Absolute instability modes due to rescattering of stimulated Raman scattering in a large nonuniform plasma

Zhao, Yao and Sheng, Zhengming and Weng, Suming and Ji, Shengzhe and Zhu, Jianqiang (2019) Absolute instability modes due to rescattering of stimulated Raman scattering in a large nonuniform plasma. High Power Laser Science and Engineering. pp. 1-11. ISSN 2095-4719 (In Press)

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    Abstract

    Absolute instability modes due to rescattering of SRS in a large nonuniform plasma is studied theoretically and numerically. The backscattered light of convective SRS can be considered as a pump light with a finite bandwidth. The different frequency components of the backscattered light can be coupled to develop absolute stimulated Raman scattering (SRS) and two plasmon decay (TPD) instability near their quarter-critical densities via rescattering process. The absolute SRS mode develops a Langmuir wave with a high phase velocity about c/ √3 with c the light speed in vacuum. Given that most electrons are at low velocities in the linear stage, the absolute SRS mode grows with much weak Landau damping. When the interaction evolves into the nonlinear regime, the Langmuir wave can heat abundant electrons up to a few hundred keV. Our theoretical model is validated by particle-in-cell simulations. The absolute instabilities may play a considerable role for the indirect-drive experiments of inertial confined fusion.