A powerful coaxial relativistic backward wave oscillator

Abstract

Conventional coaxial relativistic backward wave oscillator (CRBWO) usually operates at the quasi-TEM mode, whose intense field mainly focuses on the slow wave structures (SWSs) surface. The intense relativistic electron beam (IREB) to stimulate high power microwave (HPM) is needed to pass through the SWSs surface closely so that intense beam-wave interaction can effectively occur. Such a structure greatly limits the power capacity of the device. In the paper, a high power capacity CRBWO is introduced. The proposed CRBWO operates at the coaxial TM 01 mode, which is a volumn wave. Thus, interaction between the IREB and the electromagnetic field can be effectively performed in the area far away from the SWSs surface. It is also advantageous to advoid plasma generated by the intense field breakdown and few electrons bormbardment on the SWSs structure surface. Therefore, such a CRBWO probably have a high power capacity. To testify such a viewpoint, a discrete CRBWO operating at X band has been designed in the paper. With a 710 kV, 11 kA electron beam guided by an external magnetic field of ∼ 0.8 T, an output power of 2.7GW has been numerically obtained and the device efficiency is close to 35%. As shown in the simulation, the maximum field strength on the SWSs structure surface causing electrons emission and plasma formation is no more than 310 kV/cm, which is greatly lower than 1MV/cm mentioned elsewhere and thus make the intense field breakdown hardly occurs. Such a CRBWO will be further testified experimentally in the future.