2015A Spectroscopy Amplifier-Timing SCA User`s Manual
Contents
1. The signal flow is as follows The Amplifier The preamp signal enters either the front panel INPUT BNC J1 or rear panel INPUT BNC J101 The INPUT signal is differentiated by C1 or C2 and the appropriate am plifier input resistance selected by S2 and pole zeroed by RV1 and R1 or R2 The differentiated signal is amplified by gain amplifiers K1 and K2 Amplifier K1 is either inverting or noninverting depending on the INPUT POLARITY switch S2 position The amplified signal is next integrated by the complex pole integrator The integrated signal is used to drive the combination OUTPUT amplifier real pole integrator and dc restorer The processed signal is then connected to the SCA and front and rear panel BNC connectors J3 and J102 respectively The SCA Section The AMPlifier OUTPUT signal is connected to the LLD and the ULD discriminators A13 and A9 The LLD DISCriminator reference voltage is generated from 12 volts by R114 RV4 and R V5 and buffered by A15 The ULD reference voltage is the sum of the LLD reference and the voltage picked off of RV6 The voltage developed across RV6 is generated by current source Q27 The ULD reference voltage range is selected by the rear panel toggle switch S101 The fast amplified signal OUTPUT of gain amp K2 is ac coupled to the FAST DISCriminator A14 The FAST DISCriminator utilizes the LLD voltage modified by A16 as its reference The leading edge information from the FAST DISC A14 and L2. o e e Resolution Destroying Interfaces o stea u s s oo 4 Performance Check Equipment Required g s cae sus e gus ba acen Qua hun Q w ee QU ak W Ob e NIM Voltage Check usss ee ee a Swe AA NO GUS UW SN Current Meas temedts xe s s masas masa kuqa S W S AR aa we a Pole Zero Adj stment s Qs sua kak gerade upas ee oe QP T SUQ ok ewe ae Coarse and Fine Gain Controls a a Wa s kpa e s woa w 8 w w S Shaping Checks s s e s c ss w s n 40 845 48 Q T RA a Noise Measurement _ _ _ a a s e ez ee a e a e a s e e e ae s e oe Limearity Check is 4 esca a oe a ER Rae A e a Be 26 SCA Operational Checks s sose sosna mus ds det we we 27 SUPL a de et gue gr aa es a e ds eres E ee 27 OUIPU S 2 da vee ce ee eee ede ds eee ee bee Ee YO Dee Se Hee EE 28 Timing Walk Tests sia ee GUS a ie Be Ae ee a ew 8 28 External Lower Level Check su s s ka k SU a S uk K au ee 29 Normal Internal Control Settings e e 29 5 Circuit Description 30 Block Diagram Description ic ie ok ee ia ad Ee ee a 30 The Amplitler wS 2 Saa Ae a A RANA 30 The SCA Section o srt a Pe A we Bee i Ge Sal A 30 Description Of Carcuit a s gentes da BAR RR Ge BRA wh W S bus ee N 31 Gain Amplifier o s socs e 464 2 BEYER ES HES EERE a we ES 31 Input Amplifier KI os bk ws ed o ee Ee we ew ew a 32 Gam Amphiter KZ idas rd ee aa EE ea W e 3 0 G ee ee eee A 32 Integrator
3. Ge Li surface barrier and proportional counter applications Using the amplifier and single channel analyzer outputs the Model 2015A in conjunction with a delay module represents an ideal method for per forming energy discrimination The SCA OUTPUT can gate the multichannel analyzer to control the acceptance or rejection of the amplifier s delayed linear output signal In addition the amplifier s output allows the signal to be analyzed by other energy discriminators so that more than one energy band may be selectively studied from the same amplifier The Single Channel Analyzer section is used in either the Timing SCA TSCA or SCA mode In the timing mode the SCA OUTPUT logic pulse is placed consistently in time 200 nanoseconds past the AMPLifier OUTPUT pulse peak Thus the Model 2015A may serve to replace an amplifier and individual timing SCA sometimes re quired for coincidence experiments With its SCA and ULD or LLD DISC outputs the 2015A Amp TSCA may be used to identify two different energies or particles depend ing on the particular setting of the discriminator levels Low Level o B Counting System The Canberra LOW BACKGROUND ALPHA BETA DETECTOR SYSTEM 2200 amp 2201 depicts a particular application of the Model 2015A In this system two de tectors are used in anti coincidence to distinguish true sample events from cosmic or interference radiation associated with the local environment The system is ideally suited for
4. Amplifier AS s eos e e enoe e o 32 Amp OUTPUT Integrator and Driver oaao e 32 R st ref gas s sea c p us g S a a A a SU Guna 33 SCA OC N s ccs knob o dd al a dh ee db a 33 SCA OUTPUT l gtd aa AAA AAA A 33 Dis Output e v e zoeae eo mO e Pee A AA 35 Lower Level E Threshold Circuit s w w wa ne k kn w Erawa 35 Window AE Threshold Circuits woa www a a wa w we w ew a nh 36 Fast Discriminator Reference Voltage o o ee 36 S Volt Power SUPPLY kus as ee a QQ a 36 Troubleshooting 4 2 u w as z maaa ZO Q ae a Wapa 37 Troubleshooting Aids ss co k s lt wo RRR e W eros ERR ERE OEE WU p Q 37 Troubleshooting T chpiqueS e s s ee w as e waq a ys aP RO g B A s 37 Component Replacement 38 A Specifications aooaa O INPu OU PUE e sda sed eh ee eee REDS e a a A 39 A rsoda sqa sein S tebe Gy Si Ae A Be we s9 a 40 Internal COmtrolS si esi se eek eee era era SPS ee wr Sal Se eo ee ae ee ae 40 Performance esac he OR ee REE W wU ee Oe W QCP eS He we eee ee 3 41 CONNECTIONS 2 m cs GOR ah hints eas ee oe ek ee Ge ee A 42 Power Requirements i o u e p ee a le Mold ee wae HER ee aE a ee es 42 Physical ioc ch s e ak Ree EEE REG E SEE rs e a SU u b 6 42 Environmental Meli Go Bees Ge obvi Ak ee ea oe a AS aa Q QN eee s ni 43 B Installation Considerations 44 Notes 1 Introduction The Canberra Model 2015A combines in one singlewi
5. aid in locating the source of trouble Troubleshooting Aids Test Equipment refer to Equipment Required on page 20 NIM Module Power Extender Cable Canberra Model C 1403 Detailed Block Diagram Drawing B 17635 Circuit Schematic Drawing B 17636 Troubleshooting Techniques 1 Check Control Settings The first and most important prerequisite for successful troubleshooting is a thorough understanding of module operation and function Often suspected malfunctions are caused by improper control settings The troubleshooting aids and techniques should be applied only after 1t has been firmly established that the difficulty cannot be eliminated by the Operating Instructions refer to page 7 Check Associated Equipment An investigation should be made to ensure that the trouble is not a result of conditions external to the Model 2015A Check that the equipment used with this instrument is operating correctly Make certain that signals are properly connected and that the interconnecting cables are not defective Also check the power source The substitution method can be applied to check for proper operation of the Model 2015A if another similar type unit is available Visual Check Conduct a visual inspection of the Model 2015A for possible burned or unsoldered components broken wires or any other obvious conditions which might suggest a source of trouble Isolate Trouble to a Circuit To isolate trouble to a particular ci
6. also be used but result in a less precise pole zero adjustment However most scopes will overload for a 10 volt input sig nal when the vertical sensitivity is set for 50 mV cm Scope overload will distort the signals recovery to the baseline Thus the pole zero will be incor rectly adjusted resulting in a loss of resolution at high count rates To prevent scope overloading a clamping circuit such as the one illustrated in Figure 12 can be used at the scope input Amplifier Output B Scope HP2800 2835 Schottky diodes Figure 12 Scope Input Clamp Note 2 When adjusting the pole zero using the square wave technique the calibra tion square wave generated by the oscilloscope can be used Most scopes gen erate a 1 kHz square wave used to calibrate the vertical gain and probe compensation Connect the scope CALIBRATION output through an attenu ator to the preamp test input and repeat Performance Adjustments step 2 pole zero adjustment 4 The AMP OUTPUT DC level is factory calibrated to 0 5 millivolt 5 To get optimum resolution the Lower Level Discriminator on the MCA ADO should be set just above the noise so that the effects of pileup are minimized Resolution Versus Count Rate and Shaping A 2 us shaping is optimum for Ge Li detector systems over a wide range of incoming count rates For high resolution larger shaping time constants offer a better signal to noise ratio resulting in better resolution However as the coun
