Research On The Tuning Method Of Nonuniform Traveling-wave Accelerating Tubes

When tuning nonunifrom disk-loaded traveling-wave accelerating structures byprobes and plunges, additional cavities should be prepared and the process is awkward.The tuning method based on the non-resonant perturbationfield distributionmeasurement has been widely used in tuning uniform traveling-wave structures forits convenience, especially in tuning the constant-gradient ones. In this thesis, themethod of tuning nonuniform structures is studied on the basis of the abovetheory.First of all, a physical design of a10~12MeV traveling-wave electron linacaccelerating tube was done. The parameters of the accelerating tube and bunchingscheme were chosen and the focusing coil configuration was optimized. The particledynamics analyses were done for electrons with energy of both10MeV and12MeV.The calculation of working character was also carried out.The method of calculating RF parameters of individual cell by the resonantperturbation field measurement was studied according to the coupled cavity chaintheory and the error analysis was finished. Some experiments were done over S-bandcavities and the results demonstrated a high degree of precision of this method, whichcould simplify the microwave measurement of nonuniform structures.A method of tuning nonuniform structures was proposed. The internal reflectioncoefficient of each cell was obtained from decomposing the normalized voltage ratherthan field distribution.A numerical simulation of tuning process according to thecoupled cavity chain theory was done and a proof-of-principle experiment was carriedout over a9MeV traveling-wave accelerating tube. Both the results showedthe methodcould be used in tuning nonuniform structures.Based on the above theories, a method of optimizing the geometry parameters ofnonuniform cavities was proposed.