it does provide an easy way to test mapping operations 11 19 2008 64 DXP XMAP xManager User Manual MAN XMAP 1 0 6 5 2 Mapping Mode Data Acquisition 11 19 2008 Mapping mode acquisition is automatically enabled when the Mapping panel is active Conversely normal mode acquisition is automatically enabled when the MCA tab is active In both cases the corresponding System FPGA firmware is downloaded as evidenced by LED pattern flashing 5 2 1 The Mapping Panel Mapping Optors Restre seconds Total Nambe of Panis F retrac Aun Trois uveta seconds Mapping Oste File Pred Macoing gt 7 Save Date Figure 5 7 The Mapping panel Click the Mapping tab to display the Mapping panel Please be patient while the System FPGA firmware is downloaded during whi
44. ADC Arb Unts 1 200 250 300 350 400 Tine microseconds MCA Baseine Traces Log Figure 4 20 An ADC trace of a reset type detector with the DXP XMAP configured with the wrong polarity and a gain setting that is too low X ray steps displayed in this panel should have a rising edge and noise should span 20 or more vertical units 11 19 2008 51 DXP XMAP xManager User Manual MAN XMAP 1 0 6 11 19 2008 ADC Di Sampiegikterval 0100 xs Save Trace Zoom DI sb e vines 6400 8200 6000 7800 7600 ADC Arb Unts i i i i 1 150 200 250 300 350 400 Tene microseconds MCA Baseline Traces Log Figure 4 21 An ADC trace with correct polarity and a typical gain Note that the noise is well digitized at roughly 40 vertical units 4 7 1 2 Measuring the Preamplifier Risetime The Trace panel is useful for measuring the preamplifier signal risetime which should be done before modifying the Minimum Gap Time as described in section 4 6 1 2 As mentioned earlier the minimum sampling interval in the display is 20ns the actual ADC sampling period Acquire an ADC trace at the minimum sampling interval of 0 020us that includes at least one well separated x ray event Use the zoom tool accessed via the right click menu or through the display controls at the graph s upper left to expand the horizontal axis about the selected event Place Cursor 1 by right clicking in the display area and selecting
45. ATE Master and a SYNC Master are designated for each PCI bus segment 7 3 The Analog Signal Conditioner ASC 11 19 2008 The ASC employs a patented ramp subtraction technique to compress the dynamic range of the signal without adding significant noise or distortion to the signal The typical preamplifier output signal has dynamic range of 100dB or 16 bits The compression produces a signal that can be fully digitized by a relatively inexpensive 14 bit ADC with effectively 13 bits of resolution due to integral and differential non linearities Importantly the bandwidth of the signal is unaffected by the compression limited only by the Nyquist criterion for the ADC The digital filters thus operate on an wideband 20MHz signal The technique is illustrated in Figure 7 12 Here a resetting preamplifier output is shown which cycles between about 3 0 and 0 5 volts We observe that it is not the large signal ramp function which is of interest but rather the individual steps such as shown in Figure 6 1 that carry the x ray amplitude information Thus if we generate a sawtooth function which has the same average slope and subtract this sawtooth from the preamplifier signal we can amplify the difference signal to match the ADC s input range The generator required to produce this sawtooth function is quite simple comprising a current integrator with an adjustable offset The current which sets the slope is controlled by a DAC with DSP
46. BUS function but it is not necessary If used the left most module in each PCI bus segment will be designated as the LBUS master i e it accepts the front panel LBUS connection Make your selection and press Next Multi Bus Synchronous Run Start segment Akernatively the GATE input can be used to hold off data acquisition at the start of runs Figure 3 6 In this case LBUS will not be used 11 GATE Function The GATE function is used to selectively halt data acquisition during a run according to a user provided TTL CMOS logic signal Please review section 7 2 3 for a complete description of this feature The Enable GATE setting reserves the left most available module in each PCI bus segment as the GATE master i e it accepts the front panel GATE connection The GATE Polarity setting determines whether data is halted when the GATE logic signal is LO or HI Make your selections and press Next 11 19 2008 20 DXP XMAP xManager User Manual MAN XMAP 1 0 6 11 19 2008 Kapp Configuration Wizard x Gate Function Normal acquistion the GATE function is used to system Figure 3 7 For this system GATE is enabled set to halt acquisition when LO 3 2 3 Mapping Mode Settings The remaining settings relate to the mapping mode wherein multiple spectra are acquired for each processing channel in a single run e g to produce an elemental map of the sample in x ray scanning applications Please review section 1 2 1
47. Digital X ray Processor User s Manual SRev 12017 Model DXP XMAP Revision D With xManager Software version 1 0 x XIA LLC 31057 Genstar Road Hayward CA 94544 USA Tel 510 401 5760 Fax 510 401 5761 http www xia com Information furnished by XIA LLC is believed to be accurate and reliable However no responsibility is assumed by XIA LLC for its use nor for any infringements of patents or other rights of third parties which may result from its use No license is granted by implication or otherwise under any patent or patent rights of XIA LLC XIA LLC reserves the right to change specifications at any time without notice Patents have been applied for to cover various aspects of the design of the DXP Digital X ray Processor DXP DXP XMAP xManager User Manual MAN XMAP 1 0 6 LEE vi Specific Precautions issernida aieiaiei iana dadinda aaa daiiran vi Do Not Hot Gwap viiri ninian a iaia da iraani ias vi Servicing and Cleaning vi Manual Conventions riai eir aenieei e hera E aaae aa aa aiaei vii End Users Agreement ccceecccceeeeeeeeeeeeeeeeeeeneeseeeeneeseeenneeseeenneeseeeenneeseeeseeseseseanseeeenes viii Contact Inf rmalo Nis naii a aa a viii Tt AJptrog Hentges 1 Tal XMAP TEE 1 1 2 Data Acquisition MOOS EE 2 CNN der Me EE 2 1 2 1 1 SCA Feature in MCA Mode sseeeeeeeeeeeersesrnssrrssrrssrresrrssns 2 1 2 2 MCA Mapping Mode cesses eeeeeeseeeeeseaeeesaeeseeeeeeeee 2 1 2 3 SCA Mapping Mode 3 1 3 System H
48. E 2 E 8 ER Ge E Z E W E KF Z KF KF AE W a E g FF d KKK KKK A MK KK d d Ss GATE READY LBUS OOOO O19 o oo o oi GO o oe PCI BUS SEGMENT 1 EC BUS SEGMENT 2 _ pc BUS SEGMENT 2 Figure 7 3 A 15 module XMAP system spanning 3 PCI bus segments that employs the LBUS and GATE timing functions Note that an LBUS Master and a GATE Master are designated for each PCI bus segment 7 2 2 LBUS Run Start Synchronization A software command must be issued to each and every XMAP module to begin a data acquisition run resulting in asynchronous operation in multi module systems RUN_PXI is a PXI backplane wired OR trigger line that holds off data acquisition until all XMAP modules in the PXI bus segment have been initialized A module designated as an LBUS Master provides a connection to this wired OR line via the front panel LEMO connector This serves two purposes To complete the wired OR connection between modules in separate bus segments via the front panel LEMO connector and to provide a realtime READY output Properly implemented LBUS ensures that connected modules start acquiring data simultaneously LBUS is often used in conjunction with GATE The LBUS output connects to the user hardware that generates the GATE signal is used as a READY constraint at the beginning of a run The user generated GATE signal disables data acquisition until all such system constraints have been met In the figure below
49. For this to be true the two pulses must be separated by at least an interval of L G 2 Peaks 2 and 3 which are separated by only 1 8 us are thus seen to pileup in the present example with a 2 0 us peaking time This leads to an important first point whether pulses suffer slow pileup depends critically on the peaking time of the filter being used The amount of pileup which occurs at a given average signal rate will increase with longer peaking times We will quantify this in section 0 where we discuss throughput Because the fast filter peaking time is only 0 4 us these x ray pulses do not pileup in the fast filter channel The DXP can therefore test for slow channel pileup by measuring for the interval PEAKINT after a pulse arrival time If no second pulse occurs in this interval then there is no trailing edge pileup PEAKINT is usually set to a value close to L G 2 1 Pulse 1 passes this test as shown in the figure Pulse 2 however fails the PEAKINT test because pulse 3 follows in 1 8 us which is less than PEAKINT 2 3 ps Notice by the symmetry of the trapezoidal filter if pulse 2 is rejected because of pulse 3 then pulse 3 is similarly rejected because of pulse 2 Pulses 4 and 5 are so close together that the output of the fast filter does not fall below the threshold between them and so they are detected by the pulse detector as only being a single x ray pulse Indeed only a single though 92 DXP XMAP xManager User Manu
50. Front Panel LEMO Connections This panel displays the resulting front panel LEMO assignments This is a good time to make those connections if applicable The Start System button immediately configures the DXP XMAPs Note that after configuration the front panel LEDs also indicate the front panel LEMO connections 22 DXP XMAP xManager User Manual MAN XMAP 1 0 6 a LBUS Master Modules These modules must all be connected together using LEMO cables and T adaptors LBUS can also be used as a READY output as described in section 7 2 2 b GATE Master Modules These modules must be connected to the users GATE signal generator c SYNC Master Modules These modules must be connected to the users SYNC clock generator 17 Save Completed Configuration The INI file you have created can now be saved Select a unique name for the file e g C Program Files xia xManager 0 x xmap_32module ini Press Finish to save the INI file and exit the Configuration Wizard Note that if you did not start the system in 16 above you must load the INI file to enact your changes 3 3 Loading and Saving Initialization Files 11 19 2008 INI files can be updated at any time i e after the spectrometer settings have been optimized and existing INI files can be loaded at any time If you have previously run with xManager your registry settings will point to the most recently used INI file and xManager will automatically run with these settings u
51. I BUS 11 19 2008 111 DXP XMAP xManager User Manual MAN XMAP 1 0 6 Figure 7 14 Data flow diagram for multiple spectrum mode 7 7 3 Multiple SCA Mapping Mode The XMAP hardware supports mapping mode with multiple user defined SCAs Up to 64 SCAs can be defined for each channel A 16K word array is used to hold the mapping between MCA bins and SCA regions the user can either select to have all channels use the same SCA definitions for all channels which supports the full maximum MCA length of 16K channels or use separate definitions of the SCA regions for each channel where the maximum supported MCA length is 4K channels This format specification does allow differences in the number of SCA s between channels Two words 32 bits total are used to store the total number of events in each SCA region the low word is stored first in memory Please refer to 5 3 3 4 for further information 7 7 4 List Mode Mapping The XMAP hardware also supports mapping in list mode The events are stored in the order they are processed and so the data are not separated according to channel The channel number information is embedded into the upper two bits of the data word itself the lower 14 bits are sued to store energy information typically MCA channel number Please refer to 5 3 3 5 for further information 7 8 3 Party PCI Interface 11 19 2008 The DXP XMAP uses a PCI bus master interface controller chip manufactured by PLX technol
52. O buffered output stream of 16 bit pulse height i e energy measurements Each DXP also keeps track of its run statistics including livetime and the number of input counts detected See sections 7 2 7 8 below for a thorough description of the DXP 98 DXP XMAP xManager User Manual INPUT DXP XMAP CHANNEL ARCHITECTURE Analog Signal Conditioner ASC Filter Pulse and Pileup Inspector FiPPI ADC fast Sawtooth l good Function ee ASC monitoring and controt Digital filtering fast baseline energy Generator Gain DAC Le Pileup inspection pulse rejection Baseline processing and subtraction Slope DAC ri Event selection and pipelined output Figure 7 2 Block diagram of the DXP channel architecture 7 1 2 Rapid Data Readout MAN XMAP 1 0 6 DSP DATABUS The DXP XMAP was designed for the rapid readout of acquired data in a multi element detector system Some important changes to the architecture relative to other DXP products facilitate this goal 1 Tasks previously handled by the DSP such as baseline handling and ASC control have been offloaded to programmable logic in the FiPPIs This frees the DSP to focus on event handling during data acquisition 2 Memory management previously handled by the DSP is now tasked to programmable logic in the System FPGA This reduces the size of the DSP s event handling loop 3 The storage of MCA SCA and statistics data in external SRAM memory Previously this
53. The default position for jumpers JPx00 labeled OdB see Figure 2 1 passes the signal directly If larger signals must be processed set JPx00 to the 12dB position to reduce the input signal by a factor of four 8 SE vs RE mp mp ms g iltt E Met 3 i Gu Way w Wen 3 D a D zB Ho E E O rE en fa Witz as m i Faamaonia nn 88 iun nu Hipis pinse ge eee Hm k e 7 an nmn GEO rm s 7 ee eee mupp Is GI Hu EET MURHIIN D ae nft MERLE D s 4 3 D D D H wee torte LL rue D mmm 177 w LEGEND vm INPUT ATTENUATION JUMPERS JPx00 Figure 2 1 The DXP XMAP printed circuit board Input attenuation jumpers JPx00 are highlighted in blue 2 4 Installing DXP XMAP Cards Note XIA PXI modules are NOT hot pluggable Never attempt to install or remove an XMAP Digital Spectrometer module while the instrument crate is powered on Such action can irreparably harm the module 11 19 2008 12 DXP XMAP xManager User Manual MAN XMAP 1 0 6 Turn off the host computer and PXI crate power Install DXP MAP modules in the PXI crate making sure that the cards are fully inserted and each card s handle is secured such that it locks in the horizontal position Connect your detector outputs to the xMAP SMA input connectors 2 5 Making Connections It is possible to damage the DXP XMAP and or con
54. Time us Figure 6 11 A sequence of 5 x ray pulses separated by various intervals to show the origin of both slow channel and fast channel pileup and demonstrate how the two cases are detected by the DXP Note that PEAKINT and MAXWIDTH are both DSP parameters and are normally set automatically In particular there is almost never any benefit to a longer value of PEAKINT than the standard value as it does not improve energy resolution and only decreases throughput for a given input rate Please see section 4 6 2 1 for details on how to adjust MAXWIDTH 6 9 Input Count Rate ICR and Output Count Rate OCR During data acquisition x rays will be absorbed in the detector at some rate This is the true input count rate which we will refer to as ICR Because of fast channel pileup not all of these will be detected by the DXP s x ray pulse detection circuitry which will thus report a measured input count rate ICRm which will be less than ICRy This phenomenon it should be noted is a 11 19 2008 94 DXP XMAP xManager User Manual MAN XMAP 1 0 6 characteristic of all x ray detection circuits whether analog or digital and is not specific to the DXP Of the detected x rays some fraction will also satisfy both fast and slow channel pileup tests and have their values of Vx captured and placed into the spectrum This number is the output count rate which we refer to as the OCR The DXP normally returns in addition to the colle
55. Time 49 4 7 Diagnosues ouia niire niani TEE 49 4 7 1 The Traces Panel Oeclloscopel 49 4 7 1 1 Determining the Preamplifier Polarity and Gan 50 4 7 1 2 Measuring the Preamplifier Risetime ccccceeeeeeereees 52 4 7 1 3 Measuring the RC Decay Time t RC Feedback Preamplifiers ONY Jisses neia eene eg aeaaea ae anaana Ea aKa aiaa 53 4 7 1 4 Optimizing the Baseline Average Length 53 4 7 2 The Baseline Panel 56 4 7 2 1 The Baseline Threshold 2 00 0 ceeececceceesseceeeeseeeeeeeneeeeeeeneneees 57 4 7 3 DSP e NEE 58 4 7 3 1 Generating a Diagnostic DSP Parameters File 0 100ss0sees 59 4 7 3 2 Modifying DSP PDarameiers 59 4 7 4 Submitting a problem report 59 4 7 4 1 Generating a Full Error Report 0 cecceseeeeeeeeeeeeeeeeeeeneeeee 60 4 7 4 2 Saving MCA Datta cecceeceeceeeeeeneeeeeeeeeeaeeceeeeeseaeeesaeeeeeneeees 60 4 7 4 3 Saving Baseline Data 60 4 7 4 4 Saving Trace Data 60 5 Mapping Mode cccessecceeeeeeeeeenseeeeeenneeeeenseaeeeenseeeeeeenseeneeenseeneeseseeneesaseenenenseeeenes 61 5st PixelAdvance Settings eege ged ege Ed ena aa aa Aaa a ARa eraa AEREE 61 5 1 1 LBUS PCI Extension Run Start Synchronization 0 cceeee 61 11 19 2008 iii DXP XMAP xManager User Manual MAN XMAP 1 0 6 5 1 2 Pixel Advance on GATE Edge 61 SFAT GATE POI EE 62 5 1 2 2 GATE Ignore Gettimg ceeccceeeeeeeeeeeeeeeeeeeeeseeeeeseaeeeseeeeeaes 62 5 1 3 Pixel Advance using SYNC Clock ss
56. Windows 2000 or C Windows directory for Windows XP This file is needed to properly start xManager the first time 2 1 2 PXI Bus Segments and Slots Each PCI bus segment holds up to 8 slots Larger PXI crates employ bus extenders to provide host connectivity to two or more internal PCI bus segments Such crates have front panel markings vertical hash marks between slot identifiers to indicate where the bus segment boundaries are e g for an 18 slot crate slots 1 6 are in bus segment 1 slots 7 12 are in bus segment 2 slots 13 18 are in bus segment 3 Note that the PXI bus connects slots in each bus segment but does not extend across segment boundaries The DXP XMAP uses PXI bus trigger lines to synchronize multiple modules for timing applications If there are multiplie bus segments in your systems timing signals i e GATE and SYNC must be physically connected to one module in each bus segment That module will drive other modules in the segment via the backplane PXI trigger line 2 2 Software Installation Note Check for firmware and software updates at http www xia com DX P_ Resources html 11 19 2008 Do not attempt to install the XMAP hardware until after the software and drivers have been installed xManager operates on Windows 2000 XP and Vista machines Updates to xManager are available online at 10 DXP XMAP xManager User Manual MAN XMAP 1 0 6 11 19 2008 www xXia com DXP XMAP_Download html The up
57. ace Zoom Auto X vam v lees sl Deze ref er Arb Units 7 J i J i H o 1099 150 2000 20 E x9 4000 Tene macronecorsds Figure 4 23 The raw output of the Baseline Filter Approximately 10 x ray events are visible as trapezoid as well as a preamplifier reset spike The goal of baseline acquisition is to sample the baseline noise Now select Baseline History from the drop down list set the Sampling Interval to 10 000us and press Get Trace to view the baseline running average You want to achieve a waveform similar to that shown in Figure 4 25 where noise is filtered out but the average still tracks real variations If you see something more like Figure 4 24 or Figure 4 26 adjust the Baseline Average Samples setting in the Configuration panel and press Apply Acquire another trace and adjust as necessary In most cases the values 128 and 256 yield the best results At high rates it may be advantageous to reduce the number of samples as low as 16 For near perfect preamplifiers the average can be increased to 1024 or more In any case the optimization is not complete until you acquire a spectrum and verify the energy resolution has improved 54 DXP XMAP xManager User Manual MAN XMAP 1 0 6 Get Trace Baseine Die Senging teva 50000 as Save Trace i Zoom MM Jato x DIS Y een gt 2 A i H H i J E i i J i E k s0000 1509 20900 200 3000 35009 000 Tene microseconds MAT Do
58. addition process can be done in less than one peaking time which is usually trivial digitally then no system deadtime is produced by the capture and store operation This is a significant source of the enhanced throughput found in digital systems Once an active threshold is exceeded the DXP XMAP employs one of two methods to capture the slow energy filter output such that the best measure of V results For decimations 2 4 and 6 the slow filter output is monitored over a finite interval of time in the region of its maximum and the maximum value within that interval is captured This method is referred to as peak finding or max capture For decimation 0 the slow filter is sampled at a fixed time interval after the pulse is detected by the fast filter This method is referred to as peak sampling After describing in section 6 6 1 below how to set the Gap parameter so that there will be a quality value of the energy filter to capture we describe the two methods in detail in section 6 6 2 86 DXP XMAP xManager User Manual MAN XMAP 1 0 6 11 19 2008 6 6 1 Setting the Gap Length When starting with a new detector it is important first to set SLOWGAP to a minimum of 3 and at least one unit greater than the smallest value in decimated clock cycles see Table 6 3 that encloses the entire preamplifier risetime per section 4 7 1 2 Decimation ADC Decimated Decimated Peaking Time
