Perveance and sheath plasma expansion characteristics in high power cylindrical diode

Perveance and sheath plasma expansion characteristics for high power electron beams have been experimentally investigated in a cylindrical diode. An experimental scaling law for perveance in high power cylindrical diodes have been obtained in terms of anode-cathode (A-K) gap distance, d. It is found that the diode perveance in a high power cylindrical diode has a scaling law of /spl sim/d/sup -1.83/ in terms of the A-K gap distance, d, which is in close agreement with that of /spl sim/d/sup -2/ for infinite planar diode. It is also noted in high power cylindrical diode that the sheath plasma expansion speed is about 7 cm//spl mu/s at A-K gap distance of 4 mm, which is about two times faster than that in high power axial diode, in this experiment.