High-Resolution X-ray Spectroscopy of a Polar Direct Drive Exploding Pusher on NIF*

An absolutely-calibrated, high-resolution x-ray Bragg crystal spectrometer has been deployed at the National Ignition Facility (NIF) to diagnose plasma conditions in a polar direct drive exploding pusher (PDXP) implosion near stagnation. Two conical crystals focus the Kr He-α and He-β complexes onto a streak camera for time-resolved spectroscopy, and spectral intensities are calibrated via a cylindrical von Hamos crystal that time-integrates the intervening energy range between 12.8 and 15.6 keV. The evolution of electron density and temperature are inferred though Stark broadening and the relative intensities of dielectronic satellites. Results from collisional-radiative codes SCRAM and CRETIN are compared to relative and absolute line intensities and widths, which enables benchmarking of predicted plasma parameter profiles from 1D radiation hydrodynamic simulations of the PDXP platform.