Coherent tune shifts measured with few bunches in the SPS and comparison with resistive wall theory

Coherent tune shifts with current have been measured in the SPS with single bunches and two bunches at varying distances between them. The measurements showed the usual negative slope with intensity in the vertical plane and a small positive one in the horizontal direction. The results are compared with theoretical predictions which include estimates of tune shifts due to the impedance of resistive vacuum chambers with non-circular geometry and finite wall thickness.