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Suppression of transient beam-loading effects in storage rings via main-cavity power source feedforward scheme

PeiZhi Fang, Zhilong Pan, Yanqing Jia, Hongjuan Yao, Shuxin Zheng*, and Chuanxiang Tang

Xiujie Deng

  • *Contact author: zhengsx@tsinghua.edu.cn
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Phys. Rev. Accel. Beams 29, 114001 – Published 5 November, 2026

DOI: https://doi.org/10.1103/z3p2-lsz6

Abstract

Dual-frequency radio-frequency systems are widely deployed in high-brightness synchrotron radiation light sources to achieve electron bunch lengthening. However, the transient beam-loading (TBL) effect induced by bunch gaps causes significant synchronous phase shifts and severely compromises bunch-lengthening performance. To address this, we propose an active compensation scheme that suppresses voltage fluctuations in both the main and harmonic cavities by modulating only the driving voltage of the main cavity via a feedforward approach. To elucidate the underlying physical mechanisms, we establish a gap-induced linear decomposition analytical model, which decomposes the TBL-induced beam voltage into steady-state and transient components. Based on this model, we derive an optimization method to minimize power requirements, enabling the main-cavity TBL compensation to achieve performance levels comparable to those of broadband-cavity TBL compensation. The efficacy of this framework is demonstrated through two case studies: for an steady-state microbunching storage ring with a 7.5-MHz hardware half-bandwidth, the required single-cavity peak power is maintained at 158 kW, with normalized average radiation power improved from 78% to 97%; for the KEK light source storage ring with a 6-MHz bandwidth, the single-cavity peak power is optimized to 148 kW, successfully restoring the average bunch length from 31.1 to 40.9 ps. The proposed scheme establishes a highly efficient and cost-effective paradigm for TBL suppression, providing a promising technical pathway for next-generation light sources.

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Phys. Rev. Accel. Beams 29, 114001– Published 5 November, 2026
  • Received 23 June 2026
  • Accepted 21 October 2026
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