Modeling Target Defects in Direct-Drive Inertial Confinement Fusion

A range of evidence from both radiation-hydrodynamic simulations and experiments suggests that isolated defects on the outside of cryogenic targets are able to play a significant role in degrading direct-drive inertial confinement fusion implosion performance. The highly nonlinear growth is not ablatively stabilized and can be an important degradation even for current best-performing OMEGA cryogenic implosions. A cryogenic target may have thousands of surface defects that originate during the high-pressure permeation fill and cooling cycle and range in size from microns to tens of microns. Previous modeling of defects tens of microns in size has shown that the resulting local perturbation growth can inject ablator mass into the hot spot, contributing to radiative cooling and loss of performance [I. V. Igumenshchev et al., Phys. Plasmas 20, 082703 (2013)]. In this talk, we present the results of 2-D radiation-hydrodynamic simulations with DRACO of smaller (micron-scale) defects in the context of more-recent cryogenic target designs, addressing both the reduction in areal density and the transport of ablator material into the hot spot.

[1] I. V. Igumenshchev et al., Phys. Plasmas 20, 082703 (2013).