Matsushiro Underground Cosmic-Ray Observatory (2S0 m. w. e. Depth) and the Observation of High Energy (r1012 /!V) Cosmic Ray Intensity Variation

概要

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A new underground cosmic-ray observatory was opened in Matsushiro, Nagano City, Japan on March 22, 1984, and a multi-directional muon telescope has been installed at an effective vertical depth of 220 m. w. e. underground. The telescope consists of 50 plastic scintillation detectors totally, arranged in two layers of 25 detectors each and has 17 directional channels of observation. We have made the continuous observation of the intensity variation of cosmic ray muons (median primary energies of detection d1012 eV) since that date. The intensity has been recorded every hour, and the average muon countingrates are; ～8.7×10t counts per hour for a wide-angle vertical telescope (two-fold coincidence between upper and lower arrays of detectors) and ～2.0×10t counts per hour for a vertical component-telescope, for example. In the present report, we describe briefly the underground observatory of Matsushiro and its surroundings, including the underground tunnel, the muon detector, the multi-directional telescope constructed and some of its related characteristics. We also present some of the observed intensity variations of cosmic ray muons for a full five-year period from April 1984 through March 1989 and discuss preliminarily the analyzed results of them in solar and sidereal time.
信州大学理学部の論文
1989-10-30