Investigation of Inverse Bremsstrahlung Heating Driven by Broadband Lasers

TL;DR

This study uses particle-in-cell simulations to analyze how broadband lasers influence inverse bremsstrahlung heating in plasmas, finding that spectral broadening causes transient fluctuations but does not significantly alter overall heating efficiency.

Contribution

It provides the first systematic simulation-based comparison of broadband versus monochromatic laser effects on IB heating in plasmas, confirming theoretical predictions.

Findings

Transient oscillations in heating rate due to spectral broadening.

Long-term IB heating remains unchanged with broadband lasers.

Simulation results agree with classical absorption theory.

Abstract

Broadband lasers have become a key strategy for mitigating laser plasma instabilities in inertial confinement fusion, yet their impact on collisional inverse bremsstrahlung (IB) heating remains unclear. Using one-dimensional collisional particle-in-cell simulations, we systematically examine the effect of bandwidth-induced temporal incoherence on IB absorption in Au plasmas. The simulations are first benchmarked against classical absorption theory, verifying that the implemented Coulomb collision model accurately reproduces the theoretical IB heating rate. A direct comparison of the electron temperature evolution in the broadband and monochromatic cases shows that, although spectral broadening introduces transient picosecond-scale oscillations in the heating rate driven by stochastic intensity fluctuations, the long-term averaged heating and net IB absorption remain essentially unchanged.