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Interferometry of plasmas generated by fast discharge excitation of [Ag.sub.2]S microcapillary channels shows the formation of dense plasma waveguides capable of guiding intense laser beams. Discharge ablation of capillaries, 330 [micro]m or 440 pm in diameter, with 3-5.5-kA current pulses formed concave plasma density profiles with axial electron density > 1 x [10.sup.19] [cm.sup.-3]. These dense plasma waveguides containing highly ionized metal atoms are of interest to the development of a longitudinally pumped soft X-ray lasers.

Highly ionized Ar plasma channels were created by a fast capillary discharge and used to guide laser pulses with peak intensities up to 2.2 x [10.sup.17] W/[cm.sup.2] over a 5.5-cm distance. These plasmas are of interest for the generation of efficient soft X-ray lasers by longitudinal laser excitation. The guides were characterized using plasma interferometry, modeling, and near field imaging.

We report the characteristics of a saturated high-repetition rate Ni-like Mo laser at 18.9 nm. This table-top soft X-ray laser was pumped at a 5-Hz repetition rate by 8-ps 1-J optical laser pulses impinging at grazing incidence into a precreated Mo plasma. The variation of the laser output intensity as a function of the grazing incidence angle of the main pump beam is reported. The maximum laser output intensity was observed for an angle of 20°, at which we measured a small signal gain of 65 cm-1 and a gain-length product g×l>15. Spatial coherence measurements resulting from a Young's double-slit interference experiment show the equivalent incoherent source diameter is about 11 μm. The peak spectral brightness is estimated to be of the order of 1×1024 photons s-1 mm-2 mrad-2 within 0.01% spectral bandwidth. This type of practical, small scale, high-repetition soft X-ray laser is of interest for many applications. [ABSTRACT FROM PUBLISHER]