We report on a fast soft x-ray source consisting in a high temperature small diameter (4 mm) plasma column produced by electric discharge in a ceramic capillary. This source was developed to produce pulses of few hundred nanosecond duration for EUV lithography, x ray microscopy applications and also with the aim of developing a soft x ray amplifier. We obtained experimental results concerning the intensity and spectral analysis of the emitted x radiation pumped by a 30-40 kA, 100-200 ns, electric discharge at 1 Torr pressure in Ar gas. We refer also on the spectra obtained using CO2, as plasma medium, after the optimization of the discharge setup and electrical parameters.