Role of the wall ablation in the operation of a 46.9 nm Ar capillary discharge soft x-ray laser

A capillary discharge pumped soft x-ray laser operating at 46.9 nm on the 3p-3s transition of the Ne-like Ar has been realized by pumping the active medium with a relatively slow current pulse (dI/dt ≈ 6-1011 A/s). In order to study the role of the ablation in the production of the laser effect, the intensity of the amplified 46.9 nm line has been investigated using the same pumping current pulses in the plastic (polyacetal) and ceramic (Al2O3). We showed that the ablation of the capillary walls is unfavorable both for the compression and stability of the plasma and consequently for the soft x-ray laser production. The amplification and lasing effects are observed only in the ceramic channel. The measurements of the line intensity at 46.9 nm showed the lasing with a gain-length product of ≈ 9, a laser pulse energy of ≈ 5 μJ, a pulse duration of 1.3 ns and a beam divergence of ≈ 3.5 mrad. In addition, effect of the scaling of the time of lasing with the initial plasma diameter was demonstrated experimentally and compared with a one-dimensional MHD model.