Experimental Study of Arc Stability. I

Abstract

The stability of short arcs in gases and in metal vapors is closely related to the phenomena associated with the cathode spot. Use is made of improved techniques to study this phenomenon for a considerable range of electrode materials. The distribution of arc life for a given average current is shown to follow the survival law. These data demonstrate that a small percentage of arcs of a given current on very clean metal surfaces may have lifetimes that are extremely short or very long compared with the average life. The relation between the average life of an arc and its average current is shown generally to consist of two sharply defined sections each of the form lnt=A lnI+B. The distribution of lifetimes and the relation between average life and average current are shown for Hg, Cd, Zn, Cu₂Sb, Bi, Bi‐Cu, Cu‐In, Ag, Cu₃Sn, Al, Be, Cu, Cu‐W‐Th, Cu‐MoC, Mo, and W. It is shown that high vapor pressure materials tend to produce more stable arcs than those having low vapor pressure.