Orbit Feedback Using X-ray Beam Position Monitoring at the Advanced Photon Source

The Advanced Photon Source (APS) was commissioned in 1995 as a third-generation x-ray user facility. At that time orbit control was performed exclusively with broadband rf beam position monitors (BPMs). Since then, emphasis has been placed on incorporating x-ray beam position monitors into the orbit control algorithms. This has resulted in an order of magnitude improvement in long-term beam stability vertically, using x-ray BPMs (X-BPMs) on bending magnet beamlines. Additional processing will allow similar improvements horizontally, once systematic effects associated with variable insertion device (ID) xray beams are properly compensated. Progress to date and upgrade plans will be presented, with an emphasis on the details of the required digital signal processing.