Detailed analyses of x-ray-imaging spectroscopy data from OMEGA direct-drive inertial confinement fusion experiments to infer interspecies ion separation

We present the analyses of x-ray-imaging spectroscopy data obtained from LANL’s interspecies ion separation campaign ‘IonSepMMI-17A’ on the Omega laser facility. This campaign consisted of series of direct-drive ICF experiments and aimed for more symmetric implosions than our prior campaign.1,2 The targets were Ar-doped, D2-filled spherical plastic shells of varying D2-Ar relative and total gas pressures. We used a time- and space-integrated spectrometer, streaked crystal spectrometer, and three gated multi-monochromatic x-ray imagers (MMI) fielded along quasi-orthogonal lines of sight to record x-ray spectral features obtained from the implosions. The timing of the recording of the experimental data in the implosion was in between first-shock convergence and slightly before neutron-bang time. Detailed analyses of MMI data revealed observations of weak and strong ion species separations depending on the target fill, temporal evolution of ion densities and species separations, and implosion asymmetries in the observed results along different lines of sight. Experimental results are compared against the predictions of hydrodynamic simulations, which incorporate multi-ion species transport model. 1S. C. Hsu et al, EPL 115, 65001 (2016). 2T. Joshi et al., PoP 24, 056305 (2017).