Model CF8000 Octal Constant Fraction Discriminator
Contents
1. C from 0 to 50 C THRESHOLD CONTROL TH 20 turn front panel screwdriver adjustment for each discriminator channel variable from 10 mV to 1 V THRESHOLD MONITOR Front panel test point located to the right of the Threshold control outputs actual threshold voltage WIDTH ADJUSTMENTS TA and TB 20 turn front panel screwdriver adjustments to set the deadtime of output A and width of B Fast NIM logic outputs Both are adjustable from 20 to 200 ns DELAY Internal PCB jumper setting allows the proper shaping delay to be selected 5 possible positions 2 4 6 8 or 10 ns Other delays available on order INPUTS Front panel LEMO connector for each channel Input range O to 5 Vi protected to 100 V Impedance 50 Ohm dc coupled INHIBIT INPUT Front panel LEMO connector accepts negative Fast NIM signal Active low signal disables B logic outputs A LOGIC OUTPUTS A 8 front panel LEMO connectors provide adjustable dead time updating Fast NIM logic signal for inputs above threshold setting Rise time 5 ns fall time 20 ns amplitude 0 8 V minimum Dead time settable from 20 to 200 ns by 20 turn front panel screwdriver adjustment TA B LOGIC OUTPUTS B 16 front panel LEMO connectors provide adjustable width Fast NIM logic signal for inputs above threshold setting Rise time 5 ns fall time 20 ns amplitude 0 8 V minimum Width settable from 20 to 200 ns by 20 turn front panel screwdriver adjustment T2. SP9637 used in these modules The ORTEC 934 using the older AM687 IC does not show that behavior An improvement of the rise at large amplitudes might be possible using the already announced new IC AM 9687 For longer decay time pulses the delay of the CFD is rather insensitive as soon as it is long enough 108 10 times the rise time The course setting of the delay possible in the CF 8000 is thus sufficient The threshold setting has no influence on the performance above the threshold The temperature stability of the CF 4000 has been measured to be less than 3 ps C Due to reduce the power consumption by the circuit design the count rate capability is not higher than 15 MHz for the CF 4000 and 40 MHz for the CF 8000 depending on the dead time setting There is no decline of the performance with increasing count rate For a 5 V input signal there is not triggering of other channels as long as the threshold is higher than 3 4 mV for both the CF 4000 and the CF 8000 Ba ETON pag tur Ter t Te ye T E EN FREE Fig 1 Delay as a function of the amplitude of the input signal for different constant fraction discriminators CF4000 fraction f 0 25 delay t 5 ns 1 m threshold u 10 mV CF 8000 f 0 4 t 6 ns u 10 mV TC 454 f 0 2 t 5ns 1 m U 30 mV 12 interval attenuation ORTEC 934 f 0 2 t 5 ns 1 m u 30 mV Fig 2 Same as Fig 1 except rise time of input signal is now 1 7 ns CF 8000 REAR PANE
3. cleaning use only enough liquid to dampen the cloth or applicator e Allow the instrument to dry completely before reconnecting it to the power source VI ORTEC ESN CF 8000 OCTAL CONSTANT FRACTION DISCRIMINATOR FEATURES e B Independent CFD channels e Automatic walk adjustment e Multiplicity output e OR logic output e Analog sum output e Inhibit input e ECL Outputs e Energy Outputs e Internal delay APPLICATIONS High density timing experiments e PMT or solid state detectors ime of flight measurements The powerful Model CF 8000 Octal Constant Fraction Discriminator has the performance and features necessary for even the most demanding experiments It contains 8 constant fraction discriminators in a single width NIM module Exclusive features of the Model CF 8000 include internal shaping delay automatic walk adjustment an analog summation output and built in logic functions to minimize external logic requirements The input signals can range from 0 to 5 V Each input has a separate threshold adjustment with front panel monitor which may range from 10 mV to 1 V For each channel there are 3 fast NIM logic outputs 1 A and 2 B outputs The A output is an updating output with adjustable deadtime There is a single deadtime adjustment for all 8 A outputs and a single width adjustment for all 16 B logic outputs There are also 8 rear panel ECL outputs which h
4. B MULTIPLICITY OUTPUT M Front panel LEMO connector provides pulse signal whose amplitude is proportional to the number of B logic outputs active at any instant Amplitude range nominally O to 0 5 V with 50 Q load 3 PRINCIPLES OF OPERATION The input pulse labeled C in Fig 4 is split into two parts One part labeled A in Fig 4 is attenuated and applied to the inverting input of a fast differential discriminator The other part labeled B in Fig 4 is delayed and then applied to the non inverting input of the same discriminator The output voltage of this discriminator is determined by the difference of the input voltages This pulse labeled AB in Fig 4 crosses the threshold voltage of the following gate at V if the voltages at the inputs are equal From this crossing the timing information is derived In order to derive the timing information from a fraction of the maximum amplitude of the input pulse the timing has to be done at the time of occurrence of this maximum i e one has to wait with the timing until the maximum amplitude is known Thus one has the condition that the maximum of the attenuated pulse which corresponds to the maximum of the input pulse has to cross the delayed pulse at the particular selected fraction This condition leads immediately to the following relation Tgealer Tisel 1 7 fraction Using the idealized pulse shapes of Fig 4 Threshold ADC 2 iee gt lending ed
