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Knock out slow extraction using betatron sidebands at high harmonics

Philipp Niedermayer1,*, Rahul Singh1, Eike Feldmeier2, Christian Schömers2, and Marcel Hun2

  • *Contact author: p.niedermayer@gsi.de
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Phys. Rev. Accel. Beams 29, 022802 – Published 24 February, 2026

DOI: https://doi.org/10.1103/gndl-srhs

Abstract

Radio frequency knock out resonant slow extraction is a standard method for extracting stored particle beams from synchrotrons by transverse excitation. Excitation signals comprising many betatron sidebands have been shown to reduce intensity fluctuations of the extracted beam spill and are used at several facilities. In this contribution, the effect of individual sidebands at different harmonics on the spill quality is systematically studied using efficient noise excitation signals fully covering the respective sidebands. Particle tracking simulations show a clear correlation between the chosen excitation frequency and the spill quality. This relation is attributed to the spectrum of particle motion shortly before their extraction, and an empirical relation between the spectrum, the excitation frequency, and the resulting spill quality is given. Experiments show an additional reduction of pileup when using higher excitation frequencies. These insights have implications for an optimal design of excitation waveforms and hardware for knock out extraction systems.

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Phys. Rev. Accel. Beams 29, 022802– Published 24 February, 2026
  • Received 17 March 2025
  • Accepted 27 January 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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