The Progress in the Studies of Mode Interaction in Gyrotrons

The studies on mode interaction in gyrotrons had always been an active field of research due to their theoretical and practical importance for better understanding of the underlying physical principles and the development and optimization of various gyro-devices. However, lately, the problems that stem from the mode interaction have become more pronounced and severe due to the recently demonstrated advancement of gyrotrons towards higher (terahertz) frequencies at which, for keeping the same power level, the gyrotrons should operate in higher order modes. So the mode spectrum of the gyrotron cavity is significantly denser, and, hence, the mode competition is inevitable. In this overview, we present both the evolution and the progress of these investigations that assist the further development of high-performance sub-THz and THz gyrotrons for numerous novel and emerging applications in the broad fields of science and technologies. The targeted readership of this paper includes not only the experts in gyrotron development but rather a wider community of specialists working on other vacuum microwave devices seeking a synergy between different research fields.