Instability of vacuum arc in Ag-Cu contact alloys

To clarify the effect of contact material characteristics on the arc instability and chopping phenomena, the spectrum intensity of ionized and neutral vapor generated continuously during discharge is measured using contacts of Ag-Cu binary alloys. It is observed that arc instability and chopping are closely related to the behavior of the ionized vapor during discharge. The chopping current decreases with increased Ag content, while the instability-initiating current has a minimum value at 60 at.% Ag content. These effects are discussed from the viewpoint of the ion generation capability, including thermal properties, of contact materials