Species separation and modification of neutron diagnostics in inertial-confinement fusion

TL;DR

This paper investigates the distinct behaviors of deuterium and tritium in inertial-confinement fusion hot spots using an ion Fokker-Planck model, revealing impacts on density, temperature, and fusion yield, and emphasizing the importance of ion-kinetic effects in target design.

Contribution

It introduces a detailed ion-kinetic model to analyze species separation in ICF hot spots, showing significant differences from single-species models and aligning with experimental diagnostics.

Findings

Tritium density and temperature are higher than deuterium in the hot spot.

The hot spot is less dense but hotter with species separation.

Fusion neutron diagnostics show higher ion temperatures from DT than DD reactions.

Abstract

The different behaviours of deuterium (D) and tritium (T) in the hot spot of marginally-igniting cryogenic DT inertial-confinement fusion (ICF) targets are investigated with an ion Fokker-Planck model. With respect to an equivalent single-species model, a higher density and a higher temperature are found for T in the stagnation phase of the target implosion. In addition, the stagnating hot spot is found to be less dense but hotter than in the single-species case. As a result, the fusion reaction yield in the hot spot is significantly increased. Fusion neutron diagnostics of the implosion find a larger ion temperature as deduced from DT reactions than from DD reactions, in good agreement with NIF experimental results. ICF target designs should thus definitely take ion-kinetic effects into account.