7. cm Figure 17 Amp Output Showing a Near Gaussian Shaped Pulse 22 Amplifier Operational Checks Adjust the 1407 PULSE HEIGHT until the AMP OUTPUT amplitude is 9 9 to 10 1 volts Place jumper plug J4 in the 93 ohm position Connect a 93 ohm terminator to the tee connector at the scope input The amplitude of the pulse should be 4 8 to 5 2 volts Remove the 93 ohm terminator Place jumper plug J4 in the O ohm position Connect the 93 ohm terminator the amplitude should not decrease by more than 100 mV There should be no discernible distortion in the pulse shape Remove the terminator Remove all 1407 ATTENUATION The AMP OUTPUT pulse should be clamped at 11 5 to 12 5 volts Set the 1407 ATTENUATION to X10 Pole Zero Adjustment 1 Set the 1407 FALL TIME to 50 us Observe the AMP OUTPUT on the scope and adjust the pole zero control so that the tail of the unipolar pulse returns to the baseline as fast as possible with NO under or overshoot as in Figure 18 Scope 0 5 V cm 20 usec cm Figure 18 Pole Zero Adjust 23 Performance Check Coarse and Fine Gain Controls 1 Shaping Chec 1 24 Set the 2015A COARSE GAIN to 128 FINE GAIN to 10 0 Connect the AMP OUTPUT to the scope with RG 62 coax cable Set the 1407 ATTENUATION to X500 Adjust the Model 1407 PULSE HEIGHT until the AMP OUTPUT pulse attains an amplitude of 9 9 to 10 1 volts Measure the AMP OUTPUT on the scope for each COA
8. measuring isotopes such as 14C Sr 21Po and so forth There are two Model 2015A Amp TSCA modules involved in this system configura tion One is used in the guard channel path and the other in the sample channel path In the guard channel the Model 2015A is used as an amplifier discriminator combination where the extremely low threshold setting of the LOWER LEVEL E discriminator is used to detect the cosmic events The Model 2209A monitoring the guard 2015A DISC ULD LLD output gates off or inhibits the Scaler Timer when a cosmic INPUT signal exceeds the LOWER LEVEL E threshold Low Level o B Counting System In the sample channel the Model 2015A accepts the signal from the preamplifier shapes delays and directs 1t through the SCA section for two simultaneous discrimina tions In this application the proportional counter detector is biased to the beta plateau the output information from the detector is then indicative of both alpha and beta ener gies Typically the Single Channel Analyzer is set such that the SCA OUTPUT repre sents beta particles and the DISC ULD OUTPUT represents alpha particles the DISC LLD OUTPUT represents the sum of the alpha and beta particles The desired outputs from the single channel analyzer section are connected to the Model 2209 A AUTO FLOW METER and subsequent scalers Figure 1 shows the SCA and DISC information being routed by the 2209A to the respective scalers indi cating alpha and beta eve
9. more detailed in formation refer to Appendix A AMP IN Additional input wired in parallel with the front panel signal AMP OUT Signal specifications are identical to the front panel output INPUT BNC except for 93 ohm connector series connected output impedance Use this rear panel SCA OUT output when driving Additional output wired in parallel with the front panel SCA long lengths of interconnecting coaxial cable to OUTPUT BNC prevent distorting connector the linear signal oscillations PREAMP POWER Disc BNC connector having a multi functional capability Lower Level Provides power for any Canberra preamplifier Model 1708 preamplifier requires a special cable discriminator E output Upper Level E AE PIN FUNCTION discriminator output 1 Ground or an LLD SWEEP 2 Clean Ground input One of the 4 12 V dc three modes is 6 12 V dc internally selected 7 24 V dc with jumper plugs 9 12 V de AE RANGE MODULE POWER Rear panel 2 position Connector pena locking toggle operating voltages switch which from an AEC changes the front Standard NIM bin power supply panel WINDOW AE such as the range of 0 to Canberra Model 10 volts or 0 to 1 volt 2000 full scale PIN FUNCTION 16 12V de 17 12 V de 28 24 V de 29 24 V de 34 Ground 42 Clean Ground Figure 3 Rear Panel Connectors Controls and Connectors Internal Controls 2 pse
10. water and make sure the unit is fully dry before restoring power Because of access holes in the NIM wrap DO NOT use any liquids to clean the wrap side or rear panels 19 Performance Check 4 Performance Check The purpose of this section is for checking the performance of the Model 2015A AMP TSCA The checkout will serve to verify that the module is in good operating order If the Model 2015A should not meet the performance requirements given in this procedure it is strongly suggested that the unit be sent back to the factory for cali bration and or repair The instructions which follow are directed primarily toward the Model 2015A only Please refer to the Instruction Manuals of the other equipment used if questions or difficulties in their use arise Equipment Required In order to perform the checkout procedure detailed in subsequent steps the following equipment or equivalents will be required 1 Canberra Model 2000 BIN Power Supply Canberra Model 1407 Reference Pulser Calibrated dual trace 100 MHz oscilloscope Tektronix 454 475 or equivalent RMS Noise Meter Hewlett Packard HP 400H or equivalent 4 1 2 digit 0 1 full scale accuracy Digital Voltmeter Data Precision 3500 or equivalent Resistive Voltmeter Probe 1k ohms in series Current Meters NIM Voltage Check With a DVM measure the NIM Power Supply voltages and adjust if they are outside of the following ranges 20 Amplifier Operationa
11. 0 to 1 V depending on the position of the rear panel AE RANGE switch AE RANGE Rear panel toggle switch selects the front panel WINDOW AE range as 0 to 10 V or Oto 1 V full scale LED INDICATOR Aids in setting the LLD just above the system noise Internal Controls 40 Zout Jumper plug selects AMP OUTPUT impedance of lt 1 Q or 93 Q factory set to lt 1 DISC B Jumper plug sets the rear panel DISC BNC connector as an OUTPUT or in put factory set to OUT Performance DISC A Jumper plug sets the rear panel DISC BNC connector to OUTPUT the Lower Level E Discriminator or the Upper Level E AE discriminator when DISC B is in the OUT position factory set to ULD LLD Jumper plug sets the LOWER LEVEL discriminator threshold for INternal or EXTernal if EXTernal with DISC B set to IN the rear panel DISC BNC connector can be used as the LLD SWEEP input factory set to IN SCA MODE Jumper plug which allows the SCA to operate in the TSCA or SCA mode factory set to TSCA Performance AMPLIFIER GAIN Continuously variable from X12 to X1280 product of COARSE and FINE GAIN controls GAIN DRIFT lt 0 0075 C DC LEVEL DRIFT lt 50 u V C INTEGRAL NONLINEARITY lt 0 05 of full scale OVERLOAD RECOVERY Recovers to 2 of full scale OUTPUT in two pulse widths for a X1000 overload with pole zero cancellation properly set NOISE CONTRIBUTION lt 7 uV referred to the INPUT for gains
12. 13 Internal Shaping Components Resolution Destroying Interfaces 14 1 Vibration transmitted to the detector and cryostat This can be through the floor or mounting as well as direct audio coupling through the air Vibration isolators in the mounting and sound absorbing covers around the detector can reduce this problem The close proximity of a radio station can be picked up by the dipstick of the cryostat Good contact between the dipstick and the cryostat can often help solve this problem Beware of grounding the cryostat and dipstick as this may increase power line frequency 50 or 60 cycle ground loops Ground Loops power line frequency interference can be caused by long cable connections between the detector preamplifier and shaping amplifier There is no general solution for this problem As a first step the preamp should use the power supplied by the main shaping amplifier Second the system should have a single point house ground For example on a general system connect the NIM Bin to house ground via the ac line cord Isolate all other equipment requiring ac voltage from the house ground Connect all chassis in the system to the grounded NIM Bin using heavy braided wire SCA Operation High voltage power supplies generally the HVPS should float from power line ground with the only ground being made at the preamplifier through the high voltage connecting cable Analyzer EMI if the detector is located within
13. 2100X and 2 us SHAPING PULSE SHAPING Near Gaussian shape one differentiator two active integrators and only one secondary time constant time to peak 1 75 X shaping time constant RESTORER Active gated SPECTRUM BROADENING FWHM of a Co 1 33 MeV gamma peak for an in coming count rate of 2 kcps to 50 kcps and a 9 V pulse height will change less than 16 These results may not be reproducible if associated detector exhibits an inordi nate amount of long rise time signals PEAK STABILITY The peak position of a Co 1 33 MeV gamma peak for an in coming count rate of 2 kcps to 50 kcps and a 9 V pulse height will shift less than 0 025 41 Specifications SCA By resetting an internal jumper the SCA OUTPUT can be used as an SCA referenced to the AMP OUTPUT crossing the LOWER LEVEL E discriminator or as a Timing SCA referenced to the leading edge of the amplified preamp signal shipped in the Timing SCA mode TSCA OUTPUT TIMING 200 ns from the peak of the AMP OUT signal TSCA OUTPUT WALK lt 50 ns for a 50 1 change in the AMP OUTPUT signal amplitude INTEGRAL NONLINEARITY 0 25 of full scale range for LOWER LEVEL E and WINDOW AB PULSE PAIR RESOLUTION With the SCA driven from a rectangular shaped pulser for LOWER LEVEL E thresholds 2100 mV the pulse pair resolution is lt 500 ns over the full linear range for the DISC LLD OUTPUT TEMPERATURE DRIFT E and AE lt 0 005 of full scal
