“…Here T * , N * , W * and z * are the temperature and density of electrons and the energy and mean charge of ions at the critical point, located at the distance of d/4 from the cathode surface [5]; µ is the ion mass in atomic mass units. Assuming the solid angle of the plasma microjet to be close to one and the ratio of the ion current to the entire current to be of the order of one tenth [1,4], we have C 1 ≈ 10 −5 eV 5/2 A −1 m and C 2 ≈ 7 × 10 13 eV 1/2 A −1 m −1 . As the Coulomb logarithmic term we can adopt the modified form, proposed by Zollweg and Liebermann [6]:…”