Laboratory photoionized plasmas in steady state

Performing laboratory photoionized plasma experiments that achieve steady state is a standing challenge. This is important for testing physics models employed in the interpretation of x-ray astronomy observations. A new platform has been established at the OMEGA EP laser facility in which a tamped silicon sample is driven by a three-Cu hohlraum x-ray source that produces a 30ns-duration, broadband x-ray flux with a radiation temperature of 90eV. The long duration x-ray flux is critical for producing a photoionized plasma in steady-state in the laboratory. The x-ray source performance is monitored with VISAR and its spectral distribution is recorded with a grating spectrometer. The silicon plasma is diagnosed with K-shell absorption spectroscopy. The latter is afforded by using a laser beam to drive a separate short-duration source of backlighting photons. Probing the silicon plasma at different times provides an experimental check of the steady-state condition in the photoionized plasma. We will discuss modeling simulations done to design the experiment and the observations recorded during a series of campaigns at OMEGA EP. This work is supported by DOE NNSA NLUF Grant DE-NA0003936.