Implementing a microphysics model in hydrodynamic simulations to study the initial plasma formation in dielectric ablator materials for direct-drive implosions

TL;DR

This paper integrates a microphysics model into hydrodynamic simulations to more accurately predict initial plasma formation in dielectric ablators, improving understanding of laser-driven implosion dynamics.

Contribution

The paper introduces a physics-based microphysics model into hydrodynamic simulations, replacing ad hoc methods for initial plasma formation in dielectric materials.

Findings

Higher electron temperature and pressure predictions compared to previous models.

Numerical results align with experimental observations of shine-through.

Observed rear-end decompression matches recent experimental data.

Abstract

A microphysics model to describe the photoionization and impact ionization processes in dielectric ablator materials like plastic has been implemented into the one-dimensional hydrodynamic code LILAC for planar and spherical targets. At present, the initial plasma formation during the early stages of a laser drive is modeled in an ad hoc manner, until the formation of a critical surface. Implementation of the physics-based models predicts higher values of electron temperature and pressure than the ad hoc model. Moreover, the numerical predictions are consistent with previous experimental observations of the shine-through mechanism in plastic ablators. For planar targets, a decompression of the rear end of the target was observed that is similar to recent experiments. An application of this model is to understand the laser-imprint mechanism that is caused by nonuniform laser irradiation due to a single beam speckle.