Stimulated Brillouin Scattering from hot, multiple-species plasma with interspecies collisions

The reduction of laser energy deposition in Inertial Confinement Fusion from stimulated Brillouin backscattering (SBS) is a major concern that constrains the design space. One promising design option is the use of multiple ion species which can increase the Ion Acoustic wave (IAW) damping rate and thereby lower the amplification rate significantly provided nonlinear trapping of the ions in the IAW can be suppressed.¹  In previous work on mixtures of high-Z and low-Z ions, we have shown with Vlasov simulations² of externally driven IAWs that trapping of the light ions, which reduces the damping, can be decreased by collisional scattering of the light ions from the heavy ions. Here, we use the Vlasov code LOKI,³ to simulate SBS self-consistently where the ponderomotively driven IAWs accelerate and trap the light ions near the IAW phase velocity. Inclusion of interspecies and self-collisions leads to large reductions of SBS compared to a single species high-Z plasma or a multi-species, collisionless high-Z plasma.

¹ Berger,et al PoP 26,012709(2019), ² Berger, et al, 62 Annual Meeting of the DPP, November 11, 2020, ³ W. Banks and J. A. F. Hittinger,IEEE Trans. Plasma Sci., 38, 2198 (2010); A. M.Dimits, et al., ICOPS 2018, Denver, CO., June 25, 2018