Model 572A Spectroscopy Amplifier Operating and Service Manual
Contents
1. A Odd DUE TA Ao done P 4 22 MAGE bedarf ofthe Fa dde eee 5 2 3 INPUT aeter ROR NAN A teri LLLA LA ae Ct Ba Ete an 5 2 4 OUTPUTS e NIE C edere d None ctt dana eaa ute Sees ems 5 2 5 ELECTRICAL AND MECHANICAL e 5 3 INSTALLATION 6 Sols GENERALS 1562 tii er Ma OM he tai Ai doe AM do 6 3 2 CONNECTION TO POWER Rl 6 3 3 CONNECTION TO PREAMPLIFIER Is 6 3 4 CONNECTION OF TEST PULSE GENERATOR 6 3 5 SHAPING CONSIDERATIONS 2 ll 7 3 6 LINEAR OUTPUT CONNECTIONS AND TERMINATING CONSIDERATIONS 7 3 7 SHORTING OR OVERLOADING THE AMPLIFIER OUTPUTS 8 3 8 INHIBIT OUTPUT CONNECTION ll 8 3 9 BUSY OUTPUT CONNECTION la 8 3 10 CRM OUTPUT CONNECTION ls 8 4 OPERATING INSTRUCTIONS ssssssss ssl 8 4 1 INITIAL TESTING AND OBSERVATION OF PULSE WAVEFORMS 8 4 2 FRONT PANEL CONTROLS e 8 4 3 FRONT PANEL CONNECTORS 9 4 4 REAR PANEL CONNECTORS ls 10 4 5 STANDARD SETUP PROCEDURE2. eea 10 4 6 POEE ZERO ADJUSTMENT 5 teen ee beu 10 4 7 BLR THRESHOLD ADJUSTMENT ls 11 4 8 OPERATION WITH SEMICONDUCTOR DETECTORS 12 4 9 OPERATION IN SPECTROSCOPY SYSTEMS 15 4 10 OTHER EXPERIMENTS ll 16 6 CIRCUIT DESCRIPTION 2 1 hmmm ehe eben blue ea ees oe ee oes eee ee ee 19 6 MAINTENANCE Mel Ue teh eer Hasc us rM boe D eda ud 21 6 1 TEST EQUIPMENT REQUIRED erener renere reer 21 6 2 PULSER 7 eot etl eet et Ate 21 6 3 SUGGESTIONS FOR TROUBLESHOOTING 23 6 4 FACTORY REPAIR uter ml teet prts eost e via pi ete 23 6 5 TABULATED TEST POINT VOLTAGES 0 0 0 0 23 SAFETY INSTRUCTIONS AND SYMBOLS This manual contains up to three levels of safety instructions that must be observed in order to avoid personal injury and or damage to equipment or other property These are DANGER Indicates a hazard that could result in death or serious bodily harm if the safety instruction is not observed WARNING Indicates a hazard that could result in bodily harm if the safety instruction is not observed CAUTION Indicates a hazard that could result in property damage if the safety instruction is not observed Please read all safety i
3. Variable control Fully CW for 300 mV a Connect a positive pulser output to the 572A input and adjust the pulser to obtain 10 V at the 572A Unipolar output This should require an input pulse of 6 6 mV using a 1000 terminator at the input b Measure the positive lobe of the Bipolar output This should also be 10 V c Change the Input polarity switch to Neg and then back to Pos while monitoring the outputs for a polarity inversion d Vary the DC Adj control on the front panel while monitoring the Unipolar output Ensure that the baseline can be adjusted through a range of 0 1 to 0 1 V Readjust the control for zero e Recheck the output pulse amplitude and adjust if necessary to set it at 10 V with maximum gain Decrease the Coarse Gain switch stepwise from 1K to 20 and ensure thatthe output amplitude changes by the appropriate amount for each step Return the Coarse Gain switch to 1K f Decrease the Gain control from 1 5 to 0 5 and check to see that the output amplitude decreases by a factor of 3 Return the Gain control to maximum at 1 5 g With the Shaping switch set for uis measure the time to the peak on the unipolar output pulse this should be 2 2 us for 2 2 Measure the time to baseline crossover of the bipolar output this should be 2 8 us for 2 8T h Change the Shaping switch to 0 5 through 10 us in turn At each setting check to see that the time to the unipolar peak is 2 2T and the time to the b
4. Three general methods of termination are used The simplest of these is shunt termination at the receiving end of the cable A second method is series termination at the sending end The third is a combination of series and shunt termination where the cable impedance is matched both in series at the sending end and in shunt at the receiving end The combination is most effective but this reduces the amount of signal strength at the receiving end to 5096 of that which is available in the sending instrument To use shunt termination at the receiving end of the cable connect the 10 output of the 572A on the front panel through 930 cable to the input of the receiving instrument Then use a BNC tee connector to attach both the interconnecting cable and a 1000 terminator at the input connector of the receiving instrument Since the input impedance of the receiving instrument is normally 10000 or more the effective instrument input impedance with the 1000 terminator will be of the order of 930 and this matches the cable impedance correctly For series termination use the 930 output of the 572A for the cable connection Use 930 cable to interconnect this into the input of the receiving instrument The 10000 or more normal input impedance at the input connector represents an essentially open circuit and the series impedance in the 572A now provides the proper termination for the cable For the combination of series and shunt termina
5. Adj control for proper response according to Fig 4 4 Use the clamp circuit of Fig 4 3 to prevent overloading the oscilloscope input Figure 4 4A shows the amplifier output as a series ofalternate positive and negative Gaussian pulses In the other three pictures of this figure the oscilloscope was triggered to show both positive and negative pulses simultaneously These pictures show more detail to aid in proper adjustment 4 7 BLR THRESHOLD ADJUSTMENT After the amplifier gain and shaping have been selected and the PZ Adj control has been set to operate properly for the particular shaping time the BLR Thresh control can be used to establish the correct discriminator threshold for the baseline restorer circuit Normally the toggle switch can be set at Auto and the threshold level will be set automatically just above the noise level If desired PZProperly Adjusted Slow Trigger to Separate Pulses C Properly Adjusted Pulses Superimposed 12 B Overcompensated Fast Trigger to Superimpose Pulses D Undercompensated Pulses Superimposed Fig 4 4 Pole Zero Adjustment Using a Square Wave Input to the Preamplifier the switch can be set at Threshold and the manual control just below the switch can then be used to select the level manually as follows a Remove all radioactive sources from the vicinity of the detector Set up the system as for normal operation including detector bias b Set the BLR
6. a single width NIM module with a versatile combination of switch selectable pulse shaping and output characteristics It features extremely low noise wide gain range and excellent overload response for universal application in high resolution spectroscopy It accepts input pulses of either polarity that originate in germanium or silicon semiconductor detectors in scintillation counters with either fast or slow scintillators in proportional counters in pulsed ionization chambers in electron multipliers etc The 572A has an input impedance of approximately 5000 and accepts either positive or negative input pulses with rise times lt 650 ns and fall times gt 40 Us Six integrate and differentiate time constants are switch selectable to provide optimum shaping for resolution and count rate The first differentiation network has variable pole zero cancellation that can be adjusted to match preamplifiers with decay times gt 40 The pole zero cancellation drastically reduces the undershoot after the first differentiator and greatly improves overload and count rate characteristics In addition the amplifier contains an active filter shaping network that optimizes the signal to noise ratio and minimizes the overall resolving time Both unipolar and bipolar outputs are provided simultaneously on the front and rear panels The unipolar output should be used for spectroscopy when dc coupling can be maintained from the 572A to the analyz
