Direct excitation of TE11 mode in a relativistic backward wave oscillator

Abstract

A relativistic backward wave oscillator for directly generating TE11 mode is proposed. An axially asymmetric slow wave structure and a sectioned annular cathode are introduced to suppress the TM01 mode and excite the TE11 mode. A pre-modulation dual-cavity, which allows part of the backward power to propagate into the diode region, is adopted to optimize the electron beam bunch, indicating that the conventional design principle that the diode region and the beam-wave interaction region should be isolated can be broken to increase the interaction efficiency. Particle-in-cell simulations show that when the diode voltage is 780 kV, and beam current is 6.1 kA, a microwave with power of 2.0 GW, and frequency of 9.25 GHz can be obtained, corresponding to an efficiency of 42%. Furthermore, the main output mode is TE11 mode, and the power of the cross-polarized mode is less than 10% within the calculation time of 50 ns.

Direct generation of a circularly polarized TE11 mode in a relativistic backward wave oscillator by loading anisotropic medium

“…A relativistic backward wave oscillator (RBWO) has become one of the most popular high-power microwave (HPM) sources, owing to its remarkable operating stability, high output power, and high repetition rate [1][2][3][4][5][6][7][8][9][10][11]. Generally, an RBWO operates in either the symmetric TM 01 mode or the TEM mode [3,[12][13][14]. However, these modes are unsuitable for direct radiation because of their doughnut-shaped radiation patterns.…”

“…Xiao et al presented an RBWO that directly generated a linearly polarized TE 11 mode by using an asymmetric slow-wave structure and a sectioned annular cathode [12]. But, undesired electron movement in the azimuthal direction will result in parasitic mode generation, which increases with time gradually.…”

Research on effect of emission uniformity on X-band relativistic backward oscillator using conformal PIC code

“…In the explosive electron emission (EEE) process of the EECs, 3,4 the EEE nonuniformity is unavoidable due to the cathode surface morphology, which may result in the excitation of asymmetric modes or mode competition. 5 The nonuniformity of the EEE lies in the explosions of the micropoints in the cathode surface and the subsequent formation of the cathode plasma. Experiments have confirmed that only a few of initial emission micropoints explode in the cathode surface, thereafter, the emission micropoints will decrease the electric field in vicinity, preventing other micropoints from emitting electrons.…”