Development of a timing detector for the TOTEM experiment at the LHC

The upgrade program of the TOTEM experiment foresees the installation of timing detectors in- side vertical Roman Pots to allow the reconstruction of the longitudinal vertex position in presence of event pile-up in high β ∗ dedicated runs. The small available space inside the Roman Pot and the required time precision led to the study of a solution using single crystal CVD diamonds. The sensors are read-out using fast low-noise front-end electronics developed by the TOTEM Col- laboration, achieving a signal-to-noise ratio larger than 20 for MIPs. A prototype was designed, manufactured and tested during a test beam campaign, proving a time precision below 100 ps and an efficiency above 99%. The geometry of the detector has been designed to guarantee a uniform occupancy in the expected run conditions keeping, at the same time, the number of channels be- low ten. In fact, each detector uses four diamond crystals of 4 . 5 × 4 . 5mm 2 : one is segmented in four pixels, another in two, while the remaining pair is metallized with a single electrode. The de- tectors are read-out using the SAMPIC chip, a fast sampler designed specifically for picosecond timing measurements with high rate capabilities. Four aligned detectors will be installed in each Roman Pot to achieve a final precision below 50 ps. The first set of prototypes was successfully installed and tested in the LHC in November 2015.