14. 32 FINE GAIN Ten turn precision potentiometer selects variable gain factor from X3 to X10 Resetability within 0 03 INPUT POLARITY Toggle switch to set the Model 2015A for the polarity of the incoming preamplifier signal ime range of 30 usec to LOWER LEVEL E Ten turn precision potentiometer to WINDOW AE select a baseline from 0 1 volts to 10 volts for the Timing SCA mode and 0 15 mV to width from 24 mV 10 volts for the SCA o 10 volts or mode 24 mV to 1 volt depending on the rear panel AE LOWER LEVEL RANGE switch INDICATOR Aids the operator in setting the LOWER INPUT LEVEL E control Accepts positive or negative linear pulses from associated preamp Signal requirements are amplitude 0 to 12 volts maximum rise time less than shaping time constant decay time constant 30 usec to Z approximately 1 kilohm AMP OUTPUT Provides a positive near Gaussian linear output pulse active filter pulse shaping ust above the noise level SCA OUTPUT Provides a positive logic pulse for each amplifier event that alls within the SCA window The pulse is delayed approximately 200 nanoseconds past he peak of the AMP OUTPUT signal Reference Appendix A tor signal specifications Reference Appendix A for signal specifications Figure 2 Front Panel Controls and Connectors Rear Panel Rear Panel This is a brief description of the 2015A s rear panel connectors For
15. AMP OUTPUT and adjust the square wave generator s amplitude control attenuator for output signals of 10 volts Both positive and negative near Gaussian linear pulses will be observed at the output f Reduce the scope vertical sensitivity to 50 mV cm See Note 1 on page 11 Figure 9 shows the correct setting of the pole zero control Figures 10 and 11 show under and over compensation respectively for the preamplifier decay time constant As illustrated in Figure 9 the AMP OUTPUT signal should have a clean return to the baseline with no bumps overshoots or undershoots Spectroscopy System Operation Figure 9 Correct Pole Zero Compensation Figure 10 Undercompensation Pole Zero Scope Vertical 50 mV cm Horizontal 0 2 us cm Source Square wave pulse and preamp test input Figure 11 Overcompensation Pole Zero Note 1 HPGe detectors and Si Systems with Optical Feedback Preamps For normal Si Systems the pole zero is usually set at fully counterclockwise However on some systems the pole zero may need to be slightly tweaked for optimum overload recovery when responding to the preamps reset pulse At high Count rates the pole zero adjustment is extremely critical for main taining good resolution and low peak shift For precise and optimum pole zero setting a scope vertical sensitivity of 50 mV cm should be used 11 12 Operating Instructions Higher scope sensitivities can
16. LD DISC A13 outputs is extracted by the subsequent pulse former circuits Jumper plug J6 selects the FAST DISCriminator of LLD DISCriminator to trigger the timing monostable A7a When A7a times out its subsequent pulse former triggers mono stable A71b If monostable A7b was enabled it will generate as SCA OUTPUT pulse 30 Description of Circuit The enable for monostable A7b is generated by the LLD DISCriminator setting flip flop A6b A6c At the conclusion of the SCA OUTPUT pulse flip flop A6b A6c is cleared via A8a and Ab If the AMP OUTPUT pulse exceeds the ULD reference volt age its OUTPUT clears timing monostable A7a and flip flop A6b A6c terminating the SCA OUTPUT pulse cycle The SCA OUTPUT driver provides the additional drive capability required for driving 50 ohm terminated lines The SCA OUTPUT pulse is connected to the front and rear panel BNC connectors J2 and J103 respec tively through 47 ohm resistors Monostable A11b is triggered by the LLD or ULD DISCriminators selected by J7 pro viding the respective OUTPUT DISC pulse at BNC J104 With the aid of jumper plugs J8and J5 the rear panel DISC BNC J104 can also be used as an LLD sweep input The timing monostable trigger pulse OUTPUT of A8c or A6a also triggers mono stable Alla providing a drive signal for LED DS1 LED DS is provided asa visual aid for setting the LOWER LEVEL E control Description of Circuit Gain Amplifier Most of the gain K1 and K2 is
17. Model 2015A Spectroscopy Amplifier Timing SCA 9231694B 01 05 User s Manual ISO 9001 SYSTEN C E CERTIFIED Copyright 2005 Canberra Industries Inc All rights reserved The material in this document including all information pictures graphics and text is the property of Canberra Industries Inc and is protected by U S copyright laws and international copyright conventions Canberra expressly grants the purchaser of this product the right to copy any material in this document for the purchaser s own use including as part of a submission to regulatory or legal authorities pursuant to the purchaser s legitimate business needs No material in this document may be copied by any third party or used for any commercial purpose or for any use other than that granted to the purchaser without the written permission of Canberra Industries Inc Canberra Industries 800 Research Parkway Meriden CT 06450 Tel 203 238 2351 FAX 203 235 1347 http www canberra com The information in this document describes the product as accurately as possible but is subject to change without notice Printed in the United States of America Table of Contents 1 Introduction AADDIICQ I OS ta SS ES ETS a BS da RA ESA Low Level 10 Counting System si A e OEE RS 2 Controls and Connectors Eront Panel exorcista ra T SQ AA AA E NN 3 Operating Instructions Spectroscopy System Opera Resolution Versus Count Rate and Shapidg
18. NDOW AE settings and repeat steps 7 and 8 a plot of the AMP OUTPUT versus LOWER LEVEL E or WINDOW AE settings will give the linearity curves which should be within 0 25 of full scale or 25 mV Connect channel 2 of the oscilloscope to the rear panel DISC output When the AMP OUTPUT signal on channel 1 of the oscilloscope exceeds the LOWER LEVEL E discriminator setting a positive logic pulse will appear Change the DISC A jumper plug to the ULD position Monitor the rear panel DISC output with channel 2 of the oscilloscope When the AMP OUTPUT Reference Data on Cables signal on channel 1 of the oscilloscope exceeds the LOWER LEVEL E plus the WINDOW AE discriminators a positive logic pulse will appear Change the DISC A jumper plug back to the LLD position 12 Change the DISC B jumper plug to the IN position and the LLD jumper plug to the EXT position The LOWER LEVEL E discriminator function will no longer be controlled by the front panel LOWER LEVEL E control The function will now be controlled by an external voltage of O to 10 volts at the rear panel DISC BNC Change the DISC B jumper plug back to the OUT position and the LLD jumper plug to the INT position Reference Data on Cables Figures 14 and 15 show a typical output pulse at the load end of the designated RG 58 cable and the same point using RG 62 cable In each case Figures 14 and 15 show high impedance 1 kQ and 50 Q termination conditions Clearly th
19. RSE GAIN setting The amplitudes should reduce proportionately with each COARSE GAIN setting Set the 2015A CORSE GAIN to 128 Monitor the AMP OUTPUT on the scope and turn the 2015A FINE GAIN control to minimum The signal amplitude should decrease by approximately 2 3 Return the FINE GAIN to maximum ks Set the 2015A to 2 us shaping Set the 1407 ATTENUATION to X500 Adjust the 1407 PULSE HEIGHT until the AMP OUTPUT pulse attains an amplitude of 9 9 to 10 1 volts Observe the AMP OUTPUT pulse on the scope For each of the shapings 2 0 us and 0 5 us the unipolar pulse should appear as in Figure 19 Noise Measurement Figure 19 AMP OUTPUT Showing a an Unipolar Pulse Noise Measurement 1 Set the 2015A controls as follows COARSE GAIN 16 SHAPING 2 us Connect a 93 ohm terminator to the 2015A rear panel signal INPUT BNC connector Put side covers on the Model 2015A Using RG 62 coax cable connect one side of the tee connector to the Model 1407 pulser ATTEN OUTPUT Using RG 62 coax cable connect the other end of the tee connector to the scope input You will observe a positive tail pulse on the scope Set the 1407 ATTENUATION to X10 and adjust the 1407 PULSE HEIGHT until the tail pulse attains an amplitude of 100 mv Monitor the 2015A AMP OUTPUT on the scope and adjust the pole zero for no under or overshoots see Figure 18 Adjust the 2015A FINE GAIN for an OUTPUT pulse am
