The Calorimetric Electron Telescope (CALET) is pursuing the direct measurement of the main components of high energy cosmic rays up to ∼ 1 PeV in order to understand the cosmic ray acceleration and propagation. The detector consisting of a charge detector, an imaging calorimeter, and a total absorption calorimeter, is located on the International Space Station. The thickness of the calorimeter corresponds to 30 radiation lengths and to ∼ 1.3 proton interaction lengths. We have taken data for more than five years so far: data taking has started in October 2015 and continues stably without any serious troubles. We present the latest result of proton spectrum analysis in the energy region from 30 GeV to 60 TeV with a fiducial geometrical factor of ∼ 510 cm2 sr and proton energy resolution is 30-40%. The residual background is less than 10% in the E < 10 TeV region. Compared to our previous result published in Physical Review Letters in 2019, more than two years of additional data have been analyzed. Spectral hardening around 500 GeV is confirmed with higher statistics. We report our preliminary observation of a proton spectral softening around 10 TeV.
|Journal||Proceedings of Science|
|Publication status||Published - 2022 Mar 18|
|Event||37th International Cosmic Ray Conference, ICRC 2021 - Virtual, Berlin, Germany|
Duration: 2021 Jul 12 → 2021 Jul 23
ASJC Scopus subject areas