59. al MAN XMAP 1 0 6 11 19 2008 somewhat distorted pulse emerges from the slow filter but its peak amplitude corresponds to the energy of neither x ray 4 nor x ray 5 In order to reject as many of these fast channel pileup cases as possible the DXP implements a fast channel pileup inspection test as well The fast channel pileup test is based on the observation that to the extent that the risetime of the preamplifier pulses is independent of the x rays energies which is generally the case in x ray work except for some room temperature compound semiconductor detectors the basewidth of the fast digital filter i e 2L Gf will also be energy independent and will never exceed some maximum width MAXWIDTH Thus if the width of the fast filter output pulses is measured at threshold and found to exceed MAX WIDTH then fast channel pileup must have occurred This is shown graphically in the figure where pulse 3 passes the MAXWIDTH test while the piled up pair of pulses 4 and 5 fail the MAXWIDTH test Thus in Figure 6 11 only pulse 1 passes both pileup inspection tests and indeed it is the only pulse to have a well defined flattop region at time PEAKSAMP in the slow filter output 93 DXP XMAP xManager User Manual MAN XMAP 1 0 6 Digitized MultiPile kfig 960921 Passes Fails PEAKINT PEAKINT Test Test lt Passes MAXWIDTH Fails MAXWIDTH T Fast Filter PEAKSAMP gt Slow Filter 5 10 15 20 25 30
60. al setting is accessible in the Edit Filter Parameters panel In most cases it should be left at zero Larger values will result in a more conservative pileup inspection at the cost of increased deadtime per event 4 6 2 3 Reducing the Fast Peaking Time The default fast peaking time of 100 ns should be used in most cases Generally speaking a longer fast filter peaking time produces a lower pileup inspection threshold at the cost of a longer pileup inspection time interval Little if any real benefit is derived from increasing the fast peaking time unless the preamplifier signal is extremely noisy For good pileup rejection the fast filter peaking time should be much shorter than the energy filter which becomes a problem when the shortest energy filter peaking times are used In these cases some improvements in pileup rejection may be possible if the fast filter peaking time is reduced e g to 60ns We don t recommend using a fast gap time other than zero Open the Edit Filter Parameters panel and enter a new value for the Fast Trigger Filter Peaking Time and press Apply Note that you may have to adjust other settings as a result 1 Trigger Threshold Because of the zero gap time the Fast Trigger Filter normally produces some ballistic deficit Reducing the trigger peaking time can heighten this effect For best results the threshold be checked as described in section 4 3 3 2 2 Max Width The time over threshold is directly re
61. ally just a subset of Figure 6 3b which was digitized by a Tektronix 544 TDS digital oscilloscope at 10 MHz 10 million per second Given this data set and some kind of arithmetic processor the obvious approach to determining Vx is to take some sort of average over the points before the step and subtract it from the value of the average over the points after the step That is as shown in Figure 77 DXP XMAP xManager User Manual MAN XMAP 1 0 6 6 4 averages are computed over the two regions marked Length the Gap region is omitted because the signal is changing rapidly here and their difference taken as a measure of Vx Thus the value Vx may be found from the equation V 2 WY WV i before i after Equation 6 2 where the values of the weighting constants w determine the type of average being computed The sums of the values of the two sets of weights must be individually normalized 4 gt 2 Length 5 L So lt Gap 8 O S L Length O 2 e ete ee a seee ir me Ge en ete Te deene 5 D Digitized Step 960919 4 l 20 22 24 26 28 30 Time us Figure 6 4 Digitized version of one of the x ray steps of Figure 6 3b The primary differences between different digital signal processors lie in two areas what set of weights wi is used and how the regions are selected for the WM WY computation of i before i after Equation 6 2 Thus for example when the
62. an Right click on either the x or y axis to view the axis tools and options Some of these items are also accessible in the drop down list items above the plot area gt Y Axis Mode Fixed prevents the y axis from re scaling according to new data or user zoom or pan operations Floating prevents the y axis from re scaling according to new data but allows user to zoom and pan Auto sets the y axis dynamically such that input data is fully displayed but can be 43 DXP XMAP xManager User Manual MAN XMAP 1 0 6 overriden by user zoom or pan operations Fixed Auto sets the y axis dynamically such that input data is fully displayed and disables user zoom or pan operations gt X Axis Mode Fixed prevents the x axis from re scaling according to new data or user zoom or pan operations Floating prevents the x axis from re scaling according to new data but allows user to zoom and pan Auto sets the x axis dynamically such that input data is fully displayed but can be overriden by user zoom or pan operations Fixed Auto sets the x axis dynamically such that input data is fully displayed and disables user zoom or pan operations gt Log Scale Sets the y axis to logarithmic or linear scale 400 ee Fixed Scale AxisMode gt Floating Y Scale Log Scale Auto Scale v Fixed Auto Y Scale Events Counts 200 Figure 4 15 Right click on either the x or y axis to view the axis tools and options Alternatively
63. are combination since most problems are actually solved at the software level Please check http xia com DXP XMAP_Download html for the most up to date standard versions of the DXP software and firmware Please contact XIA at support xia com if you are running semi custom or proprietary firmware code Note It a good practice to make backup copies of your existing software and firmware before you update 1 5 2 Related Documentation As a first step in diagnosing a problem it is helpful to consult most recent data sheets and user manuals for a given DXP product available in PDF format from the XIA web site Since these documents may have been updated since the DXP unit has been purchased they may contain information that may actually help solving your particular problem All manuals datasheets and application notes as well as software and firmware downloads can be found at http xia com DXP XMAP_Download html In order to request printed copies please send an e mail to support xia com or call the company directly In particular we recommend that you download the following user manuals v xManager User Manual All users v Handel User Manual Users who wish to develop their own user interface 1 5 3 Technical Support The DXP XMAP comes with one year of e mail and phone support Support can be renewed for a nominal fee Please call XIA if your support agreement has expired The XIA Digital Processors DGF amp DXP are digi
64. assignments for each DXP XMAP module and provides for skipping individual processing channels 4 1 3 Main Window The tabbed Main Window contains the MCA Baseline oscilloscope and system calibration The MCA tab is used for normal mode spectrum acquisition The Baseline tab displays the baseline histogram The Trace tab contains the oscilloscope tool for displaying ADC filter output and baseline data The GainMatch tab contains the system wide gain calibration tool The Mapping panel is used for time resolved multi spectrum and multi SCA data acquisition 4 2 Detector and Preamplifier Settings 11 19 2008 If the Configuration Wizard was followed correctly as described in section 3 2 the system should be nearly ready for data acquisition Before taking a spectrum however we recommend verifying the Detector and Preamplifier settings 25 DXP XMAP xManager User Manual MAN XMAP 1 0 6 Note Do not confuse detector bias polarity with the polarity of the preamplifier signal they are not necessarily related 11 19 2008 ADC Are Linas g 100w 0000 Se 7 MCA Gorete tr Figure 4 2 An ADC trace displayed in the Trace panel oscilloscope tool Notice that the displayed x ray events 7 total are voltage steps with rising edges thus the polarity is set correctly Select the Trace tab in the Main Window to display the oscilloscope tool see Figure 4 2 Select ADC from the drop down list set the Sampling
65. available online at www xla com DXP_Resources html The System FGPA DSP and FiPPI are discussed in Chapter 7 Firmware file formats are further described in Error Reference source not found 1 4 4 Initialization File Handel and thus xManager uses an initialization INI file to store all necessary configuration information including the path and filename of the firmware file on the host computer number and slot location of xMAP modules in the system detector characteristics and spectrometer settings and timing and synchronization logic functions used 1 5 Support 11 19 2008 A unique benefit of dealing with a small company like XIA is that the technical support for our sophisticated instruments is often provided by the same people who designed them Our customers are thus able to get in depth technical advice on how to fully utilize our products within the context of their particular applications Please read through this brief chapter before contacting us DXP XMAP xManager User Manual MAN XMAP 1 0 6 Check for firmware and software updates at http www xia com DX P_ Resources html 11 19 2008 XIA LLC 31057 Genstar Rd Hayward CA 94544 USA Telephone 510 401 5760 Downloads http xia com DXP XMAP_Download html Hardware Support support xia com Software Support software_support xia com 1 5 1 Software and Firmware Updates It is important that your DXP unit is using the most recent software firmw
66. ave Trace Save the file in the xManager_xxxxxx_Rpt sub directory in the xManager installation directory 11 19 2008 60 DXP XMAP xManager User Manual MAN XMAP 1 0 6 5 Mapping Mode Mapping mode supports a number of time resolved experiments but is primarily intended for x ray scanning applications wherein the x ray beam is systematically scanned over a surface in order to produce a pixilated spectral map of the sample Data is stored sequentially at each pixel advance instruction which can be provided by the host computer or triggered by an external logic signal i e GATE or SYNC Mapping mode utilizes a different System FPGA configuration i e firmware must be downloaded when switching between acquisition modes A dual memory architecture allows the DXP XMAP to continuously acquire data in this mode Host readout must be synchronized with the hardware in order to sustain continuous operation 5 1 Pixel Advance Settings 11 19 2008 The pixel advance settings are included in the Configuration Wizard utility described in section 3 2 To run the utility select Configuration Wizard from the Tools menu At the beginning of a run the pixel number starts at zero corresponding to the x ray beam initial position The pixel number advances in several possible ways either using digital hardware lines for real time applications or by computer control These methods are described in detail below 5 1 1 LBUS PCI Extension Run S
67. axis modes can be selected using the drop down list items above the plot area 4 6 Optimizations Making a plot of energy resolution versus peaking time provides a useful future reference 11 19 2008 This section describes various parameter optimizations for the best performance in throughput pileup rejection and energy resolution 4 6 1 Throughput OCR The OCR depends only on the ICR and the dead time per event Tg ICRt td OCR ICR exp where Ta 2 t to To increase the OCR at a given ICR the dead time per event must be reduced The obvious first step is to reduce the energy peaking time tp Further improvements can be made by reducing the gap time ty 4 6 1 1 Peaking Time Energy Filter The peaking time is the energy filter length or integration time i e the ramping interval of the trapezoid It is the primary setting in determining the balance between count rate performance and energy resolution 44 DXP XMAP xManager User Manual MAN XMAP 1 0 6 To change advanced acquisition settings such as the Minimum Gap Time Press the Edit Filter Parameters button in the Reducing the gap time can significantly increase the data throughput at a given peaking time 11 19 2008 Oct Trace fe ergy Fler EI Sanging terval 0 020 e Save Trace icon zo zwa x viiner Geng 2 33267 Everts 3948 gy F 64900 emm Energy Filter Arb Urs 5 Figure 4 16 The output response of the E
68. ay steps are greater than 2 000 ADC units in height increase the Preamp Gain setting 4 2 4 Preamp Risetime This is an advanced setting accessible by pressing the Edit Filter Parameters in the Acquisition settings tab The preamplifier risetime should be measured and the Minimum Gap Time set accordingly This setting is described in detail in section 4 6 1 2 See section 4 7 1 2 for details on using xManager to measure the risetime for your system and section 6 3 for a theoretical discussion of the issues involved in trapezoidal filtering 4 3 Normal Spectrum Mode Data Acquisition To begin data collection Select the MCA tab and press the Start Run button 11 19 2008 4 3 1 Starting a Run Once the detector preamplifier settings have been verified you are ready to collect a sample spectrum Place a known X ray source for example an 55Fe source that produces Mn K line at 5899 eV such that x rays strike the detector s active area at a moderate to low rate i e less than 10 000 x rays absorbed per second Select the MCA tab and press the Start Run button in the data display panel to begin data collection An uncalibrated energy spectrum should appear Figure 4 3 shows a sample uncalibrated gt gt Fe spectrum Proceed to section 4 3 2 if a spectrum is displayed 27 DXP XMAP xManager User Manual MAN XMAP 1 0 6 No spectrum Check your hardware setup e g X rays present v Check your initialization settings
69. b K l Onin Matching Ber gro Lints Caite ation Peak Range Ker s i Number of Rerations F Zoom Grogh to Range and S of Cafe gv Energy 5X Lower 5 Acquston Tee 5 Se Upper Everts Carts mA Barebe Traces O Figure 4 10 The GainMatch panel after one iteration Note the significant channel to channel gain variation Oan Matching teration Linas Coffee Peak Range Kev Number of Rerations Zoom Grog to Range r of Calibration Energy 52 Lower Se Acqsston Tee 5 Upper fens tron zy Everts Carts MAT Docelina Traces Gardtatch Figure 4 11 The GainMatch panel after five iterations Note the near perfect channel to channel calibration Note that if energy calibration results in a significant change in gain it may be necessary to adjust thresholds 11 19 2008 36 DXP XMAP xManager User Manual MAN XMAP 1 0 6 gt Save your modified INI file to a unique filename Select Save Configuration As from the File menu Note The displayed Live Time does not express a relationship between the OCR and ICR The Dead Time Percentage display does relate OCR to ICR 11 19 2008 4 3 7 Saving and Loading INI Files Completion of the gain calibration is the final step in the verification of basic settings The settings should now be saved to an INI file such that they will automatically reload whenever xManager is started Because calibrataion is required any time spectrometer settings are change
70. ccurs at each falling edge 5 1 2 1 GATE Polarity The interpretation of the user provided GATE signal can be inverted such that data acquisition is halted when the signal is HI see Figure 6 2 and the pixel advance occurs on rising edges All XMAP modules ready READY n LBUS Dead gt K GATE Pixel 0 J k Pixel 1 a k Pixel 2 Start Pixel Advance Pixel Advance Figure 5 2 GATE pixel advance with data acquisition halted during the HI periods The pixel advance occurs at each rising edge 5 1 2 2 GATE Ignore Setting Normally the GATE signal is used both to advance the pixel and to halt data taking In some cases the user may prefer continuous operation through the pixel advance operations With the GATE Ignore option selected the pixel advance occurs but data acquisition is not halted Note that the data acquisition is halted at the beginning of the run until GATE is released the first time i e run start synchronization is still available 11 19 2008 62 DXP XMAP xManager User Manual MAN XMAP 1 0 6 All XMAP modules ready GATE Pixel 0 Pixel 1 Pixel 2 Start J Pixel Advance Pixel Advance Figure 5 3 GATE pixel advance with LO polarity and the Gate Ignore enabled Acquisition is halted initially until GATE is released for the first time As before the pixel advance occurs at each falling edge but acquisition continues during the LO periods The above examples al
71. ch period the controls will be grayed out The layout and functionality are similar to the MCA panel The Start Mapping button starts and stops mapping data acquisition runs Output statistics are displayed as before along the top right section of the panel Notice that data and statistics do not update in realtime This is as a result of the dual memory architecture The display is refreshed only after a memory buffer swap 5 2 2 Mapping Mode MCA or SCA The MCA and SCA mapping modes are distinct and exclusive of one another In MCA mode full spectra are stored in memory In SCA mapping mode only the tables of SCA counts are stored in memory Click the MCA or SCA radio button to select the desired mode Section 5 3 details the data formats for MCA and SCA mapping modes 5 2 3 Total Number of Pixels A data acquisition run can be ended manually via the host at any time In most cases the length of a data acquisition run corresponds to the number of pixels in the map The Total Number of Pixels setting instructs the DSP to 65 DXP XMAP xManager User Manual MAN XMAP 1 0 6 automatically end the run after that number of pixel advances have been detected If Indefinite Run is checked the run ends only upon the End Run host command 5 2 4 Buffer Control The XMAP uses a dual memory architecture to achieve continuous data acquisition The XMAP writes into one active buffer while the host reads the other inactive buffer The size
72. channel and the INI file updated Check the Apply to All Detector Elements checkbox Click in the Polarity column if xray steps generate a negative voltage step if xray steps generate a positive voltage step If you don t know the polarity keep the default negative setting Enter the gain in mV keV If you don t know the gain keep the default of 3 mV keV Press Next Hardware Synchronization Settings These settings are used to configure the front panel LEMO connection and backplane trigger lines for normal single spectrum mode If you intend only to use the DXP XMAP in single spectrum mode without the synchronization features you can skip ahead to save the generated INI file 9 Hardware Timing Synchronization If you want to use the synchronization features and or use the DXP XMAP in mapping mode select Configure hardware for synchronized run press Next and proceed to 10 below Otherwise select Skip to save current configuration press Next and skip to 17 19 DXP XMAP xManager User Manual MAN XMAP 1 0 6 10 Multi Bus Synchronous Run Start The LBUS function is used to synchronize the start time of modules in different PCI bus segments The Configuration Wizard detects whether your XMAP modules populate multiple bus segments and if not grays out the LBUS option Please review section 7 2 2 for a complete description of this feature If more than one bus segment is populated we recommend using the L
73. chive and attach the the support request email 4 7 4 1 Generating a Full Error Report If you are unable to solve your problem using the diagnostic tools in xManager the last resort is to send as much information as possible to XIA support This task is facilitated by the Generate Error Report command under the Help menu This feature creates a sub directory titled xManager_xxxxxx_Rpt where xxxxxx is the date in the xManager installation directory that contains all DSP parameters xManager registry settings INI and log files Handel log files etc 4 7 4 2 Saving MCA Data If you are having difficulty acquiring a spectrum or the spectrum looks strange please save and submit a sample MCA file with the Error Report In the MCA tab acquire a spectrum then press Save MCA Data Save the file in the xManager_xxxxxx_Rpt sub directory in the xManager installation directory 4 7 4 3 Saving Baseline Data If you are having difficulty acquiring a good baseline histogram or the spectrum looks strange please save and submit a sample baseline histogram file with the Error Report In the Baseline tab acquire a histogram then press Save Baseline Save the file in the xManager_xxxxxx_Rpt sub directory in the xManager installation directory 4 7 4 4 Saving Trace Data If your ADC or filter output traces look strange please save and submit a sample trace file with the Error Report In the Trace tab acquire a trace then press S
