Properties of laser-produced GaAs plasmas measured from highly resolved X-ray line shapes and ratios

Abstract

The properties of hot, dense plasmas generated by the irradiation of GaAs targets by the Titan laser at Lawrence Livermore National Laboratory were determined by the analysis of high resolution K shell spectra in the 9 keV to 11 keV range. The laser parameters, such as relatively long pulse duration and large focal spot, were chosen to produce a steady-state plasma with minimal edge gradients, and the time-integrated spectra were compared to non-LTE steady state spectrum simulations using the FLYCHK and NOMAD codes. The bulk plasma streaming velocity was measured from the energy shifts of the Ga He-like transitions and Li-like dielectronic satellites. The electron density and the electron energy distribution, both the thermal and the hot non-thermal components, were determined from the spectral line ratios. After accounting for the spectral line broadening contributions, the plasma turbulent motion was measured from the residual line widths. The ionization balance was determined from the ratios of the He-like through F-like spectral features. The detailed comparison of the experimental Ga spectrum and the spectrum simulated by the FLYCHK code indicates two significant discrepancies, the transition energy of a Li-like dielectronic satellite (designated t) and the calculated intensity of a He-like line (x), that should lead to improvements in the kinetics codes used to simulate the X-ray spectra from highly-charged ions.

A Critical Compilation of Experimental Data on the 1s2$l$2$l^{\prime}$ Core-Excited States of Li-like Ions from Carbon to Uranium

“…The only reported observations of spectra of Li-like Ga, Ge, and Y [137][138][139] do not contain numerical data, but present tracings of the recorded spectrograms. We extracted the data from the figures of Refs.…”

“…We extracted the data from the figures of Refs. [137,138] by using the theoretical wavelengths of He-like lines [140] and reference data on X-ray characteristic lines [119], while for the Ga spectrum of Seely et al [139] we had the original raw spectrograms in a digital format. We have not included these data in the present tables because of their low precision, but they all agree with predictions of Yerokhin and Surzhykov [6] within uncertainties.…”