Beam telescope for medium energy particles based on thin, submicron precision MAPS

A general purpose beam telescope of new generation has been constructed and tested. Four reference planes of the telescope are based on CMOS Monolithic Active Pixel Sensors (MAPS), thinned down to less than 100 microns. Noise optimized, high precision tracking pixel sensors have been designed and fabricated for this application using AMS 0.35 OPTO process. Single sensor consists of 512times512 pixel array with a pitch of 10 mum, providing an active area of 5times5 mm2. Measured signal-to-noise ratio for minimum ionizing particle (MIP) is more than 27 at room temperature and extrapolated single point (2D) resolution is below 1 mum. Use of such sensors for beam telescope provide an attractive solution for high precision tracking of minimum ionizing particles even in case of their relatively low energy. Telescope tracking performance study, including beam tests results with hundreds GeV pions is presented. Comparison of sensors fabricated using standard (14 mum thick epitaxy) and experimental (20 mum epitaxy) wafers is also discussed.