74. cond place one can show theoretically that if the noise in the signal is white i e Gaussian distributed above and below the step which is typically the case for the short shaping times used for high signal rate processing then the average in Equation 6 4 actually gives the best estimate of Vx in the least squares sense This of course is why triangular filtering has been preferred at high rates Triangular filtering with time variant filter lengths can in principle achieve both somewhat superior resolution and higher throughputs but comes at the cost of a significantly more complex circuit and a rate dependent resolution which is unacceptable for many types of precise analysis In practice XIA s design has 79 DXP XMAP xManager User Manual MAN XMAP 1 0 6 been found to duplicate the energy resolution of the best analog shapers while approximately doubling their throughput providing experimental confirmation of the validity of the approach 6 3 Trapezoidal Filtering in the DXP Decimation by N means to pre average sequential sums of length D 2N 11 19 2008 From this point onward we will only consider trapezoidal filtering as it is implemented in the DXP according to Equation 6 3 and Equation 6 4 The result of applying such a filter with Length L 20 and Gap G 4 to the same data set of Figure 6 4 is shown in Figure 6 5 The filter output Vx is clearly trapezoidal in shape and has a risetime equal to L a flattop equa
75. cted spectrum the REALTIME for which data was collected the fast channel LIVETIME for which the fast channel was below threshold and thus ready to detect a subsequent x ray together with the number FASTPEAKS of fast peaks detected and the number of Vx captured events EVTSINRUN From these values both the OCR and ICRy can be computed according to Equation 6 11 These values can then be used to make deadtime corrections as discussed in section 6 11 ICR FASTPEAKS LIVETIME OCR EVTSINRUN REALTIME Equation 6 11 Note The fast channel LIVETIME should only be used to determine the input count rate according to Equation 6 11 Specifically it is NOT related to the energy filter livetime and should not be interpreted as the inverse of the processor deadtime The DSP does calculate the energy filter livetime ELIVETIME however it is only an approximation The most accurate deadtime measurement is obtained from ICRm and OCR in Equation 6 11 as discussed in section 6 11 6 10 Throughput 11 19 2008 Figure 6 12 shows how the values of ICRm and OCR vary with true input count rate for the DXP and compare these results to those from a common analog shaping amplifier plus SCA system The data were taken at a synchrotron source using a detector looking at a CuO target illuminated by x rays slightly above the Cu K absorption edge Intensity was varied by adjusting two pairs of crossed slits in front of the input x ray beam so that the harmonic
76. d we recommend creating separate INI files for each commonly used peaking time Once the settings for a peaking time have been optimized and the system calibrated the entire setup can be restored by loading the INI file 4 3 7 1 Saving an INI File Select File Save Configuration As to open the Save Configuration File dialog Enter a unique filename and press the Save button 4 3 7 2 Loading an INI File Select File Load Configuration to open the Open Configuration File dialog Select a file and press the Open button 4 3 7 3 Creating an INI File The Configuration Wizard utility should be used to generate new INI files Select Tools Configuration Wizard to open the Save Configuration File dialog The utility allows for a previously used INI file to be used as a template Please refer to section 3 2 4 3 8 Output Statistics Global statistics such as ICR OCR and deadtime fraction are displayed along the top of the main window Statistics for defined regions of interest are displayed in the ROI table 4 3 8 1 Real Time This is simply the time elapsed between the Start Run and Stop Run operations measured in the DSP itself every 8ms with 320 ns units Intermediate values read out during the run will therefore have the lower accuracy but the value reported at the end of the run will be accurate to 320ns 4 3 8 2 Trigger Live Time This is the measured live time of the Fast Trigger Filter i e the time that
77. date installation file is a executable or EXE file 2 2 1 Running the Installer 1 Please close all applications that are currently running 2 Insert the CD into the CD ROM drive or if your copy was delivered electronically double click the setup exe program If the CD installation does not start immediately follow the instructions in steps 3 and 4 3 Click the Start button and select the Run command 4 Type X Setup exe and click OK where X is the letter of your CD ROM drive 5 After setup has completed shut down your computer and complete the hardware configuration described in sections 2 3 through 2 5 before restarting e The xManager 0 x installation will create a new directory C Program Files xia xManager 0 x e Anew Start Menu gt Program group will be created e A shortcut to the xManager executable is created on your desktop e The hardware driver file xmap9054 inf is installed in C WINNT inf for Windows 2000 or C Windows inf for Windows XP or Vista 2 2 2 File Locations The xManager default installation folder is C Program Files XIA xManager 0 x This directory contains program files libraries log files and configuration or INI files The firmware folder is xManager 0 x firmware This directory contains the normal and mapping firmware or FDD files see section 1 4 3 Updates to the firmware are available online at www xXia com DXP XMAP_Download html 2 2 3 Support
78. defines a region of interest around the peak selected with the active cursor The cursor context menu is displayed by right clicking on a cursor 4 3 5 Single Channel Gain Calibration Multi element detectors often have significant channel to channel gain variations Further the nominal gain specification provided by the manufacturer can be off by 20 or more This process modifies the variable gain stage of the currently selected processing channel and refines its Preamp Gain Due to the analog nature of the variable gain amplifier that is used the precise analog gain following a hardware gain modification is unknown until it is measured For this reason calibration is an iterative process that must be executed any time acquisition values are changed that require a hardware gain modification e g if the spectrum size is increased Section 4 3 6 describes how to use the Gain Matching tool to calibrate all processing channels simultaneously Once calibration is completed we will save the modified configuration settings each channel with its own unique Preamplifier Gain to an INI file so that they will be retrieved the next time xManager is started 4 3 5 1 Calibrating the Gain At this point you should have an energy peak bounded by a region of interest Please review section 4 3 4 if you have not created an ROI The ROI table also displays the mean energy and width of the peak in the ROIs as well as the ROI upper and lower limits Either t
79. digital filter a definite rate advantage in pileup free throughput 81 DXP XMAP xManager User Manual MAN XMAP 1 0 6 Filtered Step S kfig 960920 4 oe sdi n ze veht S 2 E ewe gt Q D 5 0 rosenen o GOOD 6 lt L gt boooopooon00000 L G 2 lt lt D A ag Je 2L G gt Preamp Output mV Filter Output mV 24 26 28 30 32 Time us Figure 6 5 Trapezoidal filtering the Preamp Output data of Figure 6 4 with L 20 and G 4 6 4 Baseline Issues 11 19 2008 6 4 1 The Need for Baseline Averaging Figure 6 6 shows the same event as is Figure 6 5 but over a longer time interval to show how the filter treats the preamplifier noise in regions when no x ray pulses are present As may be seen the effect of the filter is both to reduce the amplitude of the fluctuations and reduce their high frequency content This signal is termed the baseline because it establishes the reference level or offset from which the x ray peak amplitude Vx is to be measured The fluctuations in the baseline have a standard deviation Ge which is referred to as the electronic noise of the system a number which depends on the peaking time of the filter used Riding on top of this noise the x ray peaks contribute an additional noise term the Fano noise which arises from statistical fluctuations in the amount of charge Qx produced when the x ray is absorbed in the detector This Fano noise of adds in quadrature with the
80. e DXP XMAP cards and an x ray detector preamplifier with appropriate power supplies An alternative solution is to replace the remote computer and PXI controller with a native PXI CompactPCI computer 1 3 1 Host Computer The DXP XMAP communicates with a host computer via the CompactPCI bus The CompactPCI interface is described further in section 2 1 The host computer that runs XIA s Handel and or xManager software must have the following minimum capabilities v 300 MHz or greater processor speed running most Microsoft Windows Operating systems 2000 XP v Native PCI computer or desktop laptop equipped with PCI interface card installed e g National Instruments MXI 3 or MXI 4 1 3 2 PXI CompactPCl Crate A wide variety of PXI Crates are available We strongly recommend using standard crates from trusted vendors e g National Instruments Such vendors provid software that automatically generates the PXI System Configuration File C Windows System pxisys ini This file ensures proper communication with instruments in the crate v Make sure the crate provides a sufficient number of slots to accommodate your system v Native PCI computer or PCI interface card installed e g National Instruments MXI 3 or MXI 4 1 3 3 Detector Preamplifier The DXP XMAP accommodates nearly all preamplifier signals The two primary capacitor discharge topologies pulsed reset and resistive feedback are both supported The input voltage range
81. e energy filter peaking time is widely referred to as peaking time whereas the fast filter peaking time is referred to as fast peaking time 11 19 2008 Channel Selection Detail Channel C Skip Session Run Status 0 1 Figure 4 4 The Channel Selection Detail control in the System settings tab In the system shown MCA data readout and system wide gain matching would be skipped for channels 10 and 11 oon OO Ww bh Skipped Skipped od zech 1 E 4 3 3 Spectrometer Settings The primary spectrometer settings are immediately accesible via the Configuration tab in the settings panel 4 3 3 1 Peaking Time Energy Filter Filters Peaking Time 5 04 As Edit Filter Parameters Figure 4 5 The Peaking Time is displayed in the Configuration tab of the Settings panel The energy filter peaking time is one of the primary user controls Generally speaking a longer peaking time produces better energy resolution at the cost of increased dead time and thus lower output count rate In practice the user may set the peaking time to a shorter than optimal value in order to increase data throughput making up for degraded energy resolution with improved statistics Most detectors also have an upper limit above which the energy resolution gets worse HPGe detectors typically have optimal peaking times between Lous and 32us Silicon drift detectors often produce the best resolution at 10us or less
82. e event post processor first compares DSP scaled energies to minimum underflow and maximum overflow user defined values If the measured energy is within the allowed range the post processor performs a read increment write operation to the appropriate address in memory i e it increments the corresponding spectrum bin The DXP XMAP currently supports basic spectrum acquisition as well as time resolved multi spectrum acquisition The two data acquisition modes use different memory architectures and thus require different firmware code to be downloaded In MCA mode on board memory is configured as a single 1 MEG by 32 bit device simultaneously accessible to both the host and the on board DSP Each spectral bin is thus a 32 bit value allowing for up to 4 294 967 295 events per bin perrun The memory is normally cleared at the beginning of a run but can be preserved allowing for pause and resume functionality In 16 bit mode a data acquisition run produces multiple spectra for each DXP processing channel Spectrum memory is configured as two IMEG by 16 bit devices memory A and memory B each accessible to either the host or the on board DSP Each spectral bin is thus a 16 bit value allowing for up to 65 535 events per bin Continuous operation is achieved by reading memory A while writing memory B and vice versa 110 DXP XMAP xManager User Manual MAN XMAP 1 0 6 7 7 1 Basic 32 bit MCA Data Acquisition DSP DATABUS Syste
83. e gain changes significantly Please review section 6 4 for a detailed description of baseline acquisition and averaging Section 4 7 2 1 describes the empirical optimization of the baseline threshold 4 3 3 4 Energy Threshold The energy threshold sets the low energy limit for the slow or energy filter which is used primarily for measuring the pulse height i e energy of x ray voltage steps Triggering on the energy slowest filter can extend the detection range down to the lowest energies for a given detector however in most cases we recommend setting the Energy Threshold to zero This is 30 DXP XMAP xManager User Manual MAN XMAP 1 0 6 11 19 2008 because the dead time associated with x rays detected by the energy filter can not be directly measured It remains available primarily for two special cases e A non zero energy threshold is appropriate for ultra soft x ray detection at very low input count rates e A non zero energy threshold may be used to extend the detection range for decimation 0 i e peaking times less than 500 ns Dead time and count rate statistics will however be distorted 4 3 3 5 Dynamic Range The dynamic range setting combines with the detector gain setting to determine the variable analog gain of the DXP XMAP The variable gain is set such that an x ray with energy equal to the dynamic range value produces a voltage step of the maximum allowable amplitude at the ADC input X rays with energies e
84. e input step heights Piled up events must be discarded The minimum detectable pileup time or pulse pair resolution is proportional to the filter length plus the filter gap A tradeoff must therefore to be made between pulse pair resolution and the minimum x ray energy that can be detected 7 5 4 2 Fast Trigger Filter The fast filter is used solely to detect incoming x ray events and to determine whether a given event can be processed in the slow filter or whether it should be rejected The fast filter s peaking time tp tpf can be adjusted from 40 ns to 2 56 us When tpf is 40 ns the pulse pair resolution is typically less than 100 ns however x rays in the 0eV 2keV range may not be detected When tpf is 1 us x rays with energies below 500 eV can be detected however the pulse pair resolution is greater than 2 us We typically recommend running at tof 100ns with the fast gap time set to zero 7 5 4 3 Slow Energy Filter The slow filter trapezoid peak value is sampled for the energy measurement The slow filter s peaking time Tp Tps or simply referred to as the peaking time Tp can be adjusted from 100 ns to 164 us At low input rates Tps Should be set simply to optimize energy resolution The optimal value will depend on the detector and preamplifier At higher input rates tps should be chosen such that maximum throughput is achieved The resulting improvement in statistics will compensate for any degradation of energy
85. e it is unnecessary Please review section 7 2 2 for a complete description of this feature and run the Configuration Wizard again if you d like to enable the LBUS function If you decide to use the LBUS function the left most module in each PCI bus segment will be designated as the LBUS master i e it accepts the front panel LBUS connection 4 4 3 The GATE Function The external logic LEMO input can be configured to halt data acquisition simultaneously on all DXP channels according to an external logic signal The so called GATE function supports TTL CMOS levels Please review section 7 2 3 for a complete description of this feature and run the Configuration Wizard again if you d like to enable the GATE function 4 4 4 Resume Run Clear or Retain MCA Data When a new run is started the data from the previous run can either be cleared or retained This setting is accessed in the MCA window via the 41 DXP XMAP xManager User Manual MAN XMAP 1 0 6 Resume checkbox If the box is checked the Start Stop button has start pause functionality new data accumulates with data from the previous run If the box is unchecked data from the previous run is first cleared 4 5 Display Controls This section briefly describes tools and options related to the display of acquired data 4 5 1 MCA Auto Update Refresh Rate The MCA display can be set to refresh with a user specified interval If the Continuous box is checked xManager will aut
86. ections Ovenlew ccc ccccccececececececececeeeeeeeeueucueesaeaeauaeaeaeanaeananaes 99 7 2 2 LBUS Run Start Synchronization eeeeeeeeeeeeeeeeeeneeerreerrssneens 100 11 19 2008 iv DXP XMAP xManager User Manual MAN XMAP 1 0 6 7 2 3 GATE Function MCA Mode ssseeseeeeesiresrrssrrssrrssrnssrnssrrssrresrns 101 72A GATE Polarity iid ccseeiiececeiet ada aad ween 101 2 32 Ignore GATE sfrai aate a e EE Ed 102 7 2 3 3 GATE Real Time 102 7 2 4 GATE Function Mapping Mode cccccccceeeeeeeeeeeeeeeeaeeeeeaeeeeenees 102 7 2 4 1 Pixel Advance on GATE Edge ccccccceeeeeeeeeeteeeeeteeeeeneeees 102 F242 GATE Polarity aeaniee tat hieep ceases KE ege ene aaia ES 102 7 2 4 3 GATE Ignore Gettimg 103 7 2 5 SYNC Function Mapping Mode eseeeeeeeesessresresrssrrresrrssrrssns 103 7 2 5 1 Pixel Advance using SYNC Clock nsise 104 7 2 5 2 Synchronous Starts with GN 104 7 3 The Analog Signal Conditioner AC 105 7 4 Analog to Digital Converter 106 7 5 The Filter Pulse Detector amp Pile up Inspector EIDA 107 7 5 1 FIPPI Gonfiouraton 107 7 5 2 FIPPI Version and Vartants 107 7 5 3 EP Decimation sss tiv ciate REES deeg a aE eege 107 7 5 4 Digital Trapezoidal Filtering A 108 7 5 4 1 Noise and Pileunp 108 7 5 4 2 Fast Trigger Eier 108 7 5 4 3 Slow Energy Filter 108 7 5 4 4 Intermediate Baseline Eiter 109 TSS EE e 109 7 6 The Digital Signal Processor DPI 109 4 6 1 Event Processio aa
87. ed because of its excellent diagnostic properties When all components in the spectrometer system are working properly the baseline spectrum should be Gaussian in shape with a standard deviation reflecting op Deviations from this shape indicate various pathological conditions which may also cause the x ray spectrum to be distorted and therefore have to be fixed The situation is remedied by removing cutting outlying samples from the baseline average described below If the maximum in the baseline distribution lies at Ep then captured baseline values that deviate from E by more than ART and AE respectively are not included in the running baseline average Note that all captured baseline values are included in the Baseline Histogram however so that it is always a valid representation of the system s behavior 6 4 3 Baseline Average Settings and Recommendations A FIR running average of baseline measurements is computed which is then subtracted from sampled peak values to compute the energy of corresponding incident x rays The number of baseline samples averaged is set in xManager as Baselines Average Samples In the DSP this is converted into the parameter BLAVGDIV according to the equation baseline samples averaged 2 4VGDIV 1 Decimation Baseline Samples to BLAVGDIV Average DSP Parameter 0 64 5 2 128 6 4 256 el 6 256 7 Table 6 2 Typical values used for baseline averaging
88. ed to hold the mapping between MCA bins and SCA regions the user can either select to have all channels use the same SCA definitions for all channels which supports the full maximum MCA length of 16K channels or use separate definitions of the SCA regions for each channel where the maximum supported MCA length is 4K channels This format specification does allow differences in the number of SCA s between channels Two words 32 bits total are used to store the total number of events in each SCA region the low word is stored first in memory The format for the entire pixel data block is described in the table below Tag Word 0 0x33CC Tag Word 1 0xCC33 Pixel Number low word first 4 to 5 In the case of a mapping error where one 71 DXP XMAP xManager User Manual MAN XMAP 1 0 6 11 19 2008 pixel record combines data from several pixels this is the number of the last pixel recorded Total Pixel block size in words including header low word first SR SSES ROI Size in words 2 13 to 31 Reserved set to 0 Channel 0 Statistics Realtime 2 words low word first 32 to 39 Livetime 2 words Triggers 2 words Output events 2 words 64 2 K to 64 2 K 2 L 1 Channel 1 ROI data 64 2 K 2 L to Channel 2 ROI data 64 2 K 2 L 2 M 1 64 2 K 2 L 2 M to 64 2 K 2 L 2 M 2 N Channel 3 ROI data 1 Table 5 5 The pixel data block for Mapping Mode 2
