Dynamic compensation of dynamic multipoles
A challenge is the operation of the elliptically polarized undulator UE112 which has been installed in spring 2006. Due to the long period of 112 mm the interaction with the stored beam is much bigger than at any other undulator. To predict the required shims for sufficient dynamic aperture we used fast analytic and simplectic (i.e. phase space conserving) which have been developed at BESSY based on generating functions.