Myung Choul Choi

A study of diode perveance for high-power relativistic electron beams

The space-charge-limited current in a diode, including the relativistic effects of beam electrons on it, is investigated in connection with development of an analytical model of the perveance for high-power relativistic electron beams. A simple scaling law for perveance in a high-power diode is obtained and compared with experimental data, which agree reasonably well with theoretical predictions.

Forward current propagation beyond the virtual cathode formed by a high injection current

A virtual cathode is formed in a cavity, if the injection current from the diode exceeds the critical current. The propagation properties of the forward current beyond the virtual cathode are investigated. It is shown that the forward current increases significantly as the diode gap distance LCA increases, although the injection current from the diode decreases drastically. Experimental data agree well with theoretical results obtained analytically.

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