高エネルギー・一次宇宙線重粒子の観測 : HECRO 81 テレスコープによる測定

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Observation of high energy (>8 Gv) cosmic ray heavy particles has been made by HECRO-81 system onboard B 50-17 balloon on Sept. 30-Oct. 1,1981. The detector system consists of two Cerenkov detectors, one plastic scintillation detector and 2 pairs of crossed MPPC (multi pipe proportional counters). It has a geometric factor of 6000cm^2str. for triggering coincidence between solid Cerenkov and plastic scintillation detector. Information on the position of particles passing through the telescope was obtained from the output of MPPC's with an accuracy of about 1cm, for a part of the solid angle with the geometric factor of 3300cm^2 str. About 126,000 events were recorded by this system during 28 hours while the atmospheric depth of the balloon was between 9 to 10g cm^<-2>. The design and performance of the detector system onboard the balloon and data recording system at ground are described. The observed pulse heights and track position information are organized into 14-30 words of 21 bits each, and sent to ground via 1.68GHz transmitter with 16 Kbps PM/PCM subcarrier. Once every seconds, monitor information including the attitude of gondola, atmospheric pressure, temperature, high voltage monitor and counting rates of each detector was sent to ground through same telemeter channel with 21 words of 21 bits each. Received signal was recorded in digital casette magnetic tapes after demodulation and decoding by a micro computer. Also operating conditions of the onboard system was monitored by CRT displays using another micro computer. The chemical abundance of the primary cosmic ray particles heavier than Boron was derived from the observed pulse height distribution in the plastic Cerenkov detector. The results from all events taking account of the path length distribution are compared with that derived from selected events in which the path length in the detector was determined from MPPC data. Both results were found to be in good agreement with other results previously obtained. The dependence of the chemical abundance on the particle energy was also studied. The information on the particle path from MPPC is used to determine the incoming direction of the particle in geographic coordinate. This in turn can be used to fix the lowest rigidity for a particular particle from the knowledge of the geomagnetic cut off rigidity for this direction above Sanriku Balloon Center. There appears some indication of higher flux of even charged nuclei relative to the odd charged nuclei at higher cut off rigidity.
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高エネルギー・一次宇宙線重粒子の観測 : HECRO 81 テレスコープによる測定

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