On the State of Ionization, Non‐Ideality and Electric Conductivity of the Cathode Plasma of Vacuum Arcs

The cathode spot plasma of a metal vapour are in vacuum has a high density (10 25 –10 28 m 3 ) with a relatively low temperature (1–5 eV), therefore it is strongly non‐ideal. The degree of ionization α and the electric conductivity σ of such plasmas are discussed, considering that non‐ideality. The burning voltage of the arc U B is estimated with the help of σ‐values, obtained from theories and measurements for non‐ideal copper plasmas. It is shown, that a high current density of the cathode spot of j = 10 12 A/m 2 is not in contradiction to a low burning voltage U B = 20–30 V, but these values give a consistent picture of the spot processes.