Radiation temperature measurement of a long duration x-ray source for steady-state laboratory photoionized plasma experiments

Long duration, i.e. tens of ns, broadband x-ray sources are important for steady-state laboratory photoionized plasma experiments relevant to astrophysics. In a series of experiments performed at the OMEGA EP laser facility, we have used the Gatling-Gun source to produce an x-ray drive that lasts for 30ns with a radiation temperature T$_{r}$ =90eV. The Gatling-Gun source is comprised of three Cu hohlraums; each is filled with TPX foam and driven by a separate 10ns square pulsed laser beams with 4.4kJ of UV laser energy\footnote{D. Martinez, 2017 Annual OLUG Workshop.}. The total source duration of 30ns is achieved by driving the three hohlraums sequentially in time. The radiation temperature was monitored with a VISAR diagnostic over a series of shots to check performance and consistency, and compare with previous miniDMX data\footnote{miniDMX reference}. We present measurements of the radiation temperature obtained from VISAR data from two series of experiments performed at OMEGA EP, in conjunction with radiation-hydrodynamics simulations of the VISAR diagnostic package.