Influence of laser-induced Au-plasma plume collision on the efficiency of x-ray radiations and the energy-transport process relevant to ICF

Abstract

Experiments and simulations have been carried out to study the colliding process by two lasers irradiating a gold half-hohlraum. Via analyzing the evolutionary x-ray images, radiation fluxes and self-emission spectrum of tracers, influence on the x-ray conversion efficiency and the local plasma temperature T e,i from two gold-plasma plumes have been investigated deeply, which is similar as the configuration in intertial confinement fusion (ICF). Experimental results confirm that a region with super-high electron and ion temperatures Te,i, satisfying the strong collision condition of λi < △L, where λi and △L are respectively the ion mean-free path and the gradient length of T e. It leads to almost 30% increasing of M-band component compared to that from a single laser-irradiation case. Meanwhile ion temperature in this region increases more rapidly than electrons, reaching about T i≅(16±4)keV (T e≅(2± 0.2)keV). Thus, our studies provide the experimental evidence of quantitative x-ray enhancement and a non-equilibrium evolution simultaneously due to the plasma collision for the first time. Besides, two-dimensional simulation results reveal that this process can not be precisely described by the traditional shock-heating model by dissipating the shock energy only to ions. But by distributing the viscous heating between both electrons and ions as theoretically discussed by Douglas S. Miller [Comput. Fluids, 210,104672(2020)], numerical results can match experiments better. This discovery will be of great importance to improve the precision of numeral prediction for ICF.