Lawrence Berkeley National Laboratory

Current fluctuations of cathodic arcs were recorded with high analog bandwidth (up to 1 GHz) and fast digital sampling (up to 5 Gsamples/sec). The power spectral density of the arc current was determined by fast Fourier transform clearly showing material dependent, non-linear features in the frequency domain. These features can be associated with the non-linear impedance of the conducting channel between cathode and anode, driven by the explosive nature of electron emission and plasma formation. The characteristic times of less than 100 ns can be associated with individual explosive processes, "ectons," and therefore represent the short-time physical cutoff for the fractal model of cathodic arcs.