  We present an experimental platform for measuring hydrogen Balmer emission
and absorption line profiles for plasmas with white dwarf (WD) photospheric
conditions (T_e ~ 1 eV, n_e ~ 10^17 cm^-3). These profiles will be used to
benchmark WD atmosphere models, which, used with the spectroscopic method, are
responsible for determining fundamental parameters (e.g., effective
temperature, mass) for tens of thousands of WDs. Our experiment, performed at
the Z Pulsed Power Facility at Sandia National Laboratories, uses the large
amount of x-rays generated from a z-pinch dynamic hohlraum to drive plasma
formation in a gas cell. The platform is unique compared to past hydrogen line
profile experiments in that the plasma is radiation-driven. This decouples the
heating source from the plasma to be studied in the sense that the radiation
temperature causing the photoionization is independent of the initial
conditions of the gas. For the first time we measure hydrogen Balmer lines in
absorption at these conditions in the laboratory for the purpose of
benchmarking Stark-broadened line shapes. The platform can be used to study
other plasma species and to explore non-LTE, time-dependent
collisional-radiative atomic kinetics.
