Bahrdt, J.; Frentrup, W.; Gaupp, A.; Scheer. M.: Universal Mode Operation of the BESSY II UE112 APPLE Undulator. In: Proceedings of PAC09, Vancouver, BC, Canada, 2009, p. 1162-1164
Abstract:
The UE112 APPLE undulator operated at BESSY II covers the low photon energies down to the visible regime. Below 100eV the state of polarization is significantly modified by the optical components of the beamline. Moving three magnet rows of the APPLE undulator (universal mode) any state of polarization can be produced by the undulator which permits the compensation of the beamline effects. The dynamic multipoles in the universal mode have to be compensated for a transparent operation. An analytic model of the multipoles has been developed and compared to measurements. A real time compensation scheme is presented.