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Online electron beam trajectory correction in free-electron lasers via adaptive dictionary learning

Bowen Zhang1,2,3, Nengyuan Zhang1,2,3, Nanshun Huang1,*, Chao Feng1,†, and Zhentang Zhao1

  • *Contact author: huangnanshun@sari.ac.cn
  • †Contact author: fengc@sari.ac.cn
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Phys. Rev. Accel. Beams 29, 062801 – Published 8 June, 2026

DOI: https://doi.org/10.1103/4hx5-x1n7

Abstract

During accelerator operation, the beam trajectory in free-electron laser (FEL) facilities frequently drifts from its predefined path due to machine instabilities and environmental factors, thereby degrading beam quality. In this work, we propose an online trajectory correction method based on dictionary learning, which significantly reduces data requirements and allows real-time, continuous updates of the response matrix. Simulation studies under static and drifting conditions demonstrate that the dictionary learning method achieves a root-mean-square error of 0.2  m/rad or lower for response matrix elements, using only ∼1000 trajectory-excitation data pairs. Experimental validation at the Shanghai Soft X-ray Free Electron Laser (SXFEL) further demonstrates its robustness, achieving a correction precision better than 0.01 mm and confirming its suitability for online implementation in advanced XFEL facilities.

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Phys. Rev. Accel. Beams 29, 062801– Published 8 June, 2026
  • Received 23 February 2025
  • Accepted 8 April 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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