A theoretical investigation of the dynamics of plasma discharge, excited bythe fast 6 ns full width at half maximum current pulse with 4.5 kA peak in a0.8 mm diameter channel inside an alumina capillary filled with Ar, isperformed by computer simulation. A one-dimensional two-temperaturemagnetohydrodynamic model that takes into account plasma dynamics as well asthe ablation of the wall material under the heat flux from the plasma has beenexplored. Simulations for Ar initial pressures of 100-500 mTorr show that ahot dense uniform plasma core is formed at the centre of the dischargechannel. The parameters of this core are favourable for soft x-ray lasing at46.9 nm due to the generation of population inversion in the plasma by thecollisional electron excitation of Ne-like Ar IX ions.