Model 419 Precision Pulse Generator Operating and Service Manual
Contents
1. by the setting of the polarity switch This control is ineffective when the reference voltage switch is in the EXT position ATTENUATION FACTOR The attenuation switches control pi attenuators in the attenuated output line The maximum attenuation is 2000 1 The attenuation factor switches have an accuracy controlled by 0 1 metal film resistors and depend upon the attenuated output being terminated in 100 RISETIME The rise time of the attenuated output signal is controlled by this 6 position switch The rise time marked on the front panel is elapsed time for amplitude rise from 10 to 90 of the peak value See Section 6 1 for test performance data on pulse waveforms REFERENCE VOLTAGE The reference voltage switch allows external reference voltage to be supplied to the mercury relay through the PULSE HEIGHT control The external reference voltage is supplied through the BNC connector on the rear panel Any arbitrary voltage can be applied to the external BNC connector but the maximum voltage should not exceed 20 V refer to Section 3 3 The POLARITY and NORMALIZE controls have no effect on the output pulse when the switch is set to EXT 4 2 CONNECTOR DATA CN1 DIRECT OUTPUT BNC CONNECTOR This is a dc coupled unattenuated output which looks back directly at the wiper of the relay and has an output impedance of 100 The output of this connector provides a constant2. inverting mode of operation i e for the negative input shown the amplifier must produce a positive output pulse The impedance seen from point A to ac or signal ground via point C should be equal to the impedance seen from point A to ac or signal ground via point B The diodes D should be germanium units with high G The diodes can be replaced with high frequency germanium transistors with the base connected to the collector so that the emitter base functions as the diode Transistors suitable for this test include 2N779 2N964 2N976 2N2048 The diodes serve as bipolar voltage clamps to limit the voltage swing at point A to the forward voltage drop across the diodes The diode resistor network should be constructed so as to minimize the stray capacitance around this network The network should be physically located on the oscilloscope input connector for the same reason Initially the output of the pulse generator and amplifier should be set for 10 V This should be measured with care and consideration given for the output impedance of both the pulse generator and amplifier By observing the waveshape at point Fig 4 5 the fine gain of the amplifier and the attenuation controls should be adjusted until a null is obtained between time t t At null the sensitivity of the oscilloscope should be set to 10 mV cm for best resolution of the null measurement The actual measurement of linearity is accomplished by
3. Observe the output with a sweep of 5 ms cm and look for skipping or other erratic behavior of the relay on INT OSC operation 5 2 ADJUSTMENT OF INTERNAL OSCILLATOR FREQUENCY The internal oscillator normally oscillates at a frequency of approximately 70 Hz This frequency may be changed by changing the value of capacitor C2 which is nominally a 6 8 UF capacitor To decrease the frequency of oscillation it is necessary to increase the value of the capacitor Increasing the frequency of oscillation above approximately 80 Hz is not recommended since the mercury wetted relay will not operate reliably above this frequency In the event it is desired to change the frequency of oscillation a small amount paralleling resistors R8 or R9 with an additional resistor will be found to be satisfactory The etched circuit board is provided with holes for the addition of such resistors The frequency should not be changed by more than 1096 with this simple expedient It is frequently desirable to decrease the frequency to a very low level e g 20 Hz so that the oscillator can run at a very low rate during the collection of experimental data and not overflow in a multichannel analyzer This should accomplished by increasing the value of C2 5 3 ADJUSTMENT OF DECAY TIME OF OUTPUT PULSE As the 419 is normally supplied the decay time of the output pulse is essentially fixed The output pulse will decay with the time constant of 400 ps if
4. dialing the PULSE HEIGHT dial to 0 resulting in the amplifier output being reduced to zero Since the pulse generator supplies signals in parallel both to the bridge for null and to the amplifier varying the pulse generator output will have no effect on the null if perfect amplifier linearity is assumed AMPLIFIER Zoi Ri 20 R 2000 As an example of this method assume that the amplifier under test has essentially zero output impedance Set R1 equal to 100 O and R2 equal to 200 Let diodes D1 an D2 be 2N2048 connected as diodes One half of the change in the output voltage of the amplifier to be observed at point A results from the attenuation factor of R1 and the output impedance of the DIRECT OUTPUT of the pulse generator the rest from R2 To specify nonlinearity as a percentage of full output voltage the calibration of 10 mV cm will be equal to 10 mV 5 V or 0 2 Therefore it is seen that 0 1 is quite easily resolved VERTICAL INPUT Fig 4 5 Measuring Linearity by the Null Balance Method In addition to linearity measurements it is obvious that this method can be quite useful in measurements of temperature stability PULSE HEIGHT ANALYZER CALIBRATION With the pulser calibrated to read directly in terms of energy as described previously the calibration of a complete spectrometry system from preamplifier to multichannel analyzer i e analog to digital converter ADC can readily be accom
