Theoretical analysis of gyrotron amplifier with undulated waveguide

In this paper the interaction between a relativistic electron beam moving in a static magnetic field and a travelling electromagnetic wave is analysed by using the kinetic power theorem. The concept of the electron bunching function is introduced to illustrate the bunching process of beam electrons as a whole. By numerical calculation, the energy exchange process between gyrating electrons and the travelling wave field is obtained in detail. The results of the calculation show that the imaginary part of the axial wave number does not stay constant along the interaction length and that the gain characteristic is non-linear. Based on this analytic method, the maximum output power and efficiency of the gyrotron amplifier with a uniform waveguide are calculated and are found to depend critically on the value of the static magnetic field and the operating frequency. A new type of gyrotron amplifier is suggested here. In this device the gyrating electrons interact with the travelling wave in an undulated waveguide. Its instantaneous bandwidth is somewhat broadened and the optimum value of applied magnetic field is not too critical.