Analysis of Al precursor wire array experiments on the 1 MA zebra generator at UNR

Summary form only given. Previous experiments on the 1 MA Zebra generator at UNR studied precursor plasmas with Ni-60 cylindrical wire arrays (CWA). Those precursor plasmas were shown to consistently have electron temperatures > 400 eV¹. Continuing research on precursor plasmas at 1 MA on Zebra investigated first other mid-Z wire materials and then alternate arrays using mixed Al/mid-Z CWAs. Results found similar electron temperatures for the mid-Z elements present in the precursor with relatively colder temperatures for Al. A better understanding of the results from the mixed CWAs requires understanding pure Al CWAs. Recent experiments on Zebra using Al CWAs were performed to compare with the mixed Al/mid-Z CWAs. These CWAs consist of 6 wires evenly spaced in a 12 mm diameter, the same configuration as in previous experiments on precursor plasmas. Time-integrated spatially-resolved (TISR) and time-gated spatially-integrated (TGSI) X-ray spectral data, time-integrated and time-gated pinhole X-ray images, shadowgraphy, as well as optical streak camera images were obtained and analyzed. It was found that the Al precursor radiation starts, and stays pronounced until the main X-ray burst. This differs from the mid-Z precursors which show a defined precursor burst with an increase in radiation and decrease to zero before the main x-ray burst. Non-LTE kinetic models of Al have been applied to account for the K-shell radiation from precursor and main X-ray burst plasmas. The resulting plasma parameters from modeling of TGSI and TISR spectra together with analysis of corresponding images allow for the study of precursor plasma formation in time and in space, respectively.