20. about 6m 20 feet of a multichannel analyzer containing a ferrite core memory it can receive EMI electro magnetic interference This is due to high memory core currents during the memory cycle of the analyzer The only practical cure for this problem is to operate the analyzer in the Live Mode of accumulation In this way the memory cycle only operates while no signal is being analyzed Is the output of the spectroscopy amplifier and the input of the ADC fully compatible This may seem an obvious consideration but it is commonly overlooked The shaping time constant as stated on the spectroscopy amplifier is not the rise time of its output signal In the case of a Model 2015A Amplifier the time to peak of the AMP OUTPUT is 1 75X the shaping time constant Therefore a 12 us shaped pulse required 21 usec to reach full amplitude Many analyzers will not handle this instead of analyzing the peak of the signal they analyze a percentage of the rise time Amplifier parasitic oscillations If the cable connecting the front panel outputs of the amplifier to the ADC exceed about 3m 10 feet in length oscillations can occur The cure is to use RG 62 cable 93 ohm impedance and terminate the ADC end of the cable with a 93 1 ohm metal film resistor Alternatively the 93 ohm output impedance of the amplifier can be used with no terminator SCA Operation Setup Connect the INPUT of the 2015A to the ATTEN OUTPUT of a reference pulser such
21. accomplished before the integration occurs As a re sult the input amplifier K1 is the dominant noise source Each of the two gain stages operate at relatively low closed loop gains providing stable operation with time and temperature Amplifiers K1 Q14 through Q19 and K2 Q8 through Q13 are both basically the same configuration Therefore only K1 will be fully described The differential input pair Q19 drives the common base transistors Q18 and Q15 Transistors Q18 and 015 operate at low current levels providing a high OUTPUT im pedance to drive the OUTPUT transistors Q17 and Q14 through the common source FET Q16 The necessary current to drive the FET and circuit capacitance at high fre quencies is derived directly from the input transistor Q19 through the low impedance of Q18 and Q15 This gives a typical slew rate for the amplifier of 140 volts per mi crosecond C12 provides feedback for closed loop stability and allows the amplifier to follow a 100 nanosecond rise time input signal with very low distortion Since the gain amplifiers do not require dc stability and are operated as inverting amplifiers a con stant current source is not needed in the emitters of Q19 Transistors Q17 and Q14 are biased on by R30 and R33 with the junction of R31 and R32 providing the low im pedance OUTPUT 31 Circuit Description Input Amplifier K1 The differentiation network POLE ZERO cancellation circuitry and INPUT POLARITY selection are loca
22. also provides a temperature compensation for Q27 The ULD Cal pot RV8 is adjusted for 4 volts across RV6 Pin2 of the WINDOW AE potenti ometer is connected to the OUTPUT of the LOWER LEVEL E discriminator buffer amplifier A15 thus the voltage developed across RV6 is summed with the LOWER LEVEL reference voltage Some fraction of this additive voltage is picked off using RV6 buffered by A10 and connected to A9 pin 2 providing the WINDOW AE ref erence voltage Resistors R122 R123 and diode D20 form a 5 volt clamp preventing the buffer Amp OUTPUT A10 from exceeding 5 volts RV9 nulls out the window buffer amp A10 OUTPUT offset Fast Discriminator Reference Voltage Op amp A16 generates a reference voltage having a nonlinear characteristic for fast discriminator A14 R109 through R1 13 sets up a bias voltage of approximately 80 mV When the LOWER LEVEL E discriminator is less than 100 mV diode D19 be comes reversed biased and the junction of R110 and R1 09 is held at approximately 80 mV This is attenuated to approximately 20 mV by R109 and R1 13 and repre sents 90 mV when referenced to the AMP OUTPUT signal Diode D18 clamps the OUTPUT of A16 pin 6 to 600 mV preventing A16 from saturating As the LOWER LEVEL E control is increased above 100 mV diode D19 begins to conduct increas ing the fast discriminator reference voltage Further increases in the LOWER LEVEL E control cause further increases in the fast discrim
23. and measure the leading edge walk It should be 50 nsec maximum SCA Operational Checks 4 Move the MODE jumper to the SCA position Adjust the 1407 PULSE HEIGHT for a 2015A AMP OUTPUT of 10 volts Vary the LOWER LEVEL E discriminator the SCA OUTPUT pulse will move in time as a function of the LOWER LEVEL E discriminator 1 e the SCA is no longer a timing SCA Set the MODE jumper plug back to the TSCA position External Lower Level Check 1 Place the LLD jumper plug in the EXTernal position and the DISC B jumper in the IN position 2 With a jumper wire connect the 5 volt supply to the rear panel Disc BNC 3 Adjust the 1407 PULSE HEIGHT for a flickering SCA OUTPUT 4 Measure the AMP OUTPUT amplitude it should be 4 5 to 5 5 volts Normal Internal Control Settings Verify that the shaping switch and all jumper plugs are in the desired position before replacing the side covers The following listing is a guide to the usual positions of the jumpers see Figure 4 Zout 0 LLD INT SCA MODE TSCA DISC A LLD DISC B OUT SHAPING 2 us 29 Circuit Description 5 Circuit Description This section of the manual contains a description of the circuitry used in the Model 2015A Amplifier Timing SCA Components are referred to by reference designa tions such as Q2 C5 and R10 Throughout the following circuit analysis refer to the block diagram and circuit schematics located in the drawings section Block Diagram Description
24. as the Canberra Model 1407 Connect the AMP OUTPUT signal to channel 1 of an oscilloscope Connect the SCA OUTPUT to channel 2 of an oscilloscope Simultaneously observe both outputs on the oscilloscope or observe the AMP OUTPUT on a multichannel analyzer Set the oscilloscope vertical sensitivity for 5 V cm and sweep speed to 1 us cm Set the 2015A controls as indicated below SHAPING 2 us 15 4 10 11 16 Operating Instructions COARSE GAIN 16 FINE GAIN 2 2 INPUT POLARITY Pos LOWER LEVEL E 5 00 WINDOW E 1 00 AE RANGE 10 V Set thp internal jumpers as indicated below Disc A LLD Disc B OUT Mode TSCA LLD INT Set the 1407 pulser output polarity to POS Adjust the 1407 pulser PULSE HEIGHT until the 2015A AMP OUTPUT attains an amplitude of 4 volts Adjust the 2015A pole zero as outlined in Performance Adjustments on page 8 Slowly increase the pulser PULSE HEIGHT until the 2015A SCA OUTPUT 1s just observed Measure the AMP OUTPUT visually on the oscilloscope or on a calibrated multichannel analyzer and compare with the LOWER LEVEL E setting The AMP OUTPUT signal should have an amplitude of 5 0 0 1 volts Increase the 1407 PULSE HEIGHT until the 2015A SCA OUTPUT just begins to disappear Again measure the AMP OUTPUT visually on the oscilloscope or on a calibrated multichannel analyzer The AMP OUTPUT signal should have an amplitude of 6 0 0 1 volts Very the LOWER LEVEL E and WI
25. ase of defective software or equipment either repair or replace the software or equipment or B in the case of defective services reperform such services LIMITATIONS EXCEPT AS SET FORTH HEREIN NO OTHER WARRANTIES OR REMEDIES WHETHER STATUTORY WRITTEN ORAL EXPRESSED IMPLIED INCLUDING WITHOUT LIMITATION THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE OR OTHERWISE SHALL APPLY IN NO EVENT SHALL CANBERRA HAVE ANY LIABILITY FOR ANY SPECIAL EXEMPLARY PUNITIVE INDIRECT OR CONSEQUENTIAL LOSSES OR DAMAGES OF ANY NATURE WHATSOEVER WHETHER AS A RESULT OF BREACH OF CONTRACT TORT LIABILITY INCLUDING NEGLIGENCE STRICT LIABILITY OR OTHERWISE REPAIR OR REPLACEMENT OF THE SOFTWARE OR EQUIPMENT DURING THE APPLICABLE WARRANTY PERIOD AT CANBERRA S COST OR IN THE CASE OF DEFECTIVE SERVICES REPERFORMANCE AT CANBERRA S COST IS YOUR SOLE AND EXCLUSIVE REMEDY UNDER THIS WARRANTY EXCLUSIONS Our warranty does not cover damage to equipment which has been altered or modified without our written permission or damage which has been caused by abuse misuse accident neglect or unusual physical or electrical stress as determined by our Service Personnel We are under no obligation to provide warranty service if adjustment or repair is required because of damage caused by other than ordinary use or if the equipment is serviced or repaired or if an attempt is made to service or repair the equipment by other than our Service Personn
