Influence of the Alignment of the Main Magnets on Resonances in the CERN Proton Synchrotron

During the Long Shutdown 1 seven out of the one hundred combined function PS main magnets were removed from the tunnel to conduct maintenance. After reinstallation, the main magnets were aligned to the reference positions and within the first week of operation of the accelerator, a beam-based re-alignment campaign was performed to reduce the excursions of the closed orbit. In order to further investigate and understand the source of betatronic resonances, which, already in 2011, were found to be excited by the bare machine, tune diagram measurements before and after this beam-based magnet alignment were conducted. In both cases the same resonances as in 2011 were found to be present; however, after the alignment, an overall increase of their strengths was observed. In this paper we present the corresponding measurement results and discuss the direct impact on the daily operation of the accelerator.