X-ray emission from laser-generated plasmas recorded by a transmission crystal spectrometer

摘要

A transmission crystal spectrometer was utilized to record the hard x-ray spectra from laser-produced plasmas in the 12 keV to 60 keV energy range and with a resolving power of E/ΔE≈100. This emission is of interest for the development of hard x-ray backlighters and hot electron diagnostics. Planar foils of U and Pb were irradiated at the OMEGA laser facility by 24 beams (12 on each side of the foil) with no beam smoothing. The spectra typically exhibited a few intense and relatively narrow features in the 12 keV to 22 keV energy range. Initial analysis suggested that these hard x-ray features are inner-shell transitions resulting from L-shell vacancies created by energetic electrons. The observed transition energies were slightly higher than the neutral-atom characteristic x-ray energies, and calculations suggested that the transitions are in the Ni-like or lower ionization stages.