The integration and engineering of the ATLAS SemiConductor Tracker Barrel

The ATLAS SemiConductor Tracker (SCT) was built in three sections: a barreland two end-caps. This paper describes the design, construction and final integration of the barrelsection. The barrelis constructed around four nested cylinders that provide a stable and accurate support structure for the 2112 silicon modules and their associated services. The emphasis of this paper is directed at the aspects of engineering design that turned a concept into a fully-functioning detector, as well as the integration and testing of large sub-sections of the final SCT barreldetector. The paper follows the chronology of the construction. The main steps of the assembly are described with the results of intermediate tests. The barrelservice components were developed and fabricated in parallel so that a flow of detector modules, cooling loops, opto-harnesses and Frequency-Scanning-Interferometry (FSI) alignment structures could be assembled onto the four cylinders. Once finished, each cylinder was conveyed to the next site for the mounting of modules to form a complete single barrel. Extensive electrical and thermal function tests were carried out on the completed single barrels. In the next stage, the four single barrelsand thermal enclosures were combined into the complete SCT barreldetector so that it could be integrated with the Transition RadiationTracker (TRT) barrelto form the central part of the ATLAS inner detector. Finally, the completed SCT barrelwas tested together with the TRT barrelin noise tests and using cosmic rays.