Blast wave measurements of ICF hohlraum energy loss at Z

Inertial confinement fusion at the National Ignition Facility (NIF) is a grand challenge embraced by the nation. The designs of fusion ignition targets are based primarily on the indirect drive concept in which 351 nm laser light is absorbed by the wall of a cylindrical hohlraum, typically made of Au in current experiments. The hohlraum is an energy trapping container designed to retain as much of the incident energy as possible for use inside the walls of the hohlraum. The resulting hot wall material re-radiates a large fraction of the absorbed energy in the form of an x-ray bath at a few 100 eV, which irradiates, ablates, and implodes a DT filled capsule in which fusion occurs. The efficiency with which this can be done will depend on the atomic physics of the laser-wall interaction combined with Marshak wave energy losses into the wall, laser energy reflected back out of the hohlraum due to induced laser-plasma instabilities, and x-ray energy lost out of laser entrance holes, diagnostic holes and other imperfections in the wall. Energy loss from the hohlraum may be estimated based on the area of the missing wall or simulated by 2D radiation-hydrodynamics codes such as LASNEX[1]. This experiment was an attempt to verify that the simulations done with LASNEX are accurately capturing the x-ray energy loss out of holes and other openings in the wall of a hohlraum.