High energy primary cosmic ray observation (HECRO 81)

The system for high energy primary cosmic ray observation (HECRO 81) is introduced. The HECRO 81 is designed to study the chemical composition of heavy particle beam and the isotopic abundance. The system consists of two Cherenkov detectors, a scintillator and two MPPC systems. The solid angle of detection was 6049 cm2 str. The charge and the lower limit of the velocity of particles were measured by the Cherenkov detectors. The cut-off rigidity in the direction of incidence was determined from the direction of the gondola. The charge distribution and the average mass of each nuclide were obtained from the observed data. Light emitting diodes were installed in the Cherenkov and the scintillation detectors, and used for the calibration of the efficiency of detectors. The data obtained by the detectors were transmitted to a ground station by a telemeter system. As an example of the measured data, the zenith angle distribution of incident particles is presented. (Kato, T.)