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90. electronic noise so that the total noise or in measuring Vx is found from sqrt of 0 Equation 6 5 82 DXP XMAP xManager User Manual MAN XMAP 1 0 6 11 19 2008 Filtered Step L kfig 960920 Output mV Filter Output mV 5 10 15 20 25 30 35 40 45 Time us Figure 6 6 The event of Figure 6 5 displayed over a longer time period to show baseline noise The Fano noise is only a property of the detector material The electronic noise on the other hand may have contributions from both the preamplifier and the amplifier When the preamplifier and amplifier are both well designed and well matched however the amplifier s noise contribution should be essentially negligible Achieving this in the mixed analog digital environment of a digital pulse processor is a non trivial task however In the general case the mean baseline value is not zero This situation arises whenever the slope of the preamplifier signal is not zero between x ray pulses This can be seen from Equation 6 3 When the slope is not zero the mean values of the two sums will differ because they are taken over regions separated in time by L G on average Such non zero slopes can arise from various causes of which the most common is detector leakage current When the mean baseline value is not zero it must be determined and subtracted from measured peak values in order to determine Vx values accurately If the error introduced by this subtractio
91. ena Outpt Rate 23291 ices Everts 5552 Figure 4 12 The Run Preset settings in the MCA panel 4 4 1 1 Run To Preset choice1 Preset Value choice2 Select the MCA tab in the Main Window select a Preset Run type from the drop down list select the criteria for which the current run is stopped e None run ends when user presses Stop button e Fixed Real Time run ends after specified real time elapses e Fixed Energy Live Time run ends after specified live time elapses e Fixed MCA Events run ends after specified number of valid events have been processed into the MCA e Fixed Input Triggers run ends after specified number of input events have been detected Now enter a value in the box below e g 30 seconds or 1000 counts Start a new data acquisition run and note that the run automatically stops when the run preset criteria have been met 4 4 2 LBUS Run Start Synchronization The LBUS function is used to synchronize the start time of modules in different PCI bus segments Because a Start Run command must be issued to each module the actual start time would otherwise vary from module to module A backplane PXI_TRIG line is used to automatically synchronize all modules in a PCI bus segment The front panel LEMO connector configured for LBUS functionality extends this synchronization line between bus segments If more than one bus segment is populated we recommend using the LBUS function otherwis
92. eouirements nesr nesr nesr ner netr netrnerrnserneetnsennsnnnsnnssen nenn 4 Tit H st COMPUTE aie niet gees Ee ebe d e r uitmaak adiaui Sa 4 1 3 2 PXI CompactPCI Craie 4 1 3 3 Detector Preamplifier ccc cceceeeseeeeeeeceee esses eeeeeeeseaeeesaeeneaeeeeeeees 4 1 3 4 Power Supplies ccceccecesceceeeee cee eeeaeeeeeeeeseaeeeeaaeseeaeeseeeeesaeeeenaeeee 5 S CH Gablin E E 5 133 531 nee Hin CTT 5 1 3 5 2 TTL CMOS Logic Inputs cc cececeeeeeeeeeseceeeeeseeeeeseaeeeeaeeeeaees 5 1 4 Software and Firmware Cvervlew 5 1 4 1 User Interface xManager eessesseeseeseessrrsrnetnnsrnrernnsnnnstnnsnnnennnens 5 1 4 2 Device Driver Handel 6 1 4 3 Firmware and FDD Files A 6 1 4 4 Initialization File oo cece cceeece ee ceeeeeeeeeeeeeeeceaeeeseaeseeeeeseeeeeeaeeeeeneeee 6 EE 6 1 5 1 Software and Firmware Updates ssseesseeeseeesseeesneeenneennstnnsennenn nens 7 1 5 2 Related Documentation esseseessreesssrnnernrnesrennensnnnnnnnnnnnnnnnnennnnnnnnnne 7 1 5 3 Technical Support ssseesseesssesssessnsssnsssnsosnnosnnsssnnssnnesnnosnnosnnosnnoenneenneos 7 1 5 3 1 Submitting a problem report 8 er EE 8 1 5 4 1 Export File Formals sisike koniin sE a RNA ARE E EN 8 1 5 4 2 Calibration cece ceeeeceeeeeceeeeeaeeeeeeeseeeesaaeeeeaeeeseeeestaeeseeeeeaes 8 2 Install ationc isc222 2 so a Ee eene 10 2 1 PXI Interface Installaton AA 10 2 1 1 PXI System Configuration File DNXIGVG IN 10 2 1 2 PXI Bus Segments a
93. erent types of data acquisition 109 DXP XMAP xManager User Manual MAN XMAP 1 0 6 7 6 1 Event Processing Event processing consists of reading the event FIFOs of the DXP channels scaling the raw value of each measured pulse height to the appropriate spectrum bin number and writing the scaled events to the System FPGA s event post processor The ADSP 2183 has 16K words of 16 bit wide data memory and 16K words of 24 bit wide program memory part of which is used as data memory to hold the MCA spectrum If more memory is required for special purposes up to 4 Mbytes of extended memory can be added by specifying option M Transferring data to from these memory spaces is done through the DSP s built in IDMA port which does not interfere with the DSP program operation 7 6 2 Statistics Run statistics are updated periodically and written to the SRAM memory 7 7 System FPGA 11 19 2008 The System FPGA primarily serves as a bus interface and arbitrator for the various busses on the DXP XMAP PCI Local Bus Memory Bus the DSP Host Port and the DSP Data Bus During initialization the System FPGA routes the DSP program code from the Local Bus to the DSP Host Port The System FPGA supports diagnostic tasks such as reading oscilloscope trace data and DSP parameters via the DSP Data Bus During a run the System FPGA post processes events and negotiates host read operations from and DSP write operations to the SRAM memory Th
94. erly digitized at the ADC energy resolution will not be optimal This would result from a Preamp Gain setting that is too high resulting ina DXP XMAP variable gain setting that is tool low Set the gain so that the noise is sufficiently digitized see section 4 7 1 1 4 6 3 5 Sufficient Gap Time If the gap time is too short the trapezoid peak sample the energy sample becomes dependent on the arrival time of the x ray relative to the ADC clock Make sure that the Miminum Gap Time is longer than the preamplifier risetime as described above in section 4 6 1 2 4 6 3 6 Peak Sampling Time The optimum sampling time of the energy filter is usually fixed relative to the sum of the peaking time and gap time The Peak Sample Offset is measured backwards in time from this sum i e measured backwards from the end of the flattop period see Figure 4 18 Sampling Time Peaking Time Gap Time Peak Sample Offset The Peak Sample Offset setting is accessible in the Edit Filter Parameters panel In most cases it should not be edited An exception is when running with a very short gap time at decimation 0 see section 4 6 1 2 above In this case the Peak Sample Offset should be reduced empirically Please see section 6 6 2 for a full discussion before attempting this procedure 4 7 Diagnostics To open the Traces panel click on the Traces tab in the main window 11 19 2008 The DXP XMAP and xManager provide several diagnostic tool
95. essessessesseessessiesresrrsrrrerrennnen 63 5 1 4 Pixel Advance under Host Control 64 5 2 Mapping Mode Data Acquisition eeeccceeeeteeeeeennaeeeeeenaeeeeeeaaeeeeeeaeeeeeeaees 65 5 2 1 The Mapping Panel 65 5 2 2 Mapping Mode MCA or SCA eeeeeieeeesriesrissrrsrresrrrssrresrne 65 5 2 3 Total Number of Pixels ccccccccccccccccecececeeeeeeeeeeeeeeusueueueusueauaeaeanaes 65 E ENT uge e lu e EE 66 5 2 5 Mapping Mode Data Acquisition c cceeeeeseeceeeeeeeeeeetaeeeeeeteess 66 5 3 Mapping Mode Data 66 5 3 1 Mapping Data Options 0 ceccceeceeeeeeceeeeeeeeeeeeeaeeeeeeeeeeeeeeaeeeeeeeeea 67 5 3 2 Mapping Data Format 67 5 3 3 Single Buffer Fomat 67 5 3 3 1 Statisties Une 68 5 3 3 2 Buffer Header 68 5 3 3 3 Mapping Mode 1 Full Spectrum Mapping 69 5 3 3 4 Mapping Mode 2 Multiple SCA Mapping 71 5 3 3 5 Mapping Mode 3 List Mode Mappmg 73 6 Digital Filtering Theory of Operation and Implementation Methods 75 6 1 X ray Detection and Preamplifier Operation 75 6 1 1 Reset Type Preamplifiers A 75 6 1 2 BC Twvpebreamplfters 76 6 2 X ray Energy Measurement A Noise Filtering cccceccecessseeeeeesteeeeeeseaes 77 6 2 1 Digital Filtering Theory ccccceceecessseceeessneeeeesseeeeeesseeeessseeeenees 77 6 2 2 Trapezoidal Filtering ssossssnnenessessnnnnenessensnnnnsnessnennnnnnnnesrennnnnnnnee 79 6 3 Trapezoidal Filtering in the DX 80 6 3 1 Comparing DXP Performance
96. events per bin On board memory is configured as two devices memory A and memory B each accessible to either the host or the on board DSP Continuous operation is achieved by reading memory A while the DSP writes memory B and vice versa The data readout speed spectrum size and total number of system processing channels place a limit on the minimum pixel or dwell time The external logic LEMO input can be configured to control the pixel advance function which creates a new spectrum corresponding to a new pixel System FPGA Memory A READ MODE C sng 17301 Memory B oe PLX Interface PCI BUS Figure 1 2 Data flow diagram for multiple spectrum mode 1 2 3 SCA Mapping Mode The Single Channel Analyzer SCA mapping mode allows for up to 64 regions of the spectrum SCA windows to be defined and for which output counts are individually summed Instead of entire spectra only the tables of SCA sums are stored in memory Compressing the data in this way allows for faster readout times or conversely shorter dwell times DXP XMAP xManager User Manual MAN XMAP 1 0 6 1 3 System Requirements Windows XP 2000 CompactPCI computer or a desktop fitted with a CompactPCI optical interface card Preamplifier signal specifications must be verified 11 19 2008 The digital spectroscopy system considered here consists of a remote host computer a PXI CompactPCI crate an optical link from host to crate one or mor
97. g is correct Please read through section 4 7 1 for a thorough description and figures relating to the preamplifier signal polarity 26 DXP XMAP xManager User Manual MAN XMAP 1 0 6 4 2 2 Reset Delay The Reset Delay is the period of time after each preamplifier reset that the DXP XMAP waits before re enabling data acquisition The delay is set based on the settling time of the preamplifier reset transient waveform typically ranging from hundreds of nanoseconds to hundreds of microseconds If you are unsure enter 10 us Setting the delay shorter than the transient settling time may introduce reset artifact events into the spectrum Setting the delay longer than necessary introduces additional processor dead time which will reduce the data throughput at high count rates 4 2 3 Preamp Gain The Preamp Gain setting in combination with the dynamic range setting controls the DXP XMAPs variable gain amplifier such that the input requirements of the ADC are satisfied given the gain of the preamplifier If you know the gain of your preamplifier enter that value Otherwise we recommend using the default value of 3mV keV This setting is normally adjusted automatically during energy calibration In cases of extremely low or high preamplifier gain it may be necessary to adjust the nominal gain before taking a spectrum If the displayed x ray steps are less than 50 ADC units in height reduce the Preamp Gain setting If the displayed x r
98. g the work load of the DSP and thus improving the system throughput 7 5 1 FiPPI Configuration The FiPPI is implemented in a field programmable gate array FPGA Configuration code for the DSP and FPGAs is contained in the XIA proprietary FDD firmware file FiPPI code is downloaded to the XMAP hardware when e The hardware is initialized during startup e A new initialization INI file and or FDD file is selected e The peaking time is adjusted such that a Decimation boundary is crossed 7 5 2 FiPPI Version and Variants Not all FiPPI configuration files are the same FiPPIs are first distinguished by variant Two standard FiPPI variants are available to all users A variant for pulse reset type preamplifiers and a variant for RC decay type preamplifiers From time to time improved standard FiPPI versions are released In some cases custom FiPPI variant designs are used by certain customers It is important to make sure that you are using the latest version of the appropriate FiPPI variant Note RC decay variant FiPPIs only have fast and slow filters and the baseline is acquired from the slow filter 7 5 3 FiPPI Decimation FiPPI s are distinguished also by decimation Decimation refers to pre averaging of the ADC signal prior to the FPGA processing pipeline Each decimation accommodates a specific range of peaking times i e the shaping or integration time of the slow energy filter Typically four 4 FiPPI configuration file
99. gnal halts data acquisition when it is LO and the pixel advances on every falling edge see Figure 7 6 All XMAP modules ready READY ZEN IL BUS Dead Dead Dead J k A Lk GATE lt Pixel 0 dk Pixel 1 J k Pixel 2 Start Pixel Advance Pixel Advance Figure 7 6 Mapping mode acquisition using the GATE input with default polarity The pixel advance occurs on each falling edge of GATE and data acquisition is halted until the next rising edge 7 2 4 2 GATE Polarity The interpretation of the user provided GATE signal can be inverted such that data acquisition is halted when the signal is HI and the pixel advance occurs on rising edges 11 19 2008 102 DXP XMAP xManager User Manual MAN XMAP 1 0 6 All XMAP modules ready READY LBUS o GATE Pixel 0 k Pixel 1 J k Pixel 2 Start Pixel Advance Pixel Advance Figure 7 7 Mapping mode acquisition using the GATE input with inverted polarity The pixel advance occurs on each rising edge of GATE and data acquisition is halted until the next falling edge 7 2 4 3 GATE Ignore Setting Normally the GATE signal is used both to advance the pixel and to halt data taking In some cases the user may prefer continuous operation through the pixel advance operations With the GATE Ignore option selected the pixel advance occurs but data acquisition is not halted Note that the data acquisition is halted at the beginning of the run until GATE is released the first time i e run
100. gy x rays however its slow response precludes accuracy both in the determination of pulse pileup and the measurement of deadtime The intermediate filter which does not suffer this loss of accuracy typically provides sufficient low energy detection When present the intermediate threshold is enabled by default and should be used in most cases The slow threshold should be used cautiously and only at low rates 6 6 Peak Capture Methods 11 19 2008 As noted above we wish to capture a value of Vx for each x ray detected and use these values to construct a spectrum This process is also significantly different between digital and analog systems In the analog system the peak value must be captured into an analog storage device usually a capacitor and held until it is digitized Then the digital value is used to update a memory location to build the desired spectrum During this analog to digital conversion process the system is dead to other events which can severely reduce system throughput Even single channel analyzer systems introduce significant deadtime at this stage since they must wait some period typically a few microseconds to determine whether or not the window condition is satisfied Digital systems are much more efficient in this regard since the values output by the filter are already digital values All that is required is to capture the peak value it is immediately ready to be added to the spectrum If the
101. halted system wide according to a user provided TTL CMOS GATE signal e g to achieve a synchronous run start Sna OU Memory A B ACQUIRE READ ACCESS Figure 1 1 Data flow diagram for MCA mode 1 2 1 1 SCA Feature in MCA Mode The Single Channel Analyzer SCA feature allows for up to 32 regions of the spectrum SCA windows to be defined and for which output counts are individually summed The sums are organized into a table stored in memory in addition to the MCA data and statistics The SCA table can be accessed directly for fast readout of critical data 1 2 2 MCA Mapping Mode This mode supports x ray scanning applications where multiple spectra are generated as an x ray beam is scanned across a sample each spectrum corresponds to a scan point or pixel This mode also supports XAFS spectroscopy where each spectrum corresponds to the beam energy or monochrometer setting DXP XMAP xManager User Manual MAN XMAP 1 0 6 11 19 2008 A data acquisition run produces multiple energy spectra each with associated run statistics for each DXP processing channel Typically a user provided TTL CMOS timing signal is used to advance from one spectrum to the next during the run Data acquisition runs can be started and stopped manually or can be stopped automatically according to a preset number of spectra Spectrum size ranges from 256 bins to 16384 bins Each spectral bin is stored as a 16 bit value allowing for up to 65 535
102. he preamplifier A high frequency noise peak can result in poor relative performance at the corresponding resonant peaking time Often this problem can be mediated though not eliminated by increasing the number of baseline samples in the average for the affected peaking times On the other hand excess low frequency noise i e wandering can be remedied by reducing the number baseline samples in the average 2 High rate performance decimation 0 At higher rates i e gt 50 deadtime the slow filter returns less and less often to baseline thus the time between baseline samples grows longer This is the primary cause of degraded energy resolution at high rates Decimation 2 4 and 6 firmware now employs a proprietary circuit that virtually eliminates this problem resulting in industry leading count rate stability This improvement cannot however be implemented in the decimation 0 firmware The resolution can nonetheless be improved in most cases by reducing the number of baseline samples in the average 6 5 X ray Detection amp Threshold Setting 11 19 2008 Before capturing a value of Vx we must first detect the x ray X ray steps in the preamp output are detected by digitally comparing the output of a trapezoidal filter to a threshold In the DXP up to three trapezoidal filters are implemented fast intermediate and slow each with a threshold that can be individually enabled or disabled A fast filter very quickly detects
103. he arithmetic mean or the Gaussian mean can be displayed Similarly the FWHM full width half maximum is displayed either in kilo electron Volts or as a percentage of the mean energy Simply click on the appropriate column heading to change the display Select the Detector settings tab and make note of the Preamp Gain value To calibrate First make sure the ROI containing the selected peak is Active as set in the leftmost column and then enter the peak s known energy into the Desired field of the ROI i e for an Fe K line enter 5 899 keV 33 DXP XMAP xManager User Manual MAN XMAP 1 0 6 Then press the Calibrate ROT button then start a new run The spectrum should now appear with the peak properly calibrated For the best accuracy it is often necessary to run the calibration through a few iterations If the initial spectrum was badly out of calibration the resulting change in gain may cause the peak to jump partially or fully out of its ROI In this case readjust the ROI so that it centers on the peak before repeating the calibration 4 3 5 2 Propagating the Nominal Gain When you are satisfied with the calibration note that the Preamp Gain value has been modified Before we proceed with a system wide calibration it is good practice to propagate this nominal value to all the processing channels Make sure the Apply to All checkbox is checked Cut and paste or simply re type the Preamp Gain value and press Apply
104. high The baseline samples to the right of the noise peak are partial energy events that should be in the energy spectrum Warning Changing DSP 4 7 3 DSP Parameters parameter s without The DSP Parameters panel accessible via the Tools menu provides a P tami diagnostic display of all DSP s internal parameters for the currently selected iscouraged is 2 processing channel The Hex and Decimal radio buttons determine whether parameters are displayed in hexadecimal or decimal format Press the Update button to refresh the display Note that various active parameters will change 11 19 2008 58 DXP XMAP xManager User Manual MAN XMAP 1 0 6 11 19 2008 every time the Update button is pressed The Channel selector immediately loads the new processing channels parameters 4 7 3 1 Generating a Diagnostic DSP Parameters File The Export to File button generates a ASCII text file containing all of the parameters for the currently selected processing channel You may be asked to generated this file by technical support More likely you will be asked to generate a full Error Report as described in section Figure 4 30 The DSP Parameters panel Do not modify these values unless as instructed by XIA support staff 4 7 3 2 Modifying DSP Parameters In some cases as directed by the XIA support staff it may be necessary to modify the DSP s operating parameters directly To edit a parameter select the field using the
105. ic range value produces a voltage step of the maximum allowable amplitude at the ADC input X rays with energies exceeding the dynamic range value cannot be processed correctly The Dynamic Range setting should thus be set above the largest x ray energy present in the system In order to get the best energy resolution the gain must be set such that electronic noise is digitized sufficiently that it can be properly filtered In practice this means that the noise should span 20 or more vertical units in the display In Figure 4 20 the noise is contained in less than 10 displayed vertical units indicating that the hardware gain setting is too low This could be due either to a Preamp Gain configuration setting that is too high or to the Dynamic Range being set too large The noise displayed in Figure 4 21 spans approximately 40 vertical display units indicating that the Preamplifier Gain is set correctly and the spectrum is properly sized To adjust your own system first select the Trace tab in the main window and acquire a few traces until you have recognizable x ray events displayed Compare the polarity and noise amplitude to the figures If necessary change the Polarity and Preamp Gain You may also need to modify the Dynamic Range For best results the noise should span 20 or more vertical units in the Oscilloscope Panel display ADC Di Sempiegkterval 0100 xs Save Trace Zoom auto x auto v pUnear hd 12200 12190 12180