7. also been connected to the Preamp Power connectors on the amplifiers check the dc voltage levels from the power supply to see that they are not overloaded The ORTEC 4001 4002 Series Bins and Power Supplies have convenient test points on the power supply control panel to permit monitoring these dc levels If any one or more of the dc levels indicates an overload some of the modules will need to be moved to another bin to achieve operation 3 3 CONNECTION TO PREAMPLIFIER The preamplifier output signal is connected to the 572A through the appropriate Input BNC connector on the front or rear panel The input impedance is about 5000 and is dc coupled to ground therefore the preamplifier output must be either ac coupled or have approximately zero dc voltage under no signal conditions The 572A incorporates pole zero cancellation in order to enhance the overload and count rate characteristics of the amplifier This technique requires matching the network to the preamplifier decay time constant in order to achieve perfect compensation The pole zero adjustment should be set each time the preamplifier or the shaping time constant of the amplifier is changed For details of the pole zero adjustment see Section 4 6 An alternate method is accomplished easily by using a monoenergetic source and observing the amplifier baseline with an oscilloscope after each pulse under approximately X2 overload conditions Adjustment should be made so that th
8. is generally a compromise between operating at a shorter time constant for accommodation of high counting rates and operating with a longer time constant for a better signal to noise ratio For scintillation counters the energy resolution depends largely on the scintillator and photomultiplier and therefore a shaping time constant of about four times the decay time constant of the scintillator is a reasonable choice for Nal a 1 uis shaping time constant is about optimum For gas proportional counters the collection time is normally in the 0 5 to 5 us range and a 2 us or greater time constant selection will generally give optimum resolution For surface barrier semiconductor detectors a 0 5 to 2 us resolving time will generally provide optimum resolution Shaping time for Ge Li detectors will vary from 1 to 6 ys depending on the size configuration and collection time of the specific detector and preamplifier When a charge sensitive preamplifier is used the optimum shaping time constant to minimize the noise of a system can be determined by measuring the output noise of the system and dividing it by the system gain Since the 572A has almost constant gain for all shaping modes the optimum shaping can be determined by measuring the output noise of the 572A with a voltmeter as each shaping time constant is selected The 572A provides both unipolar and bipolar outputs The unipolar output pulses should be used in applications where t
9. measurements is with a pulse height analyzer as shown by the setup illustrated in Fig 4 8 The amplifier noise resolution spread can be measured directly with a pulse height analyzer and the mercury pulser as follows a Select the energy of interest with an ORTEC 419 Precision Pulse Generator Set the amplifier gain 14 ORTEC 030 007 300 ORTEC BA 025 050 100 ORTEC BA 025 100 1C0 D ORTEC BA 030 200 100 E ORTEC 045 450 100 RMS Noise V Bias Voltage Fig 4 7 Noise as a Function of Bias Voltage so that the energy is in a convenient channel of the analyzer b Calibrate the analyzer in keV per channel using the pulser full scale on the pulser dial is 10 MeV when calibrated as described above c Obtain the amplifier noise resolution spread by measuring the FWHM of the pulser peak in the spectrum ORTEC ORTEC ORTEC MULTI LINEAR PREAMP AMPLIFIER PULSE HEIGHT ANALYZER DETECTOR PACITOR t ORTEC PULSE GENERATOR Fig 4 8 System for Measuring Resolution with a Pulse Height Analyzer The detector noise resolution spread for a given detector bias can be determined in the same manner by connecting a detector to the preamplifier input The amplifier noise resolution spread must be subtracted as described in Detector Noise Resolution Measurements The detector noise will vary with detector size and bias conditions and possibly with ambient conditions
10. monoenergetic Source or pulser having the same decay time as the preamplifier under overload conditions The adjustment should be made so that the pulse returns to the baseline in the minimum time with no undershoot 1 3 ACTIVE FILTER When only FET gate current and drain thermal noise are considered the best signal to noise ratio occurs when the two noise contributions are equal for a given input pulse shape The Gaussian pulse shape Fig 1 3 for this condition requires an amplifier with a single RC differentiate and n equal RC integrates where n approaches infinity The Laplace transform of this transfer function is S 1 G s s 1 RC 5 1 RC n gt where the first factor is the single differentiate and the second factor is the n integrates The 572A active filter approximates this transfer function Figure 1 3 illustrates the results of pulse shaping in an amplifier Of the four pulse shapes shown the cusp would produce minimum noise but is impractical to achieve with normal electronic circuitry and would be difficult to measure with an ADC The true Gaussian shape deteriorates the signal to noise ratio by only about 12 from that of the cusp and produces a signal that is easy to measure but requires many sections of integration n With two sections of integration the waveform identified as a Gaussian approximation can be obtained and this deteriorates the sign
11. the detector for example set the dial at 547 divisions for a 5 47 MeV alpha particle energy e Turn on the pulser and use its Normalize control and attenuators to set the output due to the pulser for the same pulse height as the pulse obtained in step c Lock the Normalize control and do not move it again until recalibration is required The pulser is now calibrated the Pulse Height dial read directly in MeV if the number of dial divisions is divided by 100 AMPLIFIER NOISE AND RESOLUTION MEASUREMENTS As shown in Fig 4 6 a preamplifier amplifier pulse generator oscilloscope and wide band rms voltmeter such as the Hewlett Packard 3400A are required for this measurement Connect a suitable capacitor to the input to simulate the detector capacitance desired To obtain the resolution spread due to amplifier noise ORTEC ORTEC OSCILLO SCOPE LINEAR AMPLIFIER PREAMP DETECTOR OR CAPACITOR ORTEC PULSE GENERATOR RMS VOLTMETER Fig 4 6 System for Measuring Amplifier and Detector Noise Resolution a Measure the rms noise voltage at the amplifier output b Turn on the 419 Precision Pulse Generator and adjust the pulser output to any convenient readable voltage E as determined by the oscilloscope The full width at half maximum FWHM resolution Spread due to amplifier noise is then 2 35 E hs N FWHM where E 4 is the pulser d
