HTPD 2018

In the quest for reaching ignition of deuterium-tritium (DT) fuel capsule implosions, experiments on the National Ignition Facility have shown lower final fuel areal densities than simulated. Possible explanations for reduced compression are higher preheat that can increase the ice-ablator density jump and induce ablator-DT ice mix, or reverberating shocks. We are hence developing x-ray Refraction Enhanced Radiography (RER) to infer the inflight density profiles in layered fuel capsule implosions. The RER uses a 5 µm imaging slit backlit by a Ni 7.8 keV He-alpha laser driven x-ray source at 20 mm from the capsule to cast refracted images of the inflight capsule onto a streak camera in a high magnification (M~60x) setup. Our first experiments have validated our setup using an un-driven high density carbon capsule that recorded a streaked RER x-ray fringe from the carbon ablator surface consistent with raytracing calculations at the required ~ 6 µm and 25 ps resolution for implosions. Streaked RER will be applied to inflight layered capsule implosions using a hydrogen-tritium fuel mix rather than DT to reduce neutron yields and associated x-ray backgrounds. This work was performed under the auspices of the U.S. Department of Energy by LLNL under Contract DE-AC52-07NA27344.