EVAPORATION RATE FROM A SINGLE CATHODE SPOT ON PRECIOUS METAL-ELECTRODES IN VACUUM ARCS

Utilizing the values of a cathode spot radius and its temperature, which are calculated on the basis of the cathode mechanism theory proposed recently by Kubono, the rate of metal evaporation from a single cathode spot on Ag, Au, Ir, Pd, Pt, and Rh electrodes is expressed in simple approximate formulas as a function of arc current. In the case of Ag and Au electrodes, the calculated results are found to be in agreement with experimental data by different investigators, but it is difficult to compare calculations with measurements on the other electrodes because of few experimental data. This estimating process and these approximate formulas for the radius, temperature, and evaporation rate on the cathode spot as a function of arc current are useful, because it is very laborious to measure the cathode spot radius, temperature, and the evaporation rate.