Evaluation of external quality factor of the superconducting cavity using extrapolation method

Evaluation of external quality factor of the superconducting cavity using extrapolation method 1 2 corresp first-author Corresponding author. E-mail address: mazhenyu@sinap.ac.cn Corresponding author. E-mail address: mazhenyu@sinap.ac.cn mazhenyu@sinap.ac.cn 1 2 1 1 2 1 2 1 Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China Graduate University of Chinese Academy of Sciences, Beijing 100049, China Graduate University of Chinese Academy of Sciences, Beijing 100049, China The estimation of the external quality factor is important for designing coupling devices for the cavities. A new representation of the external quality factor calculations for single-cell cavity coupled to a coaxial transmission line is derived based on analytic analysis and numeric analysis with the help of 3D electromagnetic code, and verified with experimental measurements at room temperature. In logarithmic scale the results for the external quality factor were quasi-linear over the limited range, and the simulated and measured data could be used and extrapolated to the superconducting case. For the unpolished 1.5 GHz 3 rd harmonic superconducting cavity, the discrepancy between the evaluation value and measurement result is less than 25% within an acceptable deviation. External quality factor Vertical testing Superconducting cavity Coaxial input coupler Reference Ma G M , Zhao Z T , Liu J F . Chin Phys C , 2008 , 32 : 275 - 279 . Chin Phys C Kamigaito O . Phys Rev ST Accel Beams , 2006 , 9 : 062003 . Phys Rev ST Accel Beams Dhavale A S , Mittal K C . Rev Sci Instrum , 2006 , 77 : 066101 . Rev Sci Instrum Li D , Rimmer R . Calculation of external coupling to a single cell RF cavity , in: Proceedings of LINAC-1998 , Chicago, IL, USA , 1998 , 977 - 979 . Calculation of external coupling to a single cell RF cavity Zhou X L . Electromagnetic theory & microwave technique basics . Nanjing : Publishing House of Southeastern University , 2004 , 133 - 137 . Electromagnetic theory & microwave technique basics Padamsee H , Knoblocn J , Hays T . RF superconductivity for accelerators . New York : John Wiley & Sons, INC , 1998 , 145 - 160 . RF superconductivity for accelerators Shi J R , Chen H B , Zheng S X , et al . Comparison of Measured and Calculate Coupling between a Waveguide and an RF Cavity Using CST Microwave Studio . Proceedings of EPAC , 2006 , 1328 - 1330 . Comparison of Measured and Calculate Coupling between a Waveguide and an RF Cavity Using CST Microwave Studio Huang T M , Pan W M , Wang G W , et al . Chin Phys C , 2008 , 32 : 72 - 74 . Chin Phys C 10.13538/j.1001-8042/nst.20.65-70 Supported by project Science and Technology Commission of Shanghai Municipality (026505027, 036505011) 2009-01-07 2009-04-20 2021-01-19 2009 Nuclear Science and Techniques 02 20