Superior performance of directly driven hydrogen ablator capsules*

We investigate the unique physics of using hydrogen as the main ablation material to achieve high nuclear yields from a liquid DT-wetted layer capsule directly driven by the National Ignition Facility’s current laser capabilities. The capsule is composed of a thin plastic shell used to enclose a thick low-density annular 3D-printed matrix layer that contains the liquid hydrogen fuel. Simulations predict high laser absorption fractions consistent with previous polar direct drive (PDD) MJ-class NIF experiments where >95% capsule absorption of the laser drive energy was achieved using a 5 mm diameter plastic capsule with a surface intensity of 2.5x10¹⁴ W/cm². Moreover, superior double-digit hydro-efficiency is predicted when hydrogen is the principal ablation material - higher than any other ablator material having equal shell mass. Simulations using the HYDRA and xRAGE rad-hydro codes show superior ablation pressure from hydrogen for extended times. Development of 3D printing techniques to enable construction of these hybrid capsules is being pursued. Investigation of the heterogeneous nature of the hydrogen/lattice ablator is being performed via planar cyrogenic experiments on Omega. An overview of these multi-Laboratory efforts will be shown.

R. E. Olson et al., Phys. Plasmas 28, 122704 (2021).

M. J. Schmitt, et al., https://meetings.aps.org/Meeting/DPP22/Session/JO04.13.