5. of an external reference voltage in the 419 The external reference voltage can be of any arbitrary waveshape either dc or an arbitrary function such as a linear ramp function or any other waveform The absolute magnitude of this voltage should not exceed 20 V due to the power rating of the resistors in the pulse forming network inside the 419 When using a reference voltage other than a constant dc value ensure that the rate of change of the arbitrary waveform is slow with respect to the chopping frequency of the mercury wetted relay in the 419 If the waveform of an input signal is much faster than the chopping frequency of the relay considerable distortion in the output pulse amplitude will occur Reference to Drawing 419 0201 S1 will show that the use of an external reference voltage will cause the POLARITY and NORMALIZE controls to be ineffective when the INT EXT switch is in the EXT position Of course when the switch is placed back to INT reference the controls will again have their control function 3 4 LINEAR OUTPUT SIGNAL CONNECTIONS AND TERMINATING IMPEDANCE CONSIDERATIONS There are three general methods of termination that are used The simplest of these is shunt termination at the receiving end of the cable A second method is series termination at the sending end The third is a combination of series and shunt termination where the cable impedance is matched both in series at the sending end and in shunt at the re
6. the DIRECT OUTPUT BNC Connector CN1 This test point has a 470 Q series resistor connecting it to CN1 TP2 ATTENUATED OUTPUT TEST POINT Oscilloscope test point for monitoring signal on ATTENUATED OUTPUT BNC Connector CN2 This test point has a 470 Q series resistor connecting it to CN2 TP3 Ground test point used in conjunction with TP4 TP4 The voltage between TP4 is the dc voltage selected by the PULSE HEIGHT potentiometer on the front panel These test points provide a convenient location for continuous monitoring of the reference voltage supplied to the relay and pulse forming network POWER CONNECTOR Nuclear standard instrument module power connector 4 3 TYPICAL OPERATING CONSIDERATIONS VOLTAGE AND CHARGE TERMINATORS CHARGE TERMINATION A charge terminator which consists of a 100 O shunt resistor with a 2 pF series capacitor is supplied for use with charge sensitive preamplifiers such as the ORTEC 109A When this terminator is used the maximum output pulse is 1 V or 2 pC 44 MeV for silicon diode detectors When using the charge terminator to drive charge sensitive preamplifiers a coaxial cable having an impedance of approximately 100 RG 62 U should be used between the pulse generator and the charge terminator The terminator should be located at the input connector of the preamplifier The charge terminator may be used with or without a detector connected to the input of a p
7. 90 should be less than 10 ns the pulse fall time to one half of its maximum amplitude should be between 230 and 290 ps Do not remove the 100 O terminator from the direct output Terminate attenuated output with 100 O Measure the pulse at the attenuated output test point The pulse amplitude should be between the limits of 0 9 and 1 2 V The pulse rise time 10 90 should be less than 10 ns The pulse fall time to one half of its maximum amplitude should be between 110 and 150 us Adjust the PULSE HEIGHT dial for a pulse at the attenuated output test point of 800 mV As ATTENUATOR switches are switched in the output pulse should be between the following limits Output Pulse mV Original Lower Upper 2X 800 360 440 2X 800 360 440 5X 800 144 176 10X 800 72 88 10X 800 72 88 With 800 mV output pulse at the attenuated test point measure the 10 9096 rise time for all positions of the RISETIME switch The rise time should be within the following limits Rise Time ns Switch Setting Lower Upper Minimum 3 10 20 17 23 50 40 60 100 90 110 250 225 295 11 Set the relay switch to INT OSC Measure the frequency at the direct output The frequency limits are 61 to 79 Hz If a scaler is not available measure the time between the leading edges of two successive pulses at Q2 emitter The period should be between 12 6 and 16 4 ms Set the POLARITY switch to There should be no change in amplitude from the position
