Photoionized plasma experiments at OMEGA EP

A new platform has been established at the OMEGA EP laser facility in which a tamped silicon sample is driven by a three-Cu halfraum x-ray source that produces a 30ns-duration, broadband x-ray flux with a radiation temperature of 90eV. The x-ray source performance is monitored with VISAR and its spectral distribution is recorded with a grating spectrometer. Plasma density is determined from the expansion measurement performed with an imaging grating instrument, and charged state distribution and temperature are extracted from the analysis of the silicon K-shell line absorption spectrum recorded with a crystal spectrometer. The latter diagnostic is afforded by using a separate laser beam to drive a 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 discuss the observations recorded during a series of campaigns at OMEGA EP and the comparisons with radiation-hydrodynamics and astrophysical modeling codes.