Diamond pad detector telescope for beam conditions and luminosity monitoring in ATLAS

Beam conditions and the potential detector damage resulting from their anomalies have pushed the LHC experiments to plan their own monitoring devices in addition to those provided by the machine. ATLAS decided to build a telescope composed of two stations with four diamond pad detector modules each, placed symmetrically around the interaction point at z = ± 183.8 cm and r ∼ 55 mm ( η ∼ 4.2 ). Equipped with fast electronics it allows time-of-flight separation of events resulting from beam anomalies from normally occurring p–p interactions. In addition it will provide a coarse measurement of the LHC luminosity in ATLAS. Ten detector modules have been assembled and subjected to tests, from characterization of bare diamonds to source and beam tests. Preliminary results of beam test in the CERN PS indicate a signal-to-noise ratio of 14 ± 2 .