Analysis of a Triangular Corrugated Coaxial Cavity for Megawatt-Class Gyrotron

Field analysis for coaxial cavity with triangular corrugations on the inner rod (insert) to be used for megawatt-class gyrotron has been done. Mathematical formulation for its dispersion relation, wall losses, and quality factor has been presented. Quality factor for open-ended triangular corrugated cavity has been computed by solving Vlasov´s equation. The advantage of the mentioned structure is that it offers higher number of slots to be accommodated, which reduces the wall losses in the insert without causing heating problems between the slots. Incorporating corrugations on the insert leads to significant changes in the field structure inside the cavity. The mode eigenvalue, wall losses, and quality factor for such a cavity have been found to be heavily dependant on radii ratio (C = R₀/R_i). Quality factor of desired and competing modes can be controlled by integrating a tapered insert. A coaxial cavity design for 204 GHz, 2 MW with TE_44,26 as a desired mode is given. Wall losses, quality factor, and coupling coefficient for desired and competing modes have been calculated.