CSA4 User Manual 301109-5
Contents
1. CSA4 charge amp input output ee shaping amp input c gain polarity A SHAPER A fine gain Cc p z offset SHAPER B fine gain p z offset SHAPER C fine gain p z offset SHAPER D fine gain p z preamp power CSA4 Charge Amplifier User Manual Copyright FAST ComTec GmbH Grunwalder Weg 28a D 82041 Oberhaching Germany Version 1 0 December 4 2009 Warranty Warranty Equipment manufactured by FAST ComTec GmbH is warranteed against defects in materials and workmanship for a period of twelve months from date of shipment provided that the equipment has been used in a proper manner as detailed in the instructions manuals During the warranty period repairs or replacement will be made at FAST ComTec s option on a return to factory basis The transportation cost including insurance to FAST ComTec is the responsibility of the Costumer except for defects discovered within 30 days after receipt of equipment where shipping expense will be paid by FAST ComTec Copyright 1988 2009 FAST ComTec GmbH D 82041 Oberhaching Germany All rights reserved This manual contains proprietary information no part of it may be reproduced by any means without prior written permission of FAST ComTec Grunwalder Weg 28a D 82041 Oberhaching Germany Tel 49 89 6651800 FAX 49 89 66518040 The informa2. Rf 680 kQ and Cf 15 pF tdecay 50 us CSA4 with CR 112 Rf 68 kQ and Cf 150 pF tdecay 50 us CSA4 with CR 113 The CSA4 preamplifier module consists of e hybrid charge sensitive preamplifier e input DC block capacitor e test input with 50 ohm termination e 1 pF test capacitor high voltage path with filter circuit and power supply circuitry i FIST ComTec GmbH 4 1 Theory of Operation 4 3 General Description shaping amplifier The CSA4 is a four channel shaping amplifier intended to be used to read out the signals from charge sensitive preamplifiers Gaussian shaping amplifiers also known as pulse amplifiers linear amplifiers or spectroscopy amplifiers accept a step like input pulse and produce an output pulse shaped like a Gaussian function The purposes of this are to filter much of the noise from the signal of interest and to provide a quickly restored baseline to allow for higher counting rates The CSA4 is available with any set of four out of 7 different shaping times 100 ns 250 ns 500 ns 1 us 2 us 4 us and 8 us Each has a fixed gain of 10 100 mV input pulse shape 10V output pulse shape Figure 1 Comparison of sample input and output pulse shapes Definition of Shaping Time The shaping time is defined as the time equivalent of the standard deviation of the Gaussian output pulse A simpler measurement to make in the laboratory is the full width of the pulse at half of it s maximum v
3. Some of these noise components have different frequency distributions allowing us to use the filtering capability of the shaping amplifier to choose a shaping time that minimizes the noise for the particular detection system under design The principal sources of electronic noise in a detection system are a the thermal noise of the input JFET in the preamplifier which is proportional to the total capacitance to ground at the input node b the thermal noise of the feedback resistor and any biasing resistor attached to the detector c the shot noise of the detector leakage current i FIST ComTec GmbH 4 3 Theory of Operation d the electrical contact related 1 f noise of the detector and preamplifier input JFET and e the f noise caused by the proximity of lossy dielectric material near the preamplifier input node Of the noise components listed the noise from factor a is more heavily filtered with longer shaping times More precisely the electronic noise due to this factor is inversely proportional to the shaping time The electronic noise due to factor b on the other hand is proportional to the shaping time as is factor c Factors d and e are generally difficult to predict which means it is difficult to predict the exact noise performance of a detection system Fortunately both of these factors are independent of shaping time so they have no impact on the determination of the optimal shaping tim
