Synchronous mode locking in gyrotrons

A problem encountered in the development of high efficiency sources of coherent radiation in the microwave and millimeter wavelength regime is the competition between various modes for energy from the electron beam. Much research has focused on the suppression of unwanted modes. However little work has been done on utilizing the microwave oscillator in the overmoded state. The idea developed here is to allow the modes which are above the start oscillation threshold to grow in an unimpeded fashion and to modify the relative phases between modes to lock the modes together. Thus coherent output is obtained with a concomitant modulation in either the amplitude or frequency. Here we investigate the mode locking of axial TE/sub 11n/ modes in a closed cavity gyrotron oscillator and discuss the feasibility of mode locking in an open resonator gyrotron structure.<>