8. IONS edere e e ep eg 2 3 INSTALLATION Aen RR Rp p 3 3 E GENERALE Ales tart dor tort oe Contant lan Soul Rael dolo door oe oe ton an dace funy 3 3 2 11 0 3 3 3 USE OF EXTERNAL REFERENCE VOLTAGE EXTERNAL INTERNAL REFERENCE SWITCH eie CMM EE EE 3 3 4 LINEAR OUTPUT SIGNAL CONNECTIONS AND TERMINATING IMPEDANCE CONSIDERATIONS xx eU RED wakes eases dea Rear eee 3 4 OBERATINGINSTR GTIONS DR OR a OR a PR a PR edle 4 443 PANEL CONTROLS i veuve ae ele ENTE RN E Re Rn e 4 4 2 CONNECTOR DATA e RS e Re ur eeu e a uu ear apu oe a 5 4 3 TYPICAL OPERATING CONSIDERATIONS 5 MAINTENANGCE 55D MPRRERCECUDCEEEEUMENUCIqpUpbEQR Rer Rete eee states 10 5 1 TESTING PERFORMANCE OF THE PULSE GENERATOR 10 5 2 ADJUSTMENT OF INTERNAL OSCILLATOR FREQUENCY 11 5 3 ADJUSTMENT OF DECAY TIME OF OUTPUT PULSE 11 5 4 TABULATED TEST POINT VOLTAGES 12 5 5 SUGGESTIONS FOR TROUBLESHOOTING 12 SAFETY INSTRUCTIONS AND SYMBOLS This manual contains up to three levels of safety instructions that must be observed in order to avoi
9. Printed U S A Model 419 Precision Pulse Generator Operating and Service Manual ORTEC Part No 733180 Manual Revision C 1202 Advanced Measurement Technology Inc a k a ORTEC a subsidiary of AMETEK Inc WARRANTY ORTEC warrants that the items will be delivered free from defects in material or workmanship ORTEC makes no other warranties express or implied and specifically NO WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE ORTEC s exclusive liability is limited to repairing or replacing at ORTEC s option items found by ORTEC to be defective in workmanship or materials within one year from the date of delivery ORTEC s liability on any claim of any kind including negligence loss or damages arising out of connected with or from the performance or breach thereof or from the manufacture sale delivery resale repair or use of any item or services covered by this agreement or purchase order shall in no case exceed the price allocable to the item or service furnished or any part thereof that gives rise to the claim In the event ORTEC fails to manufacture or deliver items called for in this agreement or purchase order ORTEC s exclusive liability and buyer s exclusive remedy shall be release of the buyer from the obligation to pay the purchase price In no event shall ORTEC be liable for special or consequential damages Quality Control Before being approved for shipment each ORTEC instrument must
10. To prevent moisture inside of the instrument during external cleaning use only enough liqui to dampen the cloth or applicator Allow the instrument to dry completely before reconnecting it to the power source PRECISION PULSE GENERATOR HORMALIZE PULSE HEHE FREQ 43 VOLTAGE IHT TT T1 FOS RI SETIME Fan ATTENUATION FACTOR RUE Low ATTENUATED DUT vi 425 anv EXT CHARGE TERMINATOR PULSE HEIGHT MODEL 419 PRECISION PULSE GENERATOR 1 DESCRIPTION 1 1 GENERAL The ORTEC 419 is a modular precision pulse generator that simulates the detection of a nuclear particle reaction in a semiconductor or scintillation detector The instrument features excellent stability as a function of temperature and time 0 1 overall accuracy and a front panel NORMALIZE control so that it can be calibrated to read directly in terms of equivalent energy deposited in a detector The 419 has a rise time control on the front panel to simulate the charge collection time in a semiconductor detector The pulses are generated with a mercury wetted relay whose frequency can be selected by a front panel switch to be either ac line frequency or an internal 70 Hz oscillator The internal oscillator runs asynchronously from the line frequency so that an experimenter can measure the effects of a
11. as level controls so that the energy is in a convenient channel of the analyzer ORTEC BIASED AMP ORTEC PULSE STRETCHER Fig 4 3 Measuring Resolution with a Pulse Height Analyzer 2 Calibrate the analyzer in keV per channel using the pulser Full scale on the pulser dial is 10 MeV when calibrated as described in Calibrating the Test Pulser and Amplifier for Energy Measurements 3 The amplifier noise resolution spread can then be obtained by measuring the FWHM of the pulser spectrum The detector noise resolution spread for RMS NOISE IN VOLTS a given detector bias can be determined in the same manner by connecting a detector to the preamplifier input The amplifier noise resolution spread of course must be subtracted The detector noise will vary with detector size bias conditions and possibly with ambient conditions as indicated in Fig 4 4 BIAS VOLTAGE Fig 4 4 Amplifier and Detector Noise vs Bias Voltage AMPLIFIER LINEARITY MEASUREMENTS The measurement of amplifier linearity can be quickly and simply done by utilizing the method outlined in Fig 4 5 The method consists of bucking out two voltage signals from low impedance sources and measuring the amplitude differential at a null point The following conditions of Fig 4 5 should be considered when making linearity measurements The output impedance of the DIRECT OUTPUT must be 100 The amplifier must be set in the