26. c _ ANECA Figure 4 Internal Controls Spectroscopy System Operation 3 Operating Instructions The purpose of this section is to familiarize you with the operation and controls of the Model 2015A Amplifier TSCA so that best performance can be obtained Since it is difficult to determine the exact system configuration in which the module will be used explicit operating instructions cannot be given However if the following procedures are carried out you will gain sufficient familiarity with this instrument to permit its proper use in the system at hand Spectroscopy System Operation Setup A block diagram of a typical Canberra gamma spectroscopy system is shown in Figure J Soc O 7229 Ge Li Detector y source Monitor Scope Figure 5 Typical Gamma Spectroscopy System 1 Prior to installation and setup the internal jumper plugs should be set to their desired positions See Figure 4 Internal Controls on page 6 The Zour jumper plug controls the output impedance of the front panel only AMP OUTPUT The output impedance can be changed from 0 ohms Operating Instructions to 93 ohms The 2015A is shipped with the front panel output impedance set for lt 1 ohm The rear output has a fixed output impedance of approximately 93 ohms series connected When using the front panel low impedance output short lengths of interconnecting coaxial cable need not be terminated To prevent possible oscilla
27. cable access Blank panels to cover open front panel Bin area Compliant grounding and safety precautions for any internal power distribution The use of CE compliant accessories such as fans UPS etc Any repairs or maintenance should be performed by a qualified Canberra service representative Failure to use exact replacement components or failure to reassemble the unit as delivered may affect the unit s compliance with the specified EU requirements 44 A CANBERRA Warranty Canberra we us our warrants to the customer you your that for a period of ninety 90 days from the date of shipment software provided by us in connection with equipment manufactured by us shall operate in accordance with applicable specifications when used with equipment manufactured by us and that the media on which the software is provided shall be free from defects We also warrant that A equipment manufactured by us shall be free from defects in materials and workmanship for a period of one 1 year from the date of shipment of such equipment and B services performed by us in connection with such equipment such as site supervision and installation services relating to the equipment shall be free from defects for a period of one 1 year from the date of performance of such services If defects in materials or workmanship are discovered within the applicable warranty period as set forth above we shall at our option and cost A in the c
28. d AMP OUTPUT TP1 to0 5 mV dc SCA Section SCA OUTPUT In the following discussion Logic T is referred to as a high voltage level of 2 4 to 5 volts A Logic 0 is referred to as a low voltage level of O to 0 8 volts 33 34 Circuit Description The OUTPUT of GAIN AMP K2 is ac coupled through C64 to the fast discriminator A14 The differentiated signal is also attenuated by 2 5 through resistors R126 and R127 If the signal exceeds the fast discriminator threshold A14 pin 2 its OUTPUT goes to a logic 1 which drives the pulse former Al2d and A8c If the SCA mode jumper plug J6 is in the TSCA position the OUTPUT of A8c is inverted by Al2e and connected to the true input of A7a The positive trigger pulse sets A7a s OUTPUT to a logic 0 R146 and C78 prevent A7a from retriggering on multiple inputs The time duration A7a remains set is determined by shaping switch S3 B1 through B3 com ponent R143 R144 RV11 RV12 and C76 The OUTPUT of A7a will return to a logic 1 approximately 200 nanoseconds past the peak of the AMP OUTPUT signal Longer SCA OUTPUT delays are obtainable by readjusting RV11 and RV12 for 2 us and 0 5 us shaping respectively When monostable A7a times out and its OUTPUT returns to a logic 1 A7b pin 9 is triggered from the positive transition supplied by pulse former A8d and A12b If en abled by flip flop A6b A6c monostable A7b generates a 500 nanosecond SCA OUTPUT pulse Th
29. dth module the functions of a spectroscopy amplifier and a timing single channel pulse height analyzer The Model 2015A Amplifier TSCA uses integrated circuit construction for maximum reliability and simplicity The entire unit is designed to optimize energy resolution in spectroscopy applications with Ge and Si detectors even at high count rates The am plifier s restorer includes circuitry for use with optical feedback preamplifiers The Model 2015 s broad gain range X12 to X1280 makes it equally compatible with high purity Ge scintillation photomultipliers gas proportional and surface barrier detec tors The usefulness and application of the Canberra Model 2015A is enhanced by the fol lowing unique design features not found in comparable amplifiers internally selectable shaping time constants of 0 5 us or 2 us count rate optimization with Can berra s unique gated restorer front panel pole zero adjustment a ten turn fine gain control and low noise design less than 7 microvolts referred to the input at 2 ms shaping The Model 2015A is further enhanced by the addition of a timing SCA contained in the same package offering two modes of single channel pulse height energy analy sis In the SCA mode of operation an SCA OUTPUT is generated whenever the peak value of the unipolar falls between the energy levels defined by the front panel LOWER LEVEL E and WINDOW AE settings In the Timing TSCA mode the SCA OUTPUT is generat
30. e C 50 ppm POWER SUPPLY SENSITIVITY Both discriminators are referenced to the 12 and 24 V Bin supplies Connectors SIGNAL CONNECTORS BNC type PREAMP POWER Rear panel Amphenol 17 10090 Power Requirements 24 V de 50 mA 12 V de 160 mA 24 V de 50 mA 12 V de 70 mA Physical SIZE Standard single width NIM module 3 43 x 22 12 cm 1 35 x 8 71 in per DOE ER 0457T 42 Environmental NET WEIGHT 1 1 kg 2 5 Ib SHIPPING WEIGHT 2 3 kg 5 0 Ib Environmental OPERATING TEMPERATURE 0 to 50 C RELATIVE HUMIDITY Up to 80 non condensing Tested to the environmental conditions specified by EN 61010 Installation Category I Pollution Degree 2 43 Installation Considerations B Installation Considerations This unit complies with all applicable European Union requirements Compliance testing was performed with application configurations commonly used for this module i e a CE compliant NIM Bin and Power Supply with additional CE com pliant application specific NIM were racked in a floor cabinet to support the module under test During the design and assembly of the module reasonable precautions were taken by the manufacturer to minimize the effects of RFI and EMC on the system However care should be taken to maintain full compliance These considerations include A rack or tabletop enclosure fully closed on all sides with rear door access Single point external
31. e AMP OUTPUT signal is attenuated by 2 5 and connected to the LOWER LEVEL and the WINDOW discriminators A13 and A9 respectively If the AMP OUTPUT signal crosses the LLD discriminator threshold its OUTPUT A13 pin 7 goes to a logic l Pulse former Al 2a and A6a extracts the positive transition and sets flip flop A6b A6c The OUTPUT of A6c pin 8 is inverted by Al 2f and enables A7b to generate the internally selectable by J4 The low OUTPUT impedance can 500 nanosecond SCA OUTPUT pulse when triggered If the AMP OUTPUT signal also exceeds the WINDOW AE discriminator threshold the SCA OUTPUT pulse is aborted Flip flop A6b A6c is reset removing A7b s enable and clearing A7a ending its time out A8a and A8b also monitor the SCA OUTPUT and during each OUTPUT pulse reset flip flop A6b A6c and monostable A7a arming them for the next cycle The OUTPUT of monostable A7b is inverted by Q20 with Q21 and Q22 forming a pair of complementary low OUTPUT impedance emitter followers The SCA OUTPUT pulse is brought out through the two 47 ohm resistors R164 and R165 to the front and rear BNC connectors respectively The SCA OUTPUT is nominally 5 volts unterminated however will increase to approximately 8 volts unterminated is re sistor Rp 3 9 k ohms is removed When in the TSCA mode monostable A1 1a is triggered by the fast discriminator A14 OR Lower Level discriminator A13 The OR function is made possible by diodes D25 and D26 W
32. e fastest cleanest pulse is realized with the RG 58 cable With the source match provided loading ef fects are limited to amplitude changes only RG 58 cable is therefore recommended for best compatibility with the DISC and SCA OUTPUTS RG 58 cable Rsource 50 ohms Upper Trace Rioag Lk ohms Lower Trace Rioaa 50 ohms Scope Horizontal 0 1 us cm 17 18 Operating Instructions l La Figure 14 Typical Output Pulse Using a RG58 U Cable RG 62 cable Rsource 50 ohms Upper Trace Rioad 1k ohms Lower Trace Rioad 50 ohms Scope Horizontal 0 1 us cm Figure 15 Typical Output Pulse Using a RG62 U Cable Preventative Maintenance The Figure 16 shows the same pulses with a source mismatch caused by driving the cables with the transistor switches directly The waveforms indicate how important and effective source matching is in eliminating instabilities which cause phenomena such as multiple counting or triggering For this reason the Model 2015A provides source matched outputs 0 1 usec cm Figure 16 Typical Output Pulse with a Source Mismatch Upper Trace Riva4 Lk ohms Lower Trace Rioaa 50 ohms Scope Horizontal 0 1 us cm Preventative Maintenance Preventative maintenance is not required for this unit When needed the front panel of the unit may be cleaned Remove power from the unit before cleaning Use only a soft cloth dampened with warm
