High frequence characteristics of high power Ubitron amplifier with coaxial waveguide

The high power Ubitron amplifier with coaxial waveguide is researched using the nonlinear theory in three dimensions. The Ubitron amplifier utilizes an annular electron beam interacting with TE01 mode in a coaxial waveguide. By numerical simulations, the output power of 2.24MW with 10.9% efficiency and 35％ bandwidth in Kuband is gained. The results show that the selffields of the electron beam tend to reduce saturation power, narrow the bandwidth and lower gain. So the effects of selffields should be considered in designing the Ubitron amplifier. Using wiggler taper, the efficiency is up to 12.3%.