12. c hum in his linear system An internal external reference voltage switch in the 419 allows the experimenter to use either the highly stable internal reference voltage or a wide range external reference voltage that he supplies The external reference voltage may be of an arbitrary waveshape or an arbitrarily high voltage to a limit of 20 V When used in the external mode the external voltage is sampled by the mercury relay and subsequently applied to the output connector The unit has five attenuator toggle switches in a pi attenuator arrangement in the attenuated output line Maximum attenuation is 2000 1 The direct output precedes the attenuator switch and provides ameans of oscilloscope triggering Two terminators are provided with the unit a 100 O voltage terminator and a charge terminator The charge terminator allows the voltage output pulse of the 419 to be converted to a charge pulse for subsequent amplification by a charge sensitive preamplifier When not in use the charge terminator can be stored in a holder on the rear panel The 419 is a double width NIM standard module per TID 20893 Rev Its operating power is obtained from an ORTEC 4002A Power Supply through a 4001A modular Bin The ORTEC 400 Series is designed so that it is not possible to overload the Bin Power Supply with a full complement of modules in the Bin However this may not be the case when the Bin contains modules other than those of ORTEC design All
13. ceiving end The most effective method is the combination but termination by this method reduces the amount of signal strength at the receiving end to 50 of that which is available in the sending instrument Touse shunt termination at the receiving end of the cable connect the 1 output of the sending device through 93O cable to the input of the receiving instrument Then use a BNC tee connector to accept both the interconnecting cable and a 100 O resistive terminator at the input connector of the receiving instrument Since the input impedance of the receiving instrument is normally 1000 or more the effective instrument input impedance with the 100 terminator will be of the order of 93 and this correctly matches the cable impedance For series termination use the 93 output of the sending instrument for the cable connection Use 93 Q cable to interconnect this into the input of the receiving instrument The 1000 or more normal input impedance at the input connector represents an essentially open circuit and the series impedance in the sending instrument now provides the proper termination for the cable For the combination of series and shunt termination use the 93 O output in the sending instrument for the cable connection and use 93 O cable At the input for the receiving instrument use a BNC tee to accept both the interconnecting cable and a 100 resistive terminator Note that the signal span at the receivi
14. d personal injury and or damage to equipment or other property These are DANGER Indicates a hazard that could result in death or serious bodily harm if the safety instruction is not observed WARNING Indicates a hazard that could result in bodily harm if the safety instruction is not observed CAUTION Indicates a hazard that could result in property damage if the safety instruction is not observed Please read all safety instructions carefully and make sure you understand them fully before attempting to use this product In addition the following symbol may appear on the product ATTENTION Refer to Manual DANGER High Voltage Please read all safety instructions carefully and make sure you understand them fully before attempting to use this product SAFETY WARNINGS AND CLEANING INSTRUCTIONS DANGER Opening the cover of this instrument is likely to expose dangerous voltages Disconnect the instrument from all voltage sources while it is being opened WARNING Using this instrument in a manner not specified by the manufacturer may impair the protection provided by the instrument Cleaning Instructions 1 clean the instrument exterior Unplug the instrument from the ac power supply Remove loose dust on the outside of the instrument with a lint free cloth Remove remaining dirt with a lint free cloth dampened in a general purpose detergent and water solution Do not use abrasive cleaners CAUTION
15. es at the output In consideration of this the 419 must be disconnected from its position in any system and routine diagnostic analysis performed on the pulse generator with a vacuum tube voltmeter and oscilloscope It is imperative that testing not be performed with any amplifier system until the pulse generator performs satisfactorily by itself The testing instructions of Section 5 1 of this manual is intended to provide assistance in locating the region of trouble and repairing the malfunction The guide plate and shield cover can be completely removed from the module to enable oscilloscope and voltmeter observations with a minimum chance of accidentally short circuiting portions of the etched board The 419 may be returned to ORTEC for repair service at nominal cost Our standardized procedure requires that each repaired instrument receive the same extensive quality control tests that a new instrument receives 13 Bin Module Connector Pin Assignments For Standard Nuclear Instrument Modules per DOE ER 0457T 2 5 Function 3 V 3V Spare bus Reserved bus Coaxial Coaxial Coaxial 200 V de Spare 10 6V 41 6V 12 Reserved bus 13 Spare 14 Spare 15 Reserved 46 412V 47 12V 18 Spare bus 19 Reserved bus 20 Spare 21 Spare 22 Reserved 41 Function Reserved Reserved Reserved Spare Spare 24 V 24 V Spare bus Spare Spare 117 V ac hot Power
