Spectroscopy of single vacuum arc cathode spots with improved sensitivity

Recently, we reported on optical emission of vacuum arc discharges with a single cathode spot. The discharges were initiated by rectangular voltage pulses of 100 ns length produced by a cable generator. In combination with the application of a liquid Ga-In alloy cathode and UHV conditions a high reproducibility could be obtained. By replacing the streak camera the sensitivity and the signal-to-noise ratio could be improved. Thus, the accumulation of calibrated spectra with high temporal, spatial, and wavelength resolution has been possible. Distinct differences on the temporal development of the atomic and ionic line intensities have been found depending on the spatial position, i.e. comparing the spot core and the spot surrounding.