Post Long Shutdown 2 CERN Proton Synchrotron Transverse Impedance Model: Description and Beam-Based Validation

TL;DR

This paper updates and validates the CERN Proton Synchrotron impedance model after hardware changes during Long Shutdown 2, using beam-based measurements and simulations to ensure accurate predictions of beam behavior.

Contribution

It provides a new, validated impedance model for the CERN Proton Synchrotron post-Long Shutdown 2, incorporating detailed beam-based validation methods.

Findings

Impedance-induced tune shifts match measurements within uncertainties

Instability growth rates are accurately predicted by the model

Interplay of chromaticity, space charge, and impedance effects is characterized

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, non-linear 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.