Extreme ultraviolet spectroscopy of CU cylindrical wire arrays on zebra at UNR

Abstract

Extreme ultraviolet (EUV) radiation from z-pinch plasma sources has been shown to play a substantial role in the evolution of z-pinches, contributing significant amounts of radiation in the wire ablation, stagnation, and plasma expansion phases. Recent studies of Cu z-pinch plasmas from cylindrical wire arrays have also shown that high temperatures (up to 450 eV) exist in precursor plasmas, which have applications to inertial confinement fusion. The final expansion phase has shown that substantial EUV radiation continues even after the main x-ray bursts. In this work, EUV data were analyzed with the goal of understanding how the bulk cooler plasma might represent the main contribution to the total radiative output from z-pinch plasmas. In particular, a comparison and analysis of EUV data generated by two plasma sources is shown: the first set of experiments used Cu cylindrical wire arrays on the 1.0 MA Zebra generator at UNR. In addition to EUV data, x-ray data is also analyzed which shows dominant emission of Cu XX ions. The second set used Cu flat targets and was performed at the compact laser-plasma x-ray/EUV facility “Sparky” at UNR, which is used as a unique line calibration source. Moreover, spectral data generated by Sparky generally show more and better resolved lines. Cu L-shell lines in the range of 120-160 Å, specifically CuX to CuXIII ions, are identified. To help with the identification of lines, a non-local thermodynamic equilibrium (non-LTE) kinetic model was utilized and was also used to determine plasma parameters, such as electron temperature and density. Future studies will focus on attaining time-gated EUV spectra in order to better understand its role in the evolution of z-pinch plasmas.