Discharge behavior of the vacuum arc ion source working in pulse mode was investigated using high-speed photography and spectrum diagnosis. The evolvement of cathode spot on hydrogen-impregnated electrode was captured by high-speed photography

and the emission spectra of cathode spot at different pulse currents were analyzed. The experimental results show that in most cases

only one cathode spot can be found in the discharge zone of vacuum arc ion source

and the spot moves a little during the same discharge. Temperature of the cathode spot may rise while the discharge current increases

and ultimately the density of hydrogen ion will be increased. At the same time

sputtering of the electrode is enhanced and the quality of ion plasma will be reduced.