First liquid DT-filled double shell implosions at the National Ignition Facility

The double shell implosion presents an opportunity to explore the dynamics of a burning plasma within a volumetric burn platform. The double shell campaign and the ICF program at Los Alamos National Laboratory (LANL) are focused on achieving burning plasma using an indirectly driven double shell implosion at the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory (LLNL).

Over the last several years, the LANL double shell campaign has made considerable progress in understanding the kinetic energy transfer from the outer shell to the inner one, investigating L-shell pre-heat through keyhole geometries, improving ablator joint integrity with gold coatings, and tuning implosion symmetry via cone fraction adjustments. Significant effort has gone into manufacturing high-quality targets and developing prediction capabilities. Following the recent achievement of ignition at NIF,  there has been a strategic shift in the LANL double shell effort, speeding up its advancement. The LANL Inertial Confinement Fusion (ICF) program has set a landmark goal to incorporate liquid DT fuel into the inner shell by FY24, marking a crucial advancement in their research.

In FY24, we have a lineup of three liquid DT-filled double shell shots scheduled at NIF with a 1.25 MJ laser drive. Our debut shot carried out on April 9th, 2024, resulted in a neutron yield of 1.9E13. Our primary aim for this shot was not to achieve maximum yield but rather to execute a successful liquid DT double shell shot, focusing on assessing implosion and diagnostic performances. To enhance implosion efficiency in future shots, we plan to address major hydro instability growth from the ablator gap (2-5 microns gap between the two outer shell hemis from the assembly) using gold plating at the gap to compensate the missing mass, reducing the fill tube outer diameter, and mitigating the fill-tube jets with increased glue mass and high-Z divets, among other efforts.

This presentation will delve into the preparation, challenges, and execution of the initial three liquid DT-filled double shell shots, examining the implosion performance including neutron metrics, shape, etc. Furthermore, we will outline our future plans for LANL's double shell campaign, elucidating our strategy for advancing the double shell platform in the years to come.