Measurement of the cavity-loaded quality factor in superconducting radio-frequency systems with mismatched source impedance  

作　　者：Jin-Ying Ma Cheng-Ye Xu An-Dong Wu Guo-Dong Jiang Yue Tao Zong-Heng Xue Long-Bo Shi Tian-Cai Jiang Zheng-Long Zhu Zi-Qin Yang Zheng Gao Lie-Peng Sun Gui-Rong Huang Feng Qiu Yuan He 

机构地区：[1]Institute of Modern Physics,Chinese Academy of Sciences,Lanzhou 730000,China [2]School of Nuclear Science and Technology,University of Chinese Academy of Sciences,Beijing 100049,China

出　　处：《Nuclear Science and Techniques》2023年第8期12-23,共12页核技术（英文）

基　　金：supported by the project of Large Research Infrastructures"China initiative Accelerator-Driven System"(No.2017-000052-75-01-000590);"Studies of intelligent LLRF control algorithms for superconducting RF cavities"(No.E129851YR0);the National Natural Science Foundation of China(No.12205344).

摘　　要：The accurate measurement of parameters such as the cavity-loaded quality factor(Q_(L))and half bandwidth(f_(0.5))is essential for monitoring the performance of superconducting radio-frequency cavities.However,the conventional"field decay method"employed to calibrate these values requires the cavity to satisfy a"zero-input"condition.This can be challenging when the source impedance is mismatched and produce nonzero forward signals(V_(f))that significantly affect the measurement accuracy.To address this limitation,we developed a modified version of the"field decay method"based on the cavity differential equation.The proposed approach enables the precise calibration of f_(0.5) even under mismatch conditions.We tested the proposed approach on the SRF cavities of the Chinese Accelerator-Driven System Front-End Demo Superconducting Linac and compared the results with those obtained from a network analyzer.The two sets of results were consistent,indicating the usefulness of the proposed approach.

关 键 词：Loaded quality factor Field decay method Superconducting cavity MISMATCH Calibration Cavity differential equation Measurement Accelerator-driven system 

分 类 号：TL61[核科学技术—核技术及应用] O511[理学—低温物理]