Highly ionized uranium emission in the soft-x-ray region 50-100 A&#778

Time-resolved uranium spectra emitted from a relatively low-density (n_e~10¹³ cm^-3), high-temperature (T_e~1 keV) plasma confined in the Texas experimental tokamak (TEXT) have been recorded in the 50-100 A&#778 range. It is found that narrow emission bands originating from transitions within charge states having 5p⁶5d^k and 5s²5p^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.