The IFR Online Detector Control system at the BaBar experiment

The Instrumented Flux Return (IFR)[1] is one of the five subdetectors of the BaBar[2] experiment on the PEP II accelerator at SLAC. The IFR consists of 774 Resistive Plate Chamber (RPC) detectors, covering an area of about 2,000 m2 and equipped with 3,000 Front-end Electronic Cards (FEC) reading about 50,000 channels (readout strips). The first aim of a B-factory experiment is to run continuously without any interruption and then the Detector Control system plays a very important role in order to reduce the dead-time due to the hardware problems. The I.N.F.N. group of Naples has designed and built the IFR Online Detector Control system (IODC)[3] in order to control and monitor the operation of this large number of detectors and of all the IFR subsystems: High Voltage, Low Voltage, Gas system, Trigger and DAQ crates. The IODC consists of 8 custom DAQ stations, placed around the detector and one central DAQ station based on VME technology and placed in electronic house. The IODC use VxWorks and EPICS to implement slow control data flow of about 2500 hardware channels and to develop part of the readout module consisting in about 3500 records. EPICS is interfaced with the BaBar Run Control through the Component Proxy and with the BaBar database (Objectivity) through the Archiver and KeyLookup processes.