Beam-based model of broad-band impedance of the Diamond Light Source

Abstract

In an electron storage ring, the interaction between a single-bunch beam and a vacuum chamber impedance affects the beam parameters, which can be measured rather precisely. So we can develop beambased numerical models of longitudinal and transverse impedances. At the Diamond Light Source (DLS) to get the model parameters, a set of measured data has been used including current-dependent shift of betatron tunes and synchronous phase, chromatic damping rates, and bunch lengthening. A matlab code for multiparticle tracking has been developed. The tracking results and analytical estimations are quite consistent with the measured data. Since Diamond has the shortest natural bunch length among all light sources in standard operation, the studies of collective effects with short bunches are relevant to many facilities including next generation of light sources.