5. L ANALOG OUT AC COUPLED OUT B WIDTH TB ECL oz o Lo 16 V 0 8 V EE ert EE DIFFERENTIAL LINE LINE IMPEDANCE 112 0 DELAY TIME 26 00 10 ns USING 10 ns HYBRID DELAY PLUG IN bes tucken AVAILABLE ALSO 6 12 30ns 30 ns PLUG IN 10 20 50ns 50 ns PLUG IN CF 8000 SELECTING FRACTION BELAY 100 Q R 10 1000 Z DELAY 1 7082 re R9 so Q RB R9 1750 2 R9 17502 f 125 xf R8 175 R9 20 Q 175 62 _ po 125 2 x f 106 Q A TO CHANGE THE FRACTION RESISTORS R3 AND R4 HAVE TO BE CHANGED USING THE FOLLOWING RELATION 5 4 6 3 7 2 8 4 gs B USING CF 8000 AS A LEA DING EDGE DISCRIMINA TOR C USING CF 8000 AS A ZERO CROSSING DISCRIMINATOR 10 CF FRACTION f R7 20 R10 102 RB 17554 RI RI 12560 LE Zo Stn Z T Ze Son CF 8000 r FRACTION PLUG IN SOLDER RESISTORS AS SHOWN SOLDER RESISTORS A SHOWN DETAIL A SCALE 4 TYP 8 PLES
6. Model CF8000 Octal Constant Fraction Discriminator Operating and Service Manual Printed in U S A ORTEC Part No 753840 0305 Manual Revision D 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 inno 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 instrumen
7. ar signal from the input signal as already described Thus uniform logic signal A will be formed at the output due to the high amplification 10 and the limitation Lf s KANE JE Fig 6 Timing diagram of the timing discriminator pulses Performance of the GSI Constant Fraction Discriminators CF 4000 and CF 8000 R Albrecht O Althoff A Hohler R Schulze GSI Darmstadt Universitat Mainz Participant of the GSI student program Universitat GreBen Participant of the GSI student program Since 1980 constant fraction discriminators CFD have been built at GSI following the design of M M Maier Marburg LGL Berkeley The number of channels built has been doubled every year resulting in more than 100 channels in 1983 In 1962 the new 8 channel version with internal delay hybrids gated baseline restores inhibit input and outputs for energy time ECL common multiplicity Sum energy and logical OR was produced first for the GSI LBL Plastic Ball collaboration This CF 8000 has become available for experiments at the UNILAC in 1983 and has been added to the GSI NIM pool During the GSI student program intensive tests had been made with constant fraction discriminators The purpose of a discriminator in nuclear electronics is to produce a standard output signal from an analog input signal to define the time of an event The constant fraction discriminator gives an output signal at a fixed delay after a constant fraction of the p
8. 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 AN ATTENTION Refer to Manual AN DANGER High Voltage Please read all safety instructions carefully and make sure you understand them fully before attempting to use this product SAFETY WARNINGS AND CLEANING INSTRUCTIONS DANGER Opening the cover of this instrument is likely to expose dangerous voltages Disconnect the instrument from all voltage sources while it is being opened WARNING Using this instrument in a manner not specified by the manufacturer may impair the protection provided by the instrument Cleaning Instructions To clean the instrument exterior e Unplug the instrument from the ac power supply e Remove loose dust on the outside of the instrument with a lint free cloth e Remove remaining dirt with a lint free cloth dampened in a general purpose detergent and water solution Do not use abrasive cleaners CAUTION To prevent moisture inside of the instrument during external
9. ave the same width as the B outputs ORTEC MODEL CF8000 OCTAL CONSTANT FRACTION DISCRIMINATOR 1 INTRODUCTION Constant fraction timing makes use of the knowledge that for a given pulse shape from a detector preamplier combination there is an optimum triggering or discrimination to minimize walk This optimum fraction varies for pulses of different rise times but for pulses of constant rise time it does exist The technique operates by inverting the attenuating the pulse from which a time signal is to be derived and adding it back to the delayed non inverted non attenuated signal itself Fig 1 illustrates the process A le Amplitude A a input Amplitude B li ZJ m b inverted attenuat d dymi i A sum zero crossing Fig 1 Constant fraction pulse shaping This technique essentially eliminates the walk errors caused by signals of constant rise time but varying amplitudes The technique described above does not compensate for detector rise time variation See Fig 2 which illustrates the result with two pulses of equal amplitude but varying rise time To compensate for varying rise times requires a further elaboration of the timing system The elaboration is to modify the delay time of the non attenuated non inverted signal shown in Fig 1 c to a value less than the shortest rise time that will be encountered Fig 3 illustrates the result for two signals of the same a
