Accounting for speckle scale beam-bending in classical ray tracing schemes for propagating realistic pulses in indirect drive ignition conditions

TL;DR

This paper introduces a semi-analytical model for laser beam deviation caused by plasma flows, incorporating speckle smoothing techniques, validated within ray tracing algorithms to improve understanding of laser propagation in inertial confinement fusion experiments.

Contribution

It presents a novel semi-analytical beam bending model that accounts for speckle scale effects and integrates it into ray tracing for more accurate laser propagation simulations.

Findings

Beam bending affects refraction conditions inside hohlraums.

Model explains anomalous refraction measurements in NIF experiments.

Inclusion of speckle effects improves laser energy deposition predictions.

Abstract

We propose a semi-analytical modeling of smoothed laser beams deviation induced by plasma flows. Based on a Gaussian description of speckles, the model includes spatial, temporal and polarization smoothing techniques,through fits issued from hydrodynamic simulations with a paraxial description of electromagnetic waves. This beam bending model is then included in a ray tracing algorithm, and carefully validated. When applied as a post-process to the propagation of the inner cone in a full-scale simulation of a NIF experiment,the beam bending along the path of the laser affects the refraction conditions inside the hohlraum and the energy deposition, and could explain the anomalous refraction measurements, the so-called glint observed in some NIF experiments.