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Post long shutdown 2 CERN proton synchrotron transverse impedance model: Description and beam-based validation

Sébastien Joly*,† and Mauro Migliorati‡

Nicolas Mounet and Benoît Salvant

  • CERN, Geneva, Switzerland

  • *Contact author: sebastien.joly@helmholtz-berlin.de
  • †Also at CERN, Geneva, Switzerland.
  • ‡Also at Istituto Nazionale di Fisica Nucleare, Roma, Italy.
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Phys. Rev. Accel. Beams 29, 024201 – Published 4 February, 2026

DOI: https://doi.org/10.1103/396v-pwcr

Abstract

In the framework of the LHC injectors upgrade project, the CERN proton synchrotron underwent hardware changes during the long shutdown 2. These changes required an update of the CERN proton synchrotron impedance model and an assessment of their impact on beam quality. In the following, the updated CERN proton synchrotron impedance model is presented and then validated with beam-based measurements, comparing impedance-induced tune shifts and instability growth rates with simulations performed with a macroparticle tracking code, pyheadtail, which includes the effects of beam-coupling impedance, betatron motion, nonlinear synchrotron motion, and space charge. The interplay between first- and second-order chromaticity, space-charge forces, and their effect on beam observables is thus studied in detail. Their respective impacts have been assessed and benchmarked with measurements to validate the PS transverse impedance model.

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Phys. Rev. Accel. Beams 29, 024201– Published 4 February, 2026
  • Received 15 May 2025
  • Accepted 22 October 2025
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