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Longitudinal beam instability driven by coherent radiation in a steady-state microbunching laser modulator

Yingjie Dai1, Zhuoyuan Liu1, Tong Li1, Xiujie Deng2,*, and Lixin Yan1,†

  • *Contact author: dengxiujie@mail.tsinghua.edu.cn
  • †Contact author: yanlx@mail.tsinghua.edu.cn
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Phys. Rev. Accel. Beams 29, 103404 – Published 27 October, 2026

DOI: https://doi.org/10.1103/wrzb-js89

Abstract

Storage ring-based steady-state microbunching (SSMB) is a promising approach for generating high-average-power coherent radiation, while the instabilities driven by coherent undulator radiation in the laser modulator (LM) are important for the ring performance. In this paper, we investigate the longitudinal single-bunch multiturn LM instability using cavity-mode decomposition techniques. The evolution of the wakefield in the longitudinal beam dynamics equations is derived, and the instability growth rates are analyzed. Numerical simulations show excellent agreement with the theoretical model, validating the mode-decomposition approach. These findings provide critical insights into the design and operation of SSMB storage rings, suggesting effective mitigation strategies to suppress the instability and enhance the overall performance.

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Phys. Rev. Accel. Beams 29, 103404– Published 27 October, 2026
  • Received 29 April 2026
  • Accepted 28 September 2026
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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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