The CALET ISS High Energy Cosmic Ray Experiment: Nuclei Energy Spectra

The CALET high energy cosmic ray space experiment has been operating as an attached payload on the International Space Station (ISS) Japanese Experiment Module – Exposed Facility (JEM-EF) for more than 6 years. While the CALET design emphasizes the precise investigations of cosmic ray electrons beyond ~5 TeV, the instrument has also been used to study the energy spectra of cosmic ray nuclei from protons to the iron peak near 1,000 TeV. We summarize the instrument performance and discuss the CALET energy spectrum measurements for H, C, O, and Fe nuclei and compare CALET results with measurements reported by other experiments. In particular, we discuss the shape of the spectra at high energies including multiple changes in the H, C, and O spectral index. Our present Fe observations are consistent with a single power law up to 2 TeV / nucleon and above this limit our present statistical and systematic error limit our ability to draw conclusions about possible deviations.