Study of transient plasma physics by fast Thomson scattering system(Fostering Joint International Research)

• Project/Area Number: 15KK0245
• Research Category: Fund for the Promotion of Joint International Research (Fostering Joint International Research)
• Allocation Type: Multi-year Fund
• Research Field: Nuclear fusion studies
• Research Institution: National Institute for Fusion Science
• Principal Investigator: Yasuhara Ryo 核融合科学研究所, ヘリカル研究部, 准教授 (30394290)
• Project Period (FY): 2016 – 2019
• Project Status: Completed (Fiscal Year 2019)
• Budget Amount: ¥13,910,000 (Direct Cost: ¥10,700,000、Indirect Cost: ¥3,210,000)
• Keywords: バーストレーザー / 過渡的プラズマ現象 / トムソン散乱計測 / プラズマ電子温度 / プラズマ電子密度 / 高繰り返しレーザー / バーストモード / トムソン散乱 / パルスレーザー / 熱効果 / 高出力レーザー / バーストモードレーザー / 高時間分解能 / 高繰り返し / 熱光学効果

Outline of Final Research Achievements

By developing a "burst laser" that can improve laser repetition by 30 times, we have realized a fast Thomson scattering system that enables high time resolution measurement. It was achieved by highly repetitive laser operation without heat influence by laser amplification within a time shorter than the time scale of thermal diffusion in the laser medium. As the result, the measurable time resolution was increased to more than 1 kHz. It is at least 10 times faster than the conventional measurement, which was limited to about 30Hz. Measurements have been performed in actual plasma experiments using a large helical device at the National Institute for Fusion Science, and are used to measure transiently changing plasma such as the ablation phenomenon of solid hydrogen pellets.

Academic Significance and Societal Importance of the Research Achievements

トムソン散乱計測の高速化は、計画段階のものも含めて世界的な潮流となってきている。マックスプランクプラズマ物理研究所のW7-Xで、レーザー技術で先端を行くドイツの半導体励起固体レーザーを導入した1kHzの計測計画等、各国で取り組みが進んでいる。このような国際的な状況は、時間分解能の向上が新たな物理現象発見へのクリアな研究戦略であるためだと推測される。本課題で開発した高速トムソンシステムは世界最先端の性能であり、各国のプラズマ実験装置で行われている測定との比較や共同実験などで広く国際共同研究に寄与できる。本手法を用いることで、過渡的なプラズマ物理現象の総合理解が期待される。

Research Products

• [Int'l Joint Research] パリ国立高等化学学校(フランス) (2018)
  • Year and Date: 2018-06-17
• [Int'l Joint Research] ウィスコンシン大学マディソン校(米国) (2018)
  • Year and Date: 2018-03-19
• [Int'l Joint Research] PPPL(米国) (2018)
  • Year and Date: 2018-01-30
• [Int'l Joint Research] パリ国立高等化学学校(フランス) (2017)
  • Year and Date: 2017-10-29
• [Journal Article] Efficient visible laser operation of Tb:LiYF4 and LiTbF4 (2020)
  • Author(s): H. Chen, H. Uehara, H. Kawase, and R. Yasuhara
  • Journal Title: Optics Express Volume: 28 Issue: 8 Pages: 10951-10959
  • DOI: 10.1364/oe.385020
  • Peer Reviewed / Open Access
• [Journal Article] Efficient Pr:YAlO3 lasers at 622nm, 662nm, and 747nm pumped by semiconductor laser at 488nm (2020)
  • Author(s): Hengjun Chen, Hiyori Uehara, Hiroki Kawase, and Ryo Yasuhara
  • Journal Title: Optics Express Volume: 28 Issue: 3 Pages: 3017-3024
  • DOI: 10.1364/oe.380635
  • Peer Reviewed / Open Access
• [Presentation] Near-infrared Wavelength Dependence of Verdet Constant in Tb2Zr2O7 Transparent Ceramics (2019)
  • Author(s): R. Yasuhara, A. Ikesue
  • Organizer: CLEO&Europe-EQEC 2019
  • Int'l Joint Research
• [Presentation] High time resolution Thomson scattering on LHD (2019)
  • Author(s): Ryo Yasuhara
  • Organizer: Laser Aided Plasma Diagnostics 2019
  • Int'l Joint Research / Invited
• [Presentation] Magneto-optic Ceramics for High-power Laser Applications (2019)
  • Author(s): Ryo Yasuhara
  • Organizer: the Materials Science & Technology (MS&T)
  • Int'l Joint Research / Invited
• [Presentation] High-rep-rate Thomson scattering for LHD (2017)
  • Author(s): D.J. Den Hartog, M. T. Borchardt, D. J. Holly, O. Schmitz, R. Yasuhara, I. Yamada, H. Funaba, M. Osakabe, T. Morisaki
  • Organizer: APS DPP 2017, 2017-10-23 - 2017-10-27, Milwaukee, Wisconsin
  • Int'l Joint Research