Interpretation of transverse tune spectra in a heavy-ion synchrotron at high intensities

TL;DR

This paper presents high-precision measurements of transverse tune spectra in a heavy-ion synchrotron, revealing how space charge effects and head-tail modes influence beam dynamics at high intensities.

Contribution

It introduces two tune measurement systems and demonstrates their effectiveness in analyzing space charge effects and head-tail modes in a heavy-ion synchrotron.

Findings

Space charge tune shift can be accurately derived from spectral data.

Chromaticity can be extracted from head-tail mode structures.

Experimental evidence highlights the significance of space charge effects at high intensities.

Abstract

Two different tune measurement systems have been installed in the GSI 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.