Developments in Fabrication and Characterization of Gold/Boron-Lined Gold Hohlraums

Simulations of ignition-scale hohlraums show that the addition to the hohlraum of a submicron-thick Au/B interior liner containing [approximately]20 to 40 at. % B likely reduces laser backscatter by reducing the stimulated Brillouin scattering. By reducing the backscatter, the amount of energy available to compress the inertial confinement fusion capsule is increased while the likelihood of laser damage at National Ignition Facility (NIF) is minimized. A specialized magnetron cosputtering process is used to fabricate Au/B liners between 0.6 and 1.2 m for use on hohlraums shot at NIF to the atomic concentrations of 20 to 40 at. % B. We will discuss recent process improvements, such as LabVIEW process automation, in situ rate and thickness measurements, and optimized coating setup, all of which have increased the hohlraum yield and hohlraum throughput as well as increased control and confidence in Au/B liner thickness and B concentration uniformity and reproducibility. We will also discuss effects of various leaching mechanisms affecting B concentration in the Au/B liner.