Plasma expansion and impedance collapse in a foil-less diode for a klystronlike relativistic backward wave oscillator

• DOI: 10.1063/1.3520072
• Publication Date: 2010-12-07T23:36:09Z
• Authors: Renzhen Xiao; Jun Sun; Shaofei Huo; Xiaoze Li; Ligang Zhang; Xiaowei Zhang; Lijun Zhang
• Keywords: Backward-wave oscillator; Relativistic electron beam

Klystronlike relativistic backward wave oscillator (RBWO) can produce microwave power exceeding 5 GW with a high efficiency larger than 40%. In the experiment of klystronlike RBWO, for about 1 MV peak diode voltages, increasing magnetic field from 1.43 to 1.89 T slowed impedance collapse until it was suppressed completely. The introduction stainless steel obstructing ring aggravated collapse, whereas replacing flat provided more stable variation during pulse duration. These collapses did not affect generation seriously and may be attributed radial expansion cathode plasma initialing shank so that part reverse currents were collected at anode wall, contributing measured current. On other hand, found shot-to-shot reproducibility closely related variation. When there no or very low measured, appeared latter pulse. improved greatly after electron collector enlarged on radius mm. A possible explanation is produced expands axially enters region velocity several mm/ns. movement in beam-wave interaction affects generation, which reduces whole duration significantly.