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Beam halo from Touschek scattering in the KEK Accelerator Test Facility

R. Yang1,2,*, A. Aryshev3,4, P. Bambade5, M. Bergamaschi6,†, K. Kubo3,4, T. Naito3,4, N. Terunuma3,4, S. Wallon5, and J. Zhang7

  • *Contact author: yangrenjun@ihep.ac.cn
  • †Present address: Max Planck Institute for Physics, Munich, Germany.
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Phys. Rev. Accel. Beams 28, 101001 – Published 3 October, 2025

DOI: https://doi.org/10.1103/4qnt-3p1s

Abstract

Beam halo is one of the most crucial issues limiting the machine performance and causing radioactivation in high-intensity accelerators. Understanding halo formation is vital for high-luminosity colliders, advanced light sources, and spallation neutron sources to effectively mitigate beam loss through machine optimizations and tailored collimation systems. This article details numerical and experimental investigations of transverse and longitudinal halos at the KEK Accelerator Test Facility. Halo distributions are modeled incorporating operational beam parameters, synchrotron radiation, beam-gas scattering, and Touschek-scattering processes. A newly developed yttrium aluminum garnet/optical transition radiation monitor, positioned at the extraction line, enables direct imaging of transverse and longitudinal halo distributions. The general consistency between predictions and observations in various conditions indicates that the Touschek scattering is the dominant mechanism forming the horizontal and momentum halos.

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References (32)

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Phys. Rev. Accel. Beams 28, 101001– Published 3 October, 2025
  • Received 9 September 2021
  • Revised 9 June 2025
  • Accepted 19 September 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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