Multi-dimensional computational model of the movement of the solid–gas interface during the layering process in inertial confinement fusion targets in a non-uniform thermal environment

Abstract

The redistribution of deuterium (DD) or of a deuterium–tritium mixture (DT) to form a layer on the inside of spherical inertial confinement fusion (ICF) capsules is a challenging problem because of the symmetry requirements of the fuel layer thickness, the smoothness requirement of the inside target surface, and the time restriction on the production process. Heat- and mass-transfer processes have been identified to interact with one another to influence the outcome of the layering process. For example, the mass redistribution speed of the fuel inside the shell towards a uniform layer and the final layer thickness uniformity depend on the variation in local heat transfer coefficient along the outer target surface. The focus of this work was to develop a numerical tool to help understand the physics involved in the layering process to be able to assess the influence of key parameters on the transient layer formation. The coupled mass and heat transfer processes governing target layering have been studied numerically, implementing unique boundary conditions to track the movement of the gas–solid boundary on the inside of the shell. The model was validated through comparison with theoretical results and laboratory-scale experiments. With this model, a window of parameters can by identified, under which layering experiments are likely to be successful.