Numerical investigation on beam–wave interaction of W-band extended interaction oscillator

Based on the basic principle of energy conservation and electron disk beam–wave interaction equation, combined with the characteristic impedance and quality factor of the oscillator, a self-consistent nonlinear theoretical model of extended interaction oscillators (EIOs) is obtained. Taking the W-band EIO as an example, the effects of operating parameters and structural parameters on the oscillation, output power, and electron conversion efficiency of the extended interaction oscillator are analyzed. The numerical implementation of this model shows that the electron beam–wave synchronization interaction is a basic prerequisite for the oscillator to start, the positive feedback to energy in the resonator is a necessary condition for spontaneous oscillations, the distribution of electric field amplitude on each gap directly affects the beam–wave interaction efficiency and output power, and the electron trajectories in all gaps at steady state illustrate the conversion efficiency. At an operating voltage of 18 kV and a direct current of 0.5 A, a seven-gap EIO model with an output power of 2629 W and electron efficiency over 29% is predicted for gradually increased electric field amplitude distribution on each cavity.