The Thinned Hohlraum Optimization for Radflow Experiments (THOR) Campaign on the National Ignition Facility*

The achievement of ignition and gain on the National Ignition Facility (NIF) provides the opportunity to develop novel experiments that utilize the energy produced by the capsule implosion. High yield capsule implosions on the NIF are fielded inside of a cylindrical hohlraum, which is used to convert laser energy to X-rays that drive the implosion. In high yield implosions, X-ray fluxes from hohlraum re-heating from igniting capsules has been observed that exceed the fluxes generated from laser heating. This enables the possibility of utilizing this hohlraum re- heating or even the X-ray output directly from the capsule to drive radiation flow experiments or opacity measurements relevant to astrophysical phenomena at conditions that are otherwise impossible to achieve in the laboratory. The THOR campaign on NIF aims to develop this capability.

The primary challenge is to design windows for the hohlraum that are thin enough to allow the radiation to burn through and expose an external package to capsule-generated radiation, yet thick enough to avoid producing a long-wavelength drive asymmetry observed by the capsule implosion that could prevent ignition. We have planned a series of experiments to optimize the window thickness and quantify imposed shape asymmetries on surrogate implosions. These data will be used to optimize a high-yield layered implosion attempt with THOR windows. We will discuss the design of the campaign, planned experiments, as well as simulations of the expected results.