Update of the Helium flux measurement with CALET on the International Space Station

Brogi, P.; Kobayashi, K.; Mattiazzi, M.; Adriani, O.; Akaike, Y.; Asano, K.; Asaoka, Y.; Berti, E.; Betti, P.; Bigongiari, G.; Binns, W. R.; Bongi, M.; Bruno, A.; Cannady, N.; Castellini, G.; Checchia, C.; Cherry, M. L.; Collazuol, G.; De Nolfo, G. A.; Ebisawa, K.; Ficklin, A. W.; Fuke, H.; Gonzi, S.; Guzik, T. G.; Hams, T.; Hibino, K.; Ichimura, M.; Israel, M. H.; Kasahara, K.; Kataoka, J.; Kataoka, R.; Katayose, Y.; Kato, C.; Kawanaka, N.; Kawakubo, Y.; Kohri, K.; Krawczynski, H. S.; Krizmanic, J. F.; Maestro, P.; Marrocchesi, P. S.; Messineo, A. M.; Mitchell, J. W.; Miyake, S.; Moiseev, A. A.; Mori, M.; Mori, N.; Motz, H. M.; Munakata, K.; Nakahira, S.; Nishimura, J.; Negro, M.; Okuno, S.; Ormes, J. F.; Ozawa, S.; Pacini, L.; Papini, P.; Rauch, B. F.; Ricciarini, S. B.; Sakai, K.; Sakamoto, T.; Sasaki, M.; Shimizu, Y.; Shiomi, A.; Spillantini, P.; Stolzi, F.; Sugita, S.; Sulaj, A.; Takita, M.; Tamura, T.; Terasawa, T.; Torii, S.; Tsunesada, Y.; Uchihori, Y.; Vannuccini, E.; Wefel, J. P.; Yamaoka, K.; Yanagita, S.; Yoshida, A.; Yoshida, K.; Zober, W. V.

doi:10.22323/1.501.0019

The CALorimetric Electron Telescope (CALET) is a space-based calorimetric instrument, designed to carry out precise measurements of high energy cosmic rays. Installed on the Japanese Experiment Module – Exposed Facility on the ISS, it is collecting data with excellent performance and no significant interruptions since October 2015. We present the updated results of the direct measurement of the energy spectrum of cosmic-ray helium, based on more than 9 years of collected data, with an expected statistical increase of about 40% compared with the previously published measurement. The helium flux shows significant deviations from a single power law with a progressive hardening around a few hundred GeV followed by a softening in the multi-TeV region. The increase in statistics allows to extend the upper limit of the measured energy range and to improve the precision of the measurement itself in the high energy part of the spectrum.

Update of the Helium flux measurement with CALET on the International Space Station / P. Brogi, K. Kobayashi, M. Mattiazzi,, O. Adriani, Y. Akaike, K. Asano, Y. Asaoka, E. Berti, P. Betti, G. Bigongiari, W.R. Binns, M. Bongi, A. Bruno, N. Cannady, G. Castellini, C. Checchia, M.L. Cherry, G. Collazuol, G.A. de Nolfo, K. Ebisawa, A.W. Ficklin, H. Fuke, S. Gonzi, T.G. Guzik, T. Hams, K. Hibino, M. Ichimura, M.H. Israel, K. Kasahara, J. Kataoka, R. Kataoka, Y. Katayose, C. Kato, N. Kawanaka, Y. Kawakubo, K. Kohri, H.S. Krawczynski, J.F. Krizmanic, P. Maestro, P.S. Marrocchesi, A.M. Messineo, J.W. Mitchell, S. Miyake, A.A. Moiseev, M. Mori, N. Mori, H.M. Motz, K. Munakata, S. Nakahira, J. Nishimura, M. Negro, S. Okuno, J.F. Ormes, S. Ozawa, L. Pacini, P. Papini, B.F. Rauch, S.B. Ricciarini, K. Sakai, T. Sakamoto, M. Sasaki, Y. Shimizu, A. Shiomi, P. Spillantini, F. Stolzi, S. Sugita, A. Sulaj, M. Takita, T. Tamura, T. Terasawa, S. Torii, Y. Tsunesada, Y. Uchihori, E. Vannuccini, J.P. Wefel, K. Yamaoka, S. Yanagita, A. Yoshida, K. Yoshida, W.V. Zober. - In: POS PROCEEDINGS OF SCIENCE. - ISSN 1824-8039. - ELETTRONICO. - 501 - 39th International Cosmic Ray Conference (ICRC2025):(2025), pp. 0-0. ( 39th International Cosmic Ray Conference, ICRC 2025 Geneva, Switzerland 15-24 July 2025) [10.22323/1.501.0019].