Estimating the electron temperature from fluctuations in a vacuum arc plasma: cathode spot operation on a contaminated surface

High frequency fluctuations (up to 50 MHz) in the ion current arc voltage and plasma floating potential have been studied, together with the influence of the surface history on these fluctuations for arc currents ranging from 2 to 50 A. In the process of surface conditioning by repeated arcs, the amplitude of fluctuations increases. The fluctuations of a signal from the grounded probe situated at a distance of