Speaker
Description
For the requirements of RF phase stability in linear accelerators, especially in high-repetition-rate FELs, phase feedback techniques are important. Compared with direct RF field measurements, methods based on beam energy spread measurements can reflect the impact of RF perturbations on beam quality and are more suitable for feedback. Conventional screen-based destructive measurements are not applicable to high-repetition-rate operation and real-time feedback requirements. Therefore, nondestructive energy spread monitoring has been developed for RF phase feedback. A quadrupole moment measurement method based on the TM220 mode of a rectangular RF cavity has been proposed. Using its narrowband response, bunch-by-bunch energy spread monitoring with a high SNR is achieved. The monitor has been validated in beam experiments. At 350 pC, the energy spread measurement uncertainty is below 10$^{-5}$, and RF phase resolution is better than 1°. Meanwhile, an eight-stripline monitor system with optimized electrode structure has also been developed for bunch-by-bunch energy spread measurements in a dispersive section. The system integrates MHz repetition-rate electronics. An online resolution evaluation method based on error propagation is proposed, enabling resolution characterization using a single monitor. Beam experiments confirm stable energy spread measurement and RF phase feedback capability. This work provides a high-precision RF phase feedback approach based on beam diagnostics.
Funding Agency
This work is supported by the National Key R&D Program of China under Contract No. 2022YFA1602201, the Quality Engineering Project for Anhui Province Higher Education Institutions No.2024yjsxxsfkc001.
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