Effect of Microwave Leakage on Backward Current in an X-Band Dual-Mode RBWO Packaged With Permanent Magnet

In this article, the effect of microwave leakage into the diode region on the suppression of backward current in a relativistic backward wave oscillator (RBWO) operating at low magnetic field is investigated by the theoretical analysis, particle-in-cell (PIC) simulation, and experiments. The theoretical results show that some backward electrons are absorbed by the cathode holder due to microwave leakage, and as the microwave power increases, the microwave frequency increases, and the guiding magnetic field decreases, it will promote the absorption of electrons. The PIC simulations based on the first principle reveal that the leakage microwave partially suppresses the backward current and the suppression is enhanced when the incidence TM
₀₂
is dominant. In the
${X}$
-band dual-mode RBWO packaged with permanent magnet experiments, a microwave pulse with the power of 3.9 GW, the frequency of 9.93 GHz, and the efficiency of 33% was measured when the diode voltage was 820 kV and diode current was 14.5 kA.