Interrogation of Astrophysical Laboratory Photoionized Plasmas with Experiments at the 1MA Zebra and 26MA Z Pulsed-Power Drivers

Abstract

Due to the lack of spaceships with intergalactic capability, now and in the foreseeable future, we must find alternate methods to bring the universe to us. By studying laboratory photoionized plasmas we can further our understanding of highly energetic astrophysical environments, such as the accretion disks around black holes and neutron stars, giving rise to, active-galactic-nuclei and x-ray binary systems. These cosmic engines produce high-intensity broadband x-ray and UV radiation flux, which heats and ionizes the surrounding gas into a photoionized plasma. Laboratory data is a crucial aid in our interpretation of astrophysical observations and ability to test and validate astrophysical codes. We have used the 1MA Zebra and 26MA Z-machine pulsed-power drivers to experimentally study astrophysically relevant photoionized plasmas. On Zebra, the supersonic gas jet platform provides the first method for university-scale drivers to study such plasmas. The gas jet platform leverages the diverse diagnostic capability and robust shot rate of Zebra, providing perspectives inaccessible to that of large-scale drivers. This work has motivated the first broadband spectral characterization of Zebra’s radiation drive. Alternatively, on the Z-machine, the photoionized gas cell platform has enabled studies at the highest level of x-ray flux terrestrially possible. For the first time, we have integrated photon Doppler velocimetry into the gas cell, which has been used to answer the critical question of uniformity within the gas cell by observing spatially resolved electron number density time histories. In the broader context of Z diagnostics, this work has also demonstrated the feasibility of high-precision low-noise measurements in close proximity to the overwhelming x-ray flux of the Z-machine. These two laboratory photoionized plasma platforms each provide unique capabilities: Zebra experiments emphasize the role of L-shell atomic physics on heating and ionization of neon plasmas, while Z extends it to plasmas populated with K-shell ions. Hence, both experiments provide complementary astrophysically relevant data of photoionized plasmas.