Highly ionized uranium emission in the soft-x-ray region 50–100 Å

Time-resolved uranium spectra emitted from a relatively low-density ($n_e$∼${10}^{13}$ ${\mathrm{cm}}^{\mathrm{-}3}$), high-temperature ($T_e$∼1 keV) plasma confined in the Texas experimental tokamak (TEXT) have been recorded in the 50–100 Å range. It is found that narrow emission bands originating from transitions within charge states having 5$p^6$5$d^k$ and 5$s^2$5$p^k$ ground configurations, U xv to U xxxi, dominate these spectra. The identification of the transition arrays is based on the comparison with both ab initio intermediate-coupling relativistic level structure computations including configuration-interaction effects for the simple cases and, for complex charge states, with the predictions of the unresolved transition array model.