Identification of impedance sources responsible for longitudinal beam instabilities in the CERN PS
Longitudinal instabilities in the CERN PS are an important limitation to obtain the expected beam intensity and longitudinal emittance at the PS extraction in the framework of the LHC Injector Upgrade (LIU) project. The observed coupled-bunch instabilities lead to dipolar and quadrupolar oscillations, as well as to an uncontrolled longitudinal emittance blow-up for proton beams. A microwave instability observed with ion beams develops quickly at transition crossing. To identify the potential impedance sources of these instabilities, two strategies were adopted. Firstly, beam measurements were performed for dierent impedance configurations, i.e. by partially detuning the main RF cavities. Secondly, a thorough survey of the machine elements together with the RF studies allowed to refine the PS impedance model in order to find potentially missing contributions. Measurements were compared with particle simulations using the updated impedance model of the PS. Although the source of the dipolar coupled-bunch instability was already identified in the past, this study led to an identification of the impedance sources driving other types of longitudinal instabilities.
Copyright (c) 2021 CERN
This work is licensed under a Creative Commons Attribution 4.0 International License.
Authors who publish with this publication agree to the following terms:
- CERN retains copyright and publishes the work licensed under the Creative Commons Attribution License 4.0 that allows others to share the work with an acknowledgement of the work's authorship and initial publication in this series.
- Authors are able to enter into separate, additional contractual arrangements for distribution of the published version of the work (e.g., post it to an institutional repository or publish it in a book), with an acknowledgement of its initial publication in this series.
- Authors are permitted and encouraged to post their work online (e.g., in institutional repositories or on their website) prior to and during the submission process, as it can lead to productive exchanges, as well as earlier and greater citation of published work (See The Effect of Open Access).