106. ier A Note that the signal polarity must be distinguished from the bias voltage polarity The signal polarity is positive if the voltage step Vx is a rising edge as displayed in Figure 6 1 Whether signal polarity is positive or negative depends upon the preamplifier s design and does not depend upon bias voltage polarity which is specified on the detector and is determined by its design 6 1 1 Reset Type Preamplifiers Figure 6 la is a simplified schematic of a reset type preamplifier wherein Cf is discharged through the switch S from time to time when the amplifier s output voltage gets so large that it behaves nonlinearly Switch S may be an actual transistor switch or may operate equivalently by another mechanism In pulsed optical reset preamps light is directed at amplifier A s input FET causing it to discharge Cf In transistor reset preamps the input FET may have an additional electrode which can be pulsed to discharge Cf The output of a reset type preamplifier following the absorption of an x ray of energy Ex in detector D is a voltage step of amplitude Vy Two x ray steps are shown in Figure 6 3b as a step 75 DXP XMAP xManager User Manual MAN XMAP 1 0 6 a b Preamp Output mV D Ki 50 0 50 100 150 Time us Figure 6 1 a Reset type charge sensitive preamplifier with a negatively biased detector b Output on absorption of x ray rays Note that the steps have a rising edge so that the signal polarity is
107. ion Energy has been reached 4 3 6 1 Skipping Channels The GainMatch tool operates on all active processing channels Individual processing channels can be disabled or skipped from the calibration macro Select the System settings tab to display the Channel Selection Detail Click in the Skip Session column to de select individual channels Note Channel skipping also applies to MCA data readout as described in section 4 3 2 Channel Selection Detail Channel C Skip Session Run Status 0 1 ia Di oon OO P wh Skipped Skipped b l o Figure 4 9 The Channel Selection Detail control in the System settings tab In the system shown MCA data readout and system wide gain matching would be skipped for channels 10 and 11 4 3 6 2 Running the Calibration Macro Select the GainMatch tab in the main window Remember that this tool works best if the nominal gain has been verified as described in section 4 3 5 above The algorithm is only stable if a peak is detected within the specified range Depending on source intensity the Acquisition Time should typically range between and 10 seconds It is best to experiment with the settings to get a feel for the utility 35 DXP XMAP xManager User Manual MAN XMAP 1 0 6 Note that if the calibration routine fails to find a peak in a given channel that channel will automatically be disabled You may want to re enable channels afterwards in the System settings ta
108. l to G and a symmetrical falltime equal to L The basewidth which is a first order measure of the filter s noise reduction properties is thus 2L G 6 3 1 Comparing DXP Performance This raises several important points in comparing the noise performance of the DXP to analog filtering amplifiers First semi Gaussian filters are usually specified by a shaping time which is roughly half of the peaking Their pulses typically are not symmetric so that the basewidth is about 5 6 times the shaping time or 2 8 times their peaking time Thus a semi Gaussian filter typically has a slightly better energy resolution than a triangular filter of the same peaking time because it has a longer filtering time This is typically accommodated in amplifiers offering both triangular and semi Gaussian filtering by stretching the triangular peaking time a bit so that the true triangular peaking time is typically 1 2 times the selected semi Gaussian peaking time This also leads to an apparent advantage for the analog system when its energy resolution is compared to a digital system with the same nominal peaking time A valid energy resolution comparison must start with filters that have equal basewidths and thus equal throughput e g The energy resolution of an analog system with shaping time of 1 us should be compared to that of a DXP with a peaking time of 2 8 us 6 3 2 Decimation and Peaking Time Ranges A practical limitation on the implementation of Equati
109. l use the same cable connections shown in Figure 5 4 below Only one connection each for LBUS and GATE are necessary for each PCI bus segment a gt S Es Es Z K Ve NS Ai L LH sS Es LC E e d CO LC y Q x 5 FF ZG FF ei E e ee g e ei A d d A GATE READY LBUS OO O19 0 ol oe Pci BUS SEGMENT 1 _ pc Bus SEGMENT 2 _ PCI BUS SEGMENT 2 Figure 5 4 The LEMO cable connections for GATE pixel advance with LBUS enabled If LBUS is not used GATE connections would shift over one module to the left connecting to slots 2 7 and 13 5 1 3 Pixel Advance using SYNC Clock The SYNC signal can also be used to generate the pixel advance Using this method the pixel will advance for every N positive pulses on the SYNC line where N can be set from 1 to 65535 Note that the pulses must be greater than 40 ns wide to be guaranteed to be recognized 11 19 2008 63 DXP XMAP xManager User Manual MAN XMAP 1 0 6 All XMAP modules ready READY LBUS o Dead G Live GATE Pixel Advance N Pixel Advance N lt Pixel 0 gt lt Pixel gt Start m T Figure 5 5 SYNC pixel advance with LBUS and GATE used to synchronize the run start Acquisition is halted initially until GATE is released for the first time The pixel advance occurs every N cycles of the SYNC clock D DBD A a A PP Ji SP d ei ec Z C ELLK A ae E Es Es se Pa sf E d
110. lated to the filter length If you previously optimized Max Width i e the maximum time over threshold you may need to re optimize See section 4 6 2 1 4 6 3 Energy Resolution There are many possible reasons for poor energy resolution This section points to the most common issues 4 6 3 1 Proper Peaking Time Selection The first step in improving energy resolution is of course to optimize the Peaking Time Use your plot of energy resolution versus peaking time to select a peaking time where you get good energy resolution before making these adjustments 4 6 3 2 Baseline Acquisition Capturing good baseline values and proper averaging are vital to achieving good energy resolution The Baseline Threshold and Baseline Average Samples settings must be set properly for a given peaking time See section 4 7 2 for making adjustments in xManager and section 6 4 for more detailed explanations of baseline issues 4 6 3 3 Eliminate Noise Pickup Noise pickup can destroy performance It is very important to identify and eliminate excess noise in the hardware Typically this involves eliminating ground loops removing switching power supplies in close proximity and 48 DXP XMAP xManager User Manual MAN XMAP 1 0 6 improving shielding Please refer to section 4 7 1 below for a brief introduction to using the Trace panel to identify noise issues 4 6 3 4 Sufficient Gain to Sample Noise If the signal gain is such that noise is not prop
111. le 23 Using xManager with the DXP XMAP ccsssesceesseeeeeenseeeeeenseeeeenseeneeeenneeneeenss 24 4 1 A Quick Tour Of vManager rnnr tnnnnt trnns nnmnnn 24 G fa Mee e EE EE 24 4 1 2 Settings Gidebar AA 25 4 41 39 Main One EE 25 4 2 Detector and Preamplifier Settings ccceceeeeeeceeeeeeeeeeeeeeseeeeeseeeesaeeeeaes 25 4 2 1 Pre Amplifier Polarity c cccceeeseeceeeeeceeeeeseeeeeeaeeeseeeeeaeeeeneeeeeeees 26 42 2 Reset Delay EENS aia aa a Vean na a ee 27 4 2 3 Preamp Gaini tAa tie Atak tae ea ee 27 Ge Preamp RISCUIMNG 2 egesteerdgee ef t aa E deen ln LAE RR 27 4 3 Normal Spectrum Mode Data Acouteitton nesen rsen rernnernesr nens 27 4 3 4 Starting a RUN ANEREN deed eee 27 4 3 2 Skipping Channels ar aitaa aai iaaiaee ea ae ae aaa Re a aa eaa 28 4 3 3 Spectrometer Settings cccceceesceeeeeeeceeeeeeaeeeeneeseeeeeeeaeeeeneeesenees 29 4 3 3 1 Peaking Time Energy Filter 29 4 3 3 2 Trigger Treshold asese e eege 30 4 3 33 Baseline Threshold esrden i i 30 43 34 Energy Threshold eraen E a a eege 30 4 3 3 5 Dynamic Range orir a e e cha nen ida E AAEE 31 4 3 3 6 MCA Number of Bins and MCA Bin Width 31 4 3 3 7 Baseline AVOrage ecceccceessseceeseceeeeneeceeeeeeeeeeeeesenseeeenenees 31 4 3 4 Setting Regions of Interest POls 32 WE NR elei lu De TEE 32 4 3 4 2 AUTO EE 32 4 3 5 Single Channel Gain CGalbration 33 4 3 5 1 Calibrating the Gan 33 4 3 5 2 Propagating the Nomi
112. les is then made to reduce the noise in this measurement and the result is subtracted from instantaneous raw pulse height measurements to determine their true amplitudes Please first review section 6 4 for a thorough discussion of baseline acquisition The Baseline panel displays a histogram of the instantaneous baseline samples The histogram in combination with the Baseline History and Baseline Filter traces see section 4 7 1 4 above are powerful tools for diagnosing electronic noise and common nonlinearities in the detector and preamplifier Select the Baseline tab and press Get Baseline to acquire a baseline histogram You should see a Gaussian peak with few if any outliers as in Figure 4 27 If there are many outliers to the right of the peak as in Figure 4 28 the threshold is set too high If the right side of the peak is attenuated non Gaussian as in Figure 4 29 the threshold is set too low 11 19 2008 56 DXP XMAP xManager User Manual MAN XMAP 1 0 6 11 19 2008 e Baseire Moar B tine Qet Baseine Baseine Freet 26 3 bns Zoom Auto X DIS Y chagges 100000 Everts Courts Figure 4 27 A good baseline histogram the shape of the noise peak is Gaussian with no outlying data points 4 7 2 1 The Baseline Threshold Section 4 3 2 includes a discussion about setting thresholds based on visual feedback in the MCA panel Threshold settings also affect baseline acquisition Baseline acquisition is enabled only
113. line samples selected for use in the running average gt Energy Samples The unsigned slow filter output peak samples selected for the energy spectrum 2 Enter a value ranging 0 020 1000 microseconds in the Sampling Interval field This is the time between each displayed sample 3 Press Get Trace Figure 4 19 The Traces panel is a useful diagnostic tool 4 7 1 1 Determining the Preamplifier Polarity and Gain A common configuration error involves setting either the preamplifier signal polarity or gain incorrectly Note The preamplifier type i e pulsed reset or RC feedback is determined by the firmware file that is downloaded to the hardware see section 3 2 1 The Preamplifier Polarity configuration setting determines whether the ADC code is inverted prior to the digital filter pipeline which expects x ray pulses with a rising edge The Trace panel displays the digital signal after this optional inversion If the x ray pulses are displayed with a falling edge as shown in Figure 4 20 then the polarity setting is incorrect if pulses are displayed with a rising edge as in Figure 4 21 then the polarity setting is correct The Preamp Gain setting in the Detector panel in combination with the Dynamic Range setting in the Configuration panel determines the DXP 50 DXP XMAP xManager User Manual MAN XMAP 1 0 6 XMAP analog variable gain setting The variable gain is set such that an x ray with energy equal to the dynam
114. ltiple of 256 For at least the first version of the mapping firmware the spectra must be the same size for all channels in a system and will in general equal 256 2 n ie 256 512 1024 2048 etc The format for the entire pixel block is described in the table below Pixel Number low word first In the case of a mapping error where one pixel record combines data from several pixels this is the number of the last pixel recorded Total Pixel Block size in words including header low word first Channel 0 Statistics Realtime 2 words low word first 32 to 39 Livetime 2 words Triggers 2 words Output events 2 words 40 to 47 Channel 1 Statistics 11 19 2008 70 DXP XMAP xManager User Manual MAN XMAP 1 0 6 11 19 2008 asec 256 K to 256 K L 1 Channel 1 Spectrum OR Oe ian Channel 2 Spectrum M 1 256 K L M to Channel 3 Spectrum 256 K L M N 1 Table 5 4 The pixel data block for Mapping Mode 1 5 3 3 4 Mapping Mode 2 Multiple SCA Mapping The pixel header for multiple SCA or ROI for Region Of Interest mapping mode is described below there is no constraint on the data alignment in the buffer so the header length is shorter than the 256 words required for full spectrum mapping There are four sections in the pixel data block for this mode containing the SCA totals for each of the four detector channels Up to 64 SCA s can be defined for each channel A 16K word array is us
115. lue within this Ready for next interval is sampled x ray pulse Preamp Output l Signal Slow Filter Output G PEAKINT D KH SLOWLEN T SLOWGAP Figure 6 7 Peak finding method The slow filter output is monitored and the peak value is selected 11 19 2008 In the peak sampling method the slow filter output is instead sampled a fixed time after the x ray is detected An additional Peak Sampling timer is started when an x ray step is detected which expires after PEAKSAM decimated clock cycles PEAKSAM must be less than PEAKINT and should typically be set such that the sample point lies in the flat top region of the slow filter output SLOWLEN lt PEAKSAM lt SLOWLEN SLOWGAP Equation 6 7 The precise PEAKSAM setting has a strong effect on energy resolution and should be determined empirically for each new detector More on this below 88 DXP XMAP xManager User Manual MAN XMAP 1 0 6 Preamp Output Signal Slow Filter Output Figure 6 8 K Slow Filter Ready for next Sampled Here x ray pulse vi PEAK SAMPLE OFFSET PEAKSAM vi PEAK INTERVAL OFFSET PEAKINT gt SLOWLEN SLOWGAP Peak sampling method The slow filter output is sampled a fixed time after the x ray is detected PEAKSAM must be set properly to achieve optimum performance In our experience values at the low end i e PEAKSAM SLOWLEN tend to work better We recommend that yo
116. m FPGA sng 1v901 Memory A B INACTIVE EMPTY Figure 7 13 Data flow diagram for single spectrum mode A basic 32 bit MCA data acquisition run produces a single MCA energy spectrum ranging from 256 bins to 16384 bins for each DXP processing channel The external logic LEMO input can be configured to halt data acquisition i e implemented as a GATE function Data acquisition runs can be started and stopped manually or can be stopped automatically according to a preset real time live time or number of input or output events 7 7 2 Full Spectrum 16 bit MCA Mapping Scanning Mode This mode produces multiple spectra where an external logic signal typically is used In the mapping mode an x ray beam is scanned across a sample and each spectrum corresponds to a scan point or pixel The external logic LEMO input can be configured to control the pixel advance function which creates a new spectrum corresponding to a new pixel Data acquisition runs can be started and stopped manually or can be stopped automatically according to a preset number of pixels Pseudo normal spectrum mode operation is supported for diagnostic purposes with the following limitations Data cannot be read out during a run The 16 bit bins can easily overflow depending on the run length and input count rate Please refer to 5 3 3 3 for further information System FPGA Memory A READ MODE C sna 17301 Memory B sealg dh PLX Interface PC
117. n is not to significantly increase ot then the error in the baseline estimate op must be small compared to Oe Because the error in a single baseline measurement is oe by definition this means that multiple baseline measurements will have to be averaged This number Nj is the Baseline Average For example if Np 128 measurements are averaged then the total noise will be as shown in Equation 6 6 83 DXP XMAP xManager User Manual MAN XMAP 1 0 6 Applying a Baseline Cut can improve performance when the Baseline Histogram is non Gaussian Outlying data points are cut from the running Baseline Average though still included in the histogram 11 19 2008 o sqrt of 1 1 128 o Equation 6 6 This results in less than 0 5 eV degradation in resolution even for very long peaking times when resolutions of order 130 eV are obtained 6 4 2 Raw Baseline Measurement The output of the energy filter or a derivative of the energy filter the intermediate filter is sampled periodically in the explicit absence of an x ray step defined by a baseline threshold In practice the DXP initially makes a series of Ng baseline measurements to compute a starting baseline mean It then makes additional baseline measurements at quasi periodic intervals to keep the estimate up to date These values are stored internally and can be read out to construct a spectrum of baseline noise referred to as the Baseline Histogram This is recommend
118. n overlay First acquire a spectrum then select Open MCA Data from the File menu Notice that the statistics and ROI table operate on the current data only Note also that if new data is acquired the stored data is preserved Zooming and panning operate by default on the current data To zoom and pan the saved data right click in the display area select Active Plot and select the saved waveform To clear the stored data right click in the data display area and select Remove Ref gt Ifyou would like to analyze a stored spectrum first right click in the data display area and select Clear Graph Now select Open MCA Data from the File menu Notice that the statistics ROI table and graphical tools now operate on the stored data Note also that if new data is acquired the stored data is automatically cleared 4 3 10 2 Baseline Histogram Data The baseline histogram can be saved for later display Acquire a baseline histogram then select Save Baseline from the File menu A saved baseline histogram can be displayed at any time Again there are two methods of displaying a saved baseline histogram gt Ifyou want to compare a saved baseline histogram to currently acquired data the saved data can be displayed as an overlay First acquire a baseline histogram then select Open Baseline from the File menu Notice that the Baseline Mean and Baseline FWHM operate on the current data only Note also that if new 39 DXP XMAP xManager U
119. n the most precise measurements All FiPPI parameters including the filter peaking and gap times threshold and pileup inspection parameters are externally supplied and may be adjusted by the user to optimize performance Because the FiPPI is implemented in a Xilinx field programmable gate array FPGA it may also be reprogrammed for special purposes although this process is non trivial and would definitely require XIA contract support Decimation ADC Samples Peaking Time Shaping Time in Average Range Range 0 1 80 ns 500 ns 160 ns 1 0 us 2 4 500 ns 8 us 1 0 us 16 us 4 16 8 us 32 us 16 us 64 us 6 64 32 us 128 us 64 us 256 us Table 7 1 FiPPI decimation details 7 6 The Digital Signal Processor DSP The DXP XMAP architecture was designed for speed Because there is only one DSP for four DXP channels the processor load has therefore been minimized During a run the DSP only processes events and compiles run statistics Prior to a run the DSP initializes the FiPPIs according to user settings The DSP also performs various diagnostic tasks such as oscilloscope mode trace capture and baseline histogramming Such diagnostic tasks are 11 19 2008 performed on one DXP channel at a time The processor is an Analog Devices ADSP 2183 16 bit Fixed Point DSP optimized for fixed point arithmetic and high I O rates Different DSP program or code variants are used for diff
120. na iaa 110 6 2 Statisties nnana a eee wala eae A 110 eT OVSICM ele EE 110 7 7 1 Basic 32 bit MCA Data Acquisition eceeeeeteeeeeeteteeettaeeeeneees 111 7 7 2 Full Spectrum 16 bit MCA Mapping Scanning Mode 111 7 7 3 Other Data Acquisition Modes Error Bookmark not defined 76 3 Pany POI EE 112 ele Te 113 Appendix A DPP XMAP Revision C Circuit Board Description 113 A 1 Jumper Settings cece eeceaeeeeneeeeeeeeseaeeeeaaeseeneeseeeeeeaaeseeeeeesaes 114 Aa LED INACIO aa aa a E AANA OT EEAS E a AANE AT NATRY 114 EENHEETEN EEN 115 AA Power CONSUMPTION 0 2 cececeeeeeeeeceeeeeeeeeeeeeeeceaeeeeaaeeeeaeeeseaeeeeaeeseneeeeaes 115 11 19 2008 y DXP XMAP xManager User Manual MAN XMAP 1 0 6 Safety Please take a moment to review these safety precautions They are provided both for your protection and to prevent damage to the digital x ray processor DXP and connected equipment This safety information applies to all operators and service personnel Specific Precautions 11 19 2008 Observe all of these precautions to ensure your personal safety and to prevent damage to either the DXP XMAP or equipment connected to it Do Not Hot Swap To avoid personal injury and or damage to the DXP XMAP always turn off crate power before removing the DXP XMAP from the crate Servicing and Cleaning To avoid personal injury and or damage to the DKP XMAP do not attempt to repair or clean the unit The DXP hardwa
