The ATLAS Barrel Alignment Readout System
F.O.G.Bauer (CEA) P-F.Giraud (CERN) H.L.Groenstege, H.van der Graaf, R.G.K.Hart* (NIKHEF)
The readout system of the alignment system of the barrel part of the MUON spectrometer of ATLAS is described. It contains almost 6000 optical channels, each consisting of a camera, a light source and a lens. Three layers of multiplexing are applied which end up into 8 PC's, each one equipped with a frame-grabber, which grabs the pictures to be analyzed. Analyzed results are stored into a database for off-line corrections of the muon tracks. Controlling the multiplexers and frame-grabber is performed by a dedicated server (Rasdim). The chosen (by CERN) SCADA system is PVSS and is utilized to control the server and enables it to be part of the overall Finite State Machine (FSM) of ATLAS. The communication between the server and PVSS is performed by DIM, a distributed management system, providing a transparent inter-process communication layer. A full cycle to read and analyze all channels takes about 10 minutes.