Time resolved XUV spectroscopy from highly ionized capillary discharges

Summary Form only given, as follows. The authors have carried out time-resolved measurements of the axial emission from capillary plasmas 500 mu m in diameter and several centimeters in length, excited by short (50-100 ns FWHM) discharge pulses. Extreme-ultraviolet spectra with 5-ns resolution in a single discharge shot are obtained using a 1-m-focal-length vacuum spectrograph. Analysis of the axial spectra from a 500- mu m diameter lithium hydride capillary shows simultaneous line emission from highly ionized (Li III, O VI) and single-ionized (O II) species. The data indicate the existence of a hot core plasma (T/sub e/>25 eV) surrounded by a significantly cooler (<5 eV) plasma near the walls. The situation is consistent with a model in which ablation of the capillary wall material is assumed to form a high-density plasma layer surrounding a less dense and significantly hotter core. Diffusion of totally stripped ions at the end of the current pulse from the core plasma into the cooler surrounding plasma could lead to a recombination region of annular shape in which gain could occur under optimized plasma conditions.<>