X-ray spectroscopic diagnostics and modeling of polar-drive implosion experiments on the National Ignition Facility

摘要

A series of experiments featuring laser-imploded plastic-shell targets filled with hydrogen or deuterium were performed on the National Ignition Facility. The shells (some deuterated) were doped in selected locations with Cu, Ga, and Ge, whose spectroscopic signals (indicative of local plasma conditions) were collected with a time-integrated, 1-D imaging, spectrally resolved, and absolute-intensity calibrated instrument. The experimental spectra compare well with radiation hydrodynamics simulations post-processed with a non-local thermal equilibrium atomic kinetics and spectroscopicquality radiation-transport model. The obtained degree of agreement between the modeling and experimental data supports the application of spectroscopic techniques for the determination of plasma conditions, which can ultimately lead to the validation of theoretical models for thermonuclear burn in the presence of mix. Furthermore, the use of a lower-Z dopant element (e.g., Fe) is suggested for future experiments, since the ~2 keV electron temperatures reached in mixed regions are not high enough to drive sufficient H-like Ge and Cu line emissions needed for spectroscopic plasma diagnostics.