Development of an X-band advanced-concept input system for high-power gyroklystron

The development of an X-band triaxial input system for the high-power gyroklystron amplifier experiment at the University of Maryland, College Park, is proposed and discussed. In order to obtain high mode purity of a TE/sub 011/ mode in an overmoded coaxial input cavity while maintaining high coupling efficiency, a coaxial dual-cavity input structure with an outer TE/sub 411/ mode and an inner TE/sub 011/ mode coaxial cavity has been designed to obtain a low Q and to avoid mode distortion due to the coupling aperture between the input waveguide and the input cavity. A loaded quality factor of 73 and a resonant frequency of 8.570 GHz with high mode purity have been obtained for the inner TE/sub 011/ mode coaxial cavity. The experimental results are in good agreement with the theoretical designs. The details of the design methods and cold-test results of the X-band triaxial input system are presented in this paper.