; pr. . I . ! 1 OF L ORNL P 160 un. a .. : po . . - - - · . I SO 36 . * . . |1:25 |L.4 LE MICROCOPY RESOLUTION TEST CHART NATIONAL BUREAU OF STANDARDS – 1963 This paper was submitted for publication in the open literature at least 6 months prior to the issuance date of this Micro- card. Since the U.S.A.E.C. has no evi- dence that it has been published, the pa- per is being distributed in Microcard form as a preprint. 4 - LEGAL NOTICE This report was prepared as an account of - - - - - United States, nor the Commission, nor any person acting on behalf of the Commission: A. Makes any warranty or representa- tion, expressed or implied, with respect to the accuracy, completeness, or usefulness of the information contained in this report, or that the use of any information, appa- ratus, method, or process disclosed in this report may not infringe privately owned rights; or B. Assumes any liabilities with respect to the use of, or for damages resulting from the use of any information, apparatus, As used in the above, "person acting on behalf of the Commission" includes any em- ployee or contractor of the Commission, or employee of such contractor, to the extent that such employee or contractor of the Commission, or employee of such contractor prepares, disseminates, or provides access to, any information pursuant to his employ- ment or contract with the Commission, or his employment with such contractor. ORNL-P-160 AUG 1 1 1964 Modification of a 400-Channel Pulse-Height Analyzer to Eliminate Storage of Pulses Having Energies Below a Preset Bias* H. A. Toda and T. A. Love Oak Ridge National Lavoratory Oak Ridge, Tennessee An undesirable phenomenon has been encountered in using a commercially available transistorized 400-channel pulse-height analyzer' to measure pulse- height spectra above an arbitrarily preset energy level. It has been found that pulses having energies below the preset level are nevertheless stored, at a rate proportional to the number of such pulses present in the spectrum. This effect occurs both when the analyzer is triggered externally and when it is triggered internally, with the sensitivity set to reject small pulses. It is apparently caused by the fact that the trigger opens the linear gite ~2 usec before the concurrent signal reaches the gate. Any pulse arriving at the linear gate during this 2-usec period is stretched, and a signal is applied to the collector of the Shaper i circuit (familiarity with analyzer terminology is assumed), which results in the closing of the linear gate before the desired signal nas reached it. The circuit shown in Fig. 1 has been designed to overcome this difficulty. The eifect of the circuit is to clamp the base of Shaper i (designated as T18) for approximately 2 usec after the linear gate is opened. The linear gate, therefore, is still open when the desired signal reaches it. The trigger pair Q1 . and Q2 has a natural period of from 1.8 to 2.1 usec, while the trigger pair 23 and Q4 has a natural period longer than any pulse storage time possible in the *Research sponsored by the U. S. Atomic Energy Commission under contract with Union Carbide Corporation. Radiation Instrument Development Laboratory Model 34-12. LEGAL NOTICE This paper was submitted for publication in the open literature at least B months prior to the issuance date of this Micro- card. Since the U.S.A.E.C. has no evi- dence that it has been published, the pa- per is being distributed in Microcard form as a preprint. The roport me propered Mua Actorat al Coronunt sponsored work. Walther the wind hm, vor de Condom, mor w person active co behall of Communica: A. Kaken my n aty or topronnalla, exprimidor japun, nu respect be acry- rasy, compleanno, or wefalome of the laboracion contained la dulo roport, or what the we of way laformation, imunitu, wethod, or procw. dxclou la to report may not latring printhly o d rights, or J. Ammos wa Hamuwe will roonet to the w ol, or for damage to ting from the w of w orluiten, hunt, mone, or practu declownduo report. As und la thu whomo, porno acting an all of the Counseln" boludeo w r . porn or contractor of the Co uston, or saployee of muca contractor, to be trunt that med oploss or contractor of the countston, of employw a much conuctor preparos, demons, or provides are bo, wybiorulan pertant to M. ropognal or contact wful . Downloalon, or wo maplogst will recl contractor. ......... ...... ............-- -2. analyzer. A pilse from the trailing edge of the Shafer 1 collector waveform is used to reset trigger pair Q3 and 24 to its quiescent state at the end of conversion. The successful performance of the circuit 18 demonstrated by the spectra while the lower spectrum was accumulated after the circuit described above had been installed. Both spectra 1 Soco garma-ray pulse-height spectra) reflect a count rate of ~ 12,000 counts/sec, corresponding to an analyzer dead time of ~ 50%. It is clear that the installation of the clamping circuit has completely eliminated the accumulation of undesired pulses. The modified analyzer has been tested at count rates varying from 300 to 12,000 counts/sec and with trigger delays varying over a range of +0.5 usec. Its performance was vniformly satisfactory. List of Figures Fig. No. Title Circuit for Elimination of Storage of Pulses Below a Preset Trigger Level in a 400-Channel Analyzer. Pulse-Height Spectra of BoCo Gamma Rays Before and After Modification of the ':00-Channel Analyzer. UNCLASSIFIED ORNL-OWG 64-5578 0.047 9-35 R 220 गा 2200 3 470 3 470 32200 3 470 6800 6800 Q3 2N1300 ·02 2N130 100 2N1300 SN67A 330 330 IN67A TO COLL. 7 24 2N1307 201307 T55 18 ŽIOK 22K TOK Ź 130 L 330 0 + 10 TI +2.2 pF 2200 22K 0 + 10 560 05 2N388A or 2N1289 NOTE: ALL RESISTORS LA WATT. ALL CAPACITORS ARF EXCEPT AS NOTED. 9 + 10 9 +10 1000 31000 3 4700 - 22.2.F 20K P3 3600 220 0.1 uF TO COLLECTOR OF T 18 IN67A kt IN67A 06 2N388A or 2N1289 mm $2200 + 10 op7 - 10 OP8 GND OPS GUIDE BETWEEN PINS 7 AND 8 PIO TO BASE OF T 18 UNCLASSIFIED ORNL DWG 64-5576 . 103 A . BEFORE MODIFICATION counts / channel . 102 AFTER MODIFICATION 100 LINO COUNTS, 0 40 80 120 CHANNEL NUMBER 160 200 END DATE FILMED 81 / 2161 /165 . Z 1 in ..