Thermonuclear ignition calculations in contaminated DT fuel at high densities

Abstract

Multi-group radiation hydrodynamics simulations have been performed to investigate the margins of thermonuclear ignition in a 1 : 1 deuterium–tritium (DT) mixture that has been contaminated with an ion species that does not usefully contribute to the burning process. In this paper we examine the effects of a range of contaminant materials that may be associated with the re-entrant cone of the cone-guided fast ignition approach to inertial confinement fusion, specifically contamination by carbon, iron and gold. The effect of contamination on the ρr required for ignition is quantified for each material, for a range of contamination fractions. It is shown that, if uniformly distributed, gold contamination must be limited to values of a few 10−5 with respect to the fuel ion number density in order that the change in the required ignition hotspot ρr remain on the order of a few percent or less. In similar circumstances, carbon contamination at levels as high as a few 10−3 are found to be tolerable, suggesting that schemes which employ a cone tamping layer composed of CH plastic, or similar low-Z material, may offer significant advantages. However, it is further shown that the required ignition ρr is principally a function of the total mass of contaminant in the hotspot, and that quite high localized concentrations of high-Z material can be tolerated.