Study of high timing resolution imaging of Terrestrial Gamma-ray Flashes from aircrafts

2020 Fiscal Year Final Research Report

• Project/Area Number: 19K21899
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 17:Earth and planetary science and related fields
• Research Institution: Nagoya University
• Principal Investigator: Nakazawa Kazuhiro 名古屋大学, 素粒子宇宙起源研究所, 准教授 (50342621)
• Project Period (FY): 2019-06-28 – 2021-03-31
• Keywords: 雷ガンマ線 / 電子加速 / チェレンコフ検出器

Outline of Final Research Achievements

The Terrestrial Gamma-ray Flash (TGF), a sudden MeV gamma ray synchronized with lightning discharges, is so powerful that it can be observed from satellites, and its observational understanding is important because the radiation dose of aircraft flying near the electron acceleration regions in thunderclouds can be large. Because of the extremely high luminosity, we have developed a new detector demonstrator that uses Cherenkov light instead of the conventional scintillator detector. The direction of incidence of gamma rays can also be determined by measuring both ends of the acrylic rod with the MPPC. Although we could not conduct experiments with a 10 MeV gamma-ray source due to COVID19, we verified the direction measurements using cosmic rays. We succeeded in establishing a compact, lightweight, and low-power-consumption prototype of the device.

Free Research Field

高エネルギー宇宙物理

Academic Significance and Societal Importance of the Research Achievements

TGFの被曝量は数値上は人間に影響がないとは言えないほど強い可能性が高い。特に冬季の日本海岸では雷雲の到達高度が低く、その直上を航空機が飛行する際の被曝量の見積もりは重要である。本研究では、TeVガンマ線計測で用いられるチェレンコフ検出の原理を用いて、軽量で指向性を持ち、検出効率を下げることで高輝度のTGFで回路系が飽和しない装置を実現すべく、試作機でその概念を実証した。宇宙観測の技術を生かし、コンパクトで低消費電力なシステムとなっており、航空機への複数このシステムの搭載も容易である。今後はTGFの地上観測でも利用しつつ、より大型の予算により航空機搭載型の本格装置の開発を目指す。