Evidence for population inversion and possible lasing at 150.6, 154.6 and 187.3 Angstrom in pulsed power driven Z-pinches

This paper reports the DNA/PITHON pulsed power generator used to produce hot, dense, aluminum plasmas in a Z-pinch configuration. An annulus of neon gas was radially imploded on to a parylene capillary on axis, which was coated with aluminum. The pinch produced 3 cm and 5 cm long Al plasmas with densities ∼ 1020 cm-3 and temperatures ∼ 500 eV, with a 25 ns duration. After the implosion, the Al plasma expanded and cooled for the next 50 ns, producing Li-like Al XI ions by recombination from He-like Al XII ions. A time- gated, grazing incidence spectrograph (MCPIGS) was used to image the expanding plasma and to capture three consecutive 25 ns duration spectra. The Al XI, 4f-3d and 4d-3p lines at 154.6 and 150.6 Angstrom were observed to be anomalously bright compared to the Al XI, 4d-2p line. Also, the Ne X, 4- 3 line at 187.3 Angstrom was brighter than the Ne X, 4-2 Balmer-β line. Spatial and temporal variations of these lines suggest an inversion of the 4d and 4f levels in Al XI and of the n = 4 level in Ne X, driven by three-body recombination