Study on the effects of initial ice layer and temperature distribution on the redistribution of D₂ fuel layer in a cryogenic target

Abstract Inertial confinement fusion (ICF) is one of the primary methods for achieving controlled nuclear fusion, which is closely related to energy security and national security. High peak-power laser systems are utilized in ICF experiments to compress the capsule which contains a solid hydrogen layer, making the ice layer highly compressed so as to initiate ignition. To achieve an ignition with a cryogenic target, the fuel ice layer (deuterium–tritium (DT) or D 2 ) in the target needs to be highly symmetrical, uniform and smooth. To better control the ice preparation process, specific procedures of temperature control are crucial and needs to be investigated (Yang et al 2021 Matter Radiat. Extrem. 6 055901). Based on the level set multiphase (Tao et al 2022 Nucl. Fusion 62 076029; Stanley Osher 2003 Level Set Methods and Dynamic Implicit Surfaces (Springer)) model and the phase change model, a numerical model is established to simulate the coupled process of heat transfer, melting and multiphase flow of D 2 ice in the target. Phase change is realized using a modified heat capacity method, in which the phase change material is modeled as a liquid with temperature-dependent capacity (Gibou et al 2021 J. Comput. Phys. 353 82–109). The effects of the temperature boundary and the initial ice layer distribution on the coupled process are investigated. The results show that a vertical downward temperature gradient is more conducive to matching the melting process the fluid flow process. For an initial uniformly distributed ice layer, both the rising distance of the vapor-phase region and the melting time of the ice increase with increasing ice volume, while the rising time decreases significantly. A non-uniform initial ice layer distribution leads to a greater deviation in the melting time compared to the case of a uniform initial ice layer. As the ice volume increases, the required deviation distance for the vapor phase region to convert a non-uniform fuel layer into a uniform fuel layer after ice melting increases. Our work contributes to the optimization of the parameters involved in the preparation of D 2 ice layers, which is of great significance to enhance the energy security guarantee capability.