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Suppressing emittance growth via ion cloud traps in low-energy beam transport

Hui Liao1, Weidong Chen1,*, Benzheng Chen1, Hui Li1, Yongchuan Xiao1, Yongjia Lü1, Xiuxia Cao1, Shengjin Liu1, Huachang Liu1 et al.

Sheng Wang1,† and Liang Lu2

  • *Contact author: chenwd@ihep.ac.cn
  • †Contact author: wangs@ihep.ac.cn
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Phys. Rev. Research 8, 043023 – Published 7 October, 2026

DOI: https://doi.org/10.1103/hrgq-mrtk

Abstract

Space-charge compensation is routinely used to mitigate emittance growth in linear accelerator beam transport lines. Severe space-charge effects and incomplete compensation within low-energy beam transport sections universally induce beam divergence and emittance degradation, constituting a key bottleneck for low-energy, high-intensity beams. This work investigates the evolution of residual-gas-generated secondary-ion clouds under applied electric fields and their impact on primary beam emittance growth. By implementing barrier electrodes to confine the secondary-ion cloud, we achieve substantial reductions in both the emittance and beam radius of an H− beam while preserving full beam intensity. The proposed ion cloud trap scheme also has important implications for neutral beam injection in magnetic confinement fusion and high-current ion implanters, providing insights into low-energy charged particle transport across diverse ion-beam platforms.

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Phys. Rev. Research 8, 043023– Published 7 October, 2026
  • Received 20 January 2026
  • Accepted 19 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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