4. piz offset Preamplifier output coarse gain toggle switch setable to 1 10 and 100 Polarity Switch fine gain sect B pole zero sect B offset controle sect B D SUB 9 female connector for power supply of preamplifiers CSP10 3 1 Controls and Connectors 3 3 Internal Controls Jumper J3 Internal connection of preamplifier output to shaping amplifier input J4 Jumper for 50 Ohm shaping amplifier input termination J2 Connector for test input preamplifier 1 pF 50 Ohm terminated J1 Jumper for 50 Ohm preamplifier input termination ever eri wg Pra Fhe 4 TL SR aS J5 not used i J6 J7 J8 J9 a Junper for connection of preamplifier power outputs 24V 24V 12V 12V J1 Selects input impedance of preamplifier input 50 Q installed J2 Test input terminates signal ground terminated with 50 Q 1pF test capacitor J3 Connects output of preamp section with the input of the shaping amplifier section J4 selects input impedance of shaping amplifier in 50 Q installed 1kQ open J5 not used J6 If installed J7 If installed J8 If installed J9 If installed MNF FIST ComTec GmbH 24 V supply is available on preamp power connection 24 V supply is available on preamp power connection 12 V supply is available on preamp power connection 12 V supply is available on preamp power connection 3 2 Contr
5. 2 4 4 Equivalent circuit diagram shaping amplifier module 4 2 4 5 Pole Zero Correction d kk kak KK ek KEK K k KK K KK KK KK KK KK KK KA 4 3 4 6 Choosing the Optimal Shaping Time for your Application 4 3 2 7 Output DIVET an ee ee an 4 4 X gt D dc 5 1 5 1 Schematic of the Preamplifier Stage cc ccccccccssccceeesseeceeeeceeeseueeseeeseeessueeseeeseeess 5 1 5 2 Detailed Schematic of the Shaping Amplifier Input Stage 5 1 5 3 Schematic of the Shaping Amplifier Outputs four x 5 2 SA OU are ee eeeeoo_JovJoee egrlrmrmrmrmrb bebe er r 5 2 i FIST ComTec GmbH Il CSA4 Configuration Form CSA4 Configuration Form Preamplifier section type of preamp check one box O CR110 O CR111 O CR112 O CR113 Shaping Amplifier section shaping time per stage Shaper A Shaper B Shaper C Shaper D common for all stages individual for each stage LJ 25ns LJ 25ns LJ 25ns O 25ns output signal output impedance output amplitude DI 50ns DI 50ns DI 50ns DI 50ns inverting 1 4 V pC 150 mV pC 15 mV pC 1 5 mV pC check one box in each line LI 100ns LI 100ns LI 100ns LI 100ns O 250ns O 250ns O 250ns O 250ns input polarity coarse gain fine gain X 1 x 10 pole zero cancelation output offset control LI 500ns LI 500ns LI 500ns LI 500ns x 100 positive unipolar gaussian sh
6. 4 7 Output Driver see equivalent circuit diagram on previous page The CR200 shaping amplifier module is followed by a fast driver amplifier with a fixed gain of 2 5 and an output impedance of 50 It is capable of producing a 0 8 V signal into high impedance loads and 0 4 V amplitude into 50 Q The front panel offset controls affect the DC level of the output signal and should be adjusted for a 0 V output voltage of the base line i FIST ComTec GmbH 4 4 Appendix 5 Appendix 5 1 Schematic of the Preamplifier Stage 5 2 Detailed Schematic of the Shaping Amplifier Input Stage EL 5162 EL 5162 EL 5162 gt 6 1V gt 6 1V T gt 6 1 V 10uF 1k L IMF FAST ComTec GmbH Appendix 5 1 Appendix 5 3 Schematic of the Shaping Amplifier Outputs four x CR 200 EL 5162 S1C 100 gt 6 6V C E 10 IN 10uF Ex OUT 200k 47 220 io GND 5 4 a J4 5 6 7 560 HH a 6 8V 4 1k 10 10uF Th 10 i E amp l gt 6 66V e m ae 560 5 4 Power BCP68 BCP69 pre amp power supply L front view 24V he 24V NC NC 12V nc 12V GND GND MEAST ComTec GmbH Appendix 5 2
7. alue FWHM This value is greater than the shaping time by a factor of 2 4 For example a Gaussian shaping amplifier with a shaping time of 1 0 ps would have a FWHM of 2 4 US 4 4 Equivalent circuit diagram shaping amplifier module Figure 2 shows an equivalent circuit of the shaping amplifier modules Pin numbers corresponding with the CR 200 shaping amplifier are shown Input components Cin and Rin form a differentiating circuit The following circuitry consists of two Sallen and Key filters providing 4 poles of integration and signal gain The numerous integration stages produce an output pulse that approximates a Gaussian function 3 6 7 Figure 2 i FIST ComTec GmbH 4 2 Theory of Operation 4 5 Pole Zero Correction The long decay time of the input pulse creates a small overshoot in the shape of the output pulse unless a pole zero correction is utilized This can be done by adjusting Rp z This resistor is in parallel with the input capacitor internal to the CSA4 circuit and creates a zero in the amplifier s transfer function which cancels the pole created by the charge sensitive preamplifiers feedback resistor To achieve proper pole zero cancellation Rp z should be selected to be equal to R C Cin where R and C are the feedback resistor and feedback capacitor of the charge sensitive preamplifier and Cin is the value of the input capacitor in the CSA4 Keep in mind that the CSA4 will likely affect the DC off
