Analysis of normal and skew quadrupole errors at the ESRF

The paper summarises the methods taken and analysis made so far on the normal and skew quadrupole errors at the ESRF. With the conventional response matrix approach, normal and skew quadrupole errors are extracted respectively from the diagonal and off-diagonal parts of the matrix. Independently, the thousand-turn BPM diagnostic implemented at the ESRF is used to measure the optical asymmetry and the betatron coupling. The excellent accuracy of the turn-by-turn BPMs allows the coupling to be measured by constructing the phase space and performing the normal mode decomposition. The consistency of the results from the two methods is examined. An attempt is made to trace the origin of the obtained errors