A novel laser alignment system for tracking detectors using transparent silicon strip sensors

Modern large-area precision tracking detectors require increasing accuracy of the geometrical alignment over large distances. A novel optical multi-point alignment system has been developed for the muon spectrometer of the ATLAS detector at the Large Hadron Collider. The system uses collimated laser beams as alignment references which are monitored by semi-transparent optical position sensors. The custom designed sensors provide very precise and uniform position information on the order of 1 μm over a wide measurement range. At suitable laser wavelengths, produced by laser diodes, transmission rates above 90% have been achieved which allow one to align more than 30 sensors along one laser beam. With this capability and equipped with integrated readout electronics, the alignment system offers high flexibility for precision applications in a wide range of detector systems.