Mode Selective Azimuthally Asymmetric Cavity for Terahertz Gyrotrons

A method of improving the selectivity of open cavities of electron cyclotron masers (gyrotrons) operating at high cyclotron harmonics in the terahertz frequency range is proposed and described. This method is purely electrodynamical and based on a simple deformation of the cavity wall. The proposed approach paves the way for the increase in the gyrotron frequencies and for enhancing the selectivity of open cavities in other applications.