Experimentally-Inferred Fusion-Yield Dependencies on Target Specifications for Direct-Drive Implosions on the OMEGA Laser*

Recent progress in implosion experiments on the OMEGA laser has considerably improved the prospects for achieving ignition with megajoule-class lasers via direct drive. Those implosions exhibited a significant increase in performance resulting from a statistical approach used to predict the yield degradation from the 1D simulated value.^[1],[2] A new formulation of the statistical model has been developed to identify the experimental fusion-yield dependencies directly on the target specifications—namely, target thickness, ablator material, and laser beam-to-target radius. These new results are used to optimize the target geometry and ablator material to produce the highest fusion yield for OMEGA DT-layered implosions. It is shown that for a given target, the optimum beam radius is about 0.86x the target radius and that higher yields can be achieved by reducing both ice and ablator thicknesses while keeping the outer radius the same as current best performers.

 

[1] V. Gopalaswamy, et al., Nature 565, 581 (2019).

[2] A. Lees, et al., Phys. Rev. Lett. 127, 105001 (2021).