Inference of the electron temperature in ICF implosions from the hard X-ray spectral continuum

TL;DR

This paper investigates how suprathermal electrons affect the hard X-ray spectral continuum in ICF implosions, revealing that kinetic effects cause deviations from Maxwellian assumptions and impact electron temperature inference.

Contribution

It introduces the first kinetic model of free-free X-ray emission in ICF, accounting for suprathermal electron effects on the spectral continuum.

Findings

Kinetic modifications produce new spectral features.

Maxwellian assumption underestimates electron temperature.

Suprathermal electrons significantly influence X-ray emission.

Abstract

Using the free-free continuum self-emission spectrum at photon energies above 15 keV is one of the most promising concepts for assessing the electron temperature in ICF experiments. However, these photons are due to suprathermal electrons whose mean-free-path is much larger than thermal, making their distribution deviate from Maxwellian in a finite-size hot-spot. The first study of the free-free X-ray emission from an ICF implosion is conducted with the kinetic modifications to the electron distribution accounted for. These modifications are found to result in qualitatively new features in the hard X-ray spectral continuum. Inference of the electron temperature as if the emitting electrons are Maxwellian is shown to give a lower value than the actual one.