The study of a coaxial gyrotron with misaligned inner rod

The effects of a tiny misalignment of the inner rod in a coaxial-gyrotron on the eigenvalue, quality factor Q, resonant frequency, and electronic efficiency are investigated. As a practical application, with the electronic velocity spread and cavity wall resistivity being taken into account, the beam-wave interaction of a 170 GHz MW coaxial-gyrotron operating with TE31,12 mode has been studied. The results show that the eigenvalue of the operating mode decreases slightly when the ratio of misalignment to outer radius D/R increases for the case of smaller values of the ratio of outer to inner radius C = R/Rin, but is unchanged with the increasing value of D/R for the case of large ratio of C. The electronic efficiency decrease slightly when D/R increases within the range of 0-0.015. However it decreases at a faster rate when D/R is larger than 0.015. If D/R increases to 0.024, the efficiency decreases sharply to only about 2.2%. For both cold and hot cavity, the resonant frequency decreases slightly with D/R increasing.