UC San Diego

Target survival in the hostile chamber environment of the proposed Laser Inertial Fusion Energy (LIFE) power plant is critical. The main focus of this work is to investigate the flow properties and convective heat load imposed upon the target traveling through the high-temperature xenon environment. This rarefied flow is characterized within the continuum regime, but is approaching transition where traditional CFD codes reach the bounds of operation. Thus ANSYS, specifically the Navier-Stokes module CFX, will be used in parallel with direct simulation Monte Carlo code DS2V and empirically and analytically derived expressions of heat transfer to the target for validation. Comparison of the DS2V and ANSYS viscous and thermal boundary layers were shown to match almost identically, while the simulated heat fluxes vary less than 8% on average over the hohlraum's surface. Since melting of the laser entrance hole window or fuel capsule constitutes failure of the target, a first-order approximation of the transient thermo-mechanical behavior of the target was conducted using the multi-physics code, COMSOL. Helium internal to the target has been shown to act as tremendous heat sink for cooling the laser entrance hole windows; however, spinning the target at 15,000 RPM induced buoyancy driven swirling effects that heated the sensitive fuel capsule. From the results herein, external baffles and radiative shields that completely partition the internal helium of the hohlraum have been shown to reduce this heating and optimize target survival in conjunction with other key reactor parameters