Macgregor, Andrew Alan
The laser mirror alignment system for the LHCb RICH detectors.
PhD thesis, University of Glasgow.
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The Large Hadron Collider beauty (LHCb) experiment at the Large Hadron Collider (CERN), is the next generation B physics experiment designed to precisely constrain the Cabibbo-Kobayashi-Maskawa (CKM) matrix measurements with unprecedented accuracy, as well as search for new physics. The success of the LHCb experiment relies upon excellent particle identification. The central particle identification detectors for the LHCb experiment are the Ring Imaging Cherenkov (RICH) detectors which are reliant upon their optics being well aligned. The optical specifications for the second RICH detector (RICH2) are for the mirrors to be aligned to within 0.1 mrad so as not to degrade the inherent 0.7 mrad resolution of the detector. As the mirrors move out of alignment over time, the performance of the RICH will deteriorate, unless corrected. This thesis describes the design and characterisation of the Laser Mirror Alignment Monitoring System and its image analysis software for selected mirrors of RICH2. This thesis also describes the results of a unique method of combining data from the Laser Mirror Alignment Monitoring System and Tracking system, to recover the positions of all mirror segments in the RICH2 detector. The laser alignment monitoring system resolution has been measured to be 0.013 mrad for both θy and θx rotations, with a long term stability of 0.014 mrad in θy and 0.006 mrad in θx. The resolution of the final mirror alignment procedure using data tracks is 0.18 mrad for θy mirror rotations and 0.12 mrad for θx mirror rotations.
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