10. ge ofthe output pulse Fig 4 Pulse shapes at the specified points in the electronic circuit of Fig 5 The propagation delays of the I C s are not included in order to display the time resolutions more clearly The validity of the approximations made by assuming such idealized pulse shapes has been checked for various values of fraction and the delay time We have varied independently the fraction from 0 1 to 0 5 and the ratio of the delay time to the rise time from 0 4 to 1 0 We found that the time resolution remains essentially constant for fractions between 0 1 amp 0 3 for higher fraction e g f 0 5 the resolution deteriorates somewhat The variation of the delay time does not affect time resolution as long as it satisfied the given relation within a factor of 2 This seems plausible since the actual pulse shape is not as pointed as our idealization but varies more smoothly with time Nominally VH 0 8 V V88 1 2 V VL 1 8V see also the data sheets 4 TIMING DISCRIMINATOR This circuit is fulfilled by applying ECL integrated circuits with a propagation delay of 4 ns A signal after the main differential amplifier tract B signal at output of leading edge discriminator C signal from the coincidence gate D signal from the RS trigger Fig 6 explains the principle of the timing discriminator operation The differential amplifier in the main stage of the timing discriminator shapes a bi pol
11. mplitude but differing rise times when the delay is set to less than this critical value Use of this technique does require that certain restrictions upon minimum and maximum signal inputs must be observed Risetime A a be input Risetime B b 0 inverted attenuated c declared d SLIM zero crossings Fig 2 Constant fraction pulse shaping with varying rise times Use of this technique does require that certain restrictions upon minimum and maximum signal inputs must be observed Constant fraction timing yields greatly improved time resolution with large Ge Li detectors As an example one detector timing curve as measured by the FWHM of the time peak width for known coincident events was reduced from 6 3 ns to 4 2 ns by using constant fraction timing instead of leading edge timing with a very low energy acceptance range The improvement is much greater for wide energy range a Risetime A a m input Risetime B b A inverted attenuated Z a c e delayed a d Ba sum e zero crossings sum b expanded Fig 3 Pulse shaping for constant fraction timing with rise time compensation 2 SPECIFICATIONS WALK Less than 150 ps from 20 mV o 2 V Pulse width 10 ns delay ns threshold at minimum INPUT OUTPUT RATE 20 MHz maximum PULSE PAIR RESOLUTION Less than 50 ns TRANSMISSION DELAY 13 ns A outputs 16 ns B outputs typically THRESHOLD TEMPERATURE INSTABILITY Less than 100 ppm
12. n warranty 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 2005 Advanced Measurement Technology Inc All rights reserved ORTEC is a registered trademark of Advanced Measurement Technology Inc All other trademarks used herein are the property of their respective owners CONTENTS WARRANIY nari asa ene deed A arcy ht edet SAFETY INSTRUCTIONS AND SYMBOLS SAFETY WARNINGS AND CLEANING INSTRUCTIONS 1 INTRODUCTION versie tn Rn 2 SPEGIMIGAHIONG susanne net bmmtant 3 PRINCIPLES OF OPERATION 4 TIMING DISCRIMINATOR JJ Performance of the GSI Constant Fraction Discriminators CF 4000 and CF 8000 SAFETY INSTRUCTIONS AND SYMBOLS This manual contains up to three levels of safety instructions that must be observed in order to avoid personal injury and or damage to equipment or other property These
13. t must 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 865 482 441 1 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 i
14. ulse s rise time This guarantees good time information for pulses of constant shapes within a wide range of amplitudes For the measurement of the delay as a function of the dynamic range of input signals A pulser signal has been fed into the CFD time output stopped a time to amplitude converter TAC that was started by a reference signal The time differences have been measured using a multi channel analyzer MCA The delay of the attenuator has been taken into account The correction factors have been determined by measuring the phase differences at different attenuation factors at 200 MHz with a vestor voltmeter The systematic errors of this correction have been 8 5 ps Fig 1 shows the delay as a function of the amplitude of the input signal log scale for different constant fraction discriminators The test pulsers have had a rise time of 5 ns and a decay time of 15 ns The walk adjustments for the CF 4000 TC 454 and ORTEC 934 have been done by optimizing the performance curves The resulting walk has been about 2 mV more positive than the well known equal brightness recipe for CF 4000 and TC 454 The bigger shift of the CF 8000 is due to the symmetric walk adjust Done by the automatic baseline restorer instead of the better asymmetric adjust Fig 2 shows the performance of the CFDs at a faster rise time of the test pulses The large time shift at high pulse amplitudes for CF 4000 CF 8000 and TC 454 are a property of the fast discriminator C
Download Pdf Manuals
Related Search