The interaction of quasi-monoenergetic protons with pre-compressed inertial fusion fuels

Abstract

The interaction of a quasi-monoenergetic proton beam with a pre-compressed plasma is studied in the context of inertial fusion fast ignition (FI). Based on fundamental principles, a kinetic model is developed by considering hard collisions, nuclear scattering, and the contribution due to collective processes. The penetration depth, longitudinal straggling, and the transverse blooming are evaluated by solving the Boltzmann transport equation using the multiple scattering theory. The stopping power, transport scattering cross sections, and convenient expressions for the angular moments of the proton distribution function have been used in modeling the collisional proton transport in a three-dimensional (3D) Monte Carlo code. The transport of a proton beam with a quasi-monoenergetic energy ⟨E⟩=10 MeV is studied for pre-compressed deuterium-tritium plasma with an average density of ρ=400 g cm−3 and temperatures T=1 keV, 5 keV, and 10 keV. The net effects of multiple scattering are to reduce the penetration from 1.028 to 0.828 g cm−2 with range straggling ρΣR=0.044 g cm−2 and beam blooming ρΣB=0.272 g cm−2, for 10 MeV protons in a ρ=400 g cm−3 plasma at T = 5 keV. This model can be used for quantitatively assessing ignition requirements for proton fast ignition.