Line Gamma-ray Astronomy by the next generation Semiconductor Compton Camera

2019 Fiscal Year Final Research Report

• Project/Area Number: 16H02170
• Research Category: Grant-in-Aid for Scientific Research (A)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Astronomy
• Research Institution: The University of Tokyo (2018-2019); Japan Aerospace EXploration Agency (2016-2017)
• Principal Investigator: Takahashi Tadayuki 東京大学, カブリ数物連携宇宙研究機構, 教授 (50183851)
• Co-Investigator(Kenkyū-buntansha): 渡辺 伸 国立研究開発法人宇宙航空研究開発機構, 宇宙科学研究所, 助教 (60446599) ; 武田 伸一郎 東京大学, カブリ数物連携宇宙研究機構, 特任助教 (80553718)
• Project Period (FY): 2016-04-01 – 2020-03-31
• Keywords: ガンマ線検出器 / コンプトンカメラ / ガンマ線天文学 / MeVガンマ線

Outline of Final Research Achievements

Electron tracking based Compton imaging is a key technique to improve the sensitivity of Compton cameras by measuring the initial direction of recoiled electrons. We have developed a new Si-CMOS hybrid detector as a scatterer of Compton cameras. It is a Si detector bump-bonded to a CMOS readout integrated circuit to obtain electron trajectories. To acquire the energy and the event timing, signals from back side, in which strip electrodes are implemented. are read out with a timing resolution of few μs. Images of recoiled electron trajectories are obtained successfully from CMOS side. By combining with a 2mm thick CdTe double sided detector, we constructed a Si/CdTe Compton camera. We confirmed that the initial direction of the electron is determined properly and incident directions of gamma-ray photons are successfully reconstructed. An energy resolution of 7.4 keV (FWHM) and an angular resolution of 3.1 degree (FWHM) are obtained from the camera for 662 keV gamma-rays.

Free Research Field

宇宙物理学実験

Academic Significance and Societal Importance of the Research Achievements

感度のギャップに埋もれて進展が妨げられている数100keV から数MeVの領域でのガンマ線天文学に革新をもたらすために、エネルギー分解能が高く、また角度分解能が高い半導体コンプトンカメラの開発が重要である。本研究で新たに開発した散乱電子の方向を測定できるSi検出器とCdTeイメージャを組み合わせたコンプトンカメラは、到来するガンマ線の方向を一意に決めることができる。これを発展させることで、天体観測ばかりではなく、放射性物質の分布の可視化や医学イメージングにおいて検知力の向上につながる。