Developing an Ignition-Scale CH Ablator Implosion Design at the National Ignition Facility

We have designed a new High-AdiabaT CH ablator implosion design (HATCH) for the National Ignition Facility. It aims to achieve the same implosion velocity and total remaining mass at peak velocity as the first ignition experiment, N221204, which used a diamond (HDC) ablator [1]. Using the same hohlraum, the same inner shell radius of 1050 microns, and the same fuel layer thickness (65 microns), simulations predict that HATCH can achieve ignition conditions with only 1.7 MJ of laser drive energy, which is more than 15% less than N221204, due to the higher ablation efficiency of CH compared to high-density carbon (HDC). Compared to previous CH implosion designs [2], the capsule radius was increased, the fuel entropy was raised to improve predicted stability (including resistance to the tent perturbation), and the latest implosion symmetry control techniques were implemented. Results from the first tuning experiments, including the first fuel-layered implosion, will be presented.

[1] H. Abu-Shawareb et al., Phys. Rev. Lett. 132, 065102 (2024).

[2] T. Döppner et al., Phys. Plasmas 27, 042701 (2020).