Fokker-Planck kinetic modeling of suprathermal α-particles in a fusion plasma

We present a new ion kinetic model describing the ignition and burn of the deuterium-tritium fuel of inertial fusion targets. The analysis of the underlying physical model enables us to develop efficient numerical methods to simulate the creation, transport and collisional relaxation of fusion reaction products (α-particles) at a kinetic level. A two-energy-scale approach provides a framework for a self-consistent modeling of the coupling between suprathermal αparticles and the thermal bulk of the imploding plasma. We show that the α-particle distribution function fα can be considerered as a superposition of two components evolving on two different velocity scales [1]: a suprathermal component f ST α , fed by fusion reactions and evolving on a large velocity scale, is coupled with a thermal component f T α , corresponding to the thermalized part of the distribution function, evolving on the same velocity scale as the thermal bulk of the plasma. The original Fokker-Planck operator is then transformed into a system of two coupled equations governing the two components f ST α and f T α , respectively. Each component is discretized on a specialy-taylored velocity mesh whose resolution fits with the characteristic velocity variation scale. This method provides an accurate numerical treatment of the energy deposition and transport processes involving suprathermal particles. The numerical tools presented here are validated against known analytical and numerical results [2]. This enables us to investigate the potential role of ion kinetic effects on the physics of ignition and thermonuclear burn in inertial confinement fusion schemes.