16. for a 5 1 MeV alpha particle set the dial at 510 divisions 5 Turn on the pulser Use the NORMALIZE potentiometer the RISETIME switch and the ATTENUATION FACTOR switches to set the output due to the pulser to the same pulse height and shape as the pulse obtained in 3 above Particular ORTEC Pulse Generator Detector or Capacitor 200371 attention to the RISETIME should be given when the collection time of the detector is longer than 10 20 ns AMPLIFIER NOISE AND RESOLUTION MEASUREMENTS As shown in Fig 4 1 the preamplifier amplifier pulse generator oscilloscope and a wide band rms voltmeter such as the Hewlett Packard 400D are required for this measurement Connect a suitable capacitor to the input to simulate the detector capacitance desired To obtain the resolution spread due to noise 1 Measure the rms noise voltage at the linear amplifier output 2 Turn on the 419 pulse generator and adjust the linear amplifier output to any convenient readable voltage E as determined by the oscilloscope 3 The full width at half maximum FWHM resolution spread due to the amplifier noise is then N FWHM 2 66 Ems Eya E where Ega is the pulser dial reading in MeV and the factor 2 66 is the correction factor for rms to FWHM 2 35 and noise to rms meter correction 1 13 for average indicating voltmeters such as the Hewlett Packard 400D The resolution spread will depend upon the tota
17. ient cooled by circulating air to prevent any localized heating of the all transistor circuitry used throughout the 419 and the 4001A 4002A The temperature of equipment mounted in racks can easily exceed 120 F 50 C unless precautions are taken The 419 should not be subjected to temperatures in excess of 120 F 50 C 3 2 CONNECTION TO POWER The 419 contains no internal power supply and must obtain power from a nuclear standard bin and power supply such as the ORTEC 4001A 4002A It is recommended that the bin power supply be turned off when modules are inserted or removed The ORTEC 4001A 4002A has test points on the power supply control panel to monitor the dc voltages When using the 419 outside the 4001A 4002A Bin and Power Supply be sure that the power jumper cable used properly accounts for the power supply grounding circuits provided in the recommended standards of US DOE TID 20893 Rev Both high quality and power return ground connections are provided to ensure proper reference voltage feedback into the power supply and these must be preserved in remote cable installations Be careful to avoid ground loops when the module is operated outside the bin If the 419 is inserted in a bin which has no ac voltage the unit will operate correctly on the INT OSC position of the RELAY switch 3 3 USE OF EXTERNAL REFERENCE VOLTAGE EXTERNAL INTERNAL REFERENCE SWITCH The BNC connector on the rear panel provides for the use
18. itude output pulses through an output impedance of 100 Q ATTENUATED A front panel BNC connector with an adjacent test point furnishes the same output pulses as above with amplitudes attenuated by the factor selected with the five toggle switches PULSE HEIGHT CONTROL MONITOR Two test points on the rear panel permit a voltmeter or oscilloscope to monitor the voltage level that is applied to the pulse forming relay ACCESSORIES INCLUDED VOLTAGE TERMINATOR standard 100 0 resistive terminator is attached to the Direct Output BNC connector on the front panel to terminate the output correctly when only the Attenuated Output is being used CHARGE TERMINATOR specially constructed terminator is mounted in a rear panel clip and should be used to properly terminate the pulser output and feed a charge signal into the signal input of a charge sensitive preamplifier when the output pulses are being furnished for this type of test ELECTRICAL AND MECHANICAL POWER REQUIREMENTS 24 V 45 mA 24 V 25 mA 12 V 0 mA 12 V 5 mA 115 V 10 mA DIMENSIONS Standard double width NIM module 2 70 in wide by 8 714 in high per TID 20893 Rev SHIPPING WEIGHT 6 5 Ib 2 95 kg NET WEIGHT 4 5 lb 2 kg 3 INSTALLATION 3 1 GENERAL 419 used in conjunction with a 4001A 4002A Bin and Power Supply is intended for rack mounting and therefore any vacuum tube equipment operating in the same rack must be suffic
19. l input capacity since the capacitance degrades the signal to noise ratio much faster than the noise A typical resolution spread versus external input capacitance is shown in Fig 4 2 ORTEC Oscilloscope Amplifier RMS Voltmeter Fig 4 1 Measuring Amplifier and Detector Noise Resolution CONSTANTS MODELS 109A amp 118A o RESOLUTION FWHM keV Ge gt q ee eee 2 HR pep EET iE H e Po iaiiaeeeai 86 EEE tT Titty RESOLUTION FWHM AS A FUNCTION OF T zc INPUT CAPACITANCE AT VARIOUS SHAPING TIME prp amm THT RELATIVE AMPLITUDE LIII HEN 22512852 H i5 TT LUE A BA Misses IT 1000 INPUT n Fig 4 2 Resolution Spread vs External Input Capacity AMPLIFIER NOISE AND RESOLUTION MEASUREMENTS USING A PULSE HEIGHT ANALYZER Probably the most convenient method of making resolution measurements is with a pulse height analyzer as shown in Fig 4 3 The amplifier noise ORTEC PREAMP DETECTOR OR CAPACITOR ORTEC PULSE GENERATOR ORTEC LINEAR AMPLIFIER MULTICHANNEL PULSE HEIGHT ANALYZER resolution spread can be measured correctly with a pulse height analyzer and the 419 as follows 1 Select the energy of interest with the 419 and set the linear amplifier and biased amplifier gain and bi
