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Streun, A.

Paper Title Page
RPPA29 A Feed-Forward Procedure to Counteract Orbit Distortions and Photon Beam Displacements from Insertion Device Operation at the SLS 573
  • T. Schmidt, A. Streun, D. Zimoch, J. T.M. Chrin
    PSI, Villigen
  Insertion devices of various types provide light of high brilliance to experimenters at the SLS beamlines. Changes in the photon energy and polarization by movement of the ID gap and phase shift, however, cause orbit distortions that result in a displacement of the photon beam in both angle and position at the beamline. A feed-forward correction scheme has been developed to quantify and precisely correct these effects using designated correctors local to the photon source. The corrector settings are determined using an orbit configuration consisting of 73 digital BPMs and associated correctors; recently commissioned X-ray BPMs located at the beamline front-end are also included in the correction algorithmn and serve to constrain the photon beam to its specified position. The feed-forward table is finally implemented at the local processor level and applied at a rate of 10 Hz. A photon pointing stability at the sub-microradian level is achieved. The entire gap scan, feed-forward generation and subsequent verification can now be completed within 15 to 60 minutes depending on the complexity of the ID. The methodology of the procedure and high-level software framework is described.