12. CURRENT VOLTAGE MEASUREMENTS FOR Si and Ge DETECTORS The amplifier system is not directly involved in semiconductor detector current voltage measurements but the amplifier serves to permit noise monitoring during the setup The detector noise measurement is a more sensitive method than a current measurement of determining the maximum detector voltage that should be used because the noise increases more rapidly than the reverse current at the onset of detector breakdown Make this measurement in the absence of a source Figure 4 9 shows the setup required for current voltage measurements An ORTEC 428 Bias Supply is used as the voltage source Bias voltage should be applied slowly and reduced when noise increases rapidly as a function of applied bias Figure 4 10 shows several typical current voltage curves for ORTEC silicon surface barrier detectors 5 l micro 1 AMMETER 4 ee Current Monitoring Jacks ORTEC DETECTOR BIAS SUPPLY ORTEC LINEAR AMPLIFIER ORTEC RMS PREAMP VOLTMETER MICRO AMMETER BYPASS CAPACITOR Normal Circuit Fig 4 9 System for Detector Current and Voltage Measurements ORTEC RA 030 007 300 ORTEC BA 029 050 100 ORTEC BA 026 100 100 ORT C 4030 200 100 ORTEC BA 045 450 100 Back Current 9 20 40 50 50 100 Bias Voltage Fig 4 10 Silicon Detector Back Current vs Bias Voltage When it is possible t
13. Printed in U S A Model 572A Spectroscopy Amplifier Operating and Service Manual ORTEC Part No 785100 Manual Revision D 0904 Advanced Measurement Technology Inc alk a ORTEC a subsidiary of Inc WARRANTY ORTEC warrants that the items will be delivered free from defects in material or workmanship ORTEC makes no other warranties express or implied and specifically NO WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE ORTEC s exclusive liability is limited to repairing or replacing at ORTEC s option items found by ORTEC to be defective in workmanship or materials within one year from the date of delivery ORTEC s liability on any claim of any kind including negligence loss or damages arising out of connected with or from the performance or breach thereof or from the manufacture sale delivery resale repair or use of any item or services covered by this agreement or purchase order shall in no case exceed the price allocable to the item or service furnished or any part thereof that gives rise to the claim In the event ORTEC fails to manufacture or deliver items called for in this agreement or purchase order ORTEC s exclusive liability and buyer s exclusive remedy shall be release of the buyer from the obligation to pay the purchase price In no event shall ORTEC be liable for special or consequential damages Quality Control Before being approved for shipment each ORTEC instrument must
14. TION 2 1 1 22 Fig 1 3 Pulse Shapes for Good Signal to Noise Ratios s RC Is RC GAUSSIAN s 1 1 12 x s 1 RC Is 1 RCH ACTIVE FILTER 71 17 5 1 1 s 3 RC s 1 1 k RC 0 8 2 SPECIFICATIONS 2 1 PERFORMANCE GAIN RANGE Continuously adjustable from X1 through X1500 PULSE SHAPING Gaussian on all ranges with peaking time equal to 2 21 and pulse width at 0 196 level equal to 2 9 times the peaking time INTEGRAL NONLINEARITY 0 0596 0 025 typical using 2 us shaping NOISE 8 uV referred to the input 5 uV typical using 2 us shaping and gain 100 TEMPERATURE INSTABILITY Gain lt 0 0075 C 0 to 50 DC Level x50 yu V C 0 to 50 C CROSSOVER WALK lt 3 ns for 50 1 dynamic range including contribution of ORTEC 551 or 552 Constant Fraction Timing Single Channel Analyzer using 50 fraction and 0 5 us shaping COUNT RATE STABILITY The 1 33 MeV gamma ray peak from a source positioned at 8596 of analyzer range typically shifts 0 02496 and its FWHM broadens 1696 when its incoming count rate changes from 0 to 100000 counts s using 2 us shaping The amplifier will hold the baseline reference up to count rates in excess of 150000 counts s OVERLOAD RECOVERY Recovers to within 2 of rated output from X300 overload in 2 5 nonoverloaded unipolar pulse widths using max
15. TION The signal through the rear panel Busy output connector rises from 0 to about 5 V the onset of each linear input Pulse Its width is equal to the time the input pulse amplitude exceeds the BLR discriminator level and is extended automatically by the generation of an Inhibit output signal It can be used to provide MCA live time correction to control the generation of input pulses to observe normal operation with an oscilloscope or for any of a variety of other applications Its use is optional and no termination is required if the output is not being used 3 10 CRM OUTPUT CONNECTION One NIM standard positive logic pulse is generated to correspond to each linear input pulse into the 572A The pulses are available through the CRM Count Rate Meter output BNC on the rear panel and are intended for use in a count rate meter or counter to monitor the true input count rate into the amplifier Its use is optional and no termination is required if the output is not being used 4 OPERATING INSTRUCTIONS 4 1 INITIAL TESTING AND OBSERVATION OF PULSE WAVEFORMS Refer to Section 6 for information on testing performance and observing waveforms at front panel test points Figure 4 1 shows some typical unipolar and bipolar output waveforms 4 2 FRONT PANEL CONTROLS GAIN A coarse Gain switch and a Gain 10 turn locking precision potentiometer select and precisely adjust the gain factor for the amplification in the 572A Switch se
16. al to noise ratio by about 2296 The ORTEC active filter network in the 572A Amplifier provides the fourth waveform in Fig 1 3 this waveform has characteristics superior to the Gaussian approximation yet obtains them with four complex poles By this method the output pulse shape has a good signal to noise ratio is easy to measure and yet requires only a practical amount of electronic circuitry to achieve the desired results t enit et Ty First Differentiated x differentiation pulse network with undershoot E max Tat t Undershoot Emax T x Git ej t max r E 5 Laplace transtorm e To 0 where 07 1 Fig 1 1 Differentiation an Amplifier Without Pole Zero Cancellation t esiti ear e UT Dx Pole zero Differentiated Charge oOp cancelled output differentiation without network undershoot Emax Ta x amp ift 5 1 R4C b Emax z Laplace transform StR AG Fig 1 2 Differentiation in a Pole Zero Canceled Amplifier 0 lt lt Ry No Undershoot Pole zero cancel by letting or Emax _ Emar _ RiR sh E 5 where Ri h 3 ARG Emax seti i Noise Relative Signal usr 786 gt 0 1 00 t 0 GAUSSIAN APPROXIMA
17. ctrometry 19 LINEAR AMPLIFIER ORTEC SCINTIL LATION PREAMP ORTEC MULTI CHANNEL ANALYZER GERMANIUM DETECTOR GENERATOR ORTEC TIMING FILTER AMPLIFIER ORTEC LINEAR AMPLIFIER DELAY AMPLIFIER Fig 4 18 Gamma Gamma Coincidence Experiment 5 CIRCUIT DESCRIPTION Figure 5 1 is a block diagram of the instrument Much of the circuitry in the 572A has been designed to use ORTEC Hybrid circuits This advanced technology achieves an economical high density package with high reliability Figure 5 2 illustrates the relative timing of the signals in the 572A The solid line waveforms show a normal response to a single linear input signal from the preamplifier without any pulse pileup The broken line waveforms show the modifications that occur when there is a pileup condition The input from the preamplifier is a step change with a very long decay and this is repeated and differentiated at test point TP3 The 572A output that results from this input is shaped rising to its peak in 2 where is the selected time constant of 0 5 1 2 3 6 or 10 us The amplifier produces the fast shaped pulse from the same preamplifier input pulse and this triggers discriminator IC12 set just above the noise level The discriminator response triggers the CRM output signal The discriminator response also triggers the Busy output signal which has a duration o
