Indirect-Drive Options for Future OMEGA-Like Laser Systems Designed Primarily for Direct Drive

It is desirable that future fusion laser systems should be able to support both direct- and indirect-drive experiments. This work examines the feasibility of indirect-drive experiments with a future 60-beam OMEGA-like system designed primarily for direct drive. The 60-beam OMEGA soccer-ball geometry has been demonstrated to provide excellent direct-drive uniformity as well as a versatile platform for a large variety of user experiments. Two options are considered: one that maintains the OMEGA beam locations, and one that rotates the beams 18° around each pentagonal face to avoid opposing beams.[1] This work investigates the use of a 48-beam subset of OMEGA to drive a spherical hohlraum with six laser entrance holes in a cubic geometry and identifies some feasible beam-pointing options. The view-factor code LORE[2] is used, with a new, realistic beam propagation model that handles beam spreading from (a) phase plates with a finite spot size and (b) the f number of the incident beams, to both demonstrate the feasibility of the best options and predict on-capsule nonuniformities well below 1%. This material is based upon work supported by the Department of Energy [National Nuclear Security Administration] University of Rochester “National Inertial Confinement Fusion Program” under Award Number DE-NA0004144.

[1] R. S. Craxton et al., Bull. Am. Phys. Soc., PO06.00005 (2023).

[2] W. Y. Wang and R. S. Craxton, Phys. Plasmas 28, 062703 (2021).