Effects of Landau damping and collision on stimulated Raman scattering with various phase-space distributions

Stimulated Raman scattering (SRS) is one of the main instabilities affecting success of fusion ignition. Here, we study the relationship between Raman growth and Landau damping with various distribution functions combining the analytic formulas and Vlasov simulations. The Landau damping obtained by Vlasov-Poisson simulation and Raman growth rate obtained by Vlasov-Maxwell simulation are anti-correlated, which is consistent with our theoretical analysis quantitatively. Maxwellian distribution, flattened distribution, and bi-Maxwellian distribution are studied in detail, which represent three typical stages of SRS. We also demonstrate the effects of plateau width, hot-electron fraction, hot-to-cold electron temperature ratio, and collisional damping on the Landau damping and growth rate. They gives us a deep understanding of SRS and possible ways to mitigate SRS through manipulating distribution functions to a high Landau damping regime.

Automated summary

This study investigates the relationship between Raman growth and Landau damping in fusion ignition. By combining analytic formulas and Vlasov simulations, it is found that the Landau damping obtained from Vlasov-Poisson simulation and the Raman growth rate obtained from Vlasov-Maxwell simulation are anti-correlated, which is consistent with theoretical analysis. Different distribution functions, such as Maxwellian distribution, flattened distribution, and bi-Maxwellian distribution, representing different stages of SRS, are studied in detail. The effects of plateau width, hot-electron fraction, hot-to-cold electron temperature ratio, and collisional damping on Landau damping and growth rate are also demonstrated.