18. e pulse returns to the baseline in a minimum amount of time with no undershoot Preamplifier power at 24 V 24 V 12 V and 12 V is available through the Preamp Power connector on the rear panel When the preamplifier is connected its power requirements are obtained from the same bin and power supply as is used for the amplifier and this increases the dc loading on each voltage level over and above the requirements for the 572A at the module position in the bin When the 572A is used with a remotely located preamplifier i e preamplifier to amplifier connection through 25 ft or more of coaxial cable be careful to ensure that the characteristic impedance of the transmission line from the preamplifier output to the 572A input is matched Since the input impedance of the 572A is about 5000 sending end termination will normally be preferred the transmission line should be series terminated at the preamplifier output All ORTEC preamplifiers contain series terminations that are either 930 or variable coaxial cable type RG 62 U or RG 71 U is recommended 3 4 CONNECTION OF TEST PULSE GENERATOR THROUGH A PREAMPLIFIER The satisfactory connection of a test pulse generator such as the ORTEC 419 Precision Pulse Generator equivalent depends primarily on two considerations the preamplifier must be properly connected to the 572A as discussed in Section 3 3 and the proper input signal simulation must be applied to the preamplifi
19. er A BLR baseline restorer circuit is included in the 572A for improved performance at all count rates Baseline correction is applied during intervals between input pulses only and a front panel switch selects a discriminator level to identify input pulses The unipolar output dc level can be adjusted in the range from 100 mV to 100 mV This output permits the use of the direct coupled input of the analyzer with a minimum amount of interface problems The 572A bipolar output may be preferable for spectroscopy when operating into an ac coupled system at high counting rates Internal pulse pileup a second pulse arriving before the first pulse has been completed is sensed internally The 572A includes an Inhibit output BNC connector on the rear panel that can be used to inhibit measurement of the result of a pulse pileup when it occurs The 572A can be used for constant fraction timing when operated in conjunction with an ORTEC 551 or 552 Timing Single Channel Analyzer The ORTEC timing single channel analyzers feature a minimum of walk as a function of pulse amplitude and incorporate a variable delay time on the output pulse to enable the timing pickoff output to be placed in time coincidence with other signals The 572A has complete provisions including power for operating any ORTEC solid state preamplifier Normally the preamplifier pulses should have a rise time of 0 25 ys or less to properly match the amplifier filter netwo
20. er To ensure proper input signal simulation refer to the instruction manual for the particular preamplifier being used DIRECTLY INTO THE 572A Since the input of the 572A has 5000 of input impedance the test pulse generator will normally have to be terminated at the amplifier input with an additional shunt resistor In addition if the test pulse generator has adc offset a large series isolating capacitor is also required since the 572A input is dc coupled The ORTEC test pulse generators are designed for direct connection When any one of these units is used it should be terminated with a 1000 terminator at the amplifier input or be used with at least one of the output attenuators set at In The small error due to the finite input impedance of the amplifier can normally be neglected SPECIAL CONSIDERATIONS FOR POLE ZERO CANCELLATION When a tail pulser is connected directly to the amplifier input the PZ Adj should be adjusted if overload tests are to be made other tests are not affected See Section 4 6 for the pole zero adjustment If a preamplifier is used and a tail pulser is connected to the preamplifier test input similar precautions are necessary In this case the effect of the pulser decay must be removed i e step input should be simulated 3 5 SHAPING CONSIDERATIONS The shaping time constant on the 572A is switch selectable in steps of 0 5 1 2 3 6 and 10 us The choice of the proper shaping time constant
21. eshold is set manually by the threshold potentiometer Range is 0 to 300 mV referred to the positive output signal The BLR time constant is the same as for the Auto switch setting DC Screwdriver potentiometer adjusts the unipolar output baseline dc level range 100 mV to 100 mV 2 3 INPUT INPUT Type BNC front and rear panel connectors accept either positive or negative pulses with rise times in the range from 10 to 650 ns and decay times from 40 to 2000 us Z 5000 dc coupled linear maximum 1 V 10V with attenuator jumper set at X0 1 absolute maximum 20 V 2 4 OUTPUTS UNI Unipolar front panel BNC with Z 10 and rear panel BNC with Z 930 Short circuit proof prompt full scale linear range to 10 V active filter shaped and dc restored dc level adjustable to 100 mV Bi Bipolar front panel BNC with Z 100 and rear panel with Z 930 Short circuit proof prompt output with positive lobe leading and linear range of 10V active filter shaped BUSY Rear panel BNC with Z 100 provides 5 V logic pulse for the duration that the input pulse exceeds the baseline restorer discriminator level Connect to the ORTEC MCA Busy input for dead time correction INH Inhibit rear panel BNC with Z 100 provides a nominal 5 V logic signal when an internal pulse pileup occurs width 6 in coincidence with the pileup to be used for an MCA anticoincidence input to prevent storage of pileup data in
22. f 6T equal to the duration of the linear output signal The Inhibit output remains low in the absence of a second pulse from the preamplifier Using the broken line waveforms to show the variations when there is a pulse pileup the second pulse arrives before the Busy output signal recovers The linear output signal is distorted by the second pulse The fast amplifier generates another output that again triggers the discriminator to produce another CRM output pulse and to update the Busy output Since the bistable for the Inhibit output has been set by the first pulse the Inhibit output is generated starting at the response to the second pulse and extending through the 6r updated interval of the Busy output 20 2 Fig 5 1 Amplifier Block Diagram Lie te M Zar P4 M 24 Fig 5 2 Timing Relations in the 572A Amplifier and Pile Up Rejector 6 MAINTENANCE 6 1 TEST EQUIPMENT REQUIRED The following test equipment should be utilized to adequately test the specifications of the 572A Spectroscopy Amplifier 1 ORTEC 419 Precision Pulse Generator or 448 Research Pulser 2 Tektronix 547 Series Oscilloscope with a type 1A1 plug in or equivalent 3 Hewlett Packard 3400A RMS Voltmeter 6 2 PULSER TEST Coarse Gain 1K Gain 1 5 See IEEE Standards No 301 1976 Input Polarity Positive Shaping Time Constant 1 us BLR PZ Adj
23. f false amplitudes UNI Provides a unipolar positive output with the same characteristics as described for the front panel Uni connector the output impedance through this connector is 930 BI Provides a bipolar output with the same characteristics as described for the front panel connector the output impedance through this connector is 930 CRM Provides NIM standard 5 V slow positive logic output for each linear input pulse The output can be connected into a ratemeter or counter to monitor the true input count rate for the amplifier BUSY Provides a signal that rises to approximately 5V for the time that the input pulse amplitude exceeds the BLR discriminator level which can be controlled manually or automatically The output can be used to correct for live time in the ORTEC MCA by connecting it to the MCA Busy input PREAMP Provides power connections from the bin and power supply to the ORTEC preamplifier The dc levels include 24 V 24 V 12 V and 12 V 4 5 STANDARD SETUP PROCEDURE a Connect the detector preamplifier high voltage power supply and amplifier into a basic system and connect the amplifier unipolar output to an oscilloscope Connect the preamplifier power cable to the Preamp power connector on the rear panel of the 572A Turn on power in the Bin and Power Supply and allow the electronics of the system to warm up and stabilize 10 b Set the 572A controls initially as follows Shapin