8. aped 50 Ohm 0 8V into 1 kOhm 0 4V into 50 Ohm Power Connector section connector type pin pin pin pin pin pin iii FIT ComTec GmbH 1 OND N D Sub 9 female GND GND 12V 24V 24V 12V O ips O ips O ips O ips O 2us O 2us O 2us O 2us O 4us O 4us O 4us O 4us O 8us O 8s O 8us O 8s Introduction 1 Introduction 1 1 General Functionally the Model CSA4 provides in a single width NIM module a preamplifier and a shaping amplifier with four shaping times simultaneously selectable in the range from 100ns to 8us four values out of seven can be ordered 100ns 250ns 500ns us 2us 4us 8us A power connector D Sub 9 female is also available at the front panel for the power supply of external preamplifiers 1 2 Preamplifier section The Model CSA4 provides a charge sensitive preamlifier It is intended to be used in uncritical applications where the detector signal source needs no bias voltage supplied from the charge sensitive amplifier like integration of signals from PMT s In applications where a detector bias is needed or the signal to noise ratio is important an external charge sensitive preamplifier like our model CSP10 13 close to the detector is recommended 1 3 Typical Setup The Model CSA4 Shaping Amplifier with its selection of shaping time constants can be used in surface barrier proportional counter Nal and Ge Li detector applications The choice o
9. e In terms of reducing the electronic noise the optimal shaping time can be predicted by considering only factors a b and c The subject of noise in detection systems using charge sensitive preamplifiers is addressed in more detail in these articles Bertuccio G Pullia A A Method for the Determination of the Noise Parameters in Preamplifying Systems for Semiconductor Radiation Detectors Rev Sci Instrum 64 p 3294 1993 Radeka V Low Noise Techniques in Detectors Ann Rev Nucl Part Sci 38 p 217 1988 Goulding FS Landis DA Signal Processing for Semiconductor_Detectors IEEE Trans Nuc Sci NS 29 p 1125 1982 Output Characteristics The CR 200 shaping amplifiers have low output impedance lt 5Q and can source sink 10 mA of output current This may not be sufficient to drive a terminated cable in your application depending on the size of the signal For this reason it is best to use a cable driver circuit at the CR 200 output to make maximum use of the CR 200 output voltage swing capability The unloaded output voltage swing comes to within 0 5 volt of the power supply rails output pulse shaping width part time FWHM Ri Cin CR 200 100ns 100ns 240 ns 220 Q 470 pF CR 200 250ns 250 ns 590 ns 240 Q 1000 pF CR 200 500ns 500 ns 1 2 us 510 Q 1000 pF CR 200 1us 1 us 2 4 US 1 0 KQ 1000 pF CR 200 2us 2 US 4 7 US 2 0 KQ 1000 pF CR 200 4us 4 us 9 4 us 1 2 KQ 3300 pF CR 200 8us 8 US 19 us 2 4 KQ 3300 pF
10. e time for the preamplifier of the CSA4 this figure is approximately 7 ns Furthermore capacitance at the preamplifier input i e detector capacitance will further slow the rise time at a rate of 0 4 ns pF Keep in mind the output rise time will also be limited by the speed of the detector For example the detection current pulse from a Csl T1 photodiode scintillation detector has a duration of approximately a couple s so the expected rise time of the charge sensitive preamplifier output will be at least that long The output waveform of the preamplifier of the CSA4 using a capacitively coupled fast square wave pulser at the input is shown below to the left At long time domains the output decays due to the discharge of the feedback capacitor through the feedback resistor with an RC time constant of 140 us This decay of the output waveform is also shown below to the right 10 Ung 4 2 Detailed Circuit Description preamplifier Figure 2 shows a simplified equivalent circuit diagram of the hybrid amplifier module used in the preamplifier of the CSA4 which is a two stage amplifier The first stage is high gain and the second stage is low gain with an emphasis on supplying sufficient output current to drive a terminated coaxial cable Rf 100 MQ and Cf 1 4 pF are the feedback resistor and capacitor respectively tdecay 140us The feedback values for the other models are Rf 10 MQ and Cf 15 pF tdecay 150 us CSA4 with CR 111
