Ion kinetic effects on the ignition and burn of ICF targets

TL;DR

This paper investigates how ion kinetic effects influence the ignition and burn processes in inertial confinement fusion targets using a specialized kinetic model, revealing significant non-local alpha particle transport impacts.

Contribution

It introduces a two-velocity-scale Vlasov-Fokker-Planck model to self-consistently analyze ion kinetic effects on ICF target ignition and burn, highlighting non-local alpha transport effects.

Findings

Non-local alpha transport reduces hot spot reactivity.

Alpha particles preheat outer fuel layers.

Kinetic effects significantly decrease fusion yield.

Abstract

In this Article, we study the hydrodynamics and burn of the thermonuclear fuel in inertial confinement fusion pellets at the ion kinetic level. The analysis is based on a two-velocity-scale Vlasov-Fokker-Planck kinetic model that is specially tailored to treat fusion products (suprathermal {\alpha}-particles) in a self-consistent manner with the thermal bulk. The model assumes spherical symmetry in configuration space and axial symmetry in velocity space around the mean flow velocity. Compared to fluid simulations where a multi-group diffusion scheme is applied to model {\alpha} transport, the full ion-kinetic approach reveals significant non-local effects on the transport of energetic $\alpha$-particles. This has a direct impact on hydrodynamic spatial profiles during combustion: the hot spot reactivity is reduced, while the inner dense fuel layers are preheated by the escaping {\alpha}-suprathermal particles, which are transported farther out of the hot spot. We show how the kinetic transport enhancement of fusion products leads to a significant reduction of the fusion yield.