GRAINE 2015, a balloon-borne emulsion γγ-ray telescope experiment in Australia

S. Takahashi, S. Aoki, K. Hamada, T. Hara, T. Inoue, K. Ishiguro, A. Iyono, H. Kawahara, K. Kodama, R. Komatani, M. Komatsu, T. Kosaka, M. Miyanishi, F. Mizutani, K. Morishima, M. Morishita, N. Naganawa, M. Nakamura, T. Nakano, A. Nishio, K. Niwa, N. Otsuka, K. Ozaki, H. Rokujo, O. Sato, E. Shibayama, A. Suzuki, R. Tanaka, Y. Tateishi, S. Tawa, M. Yabu, K. Yamada, S. Yamamoto, M. Yoshimoto

gamma ray astronomy, nuclear emulsion
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We are developing the GRAINE project, which consists of a 10 MeV?100 GeV cosmic γ -ray
observation with a precise (0.08? at 1?2 GeV) and polarization-sensitive (50% or below the minimum
detectable polarization for the Vela pulsar above 100 MeV) large-aperture-area (?10 m2)
emulsion telescope, by repetitive long duration balloon flights. In 2015, we performed a Japan?
Australia JAXA collaborative balloon experiment at the Alice Springs balloon-launching station.
The telescope had a 3780 cm2 aperture and was aloft for a total of 14.4 h. The experiment aims
to detect the well-known bright Vela pulsar γ -ray source and thereby demonstrate the overall
performance of the emulsion γ -ray telescope. The design, improvements, and preparations as
well as the 2015 balloon experiment are described in this paper. Analysis of the data from this
experiment is ongoing.
PTEP

Progress of theoretical and experimental physics

073

F01

112