Special features of explosive electron emission of graphite cathode operating in pulsed-periodic regime

Emission properties of graphite cathodes, supplied by voltage pulses having an amplitude of 300 kV, a pulse width of 10^-9 s and a repetition frequency ranging from 1 to 3.5 kHz, have been studied. Dynamics of the current emission delay in correlation with the charge transferred by the beam and photographs of the cathode surface, which were taken in a scanning electron microscope, was analysed. The experiment demonstrated that smoothening of the relief led to degradation of the cathode, which could be avoided through the increase in the pulse repetition frequency in excess of some critical frequency.