24. g 2 us Coarse Gain 50 Gain 1 000 Internal Jumper X1 0 BLR PZ Adj Thresh Fully clockwise Pos Neg Match preamplifier output polarity c Use a calibration source set about 25 cm from the active face of the detector The unipolar output pulse from the 572A should be about 8 to 10 V using a preamplifier with a conversion gain of 170 mV MeV d Readjust the Gain control so that the higher peak from the 9 Co source 1 33 MeV provides an amplifier output at about 9 V 4 6 POLE ZERO ADJUSTMENT The pole zero adjustment is extremely critical for good performance at high count rates This adjustment should be checked carefully for the best possible results USING Ge Li SYSTEM AND a Adjust the radiation source count rate between 2 kHz and 10 kHz b Observe the unipolar output with oscilloscope Adjust the PZ Adj control so that the trailing edge of the pulses returns to the baseline without overshoot or undershoot see Fig 4 2 The oscilloscope used must be dc coupled and must not contribute distortion in the observed waveforms Oscilloscopes such as Tektronix 453 454 465 and 475 will overload for a 10 V signal when the vertical sensitivity is less than 100 mV cm To prevent overloading the oscilloscope use the clamp circuit shown in Fig 4 3 USING SQUARE WAVE THROUGH PREAMPLIFIER TEST INPUT A more precise pole zero adjustment in the 572A can be obtained by using a square wave signal as
25. he best signal to noise ratio resolution is most important such as high resolution spectroscopy using semiconductor detectors Use of the unipolar output with baseline restoration will also give excellent resolution at high counting rates The bipolar output should be used in high count rate systems when the analyzer System is ac coupled and noise or resolution is a secondary consideration 3 6 LINEAR OUTPUT CONNECTIONS AND TERMINATING CONSIDERATIONS Since the 572A unipolar output is normally used for spectroscopy the 572A is designed with a great amount of flexibility in order for the pulse to be interfaced with an analyzer A gated baseline restorer BLR circuit is included in this output for improved performance at all count rates A switch on the front panel permits the threshold for the restorer gate to be determined automatically according to the input noise level or manually with a screwdriver adjustment The switch also has a center PZ Adj setting that can be used to eliminate the BLR effect when making pole zero adjustments The unipolar output dc level can be adjusted from 0 1 to 0 1 V to set the zero intercept on the analyzer when direct coupling is used The bipolar output with a 0 to 10 V range can be used for crossover timing or may be preferred for spectroscopy when operating into ac coupled systems at high counting rates Typical system block diagrams for a variety of experiments are described in Section 4
26. he pulser attenuator must be adjusted to measure 0 V at the null point when the pulser output is 10 V The variation in the null point as the pulser is reduced gradually from 10 V to 0 V is a measure of the nonlinearity Since the subtraction network also acts as a voltage divider this variation must be less than 10 V full scale x 40 05 maximum nonlinearity x 1 2 for divider network 2 5 mV for the maximum null point variation OUTPUT LOADING Use the test setup of Fig 6 1 Adjust the amplifier output to 10 V and observe the null point when the front panel output is terminated in 1000 The change should be less than 5 mV NOISE Measure the noise the amplifier Unipolar output with maximum amplifier gain and 2 us shaping time Using a true rms voltmeter the noise should be less than 5 uV x 1500 gain or 7 5 mV For an average responding voltmeter the noise reading would have to be multiplied by 1 13 to calculate the rms noise The input must be terminated in 1000 during the noise measurements 6 3 SUGGESTIONS FOR TROUBLESHOOTING In situations where the 572A is suspected of a malfunction it is essential to verify such malfunction in terms of simple pulse generator impulses at the input The 572A must be disconnected from its position in any system and routine diagnostic analysis performed with a test pulse generator and an oscilloscope is imperative that testing not be performed with a Source and detector unti
27. ial reading in MeV and 2 35 is the factor for rms to FWHM For average responding voltmeters such as the Hewlett Packard 400D the measured noise must be multiplied by 1 13 to calculate the rms noise The resolution spread will depend on the total input capacitance since the capacitance degrades the signal to noise ratio much faster than the noise DETECTOR NOISE RESOLUTION MEASUREMENTS The measurement just described can be made with a biased detector instead of the external capacitor that would be used to simulate detector capacitance The resolution spread will be larger because the detector contributes both noise and capacitance to the input The detector noise resolution spread can be isolated from the amplifier noise spread if the detector capacity is known since T N x N 2 2 amp total where Nita is the total resolution spread N is the amplifier resolution spread when the detector is replaced by its equivalent capacitance The detector noise tends to increase with bias voltage but the detector capacitance decreases thus reducing the resolution spread The overall resolution spread will depend upon which effect is dominant Figure 4 7 shows curves of typical noise resolution spread versus bias voltage using data from several ORTEC silicon surface barrier semiconductor radiation detectors AMPLIFIER NOISE RESOLUTION MEASUREMENTS USING MCA Probably the most convenient method of making resolution
28. imum gain same recovery from 1000 overload for bipolar pulses 2 2 CONTROLS GAIN Ten turn precision potentiometer for continuously variable direct reading gain factor of X0 5 to X1 5 COARSE GAIN Six position selector switch selects feedback resistors for gain factors of 20 50 100 200 500 and 1 K INPUT ATTENUATOR Jumper on printed circuit board selects an input attenuation factor of 1 or 10 gain factor of X1 or 1 POS NEG Toggle switch selects input circuit for either polarity of input pulses from the preamplifier SHAPING TIME Six position switch selects time constant for active filter network pulse shaping selections are 0 5 1 2 3 6 and 10 us PZ ADJ Potentiometer to adjust pole zero cancellation for decay times from 40 us to o Factory preset at 50 us to match normal characteristics of ORTEC preamplifiers BLR Toggle switch selects a source for the gated baseline restorer discriminator threshold level from one of three positions e Auto The BLR threshold is automatically set to an optimum level as a function of the signal noise level by an internal circuit This allows easy setup and very good performance under most conditions e PZ Adj The BLR threshold is determined by the threshold potentiometer The BLR time constant is greatly increased to facilitate PZ adjustment This position may give the lowest noise for conditions of low count rate and or longer shaping times e Threshold The BLR thr
