Leaked electrons from virtual cathode oscillation

Investigated are the properties of leaked electrons from virtual cathode oscillation. It is found from the simulation that most leaking occurs from the radial edge of the beam, so that the leaked beam forms an annular beam. An axial bunching was also observed. The average leaked current was close to the space charge limiting current, and the energies of the electrons at the end of the drift tube were a fraction of the injected energies, and were nearly independent of the injection currents. A preliminary experimental result seems to support these simulation results