An axial electric field in a positive column with diffusion loss

In an ordinary low pressure discharge tube, the axial electric field in a positive column has usually been evaluated without the diffusion loss of electron energy to the wall. In a discharge tube with small radius such as laser tubes, however, we must consider this diffusion loss, since in such a case the ratio of the diffusion loss to the collision loss is not negligibly small. In this paper, we theoretically analyze the axial electric field in a positive column including this diffusion loss, together with numerical values for He and Ne. From the results, it is shown that the effect of diffusion loss becomes more pronounced if the mean free path of electron is larger than the tube radius. Furthermore, the calculated results are compared with the experimental results, and, although a satisfactory agreement can not be obtained, some qualitative characteristics show that the above statement is valid. (auth.)