Effect of Flow on Laser–Plasma Interactions near the Quarter-Critical Density in the Plasmas of Inertial Confinement Fusion

In the direct-drive approach to inertial confinement fusion (ICF), the laser–plasma interaction (LPI) in the plasma corona determines the coupling of laser power to the imploding targets. Under conditions of direct-drive ICF experiments on the OMEGA Laser System, the two most important LPI processes are the two-plasmon decay (TPD) in the plasma region near the quarter-critical density and cross-beam energy transfer (CBET). For both TPD and CBET the nonlinear saturation is determined by the level of low-frequency ion-acoustic perturbations. The resonance condition for the ion-acoustic waves strongly depends on the plasma flow, and velocities close to Mach-1 value often result in the highest levels of ion-acoustic waves. We consider the effect of plasma flow on LPI in the region near quarter-critical density where flow influences ion-acoustic perturbations and, consequently, the nonlinear saturation of both TPD and CBET, and the interplay between them. The results of 3-D simulations with the laser-plasma simulation environment (LPSE)¹ are compared with the theoretical analysis. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0003856.

[1] J. F. Myatt et al., Phys. Plasmas 24, 056308 (2017).