title: Extreme degree of ionization in homogenous micro-capillary plasma columns heated by ultrafast current pulses.
abstract: Homogeneous plasma columns with ionization levels typical of megaampere discharges are created by rapidly heating gas-filled 520-μm-diameter channels with nanosecond rise time current pulses of 40 kA. Current densities of up to 0.3  GA cm^{-2} greatly increase Joule heating with respect to conventional capillary discharge Z pinches, reaching unprecedented degrees of ionization for a high-Z plasma column heated by a current pulse of remarkably low amplitude. Dense xenon plasmas are ionized to Xe^{28+}, while xenon impurities in hydrogen discharges reach Xe^{30+}. The unique characteristics of these hot, ∼300:1 length-to-diameter aspect ratio plasmas allow the observation of unexpected spectroscopic phenomena. Axial spectra show the unusual dominance of the intercombination line over the resonance line of He-like Al by nearly an order of magnitude, caused by differences in opacities in the axial and radial directions. These plasma columns could enable the development of sub-10-nm x-ray lasers.
authors: Department of Electrical and Computer Engineering, Colorado State University, Fort Collins, Colorado 80523, USA.|Comisión Chilena de Energía Nuclear, Santiago, Chile and Center for Research and Applications in Plasma Physics and Pulsed Power, P4, Casilla 188-D, Santiago, Chile.
authors: G
authors: G
authors: Avaria
authors: Department of Electrical and Computer Engineering, Colorado State University, Fort Collins, Colorado 80523, USA.
authors: M
authors: M
authors: Grisham
authors: Department of Electrical and Computer Engineering, Colorado State University, Fort Collins, Colorado 80523, USA.
authors: J
authors: J
authors: Li
authors: Department of Electrical and Computer Engineering, Colorado State University, Fort Collins, Colorado 80523, USA.|Advanced Energy Industries, Fort Collins, Colorado 80525, USA.
authors: F G
authors: FG
authors: Tomasel
authors: Department of Electrical and Computer Engineering, Colorado State University, Fort Collins, Colorado 80523, USA.
authors: V N
authors: VN
authors: Shlyaptsev
authors: ARTEP Inc., Ellicott City, Maryland 21042, USA.
authors: M
authors: M
authors: Busquet
authors: Department of Electrical and Computer Engineering, Colorado State University, Fort Collins, Colorado 80523, USA.
authors: M
authors: M
authors: Woolston
authors: Department of Electrical and Computer Engineering, Colorado State University, Fort Collins, Colorado 80523, USA.|Department of Physics, Colorado State University, Fort Collins, Colorado 80523, USA.
authors: J J
authors: JJ
authors: Rocca