Fast Orbit Feedback and Beam Stability at the Swiss Light Source

A global, fast orbit feedback (FOFB) based on the digital beam position monitor (DBPM) system has been in user operation at the Swiss Light Source (SLS) since November 2003. The SVD‐based correction scheme acts at a sampling rate of 4 kHz using position information from all 72 DBPM stations and applying corrections with all 72 horizontal and 72 vertical corrector magnets. As a result, the FOFB successfully damps orbit distortions, which are mainly caused by ground and girder vibrations as well as the 3‐Hz booster crosstalk. It also allows fast and independent ID gap changes, which are completely transparent to all SLS users. With top‐up as a regular operation mode at SLS, global beam stability on a μm‐level has been achieved from days to milliseconds.