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

The upgrade program of the TOTEM experiment will include the installation of timing detectors inside vertical Roman Pots to allow the reconstruction of the longitudinal vertex position in the presence of event pile-up in high- $\beta^{\ast}$ dedicated runs. The small available space inside the Roman Pot, optimized for high-intensity LHC runs, 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 Collaboration, 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 100ps and an efficiency above 99%. The geometry of the detector has been designed to guarantee uniform occupancy in the expected running conditions keeping, at the same time, the number of channels below 12. The read-out electronics was developed during an extensive campaign of beam tests dedicated first to the characterization of existing solution and then to the optimization of the electronics designed within the Collaboration. The detectors were designed to be read out using the SAMPIC chip, a fast sampler designed specifically for picosecond timing measurements with high-rate capabilities, later, a modified version was realized using the HPTDC to achieve the higher trigger rates required for the CT-PPS experiment. The first set of prototypes was successfully installed and tested in the LHC in November 2015, moreover the detectors modified for CT-PPS are successfully part of the global CMS data taking since October 2016.