Influence of anode structures on long pulse operation of oversized backward wave oscillator

In order to overcome the pulse shortening problem caused by the microwave leakage inside the device, the anode of the oversized backward wave oscillator was specially designed. In the PIC simulation, oversized backward wave oscillators with different anode structure were studied under the beam voltage of 800 kV and the current of 7 kA. By adding the microwave absorbing materials in the anode, the influence of the leaked microwave on the microwave output could be significantly reduced, and the pulse duration increased. The experimental result shows that the pulse duration at the frequency of 8.58 GHz increased obviously from 70 ns to 110 ns when the efficiency was 30%.