Abstract
Two different tune measurement systems have been installed in the GSI Helmholtzzentrum f\"ur Schwerionenforschung heavy-ion synchrotron SIS-18. Tune spectra are obtained with high accuracy using these fast and sensitive systems. Besides the machine tune, the spectra contain information about the intensity dependent coherent tune shift and the incoherent space charge tune shift. The space charge tune shift is derived from a fit of the observed shifted positions of the synchrotron satellites to an analytic expression for the head-tail eigenmodes with space charge. Furthermore, the chromaticity is extracted from the measured head-tail mode structure. The results of the measurements provide experimental evidence of the importance of space charge effects and head-tail modes for the interpretation of transverse beam signals at high intensity.
Highlights
Accurate measurements of the machine tune and the chromaticity are of importance for the operation of fast ramping, high intensity ion synchrotrons
Two different tune measurement systems have been installed in the GSI Helmholtzzentrum fur Schwerionenforschung heavy-ion synchrotron SIS-18
The position of the synchrotron satellites corresponds to the head-tail tune shifts and depends on the incoherent and the coherent tune shifts
Summary
Accurate measurements of the machine tune and the chromaticity are of importance for the operation of fast ramping, high intensity ion synchrotrons. The modification of transverse signals from high intensity bunches was observed in the SIS-18 for periodically excited beams [10] and for initially kicked bunches [11], where the modified spectra was explained in terms of the space charge induced head-tail mode shifts. This contribution aims to complement the previous studies and extract the relevant intensity parameters from tune spectra measurements using the TOPOS and BBQ tune measurement systems.
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