Conditioning a Copper Cathode Surface by High-Voltage Subnanosecond Pulses

Within the article, a pre eroded copper cathode was subjected to the impact of a series of high-voltage pulse swith a duration of<1 ns for surface conditioning. An effective cathode surface area was similar to 0.01 mm(2). Pre erosion of the cathode surface was performed using a series of vacuum arc discharges of microsecond duration. As a result, a well-pronounced microrelief with a typical dimension of similar to 5-10 mu m was formed at the cathode surface. Then, to smooth the microrelief, the cathode was placed into a vacuum setup based on a RADAN pulse generator with a pulse duration of<1 ns and a pulse amplitude of up to-140 kV.About 900 discharges of a sub nanosecond duration were initiated. To estimate the conditioning effectiveness, the state of the cathode surface was controlled by studying the cathode field-emission characteristics and cathode surface imaging by scanning electron microscopy (SEM). The field-emission characteristic study made it possible to estimate the electric field enhancement factor beta near the cathode surface before and after the conditioning. It was shown that the subnanosecond conditioning led to a decrease in beta by a factor of 6-8 from similar to 170 after eroding to similar to 20-30.Employing SEM investigation of the sample surface morphology,it was found that a typical microrelief dimension was decreasedfrom similar to 5-10 to similar to 1-2 mu m or less. That is, a proposed conditioning technique allowed significant smoothing of the cathode surface