Cavity-beam instabilities on the SRS at Daresbury

Malfunctions in the water control circuitry on the RF cavities have induced beam movements in both the horizontal and vertical planes which have been observed by users. A possible cause of such movements could be a cavity higher order mode (HOM). The SRS cavity HOM spectra exhibits some dipole modes which could produce such an effect and investigations have been performed on the SRS which have tried to identify a HOM as the cause of the beam position movement. The data presented here is the result of these investigations, whereby, cavity tuner position, cavity temperature and cavity HOM spectra have been monitored (with beam) as a function of electron beam and photon beam positions.