Online ISSN: 1884-4111 Print ISSN: 0033-8303
Radioisotopes 68(12): 817-827 (2019)

特集Special Issues

CALETによる国際宇宙ステーションにおける宇宙線直接観測Direct Cosmic-ray Observations with CALET on the International Space Station

早稲田大学理工学総合研究所WISE, Waseda University ◇ 162–0044 東京都新宿区喜久井町17 ◇ 17 Kikuicho, Shinjuku-ku, Tokyo 162–0044, Japan

発行日:2019年12月15日Published: December 15, 2019

CALorimetric Electron Telescope(CALET)実験は,国際宇宙ステーションにおける高エネルギー宇宙線物理学のミッションであり,米国,イタリアとの国際共同研究として日本が主導的な役割を果たしている。CALETの主要な目的としては,高エネルギー電子の近傍加速源の探求,銀河宇宙線の加速・伝播機構の解明,及び暗黒物質の探索などがある。2015年の10月中旬に観測を開始して以来,高エネルギーシャワー(>10 GeV)をトリガーする運用が,現在まで継続的かつ安定的に行われおり,その観測成果について報告する。

The CALorimetric Electron Telescope (CALET) space experiment, which has been developed by Japan in collaboration with Italy and the United States, is a high-energy astroparticle physics mission on the International Space Station (ISS). The primary goals of the CALET mission include investigating possible nearby sources of high energy electrons, studying the details of acceleration andpropagation of galactic cosmic rays, and searching for dark matter signatures. During an expected five-year mission, the CALET experiment is measuring the flux of cosmic-ray electrons (including positrons) to 20 TeV, gamma-rays to 10 TeV and nuclei with Z=1 to 40 up to 1,000 TeV. CALET has sufficient depth, imaging capabilities and excellent energy resolution to allow for a clear separation between hadrons and electrons and between charged particles and gamma rays. Since the start of operation at the ISS from mid-October, 2015, a continuous observation has been maintained mainly by triggering high energy (>10 GeV) showers without any major interruption. The number of the triggered events is about 20 million per month, and the number will reach to nearly one billion as of mid of July, 2019. By using the data obtained, we will have a summary of the CALET observations up to the recent period.

Key words: cosmic ray; γ-ray; γ-ray burst; space experiment; international space station; calorimeter

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