Precise calibration of cavity forward and reflected signals using low-level radio-frequency system

• Published in: Nuclear science and techniques Vol. 33; no. 1; pp. 35 - 43
• Main Authors: Ma, Jin-Ying, Qiu, Feng, Shi, Long-Bo, Zhu, Zheng-Long, Jiang, Tian-Cai, Xue, Zong-Heng, Jin, Ke-An, Chen, Qi, Xu, Cheng-Ye, Ding, Xing-Hao, Gao, Zheng, Sun, Lie-Peng, Huang, Gui-Rong, He, Yuan
• Format: Journal Article
• Language: English
• Published: Singapore Springer Singapore 2022; Institute of Modern Physics,Chinese Academy of Sciences,Lanzhou 730000,China%Institute of Modern Physics,Chinese Academy of Sciences,Lanzhou 730000,China; School of Nuclear Science and Technology,University of Chinese Academy of Sciences,Beijing 100049,China%School of Nuclear Science and Technology,University of Chinese Academy of Sciences,Beijing 100049,China
• Subjects: Beam Physics; Nuclear Energy; Particle Acceleration and Detection; Particle and Nuclear Physics; Physics; Physics and Astronomy; Measurement; Forward and reflected signals; Calibration
• ISSN: 1001-8042; 2210-3147
• DOI: 10.1007/s41365-022-00985-4

Precise measurements of the cavity forward ( V f ) and reflected signals ( V r ) are essential for characterizing other key parameters such as the cavity detuning and forward power. In practice, it is challenging to measure V f and V r precisely because of cross talk between the forward and reflected channels (e.g., coupling between the cavity reflected and forward signals in a directional coupler with limited directivity). For DESY, a method based on the cavity differential equation was proposed to precisely calibrate the actual V f and V r . In this study, we verified the validity and practicability of this approach for the Chinese ADS front-end demo superconducting linac (CAFe) facility at the Institute of Modern Physics and a compact energy recovery linac (cERL) test machine at KEK. At the CAFe facility, we successfully calibrated the actual V f signal using this method. The result demonstrated that the directivity of directional couplers might seriously affect the accuracy of V f measurement. At the cERL facility, we calibrated the Lorentz force detuning (LFD) using the actual V f . Our study confirmed that the precise calibration of V f significantly improves the accuracy of the cavity LFD measurement.