Resonance density range governs two-plasmon decay saturation and enables hot-electron prediction in inertial confinement fusion

TL;DR

This paper identifies the resonance density range as key to two-plasmon decay saturation in inertial confinement fusion, enabling a predictive model for hot-electron generation based solely on laser intensity and plasma conditions.

Contribution

It introduces a novel understanding of the resonance density range's role in saturation and develops a simple, calibration-free predictive model for hot-electron energy fraction.

Findings

The resonance density range governs nonlinear saturation of ion density fluctuations.

The model accurately reproduces experimental results from OMEGA and OMEGA-EP.

Hot-electron energy fraction can be predicted from laser intensity and plasma conditions.

Abstract

The saturation level of parametric instabilities critically determines their impact on fusion plasmas. We identify the resonance density range of two-plasmon decay as the critical parameter governing nonlinear saturation of ion density fluctuations and Langmuir waves, which drive hot-electron generation. Using this insight, we develop a predictive scaling model for the hot-electron energy fraction f_{hot} that depends only on the laser intensity I, with plasma conditions encoded via plasma ablation theory. The model can work for various experimental configurations-requiring only two (I, f_{hot}) data points to calibrate coefficients-and successfully reproduces results from prior OMEGA and OMEGA-EP experiments.