First experiments on Revolver shell collisions at the OMEGA laser

Abstract

The results of recent experiments on the OMEGA laser are presented, demonstrating the ablator-driver shell collision relevant to the outer two shells of the Revolver triple-shell inertial-confinement-fusion concept [K. Molvig et al., Phys. Rev. Lett. 116, 255003 (2016)]. These nested two-shell experiments measured the pre and postcollision outer-surface trajectory of the 7.19 g/cc chromium inner shell. Measurements of the shell trajectory are in excellent agreement with simulations; the measured outer-surface velocity was 7.52 ± 0.59 cm/μs compared to the simulated value of 7.27 cm/μs. Agreement between the measurements and simulations provides confidence in our ability to model collisions with features which have not been validated previously. Notable features include the absence of ∼40 mg/cc foam between shells commonly used in double shell experiments, a dense (7.19 g/cc) inner shell representative of the densities to be used at full scale, approximately mass matched ablator payload and inner shells, and the inclusion of a tamping-layer-like cushion layer for the express purpose of reducing the transfer of high mode growth to the driver shell and mediation of the shell collision. These experiments test the modeling of the radiative heating, expansion, recompression, and acceleration of the chromium inner shell. Agreement of experimental measurements with simulation improves our confidence in the models used to design the Revolver ignition target.