Control units for APS power supplies

The Advanced Photon Source (APS) accelerator facility is made up of five major subsystems in addition to the linac: the positron accumulator ring (PAR), low energy transport (LET), booster synchrotron (SYNCH), high energy transport (HET), and the storage ring (SR). Each subsystem has multiple magnet and power supply combinations, some requiring multiple modes of operation. These magnet and power supply combinations are computer controlled and monitored. The power supply control unit (PSCU) is the first layer of hardware and software directly above the power supply itself and is described in this paper. The description includes the basic philosophy for each mode of operation and how it influences the topology and means of implementing control. The design of the analog reference blocks (ARBs) influenced the design of other custom functions as well as the feedback controls for vibration and other dynamic corrections. The command set supported by the PSCU is discussed