Realization of high-sensitivity imaging measurements of plasma radiation for divertor detachment study

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K14689
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 14020:Nuclear fusion-related
• Research Institution: National Institute for Fusion Science
• Principal Investigator: Mukai Kiyofumi 核融合科学研究所, ヘリカル研究部, 助教 (90632266)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 非接触ダイバータ / ボロメータ / イメージング / 輻射計測

Outline of Final Research Achievements

In this study, I have improved the sensitivity of the InfraRed imaging Video Bolometer (IRVB), which is a 2-D radiation diagnostic necessary for investigating the energy balance of divertor detachment. For an IRVB on GAMMA10 / PDX (University of Tsukuba) that is conducting divertor simulation experiment, (1) an infrared camera was replaced to maximize the number of pixels observing a foil detector, (2) a titanium foil with one micron thickness was selected as the detector by optimizing foil material and thickness for the measurement with the photon energy <= 1 keV. By the sensitivity improvement, I successfully measured the radiation profile even in Ne seeded plasmas. The radiation in Xe seeded plasmas is more than three times that of in Ne seeded plasmas. Therefore, it is expected that the high-sensitivity IRVB will contribute to the investigation of the physical mechanism of the divertor detachment by comparing the species of impurity gases in the future.

Free Research Field

プラズマ計測

Academic Significance and Societal Importance of the Research Achievements

核融合発電の実現には装置内壁の局所熱負荷を減らす必要があり、不純物ガスを入射し輻射損失を増やして熱負荷を分散する、非接触ダイバータと呼ばれる運転方法が検討されている。その物理機構の解明には中小型のプラズマ実験装置を活用して知見を蓄積する必要がある一方で、中小型の装置では輻射が弱いため計測器の高感度化が課題であった。
本研究では、輻射イメージング計測の主要な構成部品である赤外線カメラや薄膜検出器の材質及び膜厚を検討し、高感度化に成功した。これまで計測できなかった不純物ガス種の条件でも輻射計測が可能となったことで、今後中小型装置を活用した非接触ダイバータの物理機構の解明が進展すると期待される。