Self-similar structure and experimental signatures of suprathermal ion distribution in inertial confinement fusion implosions

TL;DR

This paper reveals that suprathermal ion distributions in inertial confinement fusion hot-spots are self-similar, and demonstrates how instabilities and ion tail depletion impact fusion reactivity and temperature measurements.

Contribution

It introduces the concept of self-similar suprathermal ion distributions and quantitatively assesses the effects of hydro-instabilities on fusion reactivity and ion temperature inference.

Findings

Hydro-instabilities significantly reduce fusion reactivity.

Ion tail depletion lowers inferred ion temperatures.

Self-similar distribution function characterizes suprathermal ions.

Abstract

The distribution function of suprathermal ions is found to be self-similar under conditions relevant to inertial confinement fusion hot-spots. By utilizing this feature, interference between the hydro-instabilities and kinetic effects is for the first time assessed quantitatively to find that the instabilities substantially aggravate the fusion reactivity reduction. The ion tail depletion is also shown to lower the experimentally inferred ion temperature, a novel kinetic effect that may explain the discrepancy between the exploding pusher experiments and rad-hydro simulations and contribute to the observation that temperature inferred from DD reaction products is lower than from DT at National Ignition Facility.