Research On X-band High Power Multi-beam Klystron

This dissertation expounds an approach to design some components for X-bandhigh power multi-beam klystron. It mainly includes the design of power combiningoutput structure, which is composed of a central circular waveguide, a waveguidetwist and a TE₀₁ output window, the design of multi-beam electron optics system andthe design of three-gap output cavity.Firstly, central to the power combining output structure is a circular waveguide,which combines power from the many input into one single output. Methods tocalculate and determine the dimension of the central circular waveguide have beenestablished. As illustration, a 4-to-1 and an 8-to-1 power combiner have beendesigned and confirmed. Besides, waveguide twist in this structure connects outputcavity and central circular waveguide, and its nodal admittance model has beenestablished to help us better understand its working. Physical realization of thewaveguide twist is accomplished through the use of optimization to CIET. After itscompletion, gap impedance of single gap output cavity loaded by the previouslydesigned power combiner and waveguide twist was calculated. TE₀₁ output windowhas its uniqueness to avoid voltage breakdown compared to traditional pillboxwindow due to its field distribution pattern. Besides the design of a TE₀₁ window forthe power combing output structure, theory of its heating effect has also beenestablished.Secondly, EGUN together with other simulation software are used in this paperto design the electron optics system of an X-band multi-beam klystron. It includes thedesign of a multi-beam electron gun and its electromagnetic focusing system.Thirdly, three-gap output cavity can reduce the chances of voltage breakdown inthe output cavity, but when traditional calculation method of gap impedance is appliedto three-gap cavity, the level of redundancy becomes unacceptable.Besides, equivalentcircuit model can also help explain the behavior of multi-gap cavity and predict itsperformance, therefore it is a useful tool for the initial design of three-gap cavity. Asthe beginning step, simplified gap impedance calculation method for single gap outputcavity and an equivalent circuit model for double gap output cavity were firstestablished, then it was extended to three gap case.