Methods for Detecting High Energy Photons in Primary Cosmic Rays

概要

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Detection of the high energy photons in primary cosmic rays provides us with useful data for the study of the origin of cosmic rays, because they move in straight lines and bring information on the directions of their sources. Two methods are described to detect such photons through the secondary particles produced by them in air. i) A part of photons can produce mesons capable of reaching the sea level through photonuclear interactions with air nuclei, although the majority of them are absorbed in the atmosphere by producing electron pairs when their energies are 10^<10>-10^<11>ev. These mesons do not suffer considerable scattering from the original direction of photons, and higher intensity of mesons in a small solid angle containing the direction of the source can be detected in comparison with the average intensity. The lower limit of the photon flux detectable by this method is estimated to be about 4・10^-6cm^-2sec^-1 for photons of 200 Gev. ii) For photons with energies near 10^<12> ev, it is possible to detect cascade showers initiated from them when observations are made at mountain altitude. Discussions are made on the detection efficiency of these showers by the special arrangement of shower detectors. Minimum detectable flux of photons of 10^<12> ev by this arrangement is estimated to be about 2・10^-7 cm^-2 sec^-1.
一般社団法人日本物理学会の論文
1961-10-25