THOR: Developing a Next-Generation Platform for Radflow and Opacity Measurements

The achievement of ignition and gain on the National Ignition Facility (NIF) enables novel experiments that leverage the energy produced by capsule implosions [1]. Capsules are fielded inside of a hohlraum used to convert laser energy into X-rays that drive the implosion. In high-yield implosions, X-ray fluxes from hohlraum re-heating have been observed to exceed the fluxes generated from the initial laser drive [2]. This opens opportunities to usethis X-ray output to drive radiation flow experiments and opacity measurements relevant to astrophysical conditions previously unreachable in the laboratory. The THOR (Thinned-Hohlraum Optimization for Radflow experiments) campaign seeks to develop this capability. A key challenge is designing windows that are thin enough to allow radiation to burn through and escape the hohlraum, yet sufficiently robust to prevent a long-wavelength drive asymmetry that could inhibit ignition. To address this, systematic studies using xRAGE have been conducted to quantify the shape distortions imposed on these implosions. Simulations predict that variations in window thickness, material density, and X-ray absorption properties induce measurable asymmetries that can be mitigated through optimized design. A series of experiments were designed to validate these models, systematically scanning window materials, thicknesses, and laser configurations to minimize perturbations while maximizing radiation throughput. These efforts culminated in the successful execution of a DT-layered implosion using THOR windows, achieving a yield of 2.40 ± 0.09 MJ, gain of 1.17, without measurable degradation to implosion symmetry. This shot marks the first demonstration of ignition in a hohlraum modified to let radiation from ignition to flow out of the hohlraum. This presentation will discuss the modeling strategy, asymmetry mitigation, and experimental results that establish THOR as a next-generation platform for radiation flow and opacity science.