This paper was produced for the 2019 NAFEMS World Congress in Quebec Canada

Resource Abstract

In a direct-drive inertial confinement fusion (ICF) implosion, a plastic target capsule containing a cryogenic deuterium–tritium (DT) ice layer and a low-density DT gas is imploded by intense laser pulses directly focused on the target. High-yield ICF targets require that the uniformity of the DT ice layer be less than 1-m rms. The uniformity of the ice layer (i.e., the solid/gas phase boundary) is affected by the surrounding helium environment and the structure that supports the target. To aid the designer of target support structures, the sensitivity of ice-layer uniformity to support structure thermal conductivity and a 3-mW heat source in the surrounding helium are studied using computational fluid dynamic simulations. Experimental data of DT ice layer’s uniformity is used to validate the multiphase conjugate heat-transfer numerical model. Simulations show that the thermal conductivity of the support directly touching the target capsule must be a close match to helium thermal conductivity to produce uniform ice layers. In addition, if heat sources are present in the helium environment, it is advantageous that the remainder of the support structure have a thermal conductivity of less than ~2 W/m/K. Finally, it is shown that for the temperature variations and helium pressures studied, multiphase conduction-only heat-transfer models yield the same results as multiphase conjugate heat-transfer models.