29. ipolar crossover is 2 8T Return the switch to 1 us OVERLOAD TESTS Start with maximum gain t 2us and 10 V output amplitude Increase the pulser output amplitude by X200 and observe that the unipolar output returns to within 200 mV of the baseline within 24 us after the application of a single pulse from the pulser It will probably be necessary to vary the PZ Adj control on the front panel in order to cancel the pulser pole and minimize the time required for return to the baseline Increase the pulser output amplitude to 1000 times the setting that provided the original 10 V output amplitude from the 572A Observe that the bipolar output returns to within 200 mV of the baseline within 26 us after the application of a single pulse from the pulser It may be necessary to use external control on the pulser to obtain the 6 6 V output required for this test LINEARITY The integral nonlinearity of the 572A can be measured by the technique shown in Fig 6 1 In effect the negative pulser output is subtracted from the positive amplifier output to cause a null point that can be measured with excellent sensitivity The pulser output must be 22 ATTENUATED OUTPUT DIRECT OUTPUT ZgiP R TRIGGER ZglP Ry Zo fA P3 520071 VERTICAL to ti ty Fig 6 1 Circuit Used to Measure Nonlinearity varied between 0 and 10V which usually requires an external control source for the pulser The amplifier gain and t
30. l the amplifier performs satisfactorily with the test pulse generator The testing instructions in Section 6 2 and the circuit descriptions in Section 5 should provide assistance in locating the region of trouble and repairing the malfunction The two side plates can be completely removed from the module to enable oscilloscope and voltmeter observations 6 4 FACTORY REPAIR This instrument can be returned to the ORTEC factory for service and repair at a nominal cost Our standard procedure for repair ensures the same quality control and checkout that are used for a new instrument Always contact Customer Services 23 at ORTEC 865 482 4411 before sending in an instrument for repair to obtain shipping instructions and so that the required Return Authorization Number can be assigned to the unit This number should be marked on the address label and on the package to ensure prompt attention when the unit reaches the factory 6 5 TABULATED TEST POINT VOLTAGES The voltages given in Table 6 1 are intended to indicate typical dc levels that can be measured on the printed circuit board In some cases the circuit will perform satisfactorily even though due to component tolerances there may be some voltage measurements that differ slightly from the listed values Therefore the tabulated values should not be interpreted as absolute voltages but are intended to serve as an aid in troubleshooting Table 6 1 Typical dc Voltages Note A
31. ll voltages measured with no input signal with the input terminated in 1000 and all controls set fully clockwise at maximum Location Voltage TP1 5 mV TP2 30 mV TP3 20 mV TP4 20 mV TP5 30 mV TP6 3 3 V TP7 6 mV Q15E 15 V 0 8 V Q16E 15 V 0 8 V IC13 pin 2 5 V 0 3 Bin Module Connector Pin Assignments For Standard Nuclear Instrument Modules per DOE ER 0457T Pin Function 1 3 2 3V 3 Spare bus 4 Reserved bus 5 Coaxial 6 Coaxial 7 Coaxial 8 200Vdc 9 Spare 10 6V 11 6V 12 Reserved bus 13 Spare 14 Spare 15 Reserved 16 12V 17 12V 18 Spare bus 19 Reserved bus 20 Spare 21 Spare 22 Reserved Function Reserved Reserved Reserved Spare Spare 24 24V Spare bus Spare Spare 117 V ac hot Power return ground Reset Scaler Gate Reset Auxiliary Coaxial Coaxial Coaxial 117 V ac neutral High quality ground Ground guide pin Pins marked are installed and wired in ORTEC s 4001A and 4001C Modular System Bins
32. nstructions carefully and make sure you understand them fully before attempting to use this product In addition the following symbol may appear on the product ATTENTION Refer to Manual DANGER High Voltage Please read all safety instructions carefully and make sure you understand them fully before attempting to use this product SAFETY WARNINGS AND CLEANING INSTRUCTIONS DANGER Opening the cover of this instrument is likely to expose dangerous voltages Disconnect the instrument from all voltage sources while it is being opened WARNING Using this instrument in a manner not specified by the manufacturer may impair the protection provided by the instrument Cleaning Instructions To clean the instrument exterior e Unplug the instrument from the ac power supply e Remove loose dust on the outside of the instrument with a lint free cloth e Remove remaining dirt with a lint free cloth dampened in a general purpose detergent and water solution Do not use abrasive cleaners CAUTION prevent moisture inside of the instrument during external cleaning use only enough liquid to dampen the cloth or applicator e Allow the instrument to dry completely before reconnecting it to the power source vi S720 e AMPLIFIER GAT 95 15 COARSE GAIN ORTEC MODEL 572A SPECTROSCOPY PILE UP AMPLIFIER 1 DESCRIPTION 1 1 GENERAL The ORTEC 572A Spectroscopy Amplifier and Pile Up Rejector is
33. o float the microammeter at the detector bias voltage the method of detector current measurement shown by the dashed lines in 15 Fig 4 9 is preferable The detector is grounded as in normal operation and the microammeter is connected to the current monitoring jack on the 428 Detector Bias Supply 4 9 OPERATION IN SPECTROSCOPY SYSTEMS HIGH RESOLUTION ALPHA PARTICLE SPECTROSCOPY SYSTEM The block diagram of a high resolution Spectroscopy system for measuring natural alpha particle radiation is shown in Fig 4 11 Alpha particle resolution is obtained in the following manner a Use appropriate amplifier gain Accumulate the alpha peak in the MCA b Slowly increase the amplifier gain until the alpha peak is spread over 5 to 10 channels c Calibrate the analyzer in keV per channel using the pulser and the known energy of the alpha peak see Calibration of Test Pulser or two known energy alpha peaks d Calculate the resolution by measuring the number of channels at the FWHM level in the peak and converting this to keV HIGH RESOLUTION GAMMA SPECTROSCOPY SYSTEM high resolution gamma spectroscopy system block diagram is shown in Fig 4 12 When germanium detectors that are cooled by a liquid nitrogen cryostat are used it is possible to obtain resolutions from about 1 keV FWHM up depending on the energy of the incident radiation and the size and quality of the detector Reasonable care is required to obtain such resul
34. of all data on a multichannel analyzer or counting a region of interest in a single channel analyzer window with a counter and timer or counting ratemeter 4 10 OTHER EXPERIMENTS Block diagrams illustrating how the 572A and other ORTEC modules can be used for experimental setups for various other applications are shown in Figs 4 15 through 4 18 Fig 4 12 System for High Resolution Gamma Spectroscopy 17 ORTEC IMULTICHANNE ye LINEAR PULSE HEIGHT COUNTER AMPLIFIER ANALYZER PREAMPLIFIE SCINTILLATION COUNTER PULSE GENERATOR merda Fig 4 14 High Resolution X Ray Energy Analysis Fig 4 13 Scintillation Counter Gamma Spectroscopy System Using a Proportional Counter System B Time Gated sd DETECTOR ORTEC MULTI SCA FOR ENERGY CHANNEL and or PULSE HEIGHT TIME PICKOFF ANALYZER ANALYZER Fig 4 15 General System Arrangement for Gating Control 18 LINEAR AMPLIFIER ORTEC MULTI CHANNEL SILICON SURFACE ANALYZER BARRIER DETECTOR J GERMANIUM DETECTOR GENERATOR ORTEC TIMING FILTER AMPLIFIER ORTEC LINEAR AMPLIFIER Fig 4 16 Gamma Ray Charged Particle Coincidence Experiment ORTEC DISCRIMI GENERATOR ORTEC ORTEC LINEAR MULTI AMPLIFIER CHANNEL ANALYZER Fig 4 17 Gamma Ray Pair Spe
