Capillary discharge-driven metal vapor plasma waveguides

We report the generation of dense plasma waveguides containing a large concentration of silver ions by means of a fast (∼55ns first half-cycle) microcapillary discharge. Concave plasma density profiles with axial electron density >1×1019cm-3 were measured from discharge ablation of 330 or 440μm diameter Ag2S capillaries with 3-5kA peak amplitude current pulses. The dynamic of this plasma waveguide was studied with interferometry, absorption measurements, and hydrodynamic model simulations. The results are relevant to the development of efficient longitudinally pumped metal vapor soft x-ray lasers, in particular those employing transient excitation of Ni-like ions. An approach to the design of a gain saturated waveguided 13.9nm laser in Ni-like Ag is discussed.