Direct-drive wetted-foam implosions on the NIF and OMEGA

Wetted foam direct-drive inertial confinement fusion (ICF) implosions offer the prospect of improved stability, mitigation of laser-plasma instabilities (LPI), and control over the convergence ratio to achieve high gain without the stringent requirements of solid fuel layering. Recent advancements in two-photon polymerization manufacturing of deterministic and reproducible foam targets have renewed interest in wetted foam as a path forward for ICF and inertial fusion energy. Dedicated experiments to study the physics of wetted-foam spherical targets have been conducted on the National Ignition Facility (NIF). First, the implosion of 18-μm thick, 3-mm diameter capsules filled with liquid D₂ demonstrated the feasibility of fielding these cryogenic targets while quantifying laser-energy coupling, while comparable experiments with a ~170-μm thick, ~40 mg/cm³ foam layer produced significantly lower stimulated Raman scattering as expected. On OMEGA, foam-lined cone-in-shell experiments filled throughout with liquid D₂ are planned to diagnose energy coupling, LPI, and shock propagation in wetted-foam ablators. Preliminary results from the first layered direct-drive wetted foam experiments on NIF with an interior vapor region and plans for future experiments towards the implementation of wetted-foam implosions on OMEGA will be discussed.



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.