量研学術機関リポジトリ「QST-Repository」は、国立研究開発法人 量子科学技術研究開発機構に所属する職員等が生み出した学術成果（学会誌発表論文、学会発表、研究開発報告書、特許等）を集積しインターネット上で広く公開するサービスです。 Welcome to QST-Repository where we accumulates and discloses the academic research results(Journal Publications, Conference presentation, Research and Development Report, Patent, etc.) of the members of National Institutes for Quantum and Radiological Science and Technology.
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Existing methods for diagnostics and control are still insufficient to deal with the various kinds of instabilities and collective dynamics that occur in magnetically confined fusion plasmas, which may impact the missions of the ITER and DEMO projects. Using small-scale laser experiments on J-KAREN-P, extensive numerical simulations on JFRS-1, and theoretical analyses, we are investigating whether short pulses (ps-fs) of a high power laser (TW-PW) may be used to address some of these issues. Based on the outcome of this feasibility study, we will make recommendations for applying accessible high-power laser technology in tokamaks for confinement control and plasma diagnostics.
A laser pulse with relativistic intensity produces an electron density wake wave on the 10 ps scale. Extrapolations from experimental data (using similarity scaling) as well as 2D and 3D simulations for tokamak-relevant parameters (low density, strong external magnetic field) consistently indicate that the electron wake is sustained long enough to transform into a longer-lived ion density channel after a few 100 ps. The external magnetic field (~ 2 T) enhances the induced magnetic vortices (~ 5×) and reduces the induced electric field (~ 1/2×). Radiation emitted from the channel may be used for diagnostics.
In the absence of thermal ion motion and collisions, the laser-induced channel is projected to survive for 100 ns. However. for typical tokamak ion temperatures (~ 3 keV), the channel will be mixed in the phase space of the gyrating ions within a few nanosecs (Landau damping). The further evolution of these phase space structures and possible echo-like recurrences of the channel in strongly magnetized plasmas are now under investigation. If sustained on the 20 ns scale, the channel may be reinforced by recycling the laser pulse. This would enhance its potential for affecting MHD-scale dynamics.
会議概要（会議名, 開催地, 会期, 主催者等）
2nd QST International Symposium: “Frontier of Quantum Beam Science with High Power Lasers”
Exploring high power laser effects on magnetically confined fusion plasmas
