BESS-polar II measurements of the cosmic-ray proton and helium spectra at solar minimum

K. Sakai, K. Abe, H. Fuke, S. Haino, T. Hams, M. Hasegawa, A. Horikoshi, K. C. Kim, A. Kusumoto, M. H. Lee, Y. Makida, S. Matsuda, Y. Matsukawa, J. W. Mitchell, J. Nishimura, M. Nozaki, R. Orito, J. F. Ormes, M. Sasaki, E. S. SeoR. Shinoda, R. E. Streitmatter, J. Suzuki, K. Tanaka, N. Thakur, T. Yamagami, A. Yamamoto, T. Yoshida, K. Yoshimura

    Research output: Chapter in Book/Report/Conference proceedingConference contribution

    Abstract

    The energy spectra of cosmic-ray protons and helium near solar minimum were precisely measured with BESS-Polar II (Balloon-borne Experiment with a Superconducting Spectrometer) during a long-duration flight over Antarctica in December 2007 and January 2008, and are discussed here. The absolute fluxes and spectral shapes of primary protons and helium probe the origin and the propagation history of cosmic rays in the Galaxy. The spectra are also essential as inputs to calculate the spectrum of cosmic-ray antiprotons, which are secondary products of cosmic-ray interactions with the interstellar gas. To optimize the measurement of the magnetic rigidity of incident particles, obtained from the curvature of their trajectories in a solenoidal magnetic field of 0.8 Tesla, an improved calibration of the central JET-type drift chamber and two inner drift chambers was developed. Using this, we obtained absolute spectra of primary cosmic-ray protons up to around 120 GeV and helium up to around 50 GeV/nucleon.

    Original languageEnglish
    Title of host publicationProceedings of the 33rd International Cosmic Rays Conference, ICRC 2013
    PublisherSociedade Brasileira de Fisica
    ISBN (Electronic)9788589064293
    Publication statusPublished - 2013
    Event33rd International Cosmic Rays Conference, ICRC 2013 - Rio de Janeiro, Brazil
    Duration: Jul 2 2013Jul 9 2013

    Publication series

    NameProceedings of the 33rd International Cosmic Rays Conference, ICRC 2013
    Volume2013-October

    Other

    Other33rd International Cosmic Rays Conference, ICRC 2013
    Country/TerritoryBrazil
    CityRio de Janeiro
    Period7/2/137/9/13

    Keywords

    • Cosmic-ray helium
    • Cosmic-ray proton
    • Solar minimum
    • Superconducting spectrometer

    ASJC Scopus subject areas

    • Nuclear and High Energy Physics

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