121. nager via the Start menu Start gt Programs gt xManager 0 x gt xManager The first time xManager 0 x starts up the xManager Configuration File Error panel will appear as shown in below 11 19 2008 15 DXP XMAP xManager User Manual MAN XMAP 1 0 6 xManager Configuration File Error Cant find configuration file in the registry Do you want to try to find it or start the Configuration Wizard to generate a new file i Generate Select File New File To open the Configuration Wizard Select Figure 3 1 The Configuration File Error appears the first time you run Configuration Wizard xManager because a valid INI file has not been selected from the Tools menu Press the Generate New File button to launch the Configuration Wizard which guides the user step by step to create an INI file 3 2 The Configuration Wizard The Configuration Wizard utility can be launched at any time from the Tools menu in xManager 3 2 1 General Settings These basic settings are the bare minimum necessary to run the DXP XMAP in normal single spectrum mode 1 Welcome to the xMAP Configuration Wizard The first panel of the Configuration Wizard is simply a welcome screen with some information about the utility Press Next in the xMAP Configuration Panel 2 Starting Template For now select lt default blank template gt and press Next Note that if you have an existing INI file you can select it now to use as a
122. nal Gan 34 4 3 6 System Wide Gain Calbratton 35 4 3 6 1 Skipping Channels sssssssesseeseeseseseesrenresnnrernrsennsnnnsennennens 35 4 3 6 2 Running the Calibration Mac 35 4 3 7 Saving and Loading INI Files eseeeeseseesirsssrrssrresrrssrrssirssrnsssrnssns 37 4 3 7 1 Saving an INI Elei 37 4 3 7 2 Loading an INI Pie 37 4 3 7 3 Creating an INI File 37 4 3 8 Output Statistics eeececccceceee cesses ceeeeeceeeeeesaeeseaeeseeeeessaeeseneeeeenees 37 ASB A Beal TINE sci cpstecesiiiiecs eege egenen 37 4 3 8 2 Trigger Live Time ocres eeen e etsin Een N E EE E 37 4 3 83 Energy Live Time eccecccceececseceeseeeeeeeeeneeeeeeenseeeeeneneeeeenenees 37 4 3 8 4 Input Count Rate CH 38 4 3 8 5 Output Count Rate OCH 38 4 3 8 6 Dead Time uieeeecccececcceeeeeceeneeeeeeeeceeeeeeaeseeaaeeeeeeesaeeseaaeeeeneeee 38 4 38 27 ROPSAISUCS niiina aa aaa e ai eed Senate 38 4 3 9 Single Channel Analyzer GC 38 ii DXP XMAP xManager User Manual MAN XMAP 1 0 6 4 3 9 1 Creating SCAS ecccecceeeeeeeeeeee cece eeeeaeeeeaaeeeeeeeseaeeetaeeeeeeeeees 38 4 3 9 2 Running with SCAS 0 ccceeceeeeeeeeeeeeeeeeeeeeeeeeeeseaeeeeaaeeeeeeeee 39 4 3 10 Saving and Loading Data cceceecececeeeeeeeeeeeseeeeeseeeeseaeeeeenes 39 43101 MGA Data EE 39 4 3 10 2 Baseline Histogram Data 39 4 3 10 3 gt Trace Dates oireet dee dE ENEE EE EE en 40 4 3 10 4 DSP Parameters cccccccceeeeeeeeeeeeeeeeeeee scenes seaeeeeaeeneee
123. nd Glots nee neer ner nserr neer nsennsennsenn 10 2 2 SOftwa re Installati n EE 10 2 2 1 Running the Mstahiki eenkeer eeke e EA EAE EER TENNES 11 Lad UE IT 11 21233 SUPPOM EE 11 2 3 Configuring the Analog Signal Condtioner 12 2 3 1 Input Attenuation JP100 JP200 JP300 JP400 cee 12 2 4 Installing DXP XMAP Cards issie ienis igsknn ensine ea akiiata Aai 12 2 5 Eu Be le 13 2 57 1 gt Signal GONMECHIONS EE 13 2 5 2 GATE SYNC LBUS Connection cccececececeeeeeneeteeeeeeeeeeseaeesennees 13 2 6 Startingcthe System ET 13 2 6 1 DXP XMAP Driver Gelechon 14 11 19 2008 i DXP XMAP xManager User Manual 11 19 2008 MAN XMAP 1 0 6 3 System Configuration cccseccssceeceseeeeeeeseseeeeeeeeeeeseeseseaeseseeeenseaeseneseseeesenseeeneees 15 3 1 Initialization FPles cece eee entree eee e ee ee eae ee ee a a ei aa 15 3 1 1 Starting xManager Without an INI File 15 3 2 The Configuration Wizard cecececceceeeeeeeeeeeeeeeeeeaeeeseaeeeeeeeeseaeeesaeeseneessaes 16 3 2 1 General Settings 0 ce eeceece ce ceeeceeeeeeeeeeceaeeeeaaeseeneeeeeaeeeeaaeeteaaeesenees 16 3 2 2 Hardware Synchronization Gettngs 19 3 2 3 Mapping Mode Settings cccccesceeeeeeeeeeeeeeeeeeeseeseneeeeseaeeeeneeseeeees 21 3 2 4 Completing the Configuration cccceceecceeseeeeeeeeceeteeeetaeeeeneeteeeeees 22 3 3 Loading and Saving Initialization Eiles eeen rssnnesnnssrnssrnnee 23 3 3 1 Loading an INI le 23 3 3 2 Saving an INI
124. nds to the input_logic_polarity setting in the INI file All XMAP modules ready READY e LBUS Dead gt k Live gt Dead lt Live GATE Start Figure 7 5 The same run start shown in Figure 7 4 above but with the GATE polarity inverted 11 19 2008 101 DXP XMAP xManager User Manual MAN XMAP 1 0 6 7 2 3 2 Ignore GATE This is a software only setting Checking the Ignore GATE checkbox disables the GATE logic Data acquisition occurs irrespective of the GATE signal level 7 2 3 3 GATE Real Time This is a hardware level setting that allows for incrementing only the real time counter when the GATE is asserted data acquisition and other statistics are halted This setting corresponds to the gate_mode setting in the INI file The default setting gate_mode 0 halts everything With gate_mode 1 the real time increments 7 2 4 GATE Function Mapping Mode In Mapping mode multiple spectra are generated as an x ray beam is rastered across the sample Each spectrum corresponds to a pixel The pixel advance controls when the XMAP changes from one pixel spectrum to the next The simplest pixel advance is implemented with the GATE signal 7 2 4 1 Pixel Advance on GATE Edge The recommended method for advancing the pixel number is to use the GATE input where the pixel number advances on every trailing edge of the signal the transition from active data acquisition to the inactive state By default the GATE si
125. nected equipment if the instructions below are not followed All electronic connections are made at the front panel of the DXP XMAP We recommend using cables under three meters in length for signal connections to the preamplifier 2 5 1 Signal Connections The DXP XMAP employs SMA connectors for size reliability and signal quality XIA provides four 4 BNC to LEMO cables with each DXP XMAP Fasten these cables to each DXP XMAP input and connect the other end to each detector preamplifier output Use BNC extension cables if necessary The default ordering starts at channel 0 upper input of the left most module in the crate and proceeds down that module then up to channel 0 of the next module to the right etc 2 5 2 GATE SYNC LBUS Connection Each DXP XMAP includes a programmable TTL CMOS level LEMO connection This connection can be configured as a GATE or SYNC timing input for time resolved spectroscopy applications Typically one DXP XMAP module of each PCI bus segment is designated the GATE or SYNC master module which accepts the LEMO connection and connects to other modules in the bus segment via a dedicated backplane PXI trigger line The LEMO connection can also be configured as an LBUS READY output to synchronize the start of data acquisition runs across multiple crates or bus segments The LBUS function utilizes a wired OR backplane PXI line to simultaneously start a run on all modules contained in a PCI bus segment the tun
126. nergy Filter with peaking time ramping time 20 1 6s and gap time flattop time 0 96us The trapezoid is the response to an x ray You will generally find it useful after making a first attempt to optimize settings to capture a set of spectra over a wide range of peaking times preferably over the full range that the DXP XMAP supports and generate a plot of energy resolution versus peaking time This will serve two purposes first to serve as a standard of comparison so that you can tell if further parameter adjustments are helping or not and second to provide you with some feedback about whether your spectroscopy system is behaving properly Later when everything is optimized and all the noise sources have been suppressed you can go back and repeat these measurements to provide hard data for use in selecting the best peaking time for a given input count rate 4 6 1 2 Gap Time Energy Filter The gap time of the energy filter sets the flattop length of the output trapezoid Because the gap time directly affects the dead time it is advantageous to set the gap time as short as possible The gap time is subject to several constraints Generally the gap time should be set to a value that exceeds the 0 100 preamplifier risetime in response to a detected x ray As long as this constraint is met the trapezoid peak is tolerant of variations of the x ray arrival time relative to the ADC clock The digital filter architecture further cons
127. nnel dead times taf as shown The maximum value of OCR can be found by differentiating Equation 6 12 and setting the result to zero This occurs when the value of the exponent is 1 i e when ICR equals Ltd At this point the maximum OCRymax is Lie multiplied by the ICR or 96 DXP XMAP xManager User Manual MAN XMAP 1 0 6 OCR max 1e tg 0 37 tg Equation 6 13 These are general results and are very useful for estimating experimental data rates Table 6 4 illustrates a very important result for using the DXP the slow channel deadtime is nearly the minimum value that is theoretically possible namely the pulse basewidth For the shown example the basewidth is 4 6 us 2Ls Gs while the deadtime is 4 73 us The slight increase is because as noted above PEAKINT is always set slightly longer than Ls Gell to assure that pileup does not distort collected values of Vx The deadtime for the analog system on the other hand is much larger In fact as shown the throughput for the digital system is almost twice as high since it attains the same throughput for a 2 us peaking time as the analog system achieves for a 1 us peaking time The slower analog rate arises as noted earlier both from the longer tails on the pulses from the analog triangular filter and on additional deadtime introduced by the operation of the SCA In spectroscopy applications where the system can be profitably run at close to maximum throughput then a single
128. ns The SYNC pixel advance occurs after the selected Number of cycles is detected on the desired Trigger Edge Note Selecting SYNC mode reserves the left most available module in each PCI bus segment as the SYNC master i e it accepts the front panel SYNC connection c User Pixel Advance Options There are no options for the this mode the utility skips to next panel Timing Mode Run Control Options The DXP XMAP can automatically stop the data acquisition run after a prescribed number of pixels The Number of Pixels Per Run setting can easily be modified later in xManager If it is set to minus one 1 the run continues until the user stops the run A dual memory architecture is used to achieve continuous operation in mapping mode Each memory device is 1 048 576 words in size The Number of Pixels Per Readout is slightly less than the total device size divided by the individual spectrum size If zero or a number greater than acceptable is selected the largest number that can be used is automatically calculated This setting can easily be modified later in xManager 3 2 4 Completing the Configuration Kaap Configuration Wizard E Front Panel LEMO Connections Click on the Start System button to apply previous settings and start system the LED wil be Muminated for making LEMO connections Figure 3 8 As expected one module in each PCI bus segment 3 and 4 has 11 19 2008 been designated as a GATE Master 16
129. nvariant systems with cusp like filters are still expensive due to the computational power required to rapidly execute strings of multiply and adds One commercial system exists which can process over 100 Keps but it too costs over 12K per channel 6 2 2 Trapezoidal Filtering The DXP processing system developed by XIA takes a different approach because it was optimized for very high speed operation and low cost per channel It implements a fixed length filter with all w values equal to unity and in fact computes this sum afresh for each new signal value k Thus the equation implemented is icek 20 G41 isk L 1 Equation 6 3 where the filter length is L and the gap is G The factor L multiplying Vx k arises because the sum of the weights here is not normalized Accommodating this factor is trivial for the DXP s host software The operations are carried out using hardwired logic in a field programmable gate array FPGA that is called the FiPPI because is implements Filtering Peak capture and Pileup Inspection In the FiPPI Equation 6 3 is actually implemented by noting the recursion relationship between Vx k and Vx k 1 which is L Vx k L Vyk Vk NL Vi L G gt Vk 2L G Equation 6 4 While this relationship is very simple it is still very effective In the first place this is the digital equivalent of triangular or trapezoidal if G 0 filtering which is the analog industry s standard for high rate processing In the se
130. o the spectrum In extreme cases it will halt data throughput entirely To optimize the fast filter threshold set the Baseline Threshold to zero so that output events are generated by fast filter triggers only edit the Trigger Threshold value and press Apply Typical values range from 600eV to 1500eV A good procedure is to initially set the value too high reduce it until the zero energy noise peak starts to become significant and then raise it again until the noise peak is eliminated The fast filter length is independent of the energy filter length or peaking time thus the trigger threshold does NOT need to be optimized every time the peaking time is changed All thresholds must be readjusted if the gain changes significantly 4 3 3 3 Baseline Threshold Note The baseline threshold is not available for decimation 0 i e peaking times less than or equal to 500 ns The baseline threshold sets the low energy limit for the intermediate or baseline filter which is used for both baseline acquisition and low energy x ray detection To optimize the baseline filter threshold first optimize the trigger threshold as described above then edit the Baseline Threshold value and press Apply Typical values range from 150 eV to 1000 eV The baseline filter length is linked to the energy filter length or peaking time thus the baseline threshold should be optimized every time the peaking time is changed All thresholds must be readjusted if th
131. of the DXP analog circuitry results in the following constraints Parameter Minimum Maximum Typical X ray pulse height 250 uV 375 mV 25 mV w input attenuator 1 mV 1 50 V Input voltage range 5 V 3 V w input attenuator 20 V Table 1 1 Analog input signal constraints for pulsed reset preamplifiers DXP XMAP xManager User Manual MAN XMAP 1 0 6 Parameter Minimum Maximum Typical X ray pulse height 250 uV 625 mV 100 mV w input attenuator 1 mV 2 50 V Input voltage range 5 V 3 V w input attenuator 20 V Decay time t 100 ns infinity 50 us Table 1 2 Analog input signal constraints for resistive feedback preamplifiers 1 3 4 Power Supplies If possible we recommend using local power to generate DC voltages for the preamplifier and HV bias voltage for the detector v The XPPS manufactured by XIA provides linear power for up to 20 NIM standard preamplifiers v The EHQxx line of CompactPCI HV bias supply modules manufacture by ISEG is available for resale from XIA If you decide to use your own supplies expect to spend some time experimenting with ground connections Switching currents in the CompactPCI crate tend to generate voltage spikes between local and external grounds that can show up in the signal path 1 3 5 Cabling 1 3 5 1 Analog Inputs The DXP XMAP uses high quality SMA connectors to accept the pream
132. ogy The PCI9054 ASIC negotiates transactions between the PCI bus and the Local Bus supports burst transfers up to 132 Mbytes second 112 DXP XMAP xManager User Manual MAN XMAP 1 0 6 Appendices Appendix A DPP XMAP Revision C Circuit Board Description This Appendix to the DXP XMAP User s Manual describes jumper settings connector locations and power consumption calculations for the DXP XMAP Revision C digital x ray processor circuit board I anan nmmusnpeut mme ZS an H Hanne c en HDH E Si EE TAPETTI LEGEND mE INPUT ATTENUATION JUMPERS JPx00 Figure A 1 Jumper device and connector locations for the DXP XMAP printed circuit card 11 19 2008 113 DXP XMAP xManager User Manual A 1 Jumper Settings MAN XMAP 1 0 6 Reference Name Position Labels Description JPx100 Input attenuation jumpers 0dB Default 0dB attenuation setting 10 0KQ input impedance 6V input range 20dB 20dB attenuation setting 1 0KQ input impedance 24V input range A 2 LED Indicators Reference Name Front Panel Labels Description Ux30 Rate Indicators These bi color LEDs are rate indicators for each channel Each flash represents a preamplifier reset Green indicates a low rate lt 50 dead time Yellow green red indicates a moderate rate gt 50 dead time but less than maximum throughput Red indicates a high
133. om a linear fit of data as in Figure 6 10 6 8 Pile up Inspection 11 19 2008 The captured value Vx see Figure 6 6 will only be a valid measure of its associated x ray s energy provided that its filtered pulse is sufficiently well separated in time from its preceding and succeeding neighbor pulses so that its peak amplitude is not distorted by the action of the trapezoidal filter on those neighbor pulses That is if the pulse is not piled up The relevant issues may be understood by reference to Figure 6 11 which shows 5 x rays arriving separated by various intervals Because the triangular filter is a linear filter its output for a series of pulses is the linear sum of its outputs for the individual members in the series In Figure 6 11 the pulses are separated by intervals of 3 2 1 8 5 7 and 0 7 us respectively The fast filter has a peaking time of 0 4 us with no gap The slow filter has a peaking time of 2 0 us with a gap of 0 4 us The first kind of pileup is slow pileup which refers to pileup in the slow channel This occurs when the rising or falling edge of one pulse lies under the peak specifically the sampling point of its neighbor Thus peaks 1 and 2 are sufficiently well separated so that the leading edge point 2a of peak 2 falls after the peak of pulse 1 Because the trapezoidal filter function is symmetrical this also means that pulse 1 s trailing edge point 1c also does not fall under the peak of pulse 2
134. omatically refresh the display To set the refresh interval select Options from the Tools menu and select the Misc tab Enter the desired interval in milliseconds If the Continuous box is unchecked the display is updated only when the Update button is pressed or when the run ends 4 5 2 Graphical Display Tools xManager features a wide array of display controls some or all of which are accessible in each graphics window i e MCA Baseline and Trace panels Most of these controls can be accessed by right clicking as shown in the figures below These tools are intuitive and redundant 4 5 2 1 Basic Tools and Options Right click in the Main window to view the basic display tools and options Some of these items are also accessible in the drop down list items above the plot area gt Full Scale Scales both axes such that all data is displayed gt Set to Logarithmic Set to Linear Sets the y axis to logarithmic or linear scale gt Clear Graph Clears all data and the cursors gt Default Mode Sets the default left click action This can be set to Zoom Create ROI or Pan on click gt Place Cursor 1 Select to place cursor 1 Notice that the data point selected by the active cursor is displayed above the plot area gt Place Cursor 2 Select to place cursor 2 Notice that delta x and delta y values relative to cursor 1 are displayed above the plot gt Remove Ref Clears a reference waveform t
135. on 6 4 is that two FIFO memories are required one of length L and one of Length L G Since memory space is limited in FPGAs we have restricted our designs to values of L G less than 128 The DXP XMAP samples at 50 MHz 20 ns clock period so this corresponds to a maximum peaking time of 2 56 us XIA overcomes this limitation by first pre averaging the data stream from the ADC by performing sequential sums of D data points where D 2 We refer to this pre averaging procedure as Decimating by N By feeding the decimated data in an Equation 6 4 filter we now obtain peaking times that are extended to L D It is important to understand that no data are lost in this procedure we have merely rearranged the order of the summations represented in Equation 6 3 By extension a Decimation N FiPPI is one that decimates the data by N before applying the energy filter The common decimation values in the DXP XMAP are 0 2 4 and 6 corresponding to averaging times of 20 ns no averaging 80 ns 320 ns and 1 28us respectively 80 DXP XMAP xManager User Manual 11 19 2008 MAN XMAP 1 0 6 Decimation ADC Clock ADC Samples Decimation Peaking Time N Period At in Average 2 Period At 2 Range 0 20 ns 1 20 ns 80 ns 2 58us 2 20 ns 4 80 ns 320 ns 10 32 us 4 20 ns 16 320 ns 1 28 us 41 28 us 6 20 ns 64 1 28 us 5 12 us 163 84 us Experience has shown that an absolute minimum slow
