Observation of transverse quadrupolar tune shifts in the Photon Factory storage ring

Abstract

The frequencies (tunes) of transverse quadrupolar oscillations were measured in the 2.5-GeV Photon Factory storage ring at the High Energy Accelerator Research Organization (KEK). As a result, remarkable shifts in the quadrupolar frequencies with the bunch current were found; they were both positive and negative in the horizontal and vertical directions, respectively. This result can be explained by a focusing effect due to short-range wakefields containing a quadrupolar component.