Fusion yield of plasma with velocity-space anisotropy at constant energy

TL;DR

This paper investigates how velocity-space anisotropy affects fusion reactivity, revealing that the impact varies with plasma temperature and distribution details, with significant effects at lower temperatures.

Contribution

It introduces a detailed analysis of fusion yield modifications due to velocity-space anisotropy for specific distribution functions, comparing anisotropic and bi-Maxwellian cases.

Findings

Anisotropic distributions can increase fusion yield at lower temperatures.

Isotropic Maxwellians yield higher at higher temperatures.

Effects of anisotropy are substantial below reactor temperatures.

Abstract

Velocity-space anisotropy can significantly modify fusion reactivity. The nature and magnitude of this modification depends on the plasma temperature, as well as the details of how the anisotropy is introduced. For plasmas that are sufficiently cold compared to the peak of the fusion cross-section, anisotropic distributions tend to have higher yields than isotropic distributions with the same thermal energy. At higher temperatures, it is instead isotropic distributions that have the highest yields. However, the details of this behavior depend on exactly how the distribution differs from an isotropic Maxwellian. This paper describes the effects of anisotropy on fusion yield for the class of anisotropic distribution functions with the same energy distribution as a 3D isotropic Maxwellian, and compares those results with the yields from bi-Maxwellian distributions. In many cases, especially for plasmas somewhat below reactor-regime temperatures, the effects of anisotropy can be substantial.