Large-incidence-angle multiple-beam two-plasmon decay instability in inertial confinement fusion

A multi-dimensional code FLAME-MD solving fluid-like laser-plasma instabilities' (LPIs) equations has been developed and is used to study multiple-beam two-plasmon decay (TPD) instability relevant to a laser-entrance-hole window burn-off scenario in inertial confinement fusion (ICF) experiments. It is found that TPD can be collectively driven by multiple beams incident at large incidence angles with respect to the electron density gradient at a very low threshold. The polarization configuration of the laser beams is a key factor determining the way of sharing common daughter electron plasma waves (EPWs). The p-polarized beams arranged on the same incidence cone can collectively drive common EPWs along the cone axis. The common-wave sharing mechanisms among the s-polarized beams are largely dependent on the geometry of the beams and are less robust. The simulation results also show that the p-polarized beams are dominating the multiple-beam TPD processes. The common EPWs along the cone axis can accelerate energetic electrons toward the capsule inside the hohlraum and, therefore, pose a fuel-preheat risk to ICF implosions.