The ATLAS/TILECAL Detector Control System

Tilecal, the barrel hadronic calorimeter of ATLAS, is a sampling calorimeter where scintillating tiles are embedded in an iron matrix. The tiles are optically coupled to wavelength shifting fibers that carry the optical signal to photo-multipliers. It has a cylindrical shape and is made out of 3 cylinders, the Long Barrel with the LBA and LBC partitions, and the two Extended Barrel with the EBA and EBC partitions. The main task of the Tile calorimeter Detector Control System (DCS) is to enable the coherent and safe operation of the calorimeter. All actions initiated by the operator, as well as all errors, warnings and alarms concerning the hardware of the detector are handled by DCS. The Tile calorimeter DCS controls and monitors mainly the low voltage and high voltage power supply systems, but it is also interfaced with the infrastructure (cooling system and racks), the laser and cesium calibration systems, the data acquisition system, configuration and conditions databases and the detector safety system. In total, about 10000 channels are managed by DCS. The SCADA software used in ATLAS is PVSS. The Finite State Machine (FSM) is the top level software for the operation of the detector. It is used to integrate the Tile calorimeter in the ATLAS DCS and is used by the shifters/operators for regular operation. The FSM includes control units, logical units as Tilecal modules, and device units. Several operational states (NOT READY , READY, UNKNOWN, etc) are defined and commands implemented on control units allow the transition between them. Calibration and other parameters used by the system are stored in the Oracle configuration database. The data is analysed online by the DCS software, generating warnings and alarms, which some of them can trigger automatic actions for the safety of the detector. Additionally, offline analysis is done to check and understand detector behaviour and to spot weaknesses of the hardware that may require future intervention.