Laboratory Generated Heat Fronts Relevant to the Epoch of Reionization*

Radiation-hydrodynamics is an active area in research across many fields such as High Energy Density Physics, Inertial Confinement Fusion, and Astrophysics. One phenomenon in radiation-hydrodynamics are photoionization fronts (PI Fronts or Ionization Fronts), which are a not well understood type of radiation-driven ionization wave. In astrophysical systems, PI fronts were formed during the Epoch of Reionization (EoR) when black holes and quasars emitted ionizing radiation into the neutral intergalactic medium (IGM). As the PI fronts propagated, they turned the neutral IGM into a cosmic ionizing background. James Webb Space Telescope (JWST) has a primary goal of measuring the EoR by surveying high red shift galaxies (z = 6-15) from this time. Stronger understanding of PI fronts can help enhance the understanding of high red shift galactic observations from JWST. In this effort, a platform has been developed to generate and measure PI fronts in the laboratory as part of the Z Astrophysical Plasma Properties Collaboration on the Z-Machine at Sandia National Laboratory. For the laboratory PI Front experiments, a radiation-driven ionization wave is driven into a nitrogen gas cell using a tungsten wire array as an x-ray source. Measurements of the front velocity have been made using photon-doppler velocimetry for a variety of gas pressures. Atomic kinetic calculations done in PrismSPECT are used to further understand the type of radiation front generated. Future work will include the verification of the radiation-driven ionization front as a PI front.