33. ed for the same E and AE conditions except that it is time referenced to the preamp s leading edge This develops a true leading edge timing technique while minimizing timing jitter In addition to the SCA output the Model 2015A offers a multifunction DISC connec tor which can be used as a LOWER LEVEL E discriminator output an Upper Level E AE discriminator output or an LLD SWEEP input One of the three modes is in ternally selected with jumper plugs The Model 2015A has one additional unique feature a LED indicator electronically linked to the LOWER LEVEL E control The LED indicator is a visual means of ad justing the LOWER LEVEL E control above the system noise level Both the LOWER LEVEL E and WINDOW AE controls are ten turn potentiom eters for maximum accuracy resolution and resetability A rear panel switch controls the WINDOW E range 0 to 10 volts or O to 1 volt Introduction Applications This section is not intended as a complete survey of applications It is intended to highlight the most important features of the module and to indicate representative ar eas where they might be applied The Model 2015A overcomes the past necessity of using two individual modules an amplifier and single channel analyzer by performing both tasks in one convenient sin gle width module The amplifier s two selectable time constants 0 5 us for high count rates and 2 us for optimum resolution makes it useful for Nal
34. el without our prior approval Our warranty does not cover detector damage due to neutrons or heavy charged particles Failure of beryllium carbon composite or polymer windows or of windowless detectors caused by physical or chemical damage from the environment is not covered by warranty We are not responsible for damage sustained in transit You should examine shipments upon receipt for evidence of damage caused in transit If damage is found notify us and the carrier immediately Keep all packages materials and documents including the freight bill invoice and packing list Software License When purchasing our software you have purchased a license to use the software not the software itself Because title to the software remains with us you may not sell distribute or otherwise transfer the software This license allows you to use the software on only one computer at a time You must get our written permission for any exception to this limited license BACKUP COPIES Our software is protected by United States Copyright Law and by International Copyright Treaties You have our express permission to make one archival copy of the software for backup protection You may not copy our software or any part of it for any other purpose Revised 1 Apr 03
35. h S3 sections Cl C2 C3 and El E2 and E3 for the desired time constant Amplifier AS is a wide band high slew rate integrated circuit operational amplifier It is connected in a non inverting configuration with a de gain of 2 determined by R5 and R The OUTPUT of integrator A5 is connected through an RC filter network R17 R24 and C15 back to the summing junction of gain amplifier K2 The integrator also serves as a buffer providing the necessary de stabilization for gain amp K2 Amp OUTPUT Integrator and Driver The unipolar OUTPUT amplifier is comprised of A3 and a power OUTPUT driver QI Q2 and 03 Integrated circuit A3 is a wide band high slew rate operational amplifier The overall amplifier op amp and driver provides an inverting gain of 2 with single pole integration C25 C26 and R35 to minimize noise introduced after the ACTIVE INTEGRATOR AS The OUTPUT driver transistors are connected Class AB Diodes D11 D14 and cur rent source Q2 form the biasing network for the OUTPUT transistors SCA Section Diodes D12 and D13 provide short circuit protection With an improper load con nected to the OUTPUT the voltage drop across R71 and R72 forward bias diodes D12 and D13 respectively For this condition the respective OUTPUT transistor is by passed the OUTPUT current is derived from the op amp and limited to approximately 200 mA Diodes D9 and D10 provide limiting preventing OUTPUT transistors satu ration wh
36. hen in the SCA mode the fast discriminator is not used and monostable Alla is triggered by the Lower Level discriminator only Monostable Alla provides a drive signal for the front panel LOWER LEVEL E LED Its time constant is approximately 100 us allowing the LED to be discernible to the eye when indicating amplifier input events The front panel LED is a user aid determining the noise threshold of both the fast and LLD discriminators SCA Section When the SCA MODE jumper plug J is in the SCA position the timing monostable A7a is now triggered from the LLD discriminator The SCA OUTPUT will be gener ated as before however the timing information is lost The timing monostable trigger point is now dependent on the AMP OUTPUT signal rise time and LOWER LEVEL E discriminator setting Disc Output Depending on the DISC A J7 jumper plug position the DISC OUTPUT can provide LLD or ULD information With the DISC A jumper plug J7 in the LLD position DISC monostable A11b is triggered from the lower level discriminator through pulse former Al2a and A6a Monostable A11b generates a 500 nanosecond pulse every time the AMP OUTPUT signal crosses the LOWER LEVEL E discriminator threshold If the DISC A jumper plug J7 is in the ULD position monostable A11b is triggered through inverter A12c from the WINDOW discriminator Monostable A11b is in verted by Q23 with Q24 and Q25 forming a pair of complementary low OUTPUT im pedance emitter f
37. ich prohibits base emitter charge storage enhancing good overload recover Two AMP OUTPUTS are provided The front panel OUTPUT provides either lt 1 ohm or 93 ohm OUTPUT impedance drive up to 10 feet of 93 ohm coax cable where the 93 ohm OUTPUT can drive a few hundred feet The rear panel has a fixed 93 ohm series connected OUTPUT impedance Restorer The restorer circuitry consists of OUTPUT amplifier A3 transistor array Al a dual differential comparator A2 and transistors Q4 through Q7 Q29 and Q30 The restorer is a transconductance type amplifier that is it monitors the AMP OUTPUT TP1 OUTPUT voltage and develops a constant current of correct polarity at its OUTPUT junction of Q4 collector and Ale pin 15 The voltage on C24 is buffered by FET Q6 and summed in at A3 pin 3 forcing the AMP OUTPUT TP1 to 0 volts maintaining the baseline The AMP OUTPUT signal TP1 is clamped by diode network D15 and D16 and connected to the comparator input A2 pins 5 and 2 If A2 detects a signal its OUTPUT turns Q29 off Q7 switches on a current sufficient to back bias current source Ala disabling the restorer Capacitor C40 ac couples the transistor Q29 pre venting potential restorer latch up problems The negative restorer gate threshold is set at 100 mV by resistors R103 and R100 The positive threshold is variable and depends on the coarse gain switch setting Sla section R2 and resistors R94 through R99 Pot RV3 adjusts the restorer offset an
38. iling edge of the unipolar pulse returns to the baseline with no over or undershoots Spectroscopy System Operation Figure 6 shows the correct setting of the pole zero control with Figures 7 and 8 show ing under and over compensation respectively for the preamplifier decay time con stant Notice some small amplitude signals with long decay times in Figure 6 These are due to charge trapping in the detector and cannot be corrected by the pole zero control Figure 6 Correct Pole Zero Compensation Figure 7 Undercompensated Pole Zero Scope Vertical 50 mV cm Horizontal 10us cm Source Co 1 33 MeV peak 9 V amplitude Count rate 3kcps Shaping 2 us Figure 8 Overcompensated Pole Zero 10 Note Operating Instructions Pole zero adjustment using a square wave and preamp test input See note 2 on page 12 Driving the preamp test input with a square wave will allow a more precise adjustment of the amplifier pole zero a The Amplifier s controls should be basically set for its intended application COARSE GAIN shaping INPUT POLARITY b Adjust the square wave generator for a frequency of approximately 1 kHz c Connect the square wave generator s output to the preamp s TEST INPUT d Remove all radioactive sources from the vicinity of the detector e Set the scope s channel 1 vertical sensitivity to 5 volts cm and adjust the main time base to 0 2 ms cm Monitor the 2015A s
