Probing kinetic enhancement of fusion reactivity in turbulent hot spots

Abstract

Traditionally, fusion reactivity in thermonuclear plasmas has been calculated by assuming a local Maxwellian ion distribution. However, recent theoretical work [Phys. Rev. Lett. 135, 155101 (2025)] suggests that turbulence in plasmas can generate non-Maxwellian tail distributions, thereby enhancing reactivity. In this paper, we investigate this effect through numerical simulations of a sinusoidal shear flow. By comparing steady-state distributions obtained with the Bhatnagar-Gross-Krook (BGK) and Fokker-Planck (FP) collision operators, respectively, we demonstrate that the BGK model overestimates the reactivity enhancement while the FP operator gives a much more modest enhancement that is nearly halved under typical ICF parameters. Particle-in-cell (PIC) simulations incorporating nuclear reactions are also conducted, which reveal that the combined effects of preferential ion heating during shear flow dissipation and tail enhancement can even amplify the reactivity enhancement to be larger than the steady-state prediction.