Commissioning of the APS real-time orbit feedback system

A unified global and local closed-orbit feedback system has been implemented at the Advanced Photon Source in order to stabilize both particle and photon beams. Beam stability requirements in the band up to 50 Hz are 17 /spl mu/m in the horizontal plane and 4.4 /spl mu/m vertically. Orbit feedback algorithms are implemented digitally using multiple digital signal processors, with computing power distributed in 20 VME crates around the storage ring. Each crate communicates with all others via a fast reflective memory network. The system has access to 320 RF beam position monitors together with X-ray beam position monitors in both insertion device and bending magnet beamlines. Up to 317 corrector magnets are available to the system. The global system reduces horizontal RMS beam motion at the X-ray source points by more than a factor of two in the frequency band from 10 mHz to 50 Hz.