187 / 2023-04-15 15:49:54

Impact of superthermal electrons on driven ion acoustic wave fluid nonlinearities

For laser-produced plasmas in inertial confinement fusion (ICF), electron distribution functions are non-Maxwellian but have more complicated shapes. For example, superthermal electrons [1,2] could be produced by strong Langmuir waves generated in stimulated Raman scattering (SRS) process. In this work, we investigate the fluid nonlinearities of driven ion acoustic waves (IAWs) in superthermal electron plasmas and a kappa velocity distribution function is used to model superthermal electrons. In the nonlinear stage, by using a perturbation method [3], the dependence of the IAW nonlinear characteristics on relevant physical parameters of the problem is studied. One-dimensional fluid simulation is performed and the results verify the conclusions of fluid theory, showing that the presence of superthermal electrons leads to stronger harmonic generation and larger nonlinear frequency shifts of IAWs.  In addition, the threshold condition of the IAW decay instability is also significantly different compared to the Maxwellian case, and it is shown that the nonlinear frequency shift has a significant effect on the threshold condition.



[1] B. J. Winjum, et al., Phys. Rev. Lett. 110, 165001 (2013).

[2] Q.S. Feng, et al, Phys. Rev. E 105, 045208 (2022).

[3] Z. J. Guo, H. B. Zhuo, et al., Phys. Plasmas 30, 022114 (2023).