20. n Pulse Generator Preliminary Procedures 1 Visually check the module for possible damage due to shipment 2 Connect ac power to nuclear standard bin ORTEC 4001A 4002A 3 Plug module into bin and check for proper mechanical alignment 4 Switch ac power on and check the dc power supply voltages at the test points on the 4002A Power Supply control panel Precision Pulse Generator Set the front panel controls on the 419 as follows 1 Relay switch to Internal Oscillator 2 Polarity switch to 4 3 Reference switch to INT 4 The NORMALIZE and PULSE HEIGHT controls to 1000 5 RISETIME to MIN 6 All ATTENUATOR switches to down position Terminate the direct output in 100 O Keep the direct output terminated throughout the test in 100 Apply power to the nuclear standard bin and listen for the mercury relay running which will be characterized by a low frequency hum of about 75 Hz Set the relay switch to OFF Measure the dc voltage from the wiper of the REFERENCE switch on the rear panel to ground It should be between 1 75 and 2 25 V Dial the NORMALIZE control to 000 and again measure the dc voltage from the wiper of the REFERENCE switch to ground should be between 0 7 and 0 85 V Return the NORMALIZE control to 1000 Set the relay switch to AC FREQ Measure the pulse at the direct output test point The pulse amplitude should be between the limits of 0 9 and 1 2 V The pulse rise time 10
21. ng end of this type of receiving circuit will always be reduced to 5096 of the signal span furnished by the sending instrument For your convenience ORTEC stocks the proper terminators and BNC tees or you can obtain them from a variety of commercial sources 4 OPERATING INSTRUCTIONS 4 1 PANEL CONTROLS PULSE HEIGHT The pulse height potentio meter controls the output pulse height from zero volts to the maximum determined by the attenuation factor toggle switches and the termination load This 10 turn potentiometer has a calibration linearity of 0 1 NORMALIZE This 10 turn 0 25 linearity potentiometer varies the output pulse height continuously over a 2 5 to 1 range approximately to allow for normalization of the PULSE HEIGHT dial setting This control is ineffective when the reference voltage switch is in the EXT position RELAY This switch allows the internal relay to be driven from either the ac line AC FREQ position or the internal oscillator INT OSC position The frequency of the ac line will be 50 to 60 Hz and the frequency of the internal oscillator will be approximately 70 Hz The RELAY switch has a center OFF position which allows the relay to be inoperative while leaving the power on to the pulse forming circuitry This position minimizes thermal transients in the pulse forming network POLARITY The polarity of the output signal will be either positive or negative as determined
22. output voltage for a given setting of the PULSE HEIGHT control independent of the position of the RISETIME and ATTENUATION FACTOR switches Output voltage range is from 0 to 1 V maximum into 100 The direct output may or may not be terminated with a 100 Q terminator If the output is terminated with a 100 terminator the decay time of the output pulse will change from a nominal value of 400 Us to a value of 200 us The polarity of the Direct Output pulse will be either positive or negative as determined by the POLARITY switch CN2 ATTENUATED OUTPUT BNC CONNECTOR The attenuated output is dc coupled output connector with an output impedance of 100 The attenuated output has in series with it the ATTENUATION FACTOR switches and the RISETIME control switch The use of these switches therefore alters the pulse shape appearing at the attenuated output for a given setting of the PULSE HEIGHT control The attenuated output should always be terminated with 100 Q The polarity of the output pulse will be either or as determined by the POLARITY switch CN3 EXT REF BNC CONNECTOR The BNC connector on the rear panel provides for the use of an external reference voltage into the 419 The external reference voltage may be any arbitrary waveshape either dc or a time varying function such as a linear ramp refer to Section 3 3 DIRECT OUTPUT TEST POINT Oscilloscope test point for monitoring signal on
23. pass a stringent set of quality control tests designed to expose any flaws in materials or workmanship Permanent records of these tests are maintained for use in warranty repair and as a source of statistical information for design improvements Repair Service If it becomes necessary to return this instrument for repair it is essential that Customer Services be contacted in advance of its return so that a Return Authorization Number can be assigned to the unit Also ORTEC must be informed either in writing by telephone 865 482 4411 or by facsimile transmission 865 483 2133 of the nature of the fault of the instrument being returned and of the model serial and revision Rev on rear panel numbers Failure to do so may cause unnecessary delays in getting the unit repaired The ORTEC standard procedure requires that instruments returned for repair pass the same quality control tests that are used for new production instruments Instruments that are returned should be packed so that they will withstand normal transit handling and must be shipped PREPAID via Air Parcel Post or United Parcel Service to the designated ORTEC repair center The address label and the package should include the Return Authorization Number assigned Instruments being returned that are damaged in transit due to inadequate packing will be repaired at the sender s expense and it will be the sender s responsibility to make claim with the shipper Instruments not in warran
