Investigation on a high power compact K-band transit-time oscillator with bilateral distributed extraction structure

With the continuous pursuit of high power and high frequency in the area of high-power microwave (HPM) sources, the overmoded ratio of HPM devices is usually designed to be larger in K and Ka-band to alleviate the issue of high electric field in the extraction structure. Nevertheless, this approach inevitably results in a large radial size, which in turn requires larger magnetic field coils and higher energy consumption. To address this challenge, we present a method of bilateral distributed energy extraction in a compact GW level K band transit time oscillator. Particle-in-cell simulations show that with a central radius of 3 cm and the output microwave power of 2.0 GW, the maximum axial electric field is controlled at 1.18 MV/cm at 18.6 GHz. By reducing the electron beam voltage from 500 kV to 475 kV, an output power exceeding 1.79 GW can be achieved and the field will decrease to 0.98 MV/cm.