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INTRODUCTION

Successful user operation of the SLS requires the reproduction and stabilization of a previously established reference orbit within 1/10th of the electron beam size. In the vertical plane this translates into $\approx$ 1 $\mu$ m at the location of the insertion devices (IDs) in the short straight sections. The corresponding required angular beam stability is

1 $\mu$ rad, corresponding to

10 $\mu$ m photon beam motion at the first optical elements of the beamlines. During the first two years of SLS operation these requirements were achieved by a central CORBA based high level application [1], the Slow Orbit Feedback (SOFB), with an update rate of $\approx$ 0.5 Hz [2]. However, in 2003 the growing number of IDs with fast gap scans and the increasing sensitivity of the experiments as well as orbit oscillations induced by ground vibrations and environmental noise necessitated stabilization by the envisaged global fast orbit feedback (FOFB). The FOFB was designed [3] to correct orbit perturbations in the relevant frequency range up to 100 Hz to $\mu$ m stability.

Michael Boege
2005-05-23