High current multicapillary dielectric cathode

Results of high-current electron beam generation in a ~200 kV, ~250 ns diode with a multicapillary dielectric cathode assisted by either velvet-type or ferroelectric plasma sources are presented. Multicapillary cathodes made of cordierite, glass, and quartz glass samples were studied. It was found that the source of electrons is the plasma ejected from capillaries. The plasma parameters inside capillary channels and in the vicinity of the cathode surface were determined during the accelerating pulse. A model of the plasma supersonic flow from dielectric capillaries is discussed. It was shown that glass multicapillary cathodes are characterized by producing less surface erosion than the cordierite cathodes. Also, it was found that multicapillary cathodes assisted by a ferroelectric plasma source showed longer lifetime and better vacuum compatibility than multicapillary cathodes assisted by a velvet-type igniter. Finally, it was found that quartz glass MCDC assisted by FPS is characterized by almost simultaneous formation of the plasma in a cross-sectional area of the dielectric sample with respect to the beginning of the accelerating pulse.