Effect of Fill Pressure and Species on Low-Convergence Implosions

Implosions present a fruitful platform for conducting atomic physics studies of mid-Z materials under compression as fusion-related design constraints can be relaxed. We will present on the use of fill pressure and dopant species to modify the thermodynamic trajectory of an imploded plastic shell with an embedded mid-Z tracer layer. To ensure that the tracer layer remains localized within the shell, a low-convergence implosion design is used, producing greater hydrodynamic stability than higher-convergence implosions traditionally used in inertial confinement fusion. Targets consist of 880-μm-outer-diameter, 30-μm-thick spherical CH capsules filled with D₂ at various pressures (2 atm or 20 atm) and with various dopant species (1.27 at % Ar or Kr); a 0.2-μm bilayer of Cr and Ni is recessed 8 μm from the inner surface. The targets were driven with 27 kJ of laser energy over 1 ns. The effect of the gas fill on radiative power loss of the core, stagnated core radius, and thermodynamic states accessed by the shell is inferred from forward-fitting synthetic data from an implosion model to observed imaging and spectral data.