Abstract
Beam coupling impedance is a fundamental parameter to characterize the electromagnetic interaction of a particle beam with the surrounding environment. Synchrotron machine performances are critically affected by instabilities and collective effects triggered by beam coupling impedance. In particular, transverse beam coupling impedance is expected to impact beam dynamics of the CERN Proton Synchrotron (PS), since a significant increase in beam intensity is foreseen within the framework of the LHC Injectors Upgrade (LIU) project. In this paper we describe the study of the transverse beam coupling impedance of the PS, taking into account the main sources of geometrical impedance and the contribution of indirect space charge at different energies. The total machine impedance budget, determined from beam-based dedicated machine measurement sessions, is also discussed and compared with the theoretical model.
Highlights
The goal of the LHC injectors upgrade (LIU) project [1], started in 2010, is to provide reliable beams with the challenging characteristics required by the High Luminosity LHC [2] program, until at least 2030
For the future operation at higher intensities and beam brightness required by the LIU project, it is of fundamental importance to detect the main sources of wakefields and estimate with precision the coupling impedance of all the machines in the LHC injection chain, in order to minimize collective effects triggered by the coupling impedance and improve quality and brightness of the colliding beams
In this paper we present the study of the Proton Synchrotron (PS) transverse beam coupling impedance
Summary
The goal of the LHC injectors upgrade (LIU) project [1], started in 2010, is to provide reliable beams with the challenging characteristics required by the High Luminosity LHC [2] program, until at least 2030. This study, together with the previous knowledge of the PS longitudinal broadband impedance model, allows us to better understand instability thresholds [6], to predict the effects of the beam intensity increase planned for the upgrade program, and in general to account for the impact of all hardware changes in the PS foreseen for the years. The paper is organized as follows: in Sec. II we describe the method we have used to determine the imaginary part of the total transverse effective impedance of the machine from betatron tune measurements, while in Sec. III we discuss the measurement results at different energies.
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