Reaching significant yield amplification at high adiabat on the National Ignition Facility with a 2-shock CH implosion design*

Implosions with high fuel entropy, or adiabat (defined as the ratio of the DT fuel layer pressure to the Fermi degenerate pressure) at the National Ignition Facility have historically resulted in the highest ratios of measured to simulated yield. For example the recent adiabat 4.3 high yield “Big Foot” experiment[1] achieved 45% of the yield predicted by 1D simulation, while the 2-shock CH cryo-layered implosion[2] achieved >90% of 1D simulated yield, albeit at minimal yield amplification.  Here we describe a series of upcoming experiments at the NIF to test the performance of 2-shock CH implosions at a scale (1150 µm fuel outer radius) large enough to generate significant yield amplification.  Initial experiments will test 2-shock CH at an adiabat of 5.5 and a yield amplification of 5, and follow-on experiments will reduce the implosion adiabat to 4.1 for a yield amplification of 20.  The strategy for achieving a symmetric implosion of such a large CH capsule will be described, as well as the proximity to the ignition threshold for the two different adiabat designs.

[1]K.L. Baker et al., Phys. Rev. E, 102, 023210 (2020)

[2]S.A. MacLaren et al., Phys. Plasmas 25, 056311 (2018)