24. plished by simply feeding into the preamplifier a calibrated energy signal and observing the corresponding channel into which it is assigned by the ADC An important consideration in this test involves ensuring that the linear system goes through zero 10 and that the output of the pulse generator is properly terminated The attenuator switches in the 419 have an accuracy controlled by 0 196 metal film resistors and can be used to digitally check the linearity of the spectrometer In addition to the attenuator accuracy the PULSE HEIGHT control has independent integral nonlinearity of 0 1 This control therefore allows an integral linearity curve of the ADC to be taken over the continuous range of the ADC i e from zero to the maximum address of the ADC The linearity of the ADC can therefore be determined by having previously taken the linearity curve of the amplifier and preamplifier as outlined in Amplifier Linearity Measurements 5 MAINTENANCE 5 1 TESTING PERFORMANCE OF THE PULSE GENERATOR The following paragraphs are intended as an aid in the installation and checkout of the 419 These instructions present information on front panel controls waveforms at test points and output connectors Test Equipment The following or equivalent test equipment is needed ORTEC 419 Pulse Generator Tektronix Model 580 Series Oscilloscope 100 O BNC Terminators Vacuum Tube Voltmeter Schematic and Block Diagram for 419 Precisio
25. reamplifier If a detector is connected to the preamplifier detector bias must be applied to reduce the effective detector capacity shunting the charge sensitive preamplifier input Also with the charge terminator used simultaneously with a semiconductor detector the charge terminator effectively shunts the detector with approximately 2 5 pF of shunt capacity which will correspondingly degrade the signal to noise performance of the preamplifier VOLTAGE TERMINATION For voltage drive to an instrument under test use coaxial cable having an impedance of approximately 100 O RG 62 U between the pulse generator and the instrument under test Place a 100 O termination at the instrument end of the cable in shunt with the input of the instrument CALIBRATING TEST PULSER AND AMPLIFIER FOR ENERGY MEASUREMENTS The 419 pulser may easily be calibrated so that the maximum PULSE HEIGHT dial reading 1000 divisions is equivalent to a specific MeV loss in a radiation detector The procedure is as follows 1 Connect the detector to be used to the spectrometer system i e preamplifier main amplifier and biased amplifier 2 Allow particles from a source of known energy alpha particles for example to fall on the detector 3 Adjust the amplifier gains and the bias level of the biased amplifier to give a suitable output pulse 4 Set the pulser PULSE HEIGHT potentiometer at the energy of the alpha particles striking the detector e g
26. return ground Reset Scaler Gate Reset Auxiliary Coaxial Coaxial Coaxial 117 V ac neutral High quality ground Ground guide pin Pins marked are installed and wired in ORTEC s 4001A and 4001C Modular System Bins
27. signal levels and impedances are compatible with other modules in the ORTEC 400 Series 1 2 BASIC FUNCTION The output pulses provided by the 419 are characterized by a fast rise time and a slow exponential decay time These pulses are generated by charging a capacitor from a reference voltage through a mercury relay and discharging the capacitor through the switching action of the mercury relay into a fixed resistive load The use of mercury wetted relay contacts provides a very fast rise time typically less than 5 ns 10 90 rise time with an absolute minimum of contact bounce or other perturbations of the waveform for the first few microseconds The output impedance of the pulse generator on both the direct and attenuated output is 100 The direct output provides a trigger pulse that synchronizes the oscilloscopes or other timing equipment from a signal which does not vary in amplitude as the attenuators are switched in and The attenuated output has a series of pi attenuators between the mercury wetted relay contacts and the output BNC connector This allows the signal to be attenuated by a fixed amount depending upon the particular switch operated in the series attenuator The primary purpose of the pulse generator is to simulate radiation detection signals therefore a rise time control is provided to simulate the charge collection time in a semi conductor detector Since the pulses are generated from an electromechanical de