39. inator reference voltage This re lationship continues until the junction of R110 and R109 reaches approximately 600 mV at which point diode D17 becomes forward biased clamping the amplifier OUTPUT Op amp A16 will no longer track the LLD control the fast discriminator reference voltage has reached its upper limit 600 mV at the junction of R109 and R110 is approximately 158 mV between pins 2 and 3 of the fast discriminator and rep resents approximately 700 mV when referenced to the AMP OUTPUT The nonlinear fast discriminator references voltage characteristic allows the LOWER LEVEL E control to adjust the fast discriminator just above the noise region while maintaining optimum timing performance 5 Volt Power Supply Resistors R170 and R39 attenuate the 12 V power supply to 5 volts Diode D24 com pensates for temperature related Vj variations of transistor Q26 Transistor Q26 is an emitter follower and supplies the necessary 5 volt current Resistor R171 acts as a current limiter protecting the 5 volt supply in the event of a short circuit Troubleshooting Troubleshooting The Model 2015A AMP TSCA is designed and constructed to provide reliable trou ble free service with normal usage and care in operation Should module malfunction occur the following information is provided to facilitate troubleshooting of the AMP TSCA Information contained in other sections of this manual should be used along with the following information to
40. l Checks 24 V de 23 98 to 24 02 V de 24 V de 23 98 to 24 02 V de 12 V dc 11 99 to 12 01 V de 12 D de 11 99 to 12 01 V de Current Measurements Apply power to the 2015A and measure the currents They should be within the fol lowing ranges 24 V dc 40 to 0 mA 12 V dc 150 to 170 mA 12 V de 60 to 80 mA 24 V de 40 to 60 mA Note A greater deviation in currents indicates a faulty unit Gross errors would probably be due to faulty or reversed capacitors shorted or open AMP Out put transistors etc Amplifier Operational Checks Setup 1 Set controls as follows Model 2015A Controls COARSE GAIN 4 FINE GAIN 10 SHAPING 2 us internal POLE ZERO fully CCW INPUT POLARITY POS 21 Model 1407 Controls PULSE HEIGHT NORMALIZE POS NEG LINE OFF 90 Hz RISE TIME FALL TIME ATTENUATION Performance Check 5 4 10 POS 90 Hz MIN 400 us X10 2 Connect a 93 or 100 ohm terminator to the 2015A rear panel INPUT 3 Connect the 1407 ATTEN OUTPUT to the 2015A front panel INPUT with RG 62 coax cable 4 Connect the 1407 NORMAL OUTPUT to the EXT TRIG input of the scope Set the scope triggering to EXT Outputs 1 Connect the AMP OUTPUT to the scope with RG 62 coax cable using a tee connector at the scope You should observe the near Gaussian shaped linear pulse shown in Figure 17 Amplitude 9 to 11 V Scope 2 V cm 2 psec
41. nts Both 2015A s use the DISC output to provide ULD in formation However the WINDOW AE control on the 2015A associated with the cosmic channel is set to 0 00 thus its threshold is equal to that provided by the LOWER LEVEL E control The equipment setup is simplified since the 2015A in ternal controls are set the same By utilizing the WINDOW AE function the cosmic channel 2015A provides LLD information The model 2015A s included in this instru mentation makes the Alpha Beta System a versatile accurate and cost effective sys tem DISC PREAMP SIGNAL GUARD a SCALER 2295 or Equivalent BSCALER Counters PREAMP SIGNAL SAMPLE Block Diagram of 2015A Application in Low Level a f Counting System Figure 1 Block Diagram of 2015A Application in Low Level o B Counting System Controls and Connectors 2 Controls and Connectors Front Panel This is a brief description of the 2015A s front panel controls and connectors For more detailed information refer to Appendix A COARSE GAIN Six position rotary switch selects gain factors of X4 X8 X16 X32 X64 and X128 multiplied by the FINE GAIN control settings POLE ZERO 22 turn screwdriver adjust potentiometer lo compensate for the undershoot caused by the preamplifier fall time constant Adjustable jor preamplifier tall Front panel ten turn recision potentiometer to select the window AMP TSCA O mu E COARSE GAIN 1
42. ollowers The DISC OUTPUT is nominally 5 volts unterminated however will increase to approximately 8 volts unterminated if resistor R 3 9k ohms is removed Lower Level E Threshold Circuit The raw 12 volts is attenuated by a 3 1 divider network composed of R114 RV4 and RV5 RV4 is calibrated so that 4 volts appears across RV5 Some fraction of this volt age is picked off using the LOWER LEVEL discriminator control RV5 and buf fered by the high input impedance amplifier A15 The OUTPUT of A15 provides the reference voltage for the LOWER LEVEL discriminator A13 When the DISC B jumper plug J8 is connected to the IN position and the LLD jumper plug J5 connected to the EXT position control of the LOWER LEVEL E discriminator is now possible by an external voltage source 0 to 10 volts through the rear panel DISC BNC The external sweep input voltage is attenuated by the 2 5 1 divider network R167 and R168 This voltage is buffered by amplifier Al 5 providing an external reference volt age for the Lower Level discriminator A13 RV7 calibrates the low end of the LOWER LEVEL E adjustment range 35 Circuit Description Window AE Threshold Circuits Here the raw 24 volts is used to generate the WINDOW E reference voltage Tran sistor Q27 is a current source generating a current through the WINDOW E control RV6 Resistors R118 pot RV8 and transistor Q28 are used to bias the current source Transistor Q28
43. p 1 Set the 2015A controls as follows LOWER LEVEL 1 0 WINDOW 12 LLD J5 INT SCA MODE J6 TSCA DISC A J7 ULD DISC B J8 OUT AE RANGE 10 COARSE GAIN 4 FINE GAIN MAX SHAPING 2 us 27 28 Outputs 1 Performance Check Connect the ATTEN OUTPUT of the 1407 to the 2015A INPUT Set the 1407 PULSER FALL TIME to 50 us RISE TIME to MIN ATTEN to X10 and the LINE OFF 90 Hz switch to 90 Hz Adjust the 1407 PULSE HEIGHT until the AMP OUTPUT on the 2015A attains an amplitude of approximately 9 volts Set the LOWER LEVEL E discriminator to 1 0 volts and the WINDOW AE discriminator to 10 0 volts Connect the SCA OUTPUT to the scope with RG 58 coax You should observe a positive logic pulse with the following parameters Amplitude 4 5 to 5 5 volts Width 350 to 650 nsec Rise Fall Time 25 nsec Max Place the DISC A jumper plug in the ULD position the DISC ULD OUTPUT should disappear Set the rear panel AE RANGE switch to 1V the DISC ULD OUTPUT should reappear Return the RANGE to 10 V The front panel LOWER LEVEL indicator should be dimly illuminated Timing Walk Test 1 Set the AE RANGE switch to 10 V LOWER LEVEL E discriminator to 0 10 volts and the WINDOW AE to 10 0 volts Adjust the Model 1407 PULSE HEIGHT until the AMP OUTPUT attains an amplitude of 10 0 volts or maximum with an SCA OUTPUT Observe the SCA OUTPUT leading edge on the scope Increase the 1407 ATTENUATION by X50
44. plitude of 9 9 to 10 1 volts Remove the tee connector and cables from the 2015A INPUT Leave the 93 ohm terminator on the rear panel INPUT Set the 1407 LINE OFF 90 Hz switch to OFF Connect the AMP OUTPUT to the Noise Meter with RG 62 coax cable and measure the noise It should be 0 58 mV maximum for an averaging meter and 0 66 mV for a true rms voltmeter 25 Performance Check Linearity Check 26 Integral nonlinearity is a measure expressed in percentage of maximum deviation when a straight line is compared to an OUTPUT versus input plot The OUTPUT is exercised over its full dynamic range A test for nonlinearity can be conducted using the resistive summing network shown in Figure 20 The test is performed by first adjusting the amplifier gain polarity and pulser attenua tion so that a negative ten volt NORMAL pulser OUTPUT produces a positive 10 volt amplifier OUTPUT The pulser NORMAL OUTPUT should be 10 volts coinci dent with the amplifier OUTPUT peak Next while observing the summing point on the oscilloscope the amplifier fine gain is carefully adjusted to bring the vertical gain should be set to obtain the desired resolution Figure 20 Test Setup Linearity Check Note The Model 1407 must be modified for a 20 V OUTPUT for this test When this condition is obtained turn the 1407 PULSE HEIGHT control downward from ten volts to the lowest level that will still trigger the oscilloscope and observe
45. rcuit note the trouble symptom The symptom often identifies the circuit in which the trouble is located When trouble symptoms appear in more than one circuit check affected circuits by taking voltage and waveform readings Incorrect operation of all circuits often indicates trouble in the power supply internal or external However defective components in the module can appear as a power supply trouble and may affect the operation of other circuits After the 37 Circuit Description defective circuit has been located proceed to locate the defective component s 5 Check Voltages and Waveforms Often the defective component s can be located by checking for the correct voltage or waveform in the malfunction circuit Logic levels and truth tables for the digital integrated circuits used in the instrument are given in the this chapter Component Replacement 38 All replacement parts should be direct replacements unless it is known that a different component will not adversely affect instrument performance Many components in the Model 2015A are standard electronic parts available locally However all parts can be obtained through Canberra Industries When ordering replacement parts from Can berra include the following information Instrument Model Number Instrument Serial Number A description of the part if electrical include circuit number A2 Q3 etc e Canberra part number if available Canberra schema
