Power capacity enhancement for klystron-like RBWOs with a TM021 extraction cavity.

We efficiently enhance the power capacity of klystron-like relativistic backward wave oscillators (RBWOs) with a TM021 mode extraction cavity. Theoretical analysis and simulation results are shown in detail. Theoretically, an electron cluster will be steadily decelerated in the whole region of the TM021 extraction cavity if the transiting time in the cavity approximates the period of microwaves. As a result, the energy of the electron beam will be efficiently extracted by the TM021 mode field. Due to the larger size, the electric field strength in a TM021 cavity can be much smaller than that in a TM020 cavity. In addition, once the extraction cavity breaks down, the emission electron will absorb less energy from the TM021 mode field than the TM020 mode field. In PIC simulations, for an X-band klystron-like RBWO with a frequency of 9.6 GHz and an output power of 2.3 GW, the maximum longitudinal electric field (Ez) in the extraction cavity decreases from 610 kV/cm to 320 kV/cm, when the TM020 extraction cavity is replaced with a TM021 extraction cavity. PIC simulation results agree well with the theoretical analysis. [ABSTRACT FROM AUTHOR]