Speaker
Description
Superconducting radio-frequency (SRF) cavities with high loaded quality factors are particularly susceptible to ponderomotive instabilities caused by the interaction between RF fields and mechanical vibrations. Predicting and suppressing these instabilities is essential for reliable operation of high-gradient continuous-wave accelerators. To address this issue, we have developed a practical analysis framework for SRF cavities under low-level RF feedback control. It combines electromechanical system identification, stability modeling, simulation, and experimental verification. Measurements on a 162.5 MHz SRF linac identified dominant mechanical modes near 118 and 280 Hz, which were included in open- and closed-loop models. Tests on two cavities with four PI gain settings showed good agreement between predicted and measured instability thresholds. The model also guided controller retuning after improper feedback gains caused frequent faults, reducing the daily fault rates from approximately 17 and 5 to below 0.4. The proposed approach provides practical guidance for LLRF tuning and improves the reliability of high-gradient SRF accelerators.
| Abstract Classification | Control Loop Modeling, Tuning and Optimization |
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