Beam Position Monitor Data Acquisition for the Advanced Photon Source*

This paper describes the Beam Position Monitor (BPM) data acquisition scheme for the Advanced Photon Source (APS) storage ring. The storage ring contains 360 beam posi-tion monitors distributed around its 1104-meter circumference. The beam position monitor data acquisition system is capable of making turn-by-turn measurements of all BPMs simultaneously. It is VXI-based with each VXI crate containing the electronics for 9 BPMs. The VXI Local Bus is used to pro-vide sustained ata transfer ates of up to 13 mega-transfers per second to a scanner module. The system provides ingle-bunch tracking, bunch-to-bunch measurements, fast digital-averaged positions, beam position history buffering, and synchronized multi-turn measurements. Data is accessible to the control sys-tem VME crates via an MXI bus. Dedicated high-speed ports are provided to supply position data to beam orbit feedback systems. 4. Measure position at each BPM on each turn ( 3.6 mi-croseconds for the storage ring). 5. Provide averaged beam position for higher accuracy. 6. Provide a beam history for each BPM. Major design goals included: 1. Minimize front panel connections by using available VXI backplane lines. I