136. onfiguration Detector Preamplifier Type Reset C RC Feedback Detector Information Reset Interval f 0 000 Cancel Back Lre Finish Figure 3 3 The Detector Configuration settings 5 Hardware Configuration If you selected lt default blank template gt in step 1 above or you have 11 19 2008 17 DXP XMAP xManager User Manual K 6 A MAN XMAP 1 0 6 changed the slot configuration or number of modules in your system select Use current system information This option will result in the parsing of the PXI system configuration file pxisys ini described in section 2 1 1 above such that xMAP modules located in the crate are organized from left to right If you selected an existing INI file in step 1 above and would like to use the slot configuration or number of modules stored therein select Use the values from template file Press Next XMAP PCI Configuration This panel displays all located DXP XMAP modules ordered by default from left to right At this point it is possible to re order the modules and or disable modules or individual processing channels if e g your system has more XMAP channels than detector elements If you are happy with the default configuration make note of whether more than one PCI bus is listed Press Next and skip to 8 below a To re order modules Simply edit the PCI Bus and PCI Device ID fields manually such that the slot order displays as desired Press Next and
137. or y ray measurements Amplifier and spectrometer controls including gain filter peaking time and pileup inspection criteria are under computer control Given the very high data transfer rates of the PCI bus the DXP XMAP is uniquely suited for high speed x ray timing and scanning applications 1 1 XMAP Features 11 19 2008 e Single PXI CompactPCI module contains 4 channels of pulse processing electronics with full MCA per channel e 4MB of high speed memory allows ample storage for timing applications such as mapping with full spectra or multiple ROT s Memory can be read at the full PCI speed e Peak PCI transfer rates exceed 100 MB sec e Peaking time range 0 1 to 164 microseconds e Maximum throughput up to 1 000 000 counts sec channel e Digitization 14 bits at 50 MHz e Low noise front end offers excellent resolution and provides excellent performance in the soft x ray region 150 1500 eV e Operates with virtually any x ray detector Preamplifier type is computer controlled e 16 bit gain DAC and input offset are computer controlled e Pileup inspection criteria are computer selectable e Accurate ICR and livetime for precise deadtime correction and count rate linearity e Multi channel analysis for each channel allows optimal use of data e Facilitates automated gain setting and calibration to simplify tuning array detectors e External GATE input allows data acquisition on all channels to be synchronized
138. ose and solve the problem v Your name and organization v Brief description of the application type of detector relevant experimental conditions etc XIA hardware name and serial number Version of the library if applicable OS Description of the problem steps taken to re create the bug SS SS Full Error Report see section 4 7 4 1 plus additional data o Saved MCA data if relevant see section 4 7 4 2 o Saved Baseline data if relevant see section 4 7 4 3 o Saved Trace data if relevant see section 4 7 4 4 Please compress the Error Report into a ZIP archive and attach the the support request email 1 5 4 Feedback XIA strives to keep up with the needs of our users Please send us your feedback regarding the functionality and usability of the DXP XMAP and xManager software We are also interested in hearing about improvements to the hardware and software In particular we are considering the following development issues 1 5 4 1 Export File Formats We would like to directly support as many spectrum file formats as possible If we do not yet support it please send your specification to software _support xia com 1 5 4 2 Calibration Currently the hardware gain of the DXP XMAP is modified during energy calibration to produce a spectrum with a user defined bin scale i e an integer electron volts per bin value The drawback is that the calibration DXP XMAP xManager User Manual MAN XMAP 1 0 6 process
139. parameter SLOPEDAC The DAC is automatically adjusted according the input rate to maintain the ASC output i e the Amplified Sawtooth Subtracted Data of Figure 7 12 within the ADC input range A side effect of this approach is that fluctuations in data arrival rate will cause the subtracted signal to pass outside the ADC input range while the 105 DXP XMAP xManager User Manual MAN XMAP 1 0 6 preamplifier output is in its operating range These signal drifts out of range high or low have been termed DRIFTUPs and DRIFTDOWNs respectively The out of range condition is corrected by auto zeroing the integrator and thus bringing the signal to the middle of the ADC input range Preamplifier resets are handled similarly though the auto zero time is extended to allow the preamplifier reset transient to settle The preamplifier settling time DSP parameter RESETINT is thus an important DXP setting Any time the ADC is out of range dead time is incurred The ASC compression technique thus incurs additional deadtime although this is typically much smaller than the deadtime caused by preamplifier resets Note When viewing the ADC trace in oscilloscope mode it is easy to mistake signal drift corrections for actual preamplifier resets ADC Max Input Amplified Sawtooth Subtracted Data 10 aDCMininput sst i tsi 3 F 5 a 5 00 7 Preamp P OO Output a E LU fi gl 4 L aA 1 0 i 2 0 7 T
140. play the Mapping Data File Options For the present release each data acquisition run generates a single binary file in the specified folder with a unique filename with the specified prefix 5 3 2 Mapping Data Format Currently the data file created is a binary concatenation of all the buffers read out during the run Table 5 1 shows the structure of the file created The following sections specify the buffer level formatting Buffer 0 Module 0 Buffer 0 Module 1 Buffer 0 Module 2 Buffer 0 Module 3 Buffer 1 Module 0 Buffer 1 Module 1 Buffer 1 Module 2 Buffer 1 Module 3 Buffer i 1 Module 0 Buffer 1 1 Module 1 Buffer i 1 Module 2 Buffer i 1 Module 3 Table 5 1 The Mapping mode binary data output file format of a 4 XMAP module system for a data acquisition run comprising 1 buffers 5 3 3 Single Buffer Format The buffer starts out with a buffer header containing general information about the data contained in the memory block followed by pixel 11 19 2008 67 DXP XMAP xManager User Manual MAN XMAP 1 0 6 11 19 2008 data For each pixel there is a pixel data block containing a header and spectra for all 4 channels The pixel data block format depends on the mapping mode MCA SCA or List Mode Table 5 3 shows the buffer level structure The following sections describe the header and pixel data blocks in detail Buffer Header Pixel X Data Block Pixel X 1 Data Block Pixel X j 1 Data Block
141. plifier signals XIA provides a BNC to SMA converter cable harness for every input 4 per XMAP module 1 3 5 2 TTL CMOS Logic Inputs The DXP XMAP uses a LEMO connector for timing and synchronization logic Depending on the application LEMO cables and T adapters may be required This hardware is available from a wide variety of vendors Please contact XIA if you need assistance with LEMO hardware 1 4 Software and Firmware Overview 11 19 2008 Two levels of software are employed to operate the DXP XMAP a user interface for data acquisition and control and a driver layer that communicates between the host software and the PCI bus In addition separate firmware code is downloaded to and runs on the DXP XMAP itself 1 4 1 User Interface xManager The user interface communicates with and directs the DXP XMAP via the driver layer and displays and analyzes data as it is received As such XIA provides xManager as a general purpose data acquisition application xManager features full control over the DXP XMAP intuitive data visualization unlimited ROI s regions of interest Gaussian fitting algorithms and the exporting of collected spectra for additional analysis Please refer to Chapter 3 of this DXP XMAP xManager User Manual MAN XMAP 1 0 6 manual for instructions on using xManager with the DXP XMAP Many users will employ xManager for configuration and system optimization but will want to develop their own software to acquire
142. pon startup 3 3 1 Loading an INI file Select Load Configuration from the File menu Browse to and select an INI file that you just created and press Open xManager will download firmware and initialize the xMAP modules in your system 3 3 2 Saving an INI file INI files can be updated at any time i e after the spectrometer settings have been optimized by selecting Save Configuration or Save Configuration As from the File menu You may find it useful to maintain several INI files e g for operating with different detectors or with different spectrometer settings 23 DXP XMAP xManager User Manual MAN XMAP 1 0 6 4 Using xManager with the DXP XMAP At this point the xManager software and drivers should be installed the DXP XMAP hardware should be powered on and identified by Windows and a valid initialization file should have been created and loaded This chapter will guide you in using xManager with the DXP XMAP module 4 1 A Quick Tour of xManager xManager is a PC based application that provides for the setup optimization and failure diagnosis of the instrument and allows for the reading out displaying analyzing and exporting of acquired energy spectra When you start the program and an initialization file has been loaded the x Manager main window should be displayed as in Figure 4 1 Bess Monager v0 7 Makk 123 with Handel v0 6 2 release xmanager Detector SCA EFT EZ C Prog am Fie
143. re in an unknown state Program code or firmware for these devices must first be downloaded via the PCI bus before data can be acquired After the devices are operational user settings are downloaded Handel and thus xManager uses an initialization INI file to store all necessary configuration information including the path and filename of the firmware file on the host computer number and slot location of xMAP modules in the system detector characteristics and spectrometer settings and timing and synchronization logic functions used In order to start properly xManager needs to have the following information v The location of the xMAP FDD firmware file DSP and FPGA code that runs on the board included in the installation package v The number and location of xMAP modules in the system v Various properties of the detector preamplifier including type polarity and gain v Which timing and synchronization functions are to be used Master and slave modules will be designated automatically Note section 7 2 describes timing and synchronization logic INI files can be updated at any time i e after the spectrometer settings have been optimized and existing INI files can be loaded at any time If you have previously run with xManager your registry settings will point to the most recently used INI file and xManager will automatically run with these settings upon startup 3 1 1 Starting xManager Without an INI File Start xMa
144. re is warranted against all defects for 1 year Please contact the factory or your distributor before returning items for service To avoid personal injury and or damage to the DXP XMAP do not attempt to repair or clean the unit vi DXP XMAP xManager User Manual 11 19 2008 Manual Conventions MAN XMAP 1 0 6 Through out this manual we will use the following conventions Convention Description Example The symbol leads you The sequence through nested menu File Page Setup Options items and dialog box directs you to pull down the options File menu select the Page Setup item and choose Options from the sub menu Bold Bold text denotes items click on the MCA tab that you must select or click on in the software such as menu items and dialog box options Bold Bold text within Start Run indicates the denotes a command command button labeled button Start Run monospace Items in this font Setup exe refers to a file denote text or called setup exe on the host characters that you computer enter from the keyboard sections of code file contents and syntax examples window Text in quotation refers Options indicates the to window titles and window accessed via quotations from other Tools Options sources Italics Italic text denotes a new peaking time refers to the term being introduced length of the slow filter or simply emphasis it is
145. resolution The slow filter gap should always be longer than the response time of the preamplifier i e the settling time of input x ray steps If the input signal displays a range of risetimes as in the ballistic deficit phenomenon the slow filter gap time should be extended to accommodate that range 108 DXP XMAP xManager User Manual MAN XMAP 1 0 6 7 5 4 4 Intermediate Baseline Filter Note The intermediate filter is not included for decimation 0 pulsed reset variant FiPPIs and all RC decay variant FiPPIs the baseline is acquired from the slow filter 7 5 5 Statistics The FiPPI also includes a livetime counter which counts the 50 MHz system clock divided by 16 so that one tick is 320 ns This counter is activated any time the DSP is enabled to collect x ray pulse values from the FiPPI and therefore provides an extremely accurate measure of the system livetime In particular as described in section 0 the DSP is not live either during preamplifier resets or during ASC out of ranges both because it is adjusting the ASC and because the ADC inputs to the FiPPI are invalid Thus the DXP measures livetime more accurately than an external clock which is insensitive to resets and includes them as part of the total livetime While the average number of resets sec scales linearly with the countrate in any given measurement period there will be fluctuations in the number of resets which may affect counting statistics i
146. roine Traces Figure 4 24 The baseline average with the number of samples set too low 16 samples in the average Notice that there is still a lot of noise as well as some real variations in the baseline Qet Trace Baseine Hettor Samgling interval 1000 aa Save Trace i et GE EE Soe Dateie History Ard Unts U i J E i i J E E Figure 4 25 The baseline average with the number of samples set properly 256 samples in the average Notice that there is virtually no noise but that real baseline variations are tracked In this case the downward variation is due to some curvature in the preamplifier output following a reset 11 19 2008 55 DXP XMAP xManager User Manual MAN XMAP 1 0 6 Get Trace Baseine Hitoy w Samplnghtervel s0000 as Save Trace i Zoom DIE sa YO lees D LE nens 3263 Kess Li 32638 32607 5 267 D D E D D 8 E D HE 15000 2000 2000 x000 35000 om Tene microseconds EAT Bares traces 6 Figure 4 26 The baseline average with the number of samples set too high 4096 samples in the average Notice that although there is no noise the average lags behind a real downward variation in the baseline 4 7 2 The Baseline Panel To open the Baseline panel click on the Baseline Baseline measurements are continually updated samplings of the output tab in the main window of the energy filter when no event is being processed A running average of these baseline samp
147. s are included in an FDD file When the peaking time is changed such that a range boundary is crossed the host software downloads the appropriate FiPPI configuration to the DXP XMAP Note Pulsed reset variant FiPPIs with decimation 0 only have fast and slow filters and the baseline is acquired from the slow filter 107 DXP XMAP xManager User Manual MAN XMAP 1 0 6 11 19 2008 7 5 4 Digital Trapezoidal Filtering The digital trapezoidal filter produces a trapezoid response to a step input A filter is defined by its length ascending or descending time of the trapezoid and its gap flat top time of the trapezoid A constant input slope input produces a constant DC offset the bigger the slope the bigger the offset This offset is referred to as the baseline The peak value of the value of the trapezoid response to an input step minus the baseline offset is directly proportional to the height of the step i e the x ray energy The goal of the FiPPI is thus to measure the baseline to determine when to sample the peak of each trapezoid and to subtract the baseline from the sampled peak 7 5 4 1 Noise and Pileup Detection occurs when the filter output crosses a constant threshold Generally speaking a longer filter length produces better noise reduction and thus allows for a lower threshold Pileup occurs when two or more successive pulses result in an output trapezoid with a peak height that is dependent on a combination of th
148. s for identifying and resolving functional and performance issues 4 7 1 The Traces Panel Oscilloscope The Traces Panel displays waveforms captured at various stages of the DXP s digital filter such as the preamplifier signal as seen at the DXP XMAP s analog to digital converter ADC Each 16 bit output is plotted over 4096 sample points with a user settable sampling interval It can be a useful diagnostic tool for checking preamplifier polarity and gain measuring the risetime and for tracking down noise pickup and baseline irregularities Note that signed waveforms are shifted such that zero is displayed at the midpoint value 32 768 To acquire and view a waveform 1 Click the drop down list to select the desired waveform gt ADC The digitized unsigned ADC waveform i e the input signal to the digital filters 49 DXP XMAP xManager User Manual MAN XMAP 1 0 6 The preamplifier Gain and Polarity settings are accessed in the Detector tab of the Settings panel 11 19 2008 gt Baseline History The signed baseline running average These are the actual values that are subtracted from the energy filter gt Trigger Filter The signed raw fast filter output gt Baseline Filter The signed raw intermediate filter output For decimation 0 this is the same as the Energy filter gt Energy Filter The signed raw slow filter output gt Baseline Samples The signed intermediate filter output base
149. schter 0 Tamap_canbera_1map ri CL Figure 4 1 The xManager main window upon startup after hardware initialization 4 1 1 Channel Selection Each DXP XMAP module provides four 4 digital x ray processing channels The Channel Selection global control sets the channel for which 11 19 2008 24 DXP XMAP xManager User Manual MAN XMAP 1 0 6 settings and data are displayed in xManager The Apply to All checkbox applies to settings only If the checkbox is checked any change to settings will be applied to all channels simultaneously Note Individual channels can be disabled see section 3 2 1 6 so that they are invisible to xManager This is appropriate when the number of detector elements is not a multiple of 4 i e some XMAP channels are not connected to the detector Alternatively individual channels can be skipped see sections 4 3 2 and 4 3 6 1 within xManager This is useful for selective data acquisition and calibration 4 1 2 Settings Sidebar The tabbed Settings sidebar provides easy access to all hardware and firmware settings It is intended to be the primary interface for setup and optimization The Configuration tab contains spectrometer settings such as peaking time and thresholds The Detector tab contains detector and preamplifier settings such as polarity and gain The SCA tab displays Single Channel Analyzer data if applicable based on user entered regions of interest The System tab displays front panel logic
150. scussion of x ray pulse processing theory both generally and as implemented in the DXP XMAP The topics include x ray detection how digital trapezoidal filter basics thresholds baselines peak sampling pileup inspection and input and output count rates Topics are covered to illustrate the theoretical issues practical implementation and how to adjust parameters to obtain best performance The acronym DXP stands for Digital X ray Processor and refers to a digital processing technology for which XIA has received several US and International patents 6 1 X ray Detection and Preamplifier Operation 11 19 2008 Energy dispersive detectors which include such solid state detectors as Si Li HPGe Holz CdTe and CZT detectors are generally operated with charge sensitive preamplifiers When an x ray is absorbed in the detector material it releases an electric charge Qx Ex s where the material constant e is the amount of energy needed to form an electron hole pair Qx is integrated onto the preamplifier s feedback capacitor Cr to produce the voltage Vx Qx Cf Ex eC Measuring the energy Ex of the x ray therefore requires a measurement of the voltage step Vx in the presence of the amplifier s noise Figure 6 1 and Figure 6 3 depict reset type and RC type charge sensitive amplifiers respectively In both figures the detector D is biased by voltage source HV either positive or negative and connected to the input of amplif
151. ser Manual MAN XMAP 1 0 6 data is acquired the stored data is preserved Zooming and panning operate by default on the current data To zoom and pan the saved data right click in the display area select Active Plot and select the saved waveform To clear the stored data right click in the data display area and select Remove Ref gt If you would like to analyze a stored baseline histogram first right click in the data display area and select Clear Graph Now select Open Baseline from the File menu Notice that the Baseline Mean and Baseline FWHM now operate on the stored data Note also that if new data is acquired the stored data is automatically cleared 4 3 10 3 Trace Data Oscilloscope traces can be saved for later display Acquire a trace then select Save Trace from the File menu A saved trace can be displayed at any time Again there are two methods of displaying a saved baseline histogram gt Ifyou want to compare a saved trace to currently acquired data the saved data can be displayed as an overlay First acquire a trace then select Open Trace from the File menu Note that if new data is acquired the stored data is preserved Zooming and panning operate by default on the current data To zoom and pan the saved data right click in the display area select Active Plot and select the saved waveform To clear the stored data right click in the data display area and select Remove Ref gt If you would like to analyze a
