Browsing by Autor "Hironori Kojima"

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    A new high energy gamma-ray observatory in the southern hemisphere: The ALPACA experiment
    (IOP Publishing, 2020) Carlos I. Calle; K. Hibino; N. Hotta; Y. Katayose; C. Kato; Shinsuke Kato; K. Kawata; W. Kihara; Y. J. Ko; Hironori Kojima
    Abstract The ALPACA experiment is a new international project between Bolivia and Japan. It is going to consist of an 83,000 m 2 surface air-shower array and a 5,400 m 2 underground water Cherenkov muon detector array, and the experimental site is at Mt. Chacaltaya plateau at an altitude of 4,740 m. Its main target is to observe 100 TeV gamma rays and explore high-energy gamma-ray sources in the southern sky. This is because such high-energy gamma rays hold the key to identify the origin of cosmic rays at the knee region of the energy spectrum. So far many high-energy gamma-ray sources have been found in the southern sky. They are emitting gamma rays of several tens of TeV, so some of them could be PeVatrons which accelerate cosmic rays to PeV energy region in the Galaxy. By observing them in higher energy region, we will obtain new knowledge of cosmic-ray acceleration to the knee region, and discover new gamma-ray sources. As the prototype experiment of ALPACA, the ALPAQUITA experiment is now under construction. In a MC simulation, we found that ALPAQUITA has the ability of detecting bright gamma-ray sources in the southern hemisphere such as Vela X within 1 year.
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    ALPAQUITA Array in the ALPACA Project
    (2017) K. Kawata; T. Asaba; K. Hibino; N. Hotta; M. Kataoka; Y. Katayose; C. Kato; Hironori Kojima; R. Mayta; P. Miranda
    We are now proposing a new project which consists of a large air shower array (83,000 m^2) and a muon detector array (5,400 m^2) located at the altitude of 4,740 m near La Paz in Bolivia to observe 100 TeV gamma rays in the southern sky. The ALPAQUITA array is a prototype air shower array which will be constructed at the ALPACA site. This array consists of 45 scintillation counters of 1 m^2 in area each, and its effective area is approximately 8,000 m^2 (1/10 of ALPACA air shower array). In the present paper, we report on the current status and the performance of the ALPAQUITA array