28. the direct output only is terminated in 100 O and will decay with a time constant of approximately 200 Us if both the direct output and attenuated output are terminated In the event that a time constant shorter than 200 Us is desired a fixed resistor should be paralleled from the normally open contact of the mercury wetted relay to ground The value of this shunting resistor will depend upon the exponential time constant The addition of this resistor should physically be in close proximity to the actual relay that is the resistor should be added directly onto the etched circuit board Decay time constants as short as 10 Us can be accomplished quite easily 5 4 TABULATED TEST POINT VOLTAGES The following voltages are intended to indicate the typical dc voltages measured on the etched circuit board In some cases the circuit will perform satisfactorily even though due to component variations there may be some voltages that measure outside the given limits Therefore the voltages given should not be taken as absolute values but rather are intended to serve as an aid in troubleshooting All voltages are measured from ground with a dvm having an input impedance of 10 or greater Set polarity switch to Location Typical dc Voltages Qlb 12 0 Dik 9 1 12 5 5 SUGGESTIONS FOR TROUBLESHOOTING If the 419 is suspected of malfunctioning it is essential to verify such malfunctioning in terms of simple pulse generator impuls
29. ty should follow the same procedure and ORTEC will provide a quotation Damage in Transit Shipments should be examined immediately upon receipt for evidence of external or concealed damage The carrier making delivery should be notified immediately of any such damage since the carrier is normally liable for damage in shipment Packing materials waybills and other such documentation should be preserved in order to establish claims After such notification to the carrier please notify ORTEC of the circumstances so that assistance can be provided in making damage claims and in providing replacement equipment if necessary Copyright 2002 Advanced Measurement Technology Inc rights reserved is a registered trademark of Advanced Measurement Technology Inc All other trademarks used herein are the property of their respective owners CONTENTS WARRANT Y EEG eR ii SAFETY INSTRUCTIONS AND SYMBOLS iv SAFETY WARNINGS AND CLEANING INSTRUCTIONS 2 1 DESCRIPTION sates setae etc eerte eee de en a eae eR e ER NE eed 1 Td GENERAL 29 ot etu EE EE E as 1 1 2 BASIG FEUNG TION x tt trt de e cet 1 2 SPEGIFIGAT
30. vice the mercury wetted relay the frequency of the pulse generator is correspondingly rather slow approximately 70 Hz when operated on INT OSC and at the frequency of the ac line for the AC FREQ position 2 SPECIFICATIONS PERFORMANCE PULSE AMPLITUDE Output peak adjustable from 0 to I V using the charge terminator supplied this is 0 to 2 picocoulombs and is equivalent to 0 to 44 MeV referred to a silicon semiconductor detector rise time selected by front panel switch fall time is an exponential decay time constant of 200 Us terminated or 400 Us unterminated AMPLITUDE STABILITY Temperature 0 005 C from 0 to 50 C Line Voltage 0 001 per 10 change in power line voltage RIPPLE AND NOISE 0 003 of pulse amplitude PULSE REPETITION RATE Either the ac power line frequency or 70 10 Hz using the internal oscillator INTERNAL OSCILLATOR STABILITY Temperature Within 0 05 C 0 to 50 C Time Within 1 day CONTROLS PULSE HEIGHT 10 turn potentiometer with a duo dial adjusts the output pulse amplitude within a total range the range is a combined function of the reference and the setting of the Normalize control Linearity 0 1 of full scale NORMALIZE A 10 turn potentiometer adjusts the total range for the Pulse Height control when using Internal Reference full scale range is from 0 5 V to 1 V linearity 0 1 of full scale RELAY A 3 position slide switch selects the ac power line frequenc
31. y or the internal 70 Hz oscillator for the output repetition rate and includes an Off position to set the pulser at standby REF VOLTAGE A 2 position slide switch selects either the internal reference voltage for a 100 Normalized full scale range of 0 to 1 V or the external reference voltage for an output full scale range and polarity that are determined by the level furnished through the rear panel BNC connector POLARITY A 2 position slide switch selects either polarity for the output pulses when they are based on use of the internal reference RISE TIME A 5 position rotary switch selects the rise time shaping for the output pulses to simulate various types of detectors selections are Minimum 5 ns and 20 50 100 and 250 ns ATTENUATION FACTOR Five toggle switches that select a step attenuation for output pulses furnished through the Attenuated Output connector the factors are 2 2 5 10 and 10 and may be used in any combination to cover a 2000 1 dynamic range using 0 196 tolerance resistors INPUT EXTERNAL REFERENCE rear panel BNC connector accepts an external reference voltage to control the full scale Pulse Height control range and polarity when the front panel Ref Voltage switch is set at Ext maximum 20V output full scale range is 50 of reference level with output terminated in 100 OUTPUTS DIRECT A front panel BNC connector with an adjacent test point furnishes the adjusted and normalized full ampl
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