New Design for Low-Mode Asymmetry Mitigation in Inertial Confinement Fusion Implosions

Andrea Kritcher | 19-FS-061

Project Overview

Radiation flux symmetry in laser-irradiated hohlraum environments is difficult to model and control, and it relies on the details of plasma evolution and laser-energy deposition in the harsh plasma-filled hohlraum over the duration of the laser pulse. In this study, we developed a conceptual design and assessed the feasibility of using lasers to create a drive for which the implosion symmetry relies primarily on radiation transport. In this design, lasers irradiate the ends of a capsule containing a hohlraum, with no direct view of the capsule. This configuration enables the use of frequency-doubled light that has a higher power and energy threshold than current hohlraums used at the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory, up to 670 terawatts and approximately 3.5 megajoules. Using VISRAD (a three-dimensional thermal radiation code that enables scoping of complex geometries) benchmarked against HYDRA's radiation hydrodynamics calculations, we estimated that the same drive conditions that are currently being achieved in experiments at the NIF HybridE platform can be reached in this new geometry with large, 6.4-millimeter-diameter hohlraums. The radiation-drive asymmetries in this design can be mitigated by shimming the capsule ablator thickness or through tailoring the shape of the shielding to the laser spots.

Mission Impact

This project supports Livermore's mission focus in stockpile stewardship, as well as the Laboratory's mission research challenge in nuclear weapons science. It also supports the Laboratory's core competency in high-energy-density science, through the development of new, indirectly driven, inertial-confinement-fusion design for more controllable drive symmetry and increased laser-energy coupling to the hohlraum.