35. pass a stringent set of quality control tests designed to expose any flaws in materials or workmanship Permanent records of these tests are maintained for use in warranty repair and as a source of statistical information for design improvements Repair Service If it becomes necessary to return this instrument for repair it is essential that Customer Services be contacted in advance of its return so that a Return Authorization Number can be assigned to the unit Also ORTEC must be informed either in writing by telephone 865 482 4411 or by facsimile transmission 865 483 2133 of the nature of the fault of the instrument being returned and of the model serial and revision Rev on rear panel numbers Failure to do so may cause unnecessary delays in getting the unit repaired The ORTEC standard procedure requires that instruments returned for repair pass the same quality control tests that are used for new production instruments Instruments that are returned should be packed so thatthey will withstand normal transit handling and must be shipped PREPAID via Air Parcel Post or United Parcel Service to the designated ORTEC repair center The address label and the package should include the Return Authorization Number assigned Instruments being returned that are damaged in transit due to inadequate packing will be repaired at the sender s expense and it will be the sender s responsibility to make claim with the shipper Instruments not in warrant
36. rk and a decay time greater than 40 us for proper pole zero cancellation The 572A input impedance is 5000 When long preamplifier cables are used the cables can be terminated in series at the preamplifier end or in shunt at the amplifier end with the proper resistors The output impedance is about 0 10 at the front panel connectors and 930 at the rear panel connectors The front panel outputs can be connected to other equipment by a single cable going to all equipment and shunt terminated at the far end of the cabling If series termination is desired the rear panel connectors can be used to connect the 572A to other modules See Section 3 for further information 1 2 POLE ZERO CANCELLATION Pole zero cancellation is a method for eliminating pulse undershoot after the first differentiating network In an amplifier not using pole zero cancellation Fig 1 1 the exponential tail on the preamplifier output signal usually 50 to 500 us causes an undershoot whose peak amplitude is roughly determined from undershoot amplitude 2 differentiated pulse amplitude differentiation time preamplifier pulse decay time For a 1 us differentiation time constant and 50 us preamplifier pulse decay time the maximum undershoot is 2 and this decays with 50 us time constant Under overload conditions this undershoot is often sufficiently large to saturate the amplifier during a considerable portion of the undershoot causing excessive dead
37. switch at Threshold and turn the control fully clockwise for 300 mV Observe the unipolar output on the 100mV cm scale of the oscilloscope using 5 us cm horizontal deflection Trigger the oscilloscope with the Busy output from the 572A d Reduce the control setting until the baseline discriminator begins to trigger on noise this corresponds to about 200 counts s from the Busy output Adjust the trigger level according to the information in Fig 4 5 If a ratemeter or counter timer is available it can be connected to the Busy output and the threshold level can then be adjusted for about 200 counts s 4 8 OPERATION WITH SEMICONDUCTOR DETECTORS CALIBRATION OF TEST PULSER An ORTEC 419 Precision Pulse Generator or equivalent is easily calibrated so that the maximum pulse height dial reading 1000 divisions is equivalent to a 10 loss in a silicon radiation detector The procedure is as follows A Set too High Adjusted Properly Fig 4 5 BLR Threshold Variable Control Settings a Connect the detector to be used to the spectrometer system i e preamplifier main amplifier and biased amplifier 13 b Allow excitation from a source of known energy for example alpha particles to fall on the detector c Adjust the amplifier gain and the bias level of the biased amplifier to give a suitable output pulse d Set the pulser Pulse Height control at the energy of the alpha particles striking
38. the input to the preamplifier Many oscilloscopes include a calibration output on the front panel and this is a good source of square wave signals at a frequency of about 1 kHz The amplifier differentiates the signal from the preamplifier so 11 compared as shown in Fig 4 4 to achieve excellent pole zero cancellation Adjusted Properly Fig 4 2 Typical Waveforms Illustrating Pole Zero Adjustment Effects Oscilloscope Trigger 572A Busy Output Co Source with 1 33 MeV Peak Adjusted 9 V Count Rate 3 kHz Shaping Time Constant 2 us that it generates output signals of alternate polarities on the leading and trailing edges of the square wave input signal and these can be FROM AMPLIFIER TO OSCILLOSCOPE OUTPUT IK INPUT HPA 2800 SCHOTTKY DIODES OR FAST Ge MODES Fig 4 3 A Clamp Circuit that Can Be Used to Prevent Overloading the Oscilloscope Input Use the following procedure a Remove all radioactive sources from the vicinity of the detector Set up the system as for normal operation including detector bias b Set the 572A controls as for normal operation this includes gain shaping and input polarity c Connect the source of 1 kHz square waves through an attenuator to the Test input of the preamplifier Adjust the attenuator so that the 572A output amplitude is about 9 V d Observe the unipolar output of the 572A with an oscilloscope triggered from the 572A Busy output Adjust the PZ
39. the spectrum CRM Count Ratemeter rear panel BNC furnishes a nominal 5 V logic signal for every linear input pulse width 300 ns to be used as an input to a ratemeter or counter PREAMP POWER Rear panel standard ORTEC power connector Amphenol 17 10090 mates with captive and non captive power cords on all standard ORTEC preamplifiers 2 5 ELECTRICAL AND MECHANICAL POWER REQUIRED not including any load on the Preamp Power connector 24 V 100 mA 24 V 105 mA 12 V 85 mA 12 V 50 FRONT PANEL DIMENSIONS NIM standard single width module 1 35 by 8 714 in per TID 20893 3 INSTALLATION 3 1 GENERAL The 572A operates on power that must be furnished from a NIM standard bin and power supply such as the ORTEC 4001 4002 Series The bin and power supply is designed for relay rack mounting If the equipment is to be rack mounted be sure thatthere is adequate ventilation to prevent any localized heating of the components that are used in the 572A The temperature of equipment mounted in racks can easily exceed the maximum limit of 50 unless precautions are taken 3 2 CONNECTION TO POWER The 572A contains no internal power supply and must obtain the necessary dc operating power from the bin and power supply in which it is installed for operation Always turn off power for the power supply before inserting or removing any modules After all modules have been installed in the bin and any preamplifiers have
