A 6.7 GHz, TM040 triple-beam monotron

Since a monotron does not require an externally-applied magnetic field, the system comprises a simple structure where the elementary functions of electron bunching and energy transfer to the RF field are performed in a single circular cylindrical cavity, which makes the monotron a compact, lightweight device. Exploring the monotron concept, the present paper describes a triple-beam TM₀₄₀, 6.7 GHz monotron where each beam is injected into the resonant cavity at 80 A current and 10 keV energy. At this injection energy, a maximal conversion efficiency of 18.5 % is predicted for optimum cavity dimensions. To verify the efficiency predicted by 1D theory, as well as to examine the viability of a triple-beam TM₀₄₀ monotron as a high-power microwave source, a particle-in-cell simulation is carried out by using the electromagnetic, PIC code KARAT.