We report on the realization of a capillary discharge soft X-ray laser operating at 46.9 nm pumped by a 30 kA peak value, 150 ns half cycle duration current pulse (corresponding to a mean current slope of about 5 x 10 exp 11 A/s). The slope of the pumping current is sufficiently high to produce the plasma compression and laser amplification on the 3p-3s, J=0-1 transition of Ne-like Ar, in 2.4-4 mm diameter alumina capillary channels. We analyzed the output pulse characteristics of the produced laser beam, such as the lasing time and the pulse duration, the saturation and the output pulse energy, and the near field image as a function of different experimental parameters. Using the same current pulse, the lasing effect was not observed in polyacetal capillaries.