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Model 142AH

Preamplifier

Operating and Service Manual

Printed in U.S.A.

 ORTEC  Part No. 733990

 0202

®

Manual Revision B

Summary of Contents for 142AH

Page 1: ...Model 142AH Preamplifier Operating and Service Manual Printed in U S A ORTEC Part No 733990 0202 Manual Revision B ...

Page 2: ... 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 proce...

Page 3: ...NNECTION TO DETECTOR 3 3 2 ENERGY OUTPUT CONNECTION TO MAIN SHAPING AMPLIFIER 3 3 3 TIMING OUTPUT CONNECTION TO TIMING MODULES 3 3 4 INPUT OPERATING POWER 3 3 5 TEST PULSE 4 3 6 DETECTOR BIAS INPUT 4 3 7 CORONA ELIMINATION 4 4 OPERATION 5 4 1 GENERAL 5 4 2 DETECTOR BIAS 5 4 3 ENERGY OUTPUT 6 4 4 TIMING OUTPUT 6 4 5 COMPENSATION ADJUSTMENT 7 4 6 INPUT PROTECTION 8 5 MAINTENANCE INSTRUCTIONS 9 5 1 T...

Page 4: ...s 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...

Page 5: ...the instrument during external cleaning use only enough liquid to dampen the cloth or applicator SAFETY WARNINGS AND CLEANING INSTRUCTIONS Cleaning Instructions To 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 ...

Page 6: ...on the 142AH is void if the protection circuit is taken out unless all of the following precautions are taken 1 COMPLETELY DISCHARGE the detector bias circuit before connecting a low impedance a cable or any other capacitive device to the Detector Input connector on the preamplifier making ANY connections to the Detector Input connector and before disconnecting the preamplifier from the detector 3...

Page 7: ...uctions carefully Timing Filter Amplifier 473A Constant Franction to prevent serious injury to yourself and or damage Discriminator and 574 Timing Amplifier to the instrument The energy range expected in typical applications Observe the steps that are included in the is from 0 to 200 MeV Two simultaneous outputs Notice on page vi to discharge the high are provided the output marked E is for energy...

Page 8: ...ed TEMPERATURE INSTABILITY 50 ppm C 0 to 50 C DETECTOR BIAS ISOLATION 5000V OPEN LOOP GAIN 40 000 2 2 INPUTS INPUT Accepts input signals from semiconductor charged particle detector and extends operating bias to the detector BIAS Accepts the detector bias voltage from a power supply TEST Accepts input voltage pulses from a pulse generator for instrument and system calibration R 93 in 2 3 OUTPUTS E...

Page 9: ...able between the detector and the preamplifier Normally corona problems in the bias cable between the bias power supply and the preamplifier are significant due to the filtering circuit within the preamplifier After the input cable has been installed the electronic noise performance of the preamplifier can be predicted by adding the capacity furnished by the detector to the capacity of the cable T...

Page 10: ...ortions of the preamplifier 1 With no cable connected to the preamplifier circuitry the transient performance of the Input operate the preamplifier at the desired bias preamplifier is best determined by connecting the voltage while observing the E output through a actual detector signal through the Input connector shaping amplifier with an oscilloscope instead of using the pulse generator signals ...

Page 11: ...n and good manufacturing control as well as extensive testing under full bias assure that each preamplifier is free from spiking problems and that no degradation of noise performance will result when the required bias voltage is applied But dust dirt and other surface contamination can collect within the Input connector and cause spiking problems due to corona discharge in the Input connector and ...

Page 12: ...ust be detector the detector output pulses are negative cautious to prevent touching the interior of the and the E output of the preamplifier is positive as connector with anything other than a good shown in Fig 4 2 insulator such as the glass tube of the blower lethal high voltages are present on the center pin of the Input connector under these conditions 4 3 ENERGY OUTPUT The charge sensitive l...

Page 13: ...check points on the E rise time are based on the Efinal level which is less than the initial overshoot On the other hand the 10 and 90 check points on the T rise time are based on the peak level of the initial overshoot which is relatively more than the final value for the E output 4 5 COMPENSATION ADJUSTMENT A bandwidth compensation adjustment is accessible to the user of the 142AH This control c...

Page 14: ...all a wire jumper across R39 and R5 Inherent to all high speed charge sensitive preamplifiers is the problem of keeping the total system stable while interconnecting the detector and preamplifier with long cables To help ease this problem and permit more flexibility for installations the protection circuit is designed to serve not only as a protection for the FET input but also to terminate the in...

Page 15: ...amplifier system The noise performance referenced in Section 2 is stated in these terms and verification methods will be described If desired the preamplifier can be tested with no external capacity on the Input connector in which case the noise width should be approximately that shown for zero external capacity In any case the input connector and capacitors when used should be completely shielded...

Page 16: ...the preamplifier has been verified as outlined in the preceding section or is otherwise not suspected a detector may be tested to some extent by duplicating the noise performance tests with the detector connected in place and with normal operating bias applied The resulting combined noise measurement made either with an analyzer or by the voltmeter method indicates the sum in quadrature of the sep...

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