Studies of single bunch instability in a double RF harmonic system of the SPS at 26 GeV/c

This note presents the analysis of the measurements that were performed on 14/07/2009 and 11/08/2009, in the context of studying the single bunch instabilities at the Flat Bottom (FB, 26 GeV/c) of the SPS cycle for a single and double harmonic RF system. A higher harmonic RF system, like the 4th harmonic in the SPS, because of the increased synchrotron frequency spread that it causes, is one of the known techniques for beam stabilization. The aim of this Machine Development (MD) study was to explore the behavior of the bunch in a single and double RF system for different phase shifts between the two RF systems and for different intensities. In the course of the first MD, acquisitions of longitudinal bunch profiles were recorded while during the second MD peak detected beam signals were used to measure the growth rate of instabilities as a function of intensity and 800 MHz RF phase