46. t rate increases the ef fects of pileup degrade the resolution much sooner The optimum shaping time con stant depends on the detector such as its size configuration and collection characteristics preamplifier and incoming count rate Below is a list of optimum shaping time constants for some other common detectors Spectroscopy System Operation Detector Optimum Shaping usec Scintillation Pholomultiplier 0 5 Gas Proportional Counters 0 5 through 2 Silicon Surface Barrier 0 5 through 2 Lithium Dialed Germanium Ge Li 2 through 4 Cooled Silicon 8 through 12 The Model 2015A is factory set for 0 5 or 2 us shaping time constants However the shaping time constants can be changed to 8 and 12 us to be compatible with cooled Silicon detectors Change the components as follows 1 Change C1 from 560 pF to 9100 pF 2 Change C2 from 1600 pF to 560 pF 3 Change R1 from 19 1 k ohms to 226 k ohms 4 Change R2 from 52 3 k ohms to 11 k ohms 5 Change C3 from 130 pF to 2000 pF 6 Change C4 from 360 pF to 1300 pF 7 Change C5 from 200 pF to 2400 pF 8 Change C6 from 510 pF to 1600 pF 9 Change C25 from 47 pF to 1000 pF 10 Change C26 from 200 pF to 510 pF 11 Change C76 from 390 pF to 1800 pF 12 Change R143 from 604 k to 499 k ohms 13 Change RV12 from 20 k to 50 k ohms All resistors are RN60Cs and capacitors are 1 silver mica or 1 ceramic NPO See Figure 13 13 Operating Instructions Figure
47. ted at the inverting input of K1 The SHAPING switch S3 sections S1 through S3 and P1 through P3 selects the passive differentiator capac itors C3 C4 and pole zero control RV1 sets the degree of pole zero compensation INPUT POLARITY is selected by switch S2 For input polarity gain is determined by R23 and R15 With input polarity the gain is determined by the combination of R23 R15 R12 and R13 Diode D1 is a fast switching protection diode for overload signals enhancing good overload recovery Gain Amplifier K2 Amplifier K2 is an inverting gain amplifier Its gain is controlled by the ratio of the se ries combination of input resistors R46 through R51 selected by the COARSE GAIN switch Sla section R1 and the feedback resistor R65 The base emitter of Q31 is re verse biased as a zener diode It and diodes D3 D4 and base collector of Q31 provide overload protection enhancing good overload recovery Capacitor C35 ac couples the signal to the amplifier summing junction Front panel control RV2 resistors R92 and R65 form the feedback network which controls the FINE GAIN function Integrator Amplifier A5 ACTIVE INTEGRATOR AS provides complex pole pairs where the locus of poles are equidistant from the abscissa on the S plane The real part of the complex poles equal that of the input differentiator The real pole of the last integrator is 1 6 times this value Active filter networks for A5 are selected by the SHAPING switc
48. the maximum difference between the baseline and the null point The integral nonlinearity of the amplifier under test is then equal to SCA Operational Checks Maximum deviation in volts x 2x 100 10 volts The maximum deviation must be less than 2 5 mV in order to meet the 0 05 specification As the input is decreased the amplifier gain should remain constant OUTPUT should decrease linearly whether or not it does is tested by comparing the OUTPUT to a sig nal known to decrease linearly with the amplifier input the pulser s direct OUTPUT meets this requirement since it is related to the amplifier input by a passive attenuator The factor of two must be included because the summing network also serves as a voltage divider decreasing the apparent deviation by a factor of two Note that nonlinearity and instability in the pulser OUTPUT do not enter into the mea surement because both direct and attenuated outputs will be affected identically save for negligible effect of the pulser s attenuator instabilities over the short time period required for the test Instabilities in the baseline level on the oscilloscope null point equal with the baseline The oscilloscope are due to oscilloscope triggering de level fluctuations and noise and need not be of concern in this test SCA Operational Checks If the SCA section of the 2015A needs to be recalibrated it is strongly suggested that the unit be sent back to the factory Setu
49. tic drawing number Inputs A Specifications Inputs Outputs INPUT Accepts positive or negative linear pulses from associated preamplifier am plitude 10 V divided by the selected gain 12 V maximum rise time less than shap ing time constant decay time constant 30 us to co Z 1 KQ front and rear panel BNC connectors AMP OUTPUT Provides prompt 10 V full scale unipolar OUTPUT active filter near Gaussian shaping dc restored dc level is factory calibrated to 0 5 mV dc short circuit protected front and rear panel BNC connectors front panel Zout lt 1 Q or 93 Q internally selectable rear panel Z ut 93 Q out SCA OUTPUT Provides a nominally 5 V unterminated 500 ns positive pulse de layed approximately 200 ns past the peak of the AMP OUTPUT signal rise time and fall time lt 25 ns Zout 50 Q BNC connectors located on front and rear panels short circuit protected OUTPUT amplitude can be changed to 8 V by means of an internal jumper Input Output DISC Rear panel BNC connector having a multi function capability lower level E DISCriminator OUTPUT upper level E AE DISCriminator OUTPUT or LLD SWEEP INPUT one of these three modes is internally selected with jumper plugs shipped in E position When used as Lower Level E DISCriminator OUTPUT Provides a positive 5 V unterminated 500 ns pulse rise time and fall time lt 25 ns Zout 50 Q the LLD pulse is generated when the posi
50. tions longer cable lengths should be terminated at the receiving end in a resistive load equal to the cable impedance 93 ohms for type RG 62 cable The rear panel 93 ohm output may be safely used with RG 62 cable up to a few hundred feet However the 93 ohm output impedance is in series with the load impedance and a decrease in the total signal range may occur For example a 50 loss will result if the load impedance is 93 ohms Insert the 2015A into a standard NIM BIN Preamp power is provided by a 9 pin connector located on the 2015A rear panel Allow the total system to warm up and stabilize Set the 2015A controls as indicated below SHAPING 2 ms internal COARSE GAIN 16 FINE GAIN 2 2 This will give approximately 9 volts output when using a preamp gain of 100 mV MeV and Co radioactive source Install a tee connector on the 2015A AMP OUTPUT Connect one end of the tee connector to the analyzer ADC input To fully exploit the count rate capabilities of the Model 2015A Amplifier the ADC should be direct coupled All Canberra ADC s are de coupled Connect the second end of the tee connector to an oscilloscope and monitor the AMP OUTPUT Performance Adjustments 1 The pole zero is extremely critical for good high count rate resolution See note 1 on page 11 Adjust the radiation source count rate between 2 kcps and 25 kcps While observing the AMP OUTPUT on the scope adjust the pole zero so that the tra
51. tive edge of the AMP OUT signal crosses the Lower Level E threshold setting OUTPUT amplitude can be changed to 8 V by internal jumper Upper Level E AE DISCriminator OUTPUT Same as lower level DISCriminator except the pulse appears when the AMP OUT signal crosses the threshold set by the sum of the LOWER LEVEL E and WINDOW AE controls 39 Controls Specifications LLD SWEEP INPUT Accepts 0 to 10 V input to externally control the SCA s lower level discriminator Z 5 1 KQ de coupled COARSE GAIN Rotary switch selects gain factors of X4 X8 X16 X32 X64 X128 FINE GAIN Ten turn precision locking dial potentiometer selects variable gain fac tor of X3 to X10 P Z Front panel multi turn screwdriver pole zero adjustment optimizes the amplifier baseline recovery and overload performance for the preamplifier fall time constant and the main amplifier pulse shaping chosen 30 us to preamp fall time constant range INPUT Toggle switch sets the Model 2015A for the polarity of the incoming preamplifier signal TIME CONSTANTS Internal pushbutton switch selects SHAPING TIME constant of 0 5 us or 2 0 us factory set to 2 0 us LOWER LEVEL E Ten turn locking dial precision potentiometer selects a base line from 0 1 V to 10 V for the timing SCA mode and 0 15 mV to 10 V for the nor mal SCA mode WINDOW AE Ten turn locking dial precision potentiometer selects window width from 0 to 10 V or
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