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On-line measurement of beam phase and energy gain based on beam-cavity interaction

Lingyun Gong1,2,3, Rihua Zeng3,*, Chengye Xu1, Zhijun Wang1,2,3,†, Francesco Grespan4, Paolo Pierini5, Muyuan Wang5, and Yuan He1,2,3

  • *Contact author: rihuazeng@gdlhz.ac.cn
  • †Contact author: wangzj@impcas.ac.cn
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Phys. Rev. Accel. Beams 28, 122801 – Published 15 December, 2025

DOI: https://doi.org/10.1103/xksl-lg3m

Abstract

On-line monitoring of beam phase and energy gain in the cavity is of great importance for the stable operation of accelerators, especially in high-power scenarios. As cavities are typically calibrated with a low-current, short-pulse beam for safety purposes, the beam behavior may deviate from the calibrated case when running high-current beams, due to the strong space charge effect and other possible factors. Motivated by the high-power operation demand at European Spallation Source and the further understanding of beam-cavity interaction, methods for beam phase and energy gain on-line measurement have been developed. The beam phase was measured based on the steady-state cavity model, as demonstrated in the half wave resonator cavity at CAFE2. In this paper, this method was not only applied to a single-cell buncher cavity but also, for the first time, extended to the more complex low-energy multicell RFQ cavity for verification. Additionally, an energy-conservation-based method for measuring beam energy gain in a cavity was proposed and validated.

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Phys. Rev. Accel. Beams 28, 122801– Published 15 December, 2025
  • Received 21 April 2025
  • Accepted 28 October 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

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