On the Impact of Empty Buckets on the Ferrite Cavity Control Loop Dynamics in High Intensity Hadron Synchrotrons

Due to technical reasons two of ten buckets have to stay empty in the planned SIS100 synchrotron at the GSI Helmholtzzentrum für Schwerionenforschung. The planned low level RF control systems consist of linear P and PI type controllers. These are responsible to maintain a desired phase and amplitude of the gap voltage. In addition the cavity is controlled to follow a prescribed resonance frequency ramp. In SIS100 the acceleration will be performed by ferrite cavities with comparatively small quality factors. Therefore, effects resulting from transient beam loading have to be expected. Influences due to empty buckets are analysed in the frequency domain and particle tracking simulations are carried out to estimate the effect on the overall system with particular consideration of emittance growth and particle loss.