[en] Numerical treatment of the charge density and the potential distribution has been done for a diffusion plasma column in a coaxial cylindrical discharge tube. The numerical results are as follows. (i) A homogeneous plasma exists in the centre region of the diffusion plasma. Therefore one may use this type of plasma column as a medium pressure plasma test chamber. (ii) The charge density distribution shows strong dependence on the volume recombination at the edge of the plasma column. This verifies the possibility for time-dependent measurements of the volume recombination coefficient as suggested by previous workers. (iii) Experimental charge density and potential distributions agree with present numerical solutions. (author)