Affiliation:
1. Institute of Applied Electronics, China Academy of Engineering Physics , Mianyang, Sichuan 621900, China
Abstract
In order to realize mode control and long pulse operation of the proposed C-band high efficiency relativistic backward wave oscillator, the asymmetric high order mode oscillation and its influences on the working mode operation are investigated in the 3D particle-in-cell simulation. The simulation shows that the quasi-TM21 mode is the dominant competing mode, which is mainly located in the two-period extraction cavity of the device. Accordingly, a simplified model of a two-period extraction cavity is established to investigate the mechanism of the high order mode excitation. It is indicated that the distance between two gaps of the two-period extraction cavity has great impact on the startup time of the competing mode. By optimizing the gap distance to delay the startup of the competing mode, as well as shortening the rising time of the input pulsed power pulse, the competing quasi-TM21 mode can be suppressed sufficiently.