Saturation of stimulated Raman side-scattering in inertial confinement fusion plasmas with a suprathermal electron tail

It is shown that the hot electrons generated by the stimulated Raman side-scattering (SRSS) can be gradually accelerated to high energies with the increase in linear density in plasmas. Meanwhile, the electron energy spectrum is strongly modified to the bi-Maxwellian distribution composed of a thermal part and a suprathermal electron tail driven by the SRSS. This characteristic causes the low-energy electrons trapped by the electron plasma waves (EPWs) with low-phase velocities to provide more particles for accelerating electrons by the EPWs with high-phase velocities, forming a progressive resonance process. This increases the number of resonant particles near the EPWs with the higher phase velocity, which can enhance the Landau damping of the EPWs. In addition, we directly investigate the evolution of SRSS in a plasma with the bi-Maxwellian distribution having a suprathermal electron tail. It is found that the presence of a suprathermal electron tail can increase the Landau damping of EPWs, thereby mitigating the development of SRSS. Furthermore, when the fraction and temperature of the suprathermal electron tail in the plasma are higher, the Landau damping is shown to be stronger, the suppression of SRSS is more obvious, and there is more laser transmission. The results are helpful for understanding the generation of hot electrons from the SRSS instability and its evolution in inertial confinement fusion.