Optical smoothing broadens cross beam energy transfer resonance

TL;DR

This paper presents a theoretical analysis showing that optical smoothing significantly broadens the resonance conditions for cross beam energy transfer in laser fusion, affecting energy transfer rates and experimental predictions.

Contribution

It introduces a simple analytical model demonstrating how optical smoothing alters CBET resonance conditions and energy transfer rates in laser fusion.

Findings

Optical smoothing broadens CBET resonance compared to plane wave models.

Flow components normal to ion acoustic waves significantly modify power transfer.

Energy transfer out of resonance is higher with optical smoothing.

Abstract

We use the theoretical framework introduced in the companion paper to provide simple formulas as regards the resonance conditions for CBET with smoothed laser beams.Our analytical CBET model with optical smoothing shows that these fusion-critical lasers produce a significantly broader resonance than conventional plane wave models predict. In particular, temporal smoothing, as used in many high energy laser facilities, and flow components normal to the CBET ion acoustic waves, significantly modify the power transfer between smoothed beams. Our model predicts that the energy transfer rate out of resonance is substantially higher with optical smoothing than without, a result that has profound implications for optimizing predicting and interpreting future fusion experiments. We provide a simple criterion which pinpoints the laser and plasma parameters for which laser smoothing impacts CBET. These findings pave the way for experimental investigations in high-energy-density physics and fusion energy.