40. time This effect can be reduced by increasing the preamplifier pulse decay time which generally reduces the counting rate capabilities of the preamplifier or compensating for the undershoot by using pole zero cancellation Pole zero cancellation is accomplished by the network shown in Fig 1 2 The pole 1 T due to the preamplifier pulse decay time is canceled by the zero of the network s K R C In effect the dc path across the differentiation capacitor adds an attenuated replica of the preamplifier pulse to just cancel the negative undershoot of the differentiating network Total preamplifier amplifier pole zero cancellation requires that the preamplifier output pulse decay time be a single exponential decay and matched to the pole zero cancellation network The variable pole zero cancellation network allows accurate cancellation for all preamplifiers having 40 or greater decay times Improper matching of the pole zero cancellation network will degrade the overload performance and cause excessive pileup distortion at medium counting rates Improper matching causes either an under compensation undershoot is not eliminated or an over compensation output after the main pulse does not return to the baseline and decays to the baseline with the preamplifier time constant The pole zero adjust is accessible from the front panel of the 572A and can easily be adjusted by observing the baseline with an oscilloscope with a
41. tion use the 93O output on the rear panel of the 572A and use 930 cable At the input for the receiving instrument use a BNC tee to attach both the signal cable and a 1000 resistive terminator Note that the signal span at the receiving end of this type of circuit will always be reduced to 50 of the signal span furnished by the sending instrument For customer convenience ORTEC stocks the proper terminators and BNC tees or they can be ordered from a variety of commercial sources 3 7 SHORTING OR OVERLOADING THE AMPLIFIER OUTPUTS All outputs of the 572A are dc coupled with an output impedance of about 0 10 for the front panel connectors and 930 for the rear panel connectors If the output is shorted with a direct short circuit the output stage will limit the peak current of the output so that the amplifier will not be harmed When the amplifier is terminated with 1000 the maximum rate allowed to maintain the linear output is 200000 cps r us x 10 V V 3 8 INHIBIT OUTPUT CONNECTION The Inhibit output on the rear panel is intended for application at the anticoincidence input of the Analyzer output pulse is generated through this connector when a pulse pileup is sensed in the 572A and the pulse can then be used to prevent the Analyzer from measuring and storing a false amplitude The signal is dc coupled and rises from 0 to about 5 V for a time equal to starting when a pileup occurs 3 9 BUSY OUTPUT CONNEC
42. trol of the BLR gate threshold using the screwdriver control immediately below the toggle switch 4 3 FRONT PANEL CONNECTORS INPUT Accepts input pulses to be shaped and or amplified by the 572A Compatible characteristics positive or negative with rise time from 10 to 650 ns decay time greater than 40 us for proper pole zero cancellation input linear amplitude range 0 to 10 V with maximum limit of 20 V Input impedance is approximately 5000 UNI Provides a unipolar positive output with characteristics that are related to input peak amplitude gain shaping time constants pole zero cancellation and baseline stabilization The dc baseline level is adjustable for offset to 0 1 V Output impedance through this connector is about 0 1 dc coupled Linear range 0 to 10V BI Provides a bipolar pulse with positive lobe leading and with characteristics that are related to input peak amplitude gain and shaping time constants Timing is prompt with respect to the input Crossover walk of this output is less than 3 ns see Specifications Output impedance through this connector is about 0 1 Linear range of 0 to 10V 4 4 REAR PANEL CONNECTORS IN Bridged with front panel input connector for optional use as an alternate input connection location INH Provides an output signal to identify a pulse pleup in the 572A Connect it to the anticoincidence input of the multichannel analyzer to inhibit measurement and storage o
43. ts So me guidelines for obtaining optimum resolution are a Keep interconnection capacities between the detector and preamplitier to an absolute minimum no long cables b Keep humidity low nearthe detector preamplifier junction c Operate the amplifier with the shaping time that provides the best signal to noise ratio d Operate atthe highest allowable detector bias to keep the input capacity low 16 MULTI CHANNEL PULSE HEIGHT ANALYZER ORTEC PULSE GENERATOR Fig 4 11 System for High Resolution Alpha Particle Spectroscopy SCINTILLATION COUNTER GAMMA SPECTROSCOPY SYSTEMS The ORTEC 572A can be used in scintillation counter spectroscopy systems as shown in Fig 4 13 The amplifier shaping time constants should be selected in the region of 0 5 to 1 us for Nal or plastic scintillators For scintillators having longer decay times longer time constants should be selected X RAY SPECTROSCOPY USING PROPORTIONAL COUNTERS Space charge effects in proportional counters operated at high gas amplification tend to degrade the resolution capabilities drastically at x ray energies even at relatively low counting rates By using a high gain low noise amplifying system and lower gas amplification these effects can be reduced and a considerable improvement in resolution can be obtained The block diagram in Fig 4 14 shows a system of this type Analysis can be accomplished by simultaneous acquisition
44. ttings are X20 50 100 200 500 and 1000 Continuous fine gain range is from X0 5 to X1 5 using markings of 500 through 1500 dial divisions internal jumper setting provides one additional gain factor selection of either X1 0 or X0 1 Collectively the range of gain can be set at Shaping EN Time 0 5 us HHH aves j Fig 4 1 Typical Effects of Shaping Time Selection on Output Waveforms any level from X1 0 through X1500 using all three of these controls POS NEG toggle switch selects an input circuit that accepts either polarity of pulses from the preamplifier PZ ADJ A screwdriver control to set the pole zero cancellation to match the preamplifier pulse decay characteristics The range is from 40 ys to infinity DC A screwdriver control adjusts the dc baseline level of the unipolar output in the range of 0 1 V to 0 1 V SHAPING A 6 position switch selects equal integrate and differentiate time constants to shape the input pulses Settings are 0 5 1 2 3 6 and 10 us A 3 position toggle switch controls the operation of the internal baseline restorer BLR circuit The center setting of the switch is effectively Off and this permits adjustment of the PZ control without interference from the BLR circuit The Auto setting of the switch selects a circuit that regulates the threshold of the BLR gate according to the output noise level The Threshold setting permits manual con
45. y should follow the same procedure and ORTEC will provide a quotation Damage in Transit Shipments should be examined immediately upon receipt for evidence of external or concealed damage The carrier making delivery should be notified immediately of any such damage since the carrier is normally liable for damage in shipment Packing materials waybills and other such documentation should be preserved in order to establish claims After such notification to the carrier please notify ORTEC of the circumstances so that assistance can be provided in making damage claims and in providing replacement equipment if necessary Copyright 2004 Advanced Measurement Technology Inc All rights reserved ORTEC is a registered trademark of Advanced Measurement Technology Inc All other trademarks used herein the property of their respective owners CONTENTS WARRANTY i ede mi eset o e aO AL ed he eer eg ii SAFETY INSTRUCTIONS AND SYMBOLS ls iv SAFETY WARNINGS AND CLEANING INSTRUCTIONS sssssssssl les V T IDESGRIPTION cnet tuac td teat bdo Tar bei br toon ave td dietus 1 Tel GENERAL ionic ones restart eate Eat m ied e 1 1 2 POLE ZERO CANCELLATION e ur lli 1 1 3 ACTIVE FILTER PERDERE NI Set ense LINES Ge AE adeptes 2 2 SPECIFICATIONS IMP PAREM 4 2 1 PEREORMANGE 3 454 P dpa
Download Pdf Manuals
Related Search