Structural Design of the Tuner for 3.9 GHz Superconducting Radiofrequency Cavity
The tuner of 3.9 GHz superconducting RF cavity in Shanghai high repetition rate X-ray free electron laser and extreme light facility will operate in harsh environments such as high vacuum,cryogenic temperature and radiation.It change the length of cavity by applying a longitudinal tension through a regulating mechanism to adjust the cavity frequency precisely.Aiming at achieving a high precise frequency tuning,an overall design featured coaxial blade is adopted.Combined theoretical calculation and finite element analysis,the blade structure and size are determined to achieve the specific technical parameters such as strength,stiffness,stability and adjustment range.Strictly controlled the manufacturing process and dimensional precision,torsion caused by the asymmetry of the stiffness of the structure is avoided.Fatigue tests are performed on simplified blade assemblies to confirm that they meet the operational lifetime.The key components are tested in the radiation environment to ensure the normal operation of the tuner.FEA analysis and motion test of the tuner prototype at both room and cryogenic temperature are carried out to further verify the adjustment performance.Through theoretical calculation,FEA,prototype manufacturing and testing,it is confirmed that the coaxial blade tuner design can meet the precise tuning requirements of 3.9 GHz superconducting high-frequency cavities operating in vacuum,cryogenic and radiation environment,which lays a foundation for subsequent cavity system horizontal test and finalization of engineering design.
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