Probing ultrafast heating and ionization dynamics in solid density plasmas with time-resolved resonant X-ray absorption and emission

TL;DR

This study uses time-resolved X-ray spectroscopy and advanced simulations to investigate ultrafast heating and ionization in solid-density plasmas created by high-intensity laser interactions, providing new insights and benchmarks.

Contribution

It combines experimental diagnostics with multi-scale simulations to better understand plasma dynamics and improve models of laser-plasma interactions in high-energy-density physics.

Findings

Extreme sensitivity of plasma parameters to models revealed

Laser spatial profiles and pre-plasma conditions significantly affect results

Provides benchmarks for high-power laser--plasma interaction models

Abstract

Heating and ionization are among the most fundamental processes in relativistic laser--solid interactions; however, their spatiotemporal evolution remains challenging to capture experimentally. Here we present detailed diagnosis of high-intensity laser interactions with wire targets, leveraging the extreme spectral brightness of an X-ray free-electron laser in sub-picosecond time-resolved resonant X-ray emission spectroscopy and absorption imaging. Experimental results are compared with comprehensive simulations using atomic collisional--radiative models, particle-in-cell, and magnetohydrodynamics codes to elucidate the underlying physics. These multi-scale simulations reveal extreme sensitivity of basic plasma parameters with widely used models, such as temperature and ionization depth, which are able to be constrained by incorporating a detailed accounting of laser spatial profiles, pre-plasma conditions, and collisional processes. These results provide new insights into heating and ionization dynamics in the high-energy-density regime relevant to inertial fusion energy research, both as an experimental platform for accessing theoretically challenging conditions and as a benchmark for improving models of high-power laser--plasma interactions.