The data acquisition and calibration system for the ATLAS Semiconductor Tracker

The Semiconductor Tracker (SCT) data acquisition (DAQ) system has been built to calibrate, configure, and control the approximately six million front-end channels of the ATLAS silicon strip detector. It provides a synchronized bunch crossing clock to the frontend modules, communicates first-level triggers to the front-end chips, and transfers information about hit strips to the ATLAS high-level trigger system. The system has been used extensively for calibration and quality assurance during SCT barrel and end-cap assembly and for performance confirmation tests after transport of the barrels and end-caps to CERN. Operating in data-taking mode, the DAQ has recorded millions of synchronously-triggered events during commissioning tests including cosmic ray triggered events both in standalone and ATLAS-wide mode. In this paper we describe the components of the data acquisition system, discuss its operation in calibration and data-taking modes and present some detector performance results from these tests.