RF (Radio Frequency) Field Profiles in Weakly Irregular Open Resonators

摘要

Open resonators are considered with longitudinal profiles described by continuous and sufficiently smooth functions in order to reduce reflections and mode conversion in the cavity. For these types of resonators, it is shown that the single mode approximation is adequate. Using a Langer transformation, the approximate solution for problems with two turning points is given in terms of a uniform expansion valid for all axial positions; for the fundamental mode, the RF field longitudinal distribution is essentially of the form exp -w sup 2 (z)/2 where w(z) is determined by the resonator profile. A comparative study of the resonant and selective properties for different resonator types is made, and the influence of the cavity profile on the electric field longitudinal distribution is analyzed. As an example of practical interest, the design of a resonant cavity for a 35Ghz gyrotron operating in the TE sub 021 mode is presented.