Measurement of the Iron Spectrum in Cosmic Rays from 10 GeV$/n$ to 2.0 TeV$/n$ with the Calorimetric Electron Telescope on the International Space Station

Abstract

The Calorimetric Electron Telescope (CALET), in operation on the International Space Station since 2015, collected a large sample of cosmic-ray iron over a wide energy interval. In this Letter a measurement of the iron spectrum is presented in the range of kinetic energy per nucleon from 10 GeV$/n$ to 2.0 TeV$/n$ allowing the inclusion of iron in the list of elements studied with unprecedented precision by space-borne instruments. The measurement is based on observations carried out from January 2016 to May 2020. The CALET instrument can identify individual nuclear species via a measurement of their electric charge with a dynamic range extending far beyond iron (up to atomic number $Z$ = 40). The energy is measured by a homogeneous calorimeter with a total equivalent thickness of 1.2 proton interaction lengths preceded by a thin (3 radiation lengths) imaging section providing tracking and energy sampling. The analysis of the data and the detailed assessment of systematic uncertainties are described and results are compared with the findings of previous experiments. The observed differential spectrum is consistent within the errors with previous experiments. In the region from 50 GeV$/n$ to 2 TeV$/n$ our present data are compatible with a single power law with spectral index -2.60 $\pm$ 0.03.

main text: 7 pages, 4 figures; supplemental material: 10 pages, 12 figures, 1 table. arXiv admin note: text overlap with arXiv:2012.10319

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Cited by in corpus (15)

• Observation of Spectral Structures in the Flux of Cosmic-Ray Protons from 50 GeV to 60 TeV with the Calorimetric Electron Telescope on the International Space Station
• Measurement of the Iron Spectrum in Cosmic Rays from 10 GeV$/n$ to 2.0 TeV$/n$ with the Calorimetric Electron Telescope on the International Space Station
• Direct Measurement of the Cosmic-Ray Helium Spectrum from 40 GeV to 250 TeV with the Calorimetric Electron Telescope on the International Space Station
• Cosmic-ray Boron Flux Measured from 8.4 GeV$/n$ to 3.8 TeV$/n$ with the Calorimetric Electron Telescope on the International Space Station
• A cosmic-ray database update: CRDB v4.1
• Direct Measurement of the Nickel Spectrum in Cosmic Rays in the Energy Range from 8.8 GeV/n to 240 GeV/n with CALET on the International Space Station
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• Precision spectral measurements of Chromium and Titanium from 10 to 250 GeV$/n$ and sub-Iron to Iron ratio with the Calorimetric Electron Telescope on the ISS
• Analyzing Cosmic Ray Spectral Features: A Numerical Investigation