Spatial Synchronization of TE-Modes in a Slit-Type Gyrotron Cavity

We propose a variant of a slitted cavity for gyrotrons based on spatial synchronization of TE-type modes with azimuthal indexes equal to multiples of the slit number and close eigenfrequencies. A simplified theory of such a cavity is presented demonstrating its basic properties. High selectivity of the novel cavity was confirmed by 3-D PIC simulation of a 0.3-THz gyrotron energized by a helical electron beam with an energy of 500 keV and a current of 2 kA. This simulation demonstrates that, using the slit-type cavity, stable single-frequency operation at TE
_6,4
–TE
_12,2
mode combined with an output power of more than 80 MW and an efficiency of about 8%. The same arrangement with a conventional solid-wall cavity demonstrates no single-frequency regimes at all.