Design and analysis of the output windows of a doorknob structure for high-power P-band klystron

This article presents the design, analysis, and simulation for the klystron coaxial radio frequency (RF) output windows. Three new RF windows (Type-2, 3, and 4) are proposed based on the coaxial RF window with a doorknob structure (Type-1) to improve its performances. The proposed RF windows are simulated in high frequency simulator structure. At the operating frequency, the return loss are obtained as −49, −60, −56, and −52 dB, and the insert loss as −0.003 62, −0.002 51, −0.002 74, and −0.003 dB, respectively, for Type1, 2, 3, and 4. Moreover, for Type-1, the E-field near the short-circuit surface is significantly greater than that near the output port side due to the asymmetrical structure of RF window. However, this phenomenon has been greatly improved in the proposed RF windows. The heat load because of RF power absorption over the ceramic has been calculated. The distribution of heat load in three new windows is more uniform and less than that in Type-1, and the heat load in Type-2 is about half of that in Type-1. The thermal and structural analyses of RF windows predict the lower temperature and less mechanical deformation for the three new RF windows. Multipactor analysis is carried out to determine the safety at the operating power level.