Speaker
Description
Author: Kazuki Yamamoto
Co-author: Shojun Ogasawara, Joshi Aryaa Rajendra, Soichiro Kojimaa, Kosuke Sato, Kazuo Tanaka, Jun Kataoka, Yoichi Yatsu, Toshihiro Chujo, Hiroki Nakanishi, Makoto Arimoto, Satoshi Hatori, Kyo Kume, Satoshi Mizushima, Shinko Sando, Takashi Hasegawa
Observations in the MeV gamma-ray band are known to be extremely challenging because gamma rays in this energy range cannot be focused with conventional optics and background radiation such as the cosmic X-ray background (CXB) and albedo gamma-ray dominates over source signals. Therefore, observations in this energy range have stagnated for nearly 30 years since the Compton Gamma Ray Observatory (CGRO) conducted measurements in the 1990s. In this context, Waseda University and Science Tokyo are developing a small satellite called GRAPHIUM, which is scheduled for launch in 2027. The onboard X-ray and gamma-ray camera, INSPIRE, is a hybrid Compton camera that adopts GAGG and BGO scintillators. GAGG has excellent characteristics, such as high light output and non-hygroscopicity; however, because GAGG is developed recently, its performance has not yet been sufficiently demonstrated in satellite missions.
In this study, GAGG was irradiated for two hours with protons corresponding to ten years of orbital exposure at the Wakasa Wan Energy Research Center. Gamma-ray spectra were then measured over a period of three months using a high-purity germanium detector. Based on the results, we investigated the activation characteristics of GAGG and estimated the extent to which activation-induced background affects the sensitivity of INSPIRE.
