Extended measurement of the proton spectrum with CALET on the International Space Station

CALET Collaboration

Research output: Contribution to journalConference articlepeer-review


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.

Original languageEnglish
Article number098
JournalProceedings of Science
Publication statusPublished - 2022 Mar 18
Event37th International Cosmic Ray Conference, ICRC 2021 - Virtual, Berlin, Germany
Duration: 2021 Jul 122021 Jul 23

ASJC Scopus subject areas

  • General


Dive into the research topics of 'Extended measurement of the proton spectrum with CALET on the International Space Station'. Together they form a unique fingerprint.

Cite this