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A Counter Controlled Cloud Chamber Triggering on Rare Events in the Synchro-Phasotron Beam

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A Counter Controlled Cloud Chamber Triggering on Rare Events in the Synchro-Phasotron Beam A COUNTER CONTROLLED CLOUD CHAMBER TRIGGERING ON RARE EVENTS IN THE SYNCHRO-PHASOTRON BEAM N. M. Viryasov, G. G. Vorob'ev, Kim Khi In, L. N. Strunov and I. V. Chuvilo Joint Institute for Nuclear Research, Dubna (presented by Kim Khi In) The rate of detection of rare events by the use momentum is described in the paper by Viryasov of track chambers is limited by the fact that, for et al.2). The expansion of the cloud chamber took normal scanning of the photographs obtained from place only in the case when an anti-proton passed a chamber of average dimensions, it is necessary through the channel. The time of radiation from that no more than several tens of particle tracks be the synchro-phasotron target was equal to 0.25-0.30 photographed each time. This fact restricts the s. The fraction of anti-protons in the beam application of track chambers for detecting pro­ was equal to (1—2) × 10-4, with respect to other cesses arising in the interaction between Κ mesons particles which are viewed as a background2). The and anti-protons, which are contained as a very discrimination of background particle tracks in the small contaminant in the beams ejected from the cloud chamber was made by means of two operations : accelerators, if special methods of separation are not 1. The electric field, of some hundreds of volts used. per cm "dragged" ions of tracks of particles which Our technique for the use of a cloud chamber, appeared in the chamber before the arrival of the which is counter-controlled by definite events, enables counter controlled master-pulse. This master-pulse us to decrease sharply the times for the detection of switched off the clearing electric field and triggered a rare event. An analogous method has been de­ the expansion of the chamber and the photographic scribed in a paper by Birge et al.1). system. The above technique is applied by us for the study 2. To prevent particles from arriving in the cham­ of processes taking place in the interaction of fast ber after an anti-proton, the master-pulse controlled anti-protons with the matter of solid targets. the radio-frequency of the synchro-phasotron to The cloud chamber is 500 × 500 × 150 mm3 in a remove the proton beam from the internal target. magnetic field of 16 500 Oe and is filled with helium This way of operation allowed us to increase to a pressure of 2.8 atmospheres and with vapours more than ten times the intensity of the beam falling of ethyl alcohol (70%) and water (30%). When on the chamber. A typical photograph obtained operating with a slow intermediate expansion, the at a beam intensity of 250 particles and for a radia­ dead time of the cloud chamber was equal to 80 s. tion time of 0.25 s is given in Fig. 1. A clearing The clearing field voltage was applied to a conducting field of 4 000 V in the form of packets of short pulses layer on the glass through which the photographs has been used. One can see, together with the anti-proton were taken. The conducting layer resistance is tracks, only those particles that had appeared in 3.5 kΩ. the chamber earlier. A "master-pulse" controlling the chamber was The clearing of the chamber from "background" received from a coincidence circuit which triggered tracks will evidently be better if one uses a longer at the moment when an anti-proton passed through the machine pulse with a uniform intensity. channel. The system selecting anti-protons of momen­ The magnitude of the maximum permissible clear­ tum of 2.8 GeV/c from π- and K- mesons of the same ing field strength is determined by the effect of fogging Fig. 1 Typical photograph of the cloud chamber obtained at a beam intensity of 250 particles per pulse, and with a radiation time of 0.25 s. 580a Counters and other high-energy particle detectors 581 the working volume of the chamber underWhen thi sthe duratio expansion.n was 0.3 s at V = 2 600 V one The experiment showed that the operationobserved the of increas e of the droplet background. the chamber depends on whether the clearing fieldOn the other hand the background was not increased voltage is applied to the chamber constantly orat i sV = 7 500 V when, during the radiation from the increased by pulses starting from a certain not higsynchro-phasotroh n (0.3 s), the voltage was applied level (about 700-1 000 V) to very large values. Iinn th thee form of a packet of short pulses. The duration first case the chamber already begins to become of each pulse in this packet was about 30 ms. The fogged at a constant voltage of 1 800-1 900 V. Iclearinn theg field is turned off about 3 μs after the arrival of second case, one succeeded in applying the voltagthee master-pulse. up to 7 500 V and the fogging was not yet observedTo. determine the co-ordinates of the incoming antiproton, The magnitude of the voltage at which foggingone then uses a hodoscopic system involving occurs depends on the duration of the voltage pulsepulse.d gas-discharge counters3). LIST OF REFERENCES 1. Birge, R. W., Courant, H. W. J., Lanou, R. E. and Whitehead, M. N. A technique for the use of a multiple cloud chamber at the bevatron. Societa Italiana di Fisica. International conference on mesons and recently discovered particles and 43° Congresso nazionale di fisica. Padova-Venezia, 22-28 settembre 1957. Comunicazioni, Session XVII, p. 8. 2. Viryasov, N. M., Vovenko, A. S., Vorob'ev, G. G., kirillov, A. D., Kim Khi In, Kulakov, Β. Α., Lyubimov, A. L., Matulenko, Yu. Α., Savin, Ι. Α., Chuvilo, A. V. and Strunov, L. N. (Antiproton channel with momentum of 2.8 Bev/C.). Joint Institute for Nuclear Research, Dubna. (To be published). 3. Vishnyakov, V. V. and Tyapkin, A. A. (Investigation of work of gas-discharge counters at controlled pulse supply.). Atomnaya Energiya. (To be published). THE COUPLING OF COUNTER EXPERIMENTS TO COMPUTERS(*) C. Wiegand Lawrence Radiation Laboratory, University of California, Berkeley, Cal. INTRODUCTION It has become clear to many of us who do countethe rgian t accelerators now in operation and those experiments that we must use systems which willwhic h are about to go into operation such as the automatically record data and store it in a suitablprotoe n synchrotron here at CERN. form for analysis by electronic computers. We One means of increasing the efficiency of counter realize the huge expenditures in resourcesexperiments is andto us technicale arrays of counter s with more manpower that are being expended inelements the. field This wil l effectively increase the solid of high energy nuclear physics, and we are concerneanglde explored or improve spatial resolution. Taking about how to make efficient use of the beams fromorme data simultaneously can obviously improve (*) Work done under auspices of the U.S. Atomic Energy Commission. .
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