152. skip to 8 below b To disable module s Simply edit the Number of Modules field By default the right most slot is disabled Press Next and skip to 8 below c To disable individual channels Edit the Number of Active Channels field check the Configure Individual Channels checkbox Press Next and proceed to 7 below BMAP Configuration Wizard Figure 3 4 This three module system occupies slots 2 3 and 7 Two channels 11 19 2008 are to be disabled 7 XMAP Channels Configuration This panel displays only if you checked the Configure Individual 18 DXP XMAP xManager User Manual 11 19 2008 MAN XMAP 1 0 6 Channels checkbox in the previous panel By default the right most highest numbered channels are disabled first To change which channels are disabled simply click in the Enable column K xMAP Configuration Wizard 8 i xMap Channels Configuration Module Slot Channel 2 0 2 1 2 2 2 3 3 4 3 5 3 amp 3 7 7 S 7 3 7 10 7 11 Figure 3 5 This panel allows you to choose which channels are disabled if for example your system has more XMAP channels than detector elements 8 Detector Element Property 3 2 2 Each DXP XMAP processing channel 4 per module includes a programmable gain analog stage to compensate for the detector gain Initially the same polarity and gain should be used for all channels During the calibration process the gain can be fine tuned for each
153. stored trace first right click in the data display area and select Clear Graph Now select Open Trace from the File menu Notice that zooming panning and cursor operations now operate on the stored data Note also that if new data is acquired the stored data is automatically cleared 4 3 10 4 DSP Parameters The DSP Parameters panel allows for the export of displayed data to a file Select Tools DSP Parameters then press the Export to File button 4 4 Run Control Run Control settings are accessed in the MCA Panel select a preset type from the drop down list and enter a value to select the criteria for which the current run is stopped 11 19 2008 This section covers run synchonization Automatic run termination is achieved by setting run Presets Run start synchronization is achieved in multi module systems using the LBUS hardware function Runs can be disabled in realtime according to a user provided logic signal using the GATE function After stopping a run the run can be resumed without first clearing the data 4 4 1 Run Presets Automatic Run Termination Run presets determine the duration of the data acquisition run The DXP XMAP can end the run when a specified preset real or live time has elapsed or when a specified number of events have been detected or processed 40 DXP XMAP xManager User Manual MAN XMAP 1 0 6 11 19 2008 Lvetrne 1 B87 seconds Seve SCA Save Run roa Rate 3 831 keps sm
154. t the Minimum Gap Time to a smaller value even to zero This setting will only have an effect for decimation 0 i e for peaking times less than 0 50us For other decimations the gap time will be set to the minimum value of 3 decimated clock cycles Note that you may have to adjust other settings as a result 1 Peak Sample Offset Because you are reducing or even eliminating the flattop section of the trapezoid performance becomes more sensitive to the energy sampling time Refer to section 4 6 3 6 2 Gain Calibration A consequence of setting the gap time less than the preamplifier risetime is ballistic deficit The peak value of the trapezoid is reduced As a result you will almost certainly have to increase the gain after the gap time has been changed See sections 4 3 5 and 4 3 6 46 DXP XMAP xManager User Manual MAN XMAP 1 0 6 Preamp Output Signal K E Slow Filter Output KI 4 6 2 Pileup Rejection Pileup inspection is described in detail in section 6 8 These settings should only be modified by users with a good understanding of the principles of pileup inspection Slow Filter Ready for next Sampled Here x ray pulse vk PEAK SAMPLE OFFSET PEAKSAM lt i PEAK INTERVAL OFFSET PEAKINT gt SLOWLEN cc SLOWGAP Figure 4 18 Slow or Energy filter output waveform diagram CAUTION When set too low the MAXWIDTH criterion can reject non piled up x rays resulting in attenuation at higher
155. tally controlled high performance products for X ray and gamma ray spectroscopy All settings can be changed under computer control including gains peaking times pileup inspection criteria and ADC conversion gain The hardware itself is very reliable Most problems are not related to hardware failures but rather to setup procedures and to parameter settings XIA s DXP software includes several consistency checks to help select the best parameter values However due to the large number of possible combinations the user may occasionally request parameter values which conflict among themselves This can cause the DXP unit to report data which apparently make no sense such as bad peak resolution or DXP XMAP xManager User Manual MAN XMAP 1 0 6 11 19 2008 even empty spectra Each time a problem is reported to us we diagnose it and include necessary modifications in the new versions of our DXP control programs as well as adding the problem description to the FAQ list on our web site 1 5 3 1 Submitting a problem report XIA encourages customers to report any problems encountered using any of our software via email In most cases the XIA engineering team will need to review bug information and run tests on local hardware before being able to respond All software related bug reports should be e mailed to software_support xia com and should contain the following information which will be used by our technical support personnel to diagn
156. tart Synchronization It is assumed that the LBUS PCI bus extension connections are used see also section 7 2 2 In the figures below Start rom commands have been issued by the host to all XMAP modules The transition from LO to HI on LBUS indicates that all XMAP modules are ready and in fact have started simultaneously however data acquisition does not actually begin until the GATE signal is released The LBUS output can thus be used as a READY logic input to the beam rastering hardware at the start of each run i e the user generated GATE signal disables data acquisition until all such system constraints have been met The alternative is to use a fixed conservative waiting period between the Start Run command and the GATE release 5 1 2 Pixel Advance on GATE Edge The recommended method for advancing the pixel is to use the GATE digital input where the pixel advance occurs on every trailing edge of the signal the transition from active data acquisition to the inactive state By default the GATE signal also halts data acqusition when it is LO and the pixel advances on every falling edge as in Figure 5 1 61 DXP XMAP xManager User Manual MAN XMAP 1 0 6 All XMAP modules ready READY EE RE LBUS Dead Dead Dead gt K gt kK GATE lt Pixel 0 J k Pixel 1 J k Pixel 2 Start Pixel Advance Pixel Advance Figure 5 1 GATE pixel advance with data acquisition halted during the LO periods The pixel advance o
157. ted The first edge detected on SYNC itself can be used see Figure 7 9 where LBUS should checked before enabling the SYNC clock Alternatively GATE and LBUS can be used as before see Figure 7 10 and Figure 7 11 All XMAP modules ready READY n LBUS Dead gt Live Start Pixel Advance Pixel Advance lt Pixel 0 gt Pixel 1 i Figure 7 9 Mapping mode acquisition using the SYNC input with N 8 The pixel advance occurs every 8 SYNC cycles In this example GATE is not used and SYNC itself is used to synchronize the run start Data acquisition does not begin until the first rising edge is detected User hardware must not start the SYNC clock until LBUS READY is asserted HI All XMAP modules ready READY e LBUS Dead ge Live GATE Pixel Advance _ Pixel Advance ZS Pixel 0 gt lt Pixel 1 gt Start 11 19 2008 104 DXP XMAP xManager User Manual MAN XMAP 1 0 6 Figure 7 10 Mapping mode acquisition using the SYNC input with N 8 The pixel advance occurs SYNC gt GATE READY LBUS every 8 SYNC cycles Note that LBUS and GATE are used to achieve a system wide synchronous start as in previous figures O ES TOLL ADPO ODO OlO OO OO o oe omg o oe PCI BUS SEGMENT 1 __ DO BUS SEGMENT 2 _ pc BUS SEGMENT 2 Figure 7 11 A 15 module XMAP system spanning 3 PCI bus segments that employs the SYNC GATE and LBUS Note that an LBUS Master a G
158. tes which ROI is active only one ROI can be active at a time Note that the displayed color and visibility can be set and that each ROI can be locked The Lower and Upper bounds of the ROI can be entered manually in the table or automatically created for a given peak using the Auto ROI function Zoom lag GIS Y xire EN 0 0 x0 v Ful Seale Set to Logitik Coe Gah Everts Courts S Dei af Mode p i 7 i i J J i H 2 4 0 12 4 16 D E Energy deen Figure 4 6 The full spectrum window right click menu is displayed Context sensitive menus are available if the mouse pointer is located over the x axis or y axis or over the cursor 4 3 4 2 Auto ROI The Auto ROI function generates lower and upper bounds for the active ROI about a selected energy peak Place the mouse pointer over the spectrum peak of interest Right click and select Place Cursor 1 Drag the Cursor to the center of the calibration peak right click on Cursor 1 and select Auto ROP A region of interest should automatically appear on the peak In some cases where few events have been collected the Auto ROI feature will not properly enclose the peak In these cases the ROI can be adjusted directly in the Spectrum Window 32 DXP XMAP xManager User Manual MAN XMAP 1 0 6 11 19 2008 Everts Courts fv Energy keV Figure 4 7 The Auto ROI function found in the cursor context menu automatically
159. tic mean or the Gaussian mean Similarly the peak width or FWHM Full Width Half Maximum can be displayed in units of energy eV or as a fraction of the peak centroid energy Click on the column heading to toggle the display The number of events and the OCR are also displayed for each ROI 4 3 9 Single Channel Analyzer SCA An SCA window is similar to a region of interest ROT It is a user defined range of the energy spectrum While an ROI is a software level construct used in analyzing a spectrum an SCA window is processed at the hardware level The DSP counts all events within the window and stores the result the SCA Counts in memory SCA windowing thus allows for faster readout Instead of reading the entire spectrum it is only necessary to read a single word for each SCA Select the SCA tab in the settings panel to view and modify SCAs 4 3 9 1 Creating SCAs SCA windows can be transferred from the ROI table Simply select the desired ROI from the table such that the ROI column reads ACT then press the Insert Active ROT button All defined ROIs can be transferred in one step by pressing the Insert All ROT button To manually define SCAs first enter the number of SCA windows desired and press Apply Notice that the corresponding number of rows is added to the SCA table To define an SCA all that is required is the Low keV and High keV bounds These values can be entered manually 38 DXP XMAP xManager User
160. trains the gap time to an integer between 3 and 64 decimated clock intervals In xManager the user sets the Minimum Gap Time slightly larger than the the measured preamplifier risetime and xManager automatically maintains the gap time based on the decimation dependent filter constraints Pleaser refer to section 4 7 1 2 for details on using xManager to measure the risetime for your system and section 6 3 2 for a discussion of decimation and decimated clock periods 45 DXP XMAP xManager User Manual MAN XMAP 1 0 6 11 19 2008 r Energy Filter gt Peaking Time fois Rs Minimum Gap Time be xs Actual Gap Time Ps se r Pileup Inspection Interval Peaking Time Gap Tine f Hrs Use detaut offset value Decimation 4 tick 0 320 us r Peak Sampling Time f EZ Peaking Time Gap Tine 2 4 V Use defaut offset value Decimation d tick 0 320 us Fast Trigger Fiter Peaking Time ba as Gap Time be xs Max Width 0 32 e Figure 4 17 The Edit Filter Parameters panel 4 To edit the Minimum Gap Time time press the Edit Filter Parameters button in the Configuration settings panel to open a dialog Enter the desired value for Minimum Gap Time and press OK Normally the is Minimum Gap Time should be set to a value that exceeds the preamplifier risetime in response to a detected x ray however there is one exception At very high count rates where resolution is less of a concern it can be advantageous to se
161. u record the initial value of PEAKSAM and then change it in steps of 1 working out from the initial value Certain PEAKSAM values may cause the DXP XMAP to crash Do not be alarmed just restart and be sure to enter a valid PEAKSAM value before proceeding Making a plot of energy resolution versus PEAKSAM will indicate the best value to select This determination need only be done for one peaking time per decimation The result can then be applied to any value of SLOWLEN and SLOWGAP using the following recipe PEAKSAM SLOWLEN SLOWGAP X Equation 6 8 6 7 Energy Measurement with Resistive Feedback Preamplifiers 11 19 2008 In previous sections the pulse height measurement was shown for the case of reset type preamplifiers The reset type scheme is most often used for optimum energy resolution x ray detectors Other detectors use an RC type preamplifier as described in section 6 1 2 Resistive feedback is most often used for gamma ray detectors which cover a larger dynamic range and where the electronic noise is not as significant a contribution to energy resolution 89 DXP XMAP xManager User Manual MAN XMAP 1 0 6 11 19 2008 t t to gt lt GAt t Figure 6 9 RC preamplifier output voltage An x ray step of amplitude A occurs at time t 0 Where analog shaping amplifiers typically have a pole zero adjustment to cancel out the exponential decay the DXP uses a patented digital
162. w move Cursor 1 to the point on the decay curve that produces a new dY value that is Lie times the measured pulse height dY 1 e dY 0 37 dY The cursors should now be separated by the time constant t displayed in us in the dX field 4 7 1 4 Optimizing the Baseline Average Length The Trace panel is also useful for optimizing the number of samples in the baseline average Please first review section 6 4 for a thorough discussion of baseline acquisition The Baseline Average Length refers to the number of samples of the Baseline Filter raw output in the running average of baseline samples which should be e Large enough to average out electronic noise at the higher frequencies 53 DXP XMAP xManager User Manual MAN XMAP 1 0 6 11 19 2008 e Small enough to track low frequency fluctuations in the front end i e detector dark current The precise noise distribution and the low frequency signal characteristics of the detector and preamplifier together yield an optimum number of samples in the average Too small a value will not allow for proper filtering of electronic noise Too large a value will not allow proper tracking of low frequency signals e g due to EMI that can be cancelled out with double correlation First select Baseline Filter from the drop down list set the Sampling Interval to 1 000us and press Get Trace to view the raw output of the baseline filter Oet Trace Baseine Feer sl BETEN 000 at Save Tr
163. waveform is a single pole RC decay The discussion in section 6 2 through section 6 6 2 assumes a reset type preamplifier but is mostly applicable to RC type preamplifiers section 6 7 describes the few key differences in the processing of RC type preamplifier signals 10 b T 0 E S 10 O a 20 E 2 Qa 30 40 50 0 50 100 150 200 250 Time us Figure 6 3 a RC type charge sensitive preamplifier with a positively biased detector b Output on absorption of an x ray Note that the step has a falling edge thus the signal polarity is 6 2 X ray Energy Measurement amp Noise Filtering 11 19 2008 Reducing noise in an electrical measurement is accomplished by filtering in the frequency or conversely the time domain When discussing digital pulse processor filters it s more straightforward to use the time domain Traditional analog pulse processing filters use combinations of a differentiation stage and multiple integration stages to convert the preamp output steps such as shown in Figure 6 1b into either triangular or semi Gaussian pulses whose amplitudes with respect to their baselines are then proportional to Vx and thus to the x ray s energy 6 2 1 Digital Filtering Theory Digital filtering proceeds from a slightly different perspective Here the signal has been digitized and is no longer continuous but is instead a string of discrete values such as shown in Figure 6 4 The data displayed are actu
164. when the Fast Trigger Filter output is below Trigger Threshold and the Baseline Filter output is below the Baseline Threshold Itis assumed that the Trigger Threshold is set conservatively so that baseline acquisition is dominated by the Baseline Threshold Note The baseline threshold is not available for decimation 0 i e peaking times less than or equal to 500 ns Edit the Baseline Threshold value in the Configuration tab and press Apply Typical values range from 150 eV to 1000 eV The baseline filter length is linked to the energy filter length or peaking time thus the baseline threshold should be optimized every time the peaking time is changed All thresholds must be readjusted if the gain changes significantly For this reason it is useful to save INI files for commonly used peaking times after optimizations are complete 57 DXP XMAP xManager User Manual MAN XMAP 1 0 6 CG Baseline Mean 2 tins Lae Qet Baseine Baseire Fees MS bns Baseine aS CS CoS oo 100000 10000 Everts Courts Figure 4 28 A baseline histogram with the threshold too low Notice that the right side of the noise peak is attenuated The rest of the noise peak will show up in the energy spectrum Baretre Mean 5 tins Save Get Baseine Baseline Fee 26 0 tins Baseine Zoom suen sa Y sfioro D 100000 000 Everts Courts 100 Energy eV MCA Baseline Garber va org Figure 4 29 A baseline histogram with the threshold too
165. xceeding the dynamic range value cannot be processed correctly The presence of such x rays can result in a significant reduction in the output count rate The Dynamic Range setting should be set above the largest x ray energy present in the system Typical values range from 40keV to 100keV Edit the Dynamic Range value and press Apply 4 3 3 6 MCA Number of Bins and MCA Bin Width The size and granularity of the spectrum can be adjusted The number of spectrum bins sets the granularity of the acquired spectrum The eV Bin setting determines the size of each MCA bin in electron Volts Together these settings determine the energy span of the MCA The spectrum ranges from zero to a maximum energy equal to the number of spectrum bins multiplied by the MCA bin width e g a 40 96keV spectrum results from 2048 bins at 20eV bin Note that these digital spectrum controls are independent of the Preamp Gain and Dynamic Range settings that control the variable analog gain If the MCA energy range is less than the dynamic range the entire spectrum will be free of distortion If the MCA energy range exceeds the dynamic range setting the spectrum will be distorted Higher energy x ray data will be attenuated or cut off For this reason the product of Number of Bins and MCA Bin Width i e the MCA energy range should be less than the dynamic range Edit the Number of Bins and MCA Bin Width values and press Apply Start a new run 4 3 3 7 Baseline Average
166. ypically loaded from a file from the display gt Double Click Sets the default double left click action gt Active Plot Selects either the current data or data loaded from file to be active for zooming and panning 11 19 2008 42 DXP XMAP xManager User Manual MAN XMAP 1 0 6 11 19 2008 L Full Scale Set to Logrithmic Clear Graph Default Mode Place Cursor 1 Place Cursor 2 Remove Ref Double Click Active Plot Figure 4 13 Right click in the Main display window to view the basic display tools and options Alternatively a default mode e g zoom ROI or pan can be selected using the drop down list menus above the plot area The default mode applies when you left click in the display area Left click on either axis to pan Most of the tools are intuitive and redundant 4 5 2 2 Cursor Tools and Options After placing a cursor right click on the cursor itself to view the cursor tools and options gt Auto ROI MCA panel only If the cursor was placed on an energy peak this will automatically set the bounds of the active ROI to enclose the peak gt Crosshair The default cursor is a vertical line This option sets the cursor to an x y crosshair gt Delete Deletes the cursor Auto ROI Crosshair Delete Figure 4 14 After placing a cursor right click on the cursor itself to view the cursor tools and options 4 5 2 3 Axis Tools and Options Left click and drag on an axis to p

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