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

We propose a semi-analytical modeling of smoothed laser beam deviation induced by plasma flows. Based on a Gaussian description of speckles, the model includes spatial, temporal, and polarization smoothing techniques, through fits coming from hydrodynamic simulations with a paraxial description of electromagnetic waves. This beam bending model is then incorporated into 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 National Ignition Facility (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 some anomalous refraction measurements, namely, the so-called glint observed in some NIF experiments.

Automated summary

We propose a semi-analytical model to describe the laser beam deviation caused by plasma flows, which includes spatial, temporal, and polarization smoothing techniques based on a Gaussian description of speckles. The model is incorporated into a ray tracing algorithm and validated by applying it to a full-scale simulation of a National Ignition Facility (NIF) experiment. The beam bending affects the refraction conditions and energy deposition inside the hohlraum, potentially explaining anomalous refraction measurements observed in some NIF experiments, known as glint.