First demonstration of gamma-ray imaging using balloon-borne emulsion telescope

Hiroki Rokujo; Shigeki Aoki; Kaname Hamada; Toshio Hara; Tatsuki Inoue; Katsumi Ishiguro; Atsushi Iyono; Hiroaki Kawahara; Koichi Kodama; Ryosuke Komatani; Masahiro Komatsu; Tetsuya Kosaka; Fukashi Mizutani; Motoaki Miyanishi; Kunihiro Morishima; Misaki Morishita; Mitsuhiro Nakamura; Toshiyuki Nakano; Akira Nishio; Kimio Niwa; Naoto Otsuka; Keita Ozaki; Osamu Sato; Emi Shibayama; Satoru Takahashi; Atsumu Suzuki; Ryo Tanaka; Yurie Tateishi; Shuichi Tawa; Misato Yabu; Kyohei Yamada; Saya Yamamoto; Masahiro Yoshimoto

arXiv · 1711.01544

First demonstration of gamma-ray imaging using balloon-borne emulsion telescope

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Abstract

We promote the precise gamma-ray observation project Gamma-Ray Astro-Imager with Nuclear Emulsion (GRAINE), which uses balloon-borne emulsion gamma-ray telescopes. The emulsion telescope realizes observations with high angular resolution, polarization sensitivity, and large aperture area in the 0.01--100 GeV energy region. Herein, we report the data analysis of emulsion tracks and the first demonstration of gamma-ray imaging via an emulsion telescope by using the flight data from the balloon experiment performed in 2015 (GRAINE 2015). The emulsion films were scanned by the latest read-out system for a total area of 41 m$^2$ in three months, and then the gamma-ray event selection was automatically processed. Millions of electron-pair events are accumulated in the balloon-borne emulsion telescope. The emulsion telescope detected signals from a calibration source (gamma rays from the interaction of cosmic rays with an aluminum plate) with a high significance during the balloon observation and created a gamma-ray image consistent with the source size and the expected angular resolution in the energy range of 100--300 MeV. The flight performance obtained in the GRAINE 2015 experiment proves that balloon-borne emulsion telescope experiments with larger area are feasible while maintaining expected imaging performance.

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Hiroki Rokujo, Shigeki Aoki, Kaname Hamada, Toshio Hara, Tatsuki Inoue, Katsumi Ishiguro, Atsushi Iyono, Hiroaki Kawahara, Koichi Kodama, Ryosuke Komatani, Masahiro Komatsu, Tetsuya Kosaka, Fukashi Mizutani, Motoaki Miyanishi, Kunihiro Morishima, Misaki Morishita, Mitsuhiro Nakamura, Toshiyuki Nakano, Akira Nishio, Kimio Niwa, Naoto Otsuka, Keita Ozaki, Osamu Sato, Emi Shibayama, Satoru Takahashi, Atsumu Suzuki, Ryo Tanaka, Yurie Tateishi, Shuichi Tawa, Misato Yabu, Kyohei Yamada, Saya Yamamoto, Masahiro Yoshimoto. 2017-11-05. First demonstration of gamma-ray imaging using balloon-borne emulsion telescope. https://arxiv.org/abs/1711.01544

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