11. f shapings also allows the best possible performance by tailoring the system for the conflicting requirement of optimum signal to noise ratio and high count rate performance The excellent Stability and low noise contribution enhances the use of this amplifier in most applications It is intended to be used to read out the signals from a charge sensitive preamplifier first CSA4 section CSP1x or equivalent Gaussian shaping amplifiers also known as spectroscopy amplifiers shaping amplifiers linear amplifiers or pulse amplifiers accept a step like input pulse fast rise time slow fall time and produce an output pulse shaped like a gaussian function The purpose of this are to filter much of the noise from the signal of interest and provide a quickly restored baseline to allow high count rates Shaping Amplifier CSA4 High Voltage Supply NHQ 102 104 Tail Pulse Generator optional PBS BH1 Oscilloscope Histogramm Detector optional CSP10 Multichannel Analyzer MCA3 i FIST ComTec GmbH 1 1 Specifications 2 Specifications 2 1 Inputs INPUT Accepts positive or negative pulses from a associated preamplifier 8 volts divided by selected gain 10 volts maximum rise time less than SHAPING TIME constant decay time constant 40 usec to for 0 1 0 25 0 5 1 and 2 usec shaping time constants 100 usec to for 4 and 8 usec shaping time constant input impedance approximately 1k ohms
12. he exception of the PREAMP POWER connector all signal connectors are BNC type PREAMP POWER Amphenol type 17 10070 i FIST ComTec GmbH 2 1 Specifications 2 5 Power Requirements 12 V dc 200 mA current drawn from the preamp power connector 12 V dc 100 mA current drawn from the preamp power connector 24 V dc 0 mA current drawn from the preamp power connector 24 V dc 0 mA current drawn from the preamp power connector 2 6 Physical Size Standard single width NIM module 3 41 x 22 13 cm 1 35 x 6 71 inch NET WEIGHT 1 0 kg 2 2 Ibs i FIST ComTec GmbH 2 2 Controls and Connectors Controls and Connectors 3 1 General This section describes the functions of the controls and connectors located on the front panels of the Model CSA4 It is recommended that this section be read bevor proceeding with the operation of the amplifier 3 2 Front Panel Controls Preamplifier Section Preamplifier input Main Amplifier Section Shaping amp input Section A pulse output sect A Section B pulse output sect B Section C pulse output sect C Section D pulse output sect D MMF FIST ComTec GmbH Qy CSA4 charge amp input output A shaping amp input c gain An jio 100 polarity SHAPER A fine gain offset SHAPER B fine et ga n 2 p z e offset SHAPER C fine a gain Ce a offset SHAPER D fine Za gain
13. input BNC connectors located on front panel 2 2 Outputs UNIPOLAR OUTPUTS Provide positive linear active filter near Gaussian shaped pulses amplitude linear to 8 volts R gt 1kOhm 4 volts R 50 Ohm 10 volt max output dc level adjustable front panel output impedance approximately 50 ohms BNC connectors located on front panels 2 3 Performance GAIN RANGE Continuously variable x1 to x2500 product of COARSE and FINE GAIN controls OPERATING TEMPERATURE 0 to 50 C GAIN DRIFT Less than or equal to 0 0075 C DC LEVEL DRIFT Less than or equal to 0 1mV C INTEGRAL NON LINEARITY Less than or equal to 0 05 over total output range for 2 usec shaping OVERLOAD RECOVERY UNIPOLAR output recovery to within 2 1 of full scale output from X1000 overload in 2 5 2 0 non overloaded pulse widths at full gain any shaping time constant and pole zero cancellation properly set NOISE CONTRIBUTION Less than or equal to 3 4 uV true rms referred to input 3 usec shaping and amplifier gain greater than or equal to 100 PULSE SHAPING Near Gaussian shape one differentiator two active filter integrators time to peak 2 35 x shaping time pulse width FWHM 2 4 x shaping time time to peak pulse width measured at 0 1 of full scale output 1 usec SHAPING center frequency 150 kHz band width 180 kHz fs and BW for other shapings are multiples of that given for 1 usec 2 4 Connector Types With t
