Time-resolved measurements of laser-driven electron clouds and their dynamics

2023 Fiscal Year Final Research Report

• Project/Area Number: 22K14021
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 14010:Fundamental plasma-related
• Research Institution: National Institutes for Quantum Science and Technology
• Principal Investigator: Kojima Sadaoki 国立研究開発法人量子科学技術研究開発機構, 関西光量子科学研究所 量子応用光学研究部, 主任研究員 (40815156)
• Project Period (FY): 2022-04-01 – 2024-03-31
• Keywords: 高強度レーザー / イオン加速 / ビーム物理

Outline of Final Research Achievements

A high-time-resolved measurement technique for electron clouds was developed based on the spectral imaging technique. A high-intensity laser was split into two parts, and the shadow of the electron cloud produced by the main laser for ion acceleration was measured with a probe laser. The results indicated that the electron cloud expanded rapidly in the lateral direction along the target to a diameter of approximately 150um in only 2 ps after the laser irradiation.

Subsequently, a knife-edge was employed to quantify the area of the electron cloud that contributes to ion acceleration. It was demonstrated that high-energy protons in proximity to the energy cutoff, constrained by the steric angle limitation of the knife-edge, could only be accelerated from a limited source region (electron cloud) of approximately 25um. This result validated the hypothesis that the good emittance of laser-driven ions is attributed to small source size.

Free Research Field

レーザー・プラズマ相互作用

Academic Significance and Societal Importance of the Research Achievements

レーザー駆動イオン加速の加速プロセスはわずか数ピコ秒で生じる。その速さ故に、これまでの研究では実験値は時間積算で取得され、加速プロセスの理解は時間分解したシミュレーションとの比較によって主に進められてきた。本研究では、近年発展したスペクトラルイメージング技術を用いてレーザー駆動イオン加速において加速管の役割を果たす電子雲膨張の高時間分解観測に取り組んだ。急速に膨張する電子雲を定量的に計測できるようになった。今後この計測技術を用いることでレーザー駆動イオン加速の安定性の向上に寄与する計画である。