Arc velocity and erosion for stainless steel and aluminium cathodes

The velocity of vacuum arcs in a magnetic field and the erosion at the cathode have been investigated for Al + 3% Mg and stainless steel. The arc currents were adjusted between 16.6 A and 70 A and a magnetic induction of 0.02 to 0.1 T was applied. The arc current and the arc velocity can be measured reproducibly only after conditioning of the cathode surface by 20 to 40 arc operations. For conditioned cathodes at room temperature the arc velocities increase with arc current and magnetic induction. For higher cathode temperatures the arc velocity decreases while the erosion yields and the crater size increases. (orig.)