Surface Roughness Impact on Double Shell Target Designs

Double shell targets on the National Ignition Facility (NIF) provide for an alternative path to robust burn¹. The target relies upon kinetic energy transfer from an ablator to a high Z and high-density pusher that is adjacent to the fuel. This has the advantage of achieving burn conditions in DT gas with a lower convergence and internal temperature compared to single shell designs. With the multiple layers with large density jumps, hydrodynamic instability growth is a concern. This work will examine the impact of surface roughness on the performance of two different double shell designs. The first is an 1100µm outer radius target inside a cylindrical hohlraum, and the second is a 1510µm outer radius target inside a rugby hohlraum. Due to differences in the maximum temperature in the hohlraum, the targets are driven differently, which affects the overall performance. In addition to impacts of the surface roughness, several mitigation strategies are investigated, including changing the tamper material, foam density, and foam composition.

1. 1. P. Amendt, et al., Physics of Plasmas 9, 2221 (2002)