Vlasov-Fokker-Planck modeling of plasma near hohlraum walls heated with nanosecond laser pulses calculated using the ray tracing equations

摘要

Summary form only given. Here, we present 2D numerical modeling of near critical density plasma using a fully implicit Vlasov-Fokker-Planck code, IMPACTA, with an implementation of a ray tracing add-on package. This allows to model inverse brehmsstrahlung heating as a laser travels through a plasma by solving the ray tracing equations. In certain situations, such as those at the critical surface at the walls of a hohlraum, magnetic fields are generated through the crossed temperature and electron density gradients (the Biermann Battery effect). Magnetic field generation on the order of MG from the laser heating is shown using a 1 micron laser obliquely incident upon a density ramp. These strong fields along with plasma heating cause the plasma to become strongly magnetized (ωτ > 10). Heat flows are noticeably modified and the temperature profile shows a non-uniformity that does not exist in the case without magnetic fields. The non-uniformities arise because of relatively strong distortions in the distribution function, with different modifications at different spatial points. The distortions in the distribution functions suggest that modification of transport theory may have to be considered for complete understanding of the plasma at hohlraum wall.