Spectroscopic studies of shell mix in directly driven implosion on SGIII prototype laser facility

Abstract

We study shell mix during implosion using a capsule with a Cl-doped gas-shell interface that is also filled with Ar-doped deuterium gas. The Ar and Cl K-shell emissions are recorded with a flat crystal spectrometer. The He-β complex is analyzed to infer the electron temperature and density in the hotspot. Two regions of different hydrodynamic states are observed: a region of Te ∼ 1.2 ± 0.2 keV and ne ∼ (4 ± 0.5) × 1023 cm−3 and another of Te ∼ 0.6 ± 0.2 keV and ne ∼ (4 ± 0.5) × 1022 cm−3 probed by Ar and Cl ions, respectively. The neutron yield was also recorded and found to have reduced by a factor of ten for the Cl-doped capsule. By attributing the degradation of the neutron yield to the enhanced radiation loss due to the presence of mixed Cl ions and using the conservation of hotspot internal energy, the amount of mixed Cl ions is estimated to be ∼1.4 × 1014, corresponding to a 0.1 μm thickness of the initial shell material and a mixing width of about 16 μm.