Copper Hohlraum Radiation Emission Characterization Relevant to Long Duration Astrophysics Experiments

Here we present characterization of a long-duration, broadband x-ray flux source for laboratory astrophysics experiments. These experiments performed at the OMEGAEP high-power laser facility utilized a four-beam laser system that can deliver up to 4.4 kJ of UV laser energy in pulses of 10 ns duration. By driving sequentially in time three individual copper hohlraums for 10 ns, we produce and sustain 90 eV of radiation temperature x-ray flux for 30 ns. This is informally named the “Gatling-Gun” x-ray source. Characterization is vital to monitor the performance of the Gatling-Gun. We field three diagnostics, namely VISAR, SOP and a gated grating spectrometer for characterization. The VISAR (velocity interferometry system for any reflector) is an optical laser interferometry diagnostic that measures the speed of a shock driven by the Gatling-Gun x-ray flux. The measured shock speed relates to the radiation temperature of the x-ray flux. The SOP, a streaked optical pyrometer, extracts the brightness temperature of the shock front. The gated grating spectrometer records the spectral distribution of the broadband x-ray flux over a photon energy interval of almost 2keV; this spectral information is important for understanding the experiment driven by the x-ray flux, it shows the thermalization of the x-ray field in the hohlraums. These observations are vital to properly modeling and understanding the photoionized plasma produced. This work was supported by DOE NLUF grants DE-NA0003533 and DE-NA0003936.