Study of a Coaxial Gyrotron Cavity With Improved Mode Selection

The resonant frequency, the diffractive quality factor, and the mode competition in the coaxial gyrotron cavity with a tapered inner rod have been investigated. The resonant frequency and the diffractive quality factor can be adjusted by changing the tilt angle and the radius of the tapered inner rod. When the inner rod radius is far smaller than the caustic radius of the given mode, the resonant frequency and the diffractive quality factor are hardly affected by the tilt angle of the tapered inner rod; the resonant frequency increases slightly but the diffractive quality factor increases noticeably with the increase of the tilt angle of the tapered inner rod when the inner rod radius is a little smaller than the caustic one; the resonant frequency and the diffractive quality factor decrease with the increase of the tilt angle of the tapered inner rod when the inner rod radius is larger than the caustic one. The mode competition can be improved with an appropriate design of the tilt angle and the radius of the tapered inner rod in a coaxial gyrotron cavity with a tapered inner rod.