14. ols and Connectors 3 4 Internal Module Positions Preamplifier module CR110 CR111 CR112 or CR113 i label is not visible ja aoe Em B Z bee ie a e EE a 9 a LE CE 4 oF rm 4 PE ELLES gt y ES 4 e Shaping amplifier a 9 module CR200 X seems 3ng e e FE label is visible EL Z 3 st 002 4 ou ewa baz output pulse shaping width part time FWHM Rin Cin CR 200 100ns 100 ns 240 ns 2209 470pF CR 200 250ns 250 ns 590 ns 240 Q 1000 pF CR 200 500ns 500 ns 1 2 us 510 Q 1000 pF CR 200 1us 1 us 2 4 US 1 0 kQ 1000 pF CR 200 2us 2 US 4 7 US 2 0 kQ 1000 pF CR 200 4us 4 us 9 4 us 1 2 kKQ 3300 pF CR 200 8us 8 us 19 us 2 4 KQ 3300 pF see equivalent circuit diagram on previous page i FIST ComTec GmbH 3 3 Theory of Operation 4 Theory of Operation 4 1 Functional Description preamplifier Charge sensitive preamplifiers are used when radiation is detected as a series of pulses resulting in brief bursts of current flowing into or out of the preamplifier input Depending on the type of detector this burst of current may be very brief lt 1 ns or as long as a few seconds For an idealized detection current pulse taking the form of a delta function the detected charge time integral of the input current will ideally take the form of a step function The output waveform of an actual charge sensitive preamplifier will of course have a non zero ris
15. set of the shaping amplifier output This is because Rp z directly couples the DC offset from the charge sensitive preamplifier output into the shaping amplifier input Some fraction of this DC offset is amplified along with the pulse It is recommended to use the DC offset adjustment at the frontpanel to correct for this Rp z resistance too high Rpzresistance proper Rp z resistance too low Figure 3 4 6 Choosing the Optimal Shaping Time for your Application Choosing the Optimal Shaping Time for your Application There are a number of considerations in the choice of the optimal shaping time for your application Consider 1 The shaping time must be long enough to collect the charge from the detector This may be a limiting factor in slow detectors such as gas based drift chambers or when collecting the light from slow decay scintillators 2 The shaping time must be short enough to achieve the high counting rates you require Assuming randomly spaced pulses long shaped pulses have a higher probability of piling up than short pulses Note that pile up will only be a problem at very high count rates Baseline shift will start to be a problem at somewhat lower count rates See the previous section regarding Baseline Restoration 3 Choose a shaping time that filters as much of the electronic noise as possible Electronic noise at the preamplifier output is created by a number of different aspects of the detection system
16. tion in this manual describes the hardware and the software as accurately as possible but is subject to change without notice i FIST ComTec GmbH Il Table of Contents Table of Contents s PTSD CTR UU ON ete ce acters ees eee Parner ce E stn ce nie ic severe sce cies ce rl r sense enemas 1 1 e PR GENS Dee en nce ee 1 1 1 22 Preamplihier Secon a si m xu lk lak naa k kay biya akar seen een eee dual Wl sa b k WADA b K waq 1 1 rr BE SJ E ND rrr ee ee cree 1 1 oe zelel ea SC ae a N E E A ee ee eee 2 1 RS ee E ee eee een o 2x a_R8 2 1 D OO a ee ee ne eee ee ee E 2 1 20 FP CE ae ee a E 2 1 2 4 Conhector TYDeS 8 sent kl ke kya wak a a bu aa KRA A sana d ka k we a k e NEEE 2 1 2 5 Power Requirements kak kk KEKE KK KK K KK K KK k k KAK KK KA k KAK KK KA 2 2 2o ah HD PERRET 2 2 u Controls and CONMESCIONS 5 ci onasntadadvansvncnineyain kada kake kanal an bu ke k warl kk b kek k dia sal Q Wa EE m dik u W HAWA dine 3 1 SAD _or rrrs ___ n ll sZX M hb ma a err in 3 1 3 2 FONE Pane CONOIS Sanaa aE be tas a KA y w ka 3 1 3 3 Internal Controls Jumper iii 3 2 3 4 Internal Module Positions uk EKE KAK KK KAK KK KRA 3 3 ANCON O ODE bro rr r rr bxp p rXr rr r r mn 4 1 4 1 Functional Description preamplifi er L u KK 4 1 4 2 Detailed Circuit Description preamplifier EE 4 1 4 3 General Description Shaping amplifier 4
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