Design and test of a timing optimized 3D silicon sensor for HL-HLC experiments

The future High Luminosity Large Hadron Collider (HL-LHC) is a large upgrade program of the LHC at CERN which will allow to run all experiments at higher luminosity after 2025. The advantage of running experiments at higher luminosity is an increment of the collected data at the cost of a stronger impact on the detector systems lifespan, track reconstruction efficiency and data acquisition due to an increased radiation damage and the high event pile-up. Especially for tracking detectors close to the interaction point, like the LHCb VELO detector, those problems will be a greater issue, with a potential radiation damage above 1∗1015 MeV neqcm−2 and a pile-up above 100 events per bunch crossing for ATLAS and 40 for LHCb. The need for a new generation of tracking detectors capable of operating at those conditions, with same or better track reconstruction performances, leads to the development of new methods and technologies. For example, according to simulations performed by the LHCb collaboration, using as reference the upgrade-I model of the VELO and running the detector in high luminosity environment, the best way to ensure high track reconstruction efficiency is using particle tracking with high space resolution coupled with high resolution time measurement below 200 ps. Radiation damage on the other hand forces the development of new sensor technologies, like 3D sensors or diamond sensors which present an intrinsic high radiation hardness compared to classic planar devices. The INFN-CSN5 TIMESPOT project aims to develop a first prototype of a next generation 4D tracking detector, featuring small pitch and timing optimised 3D silicon and diamond sensors, a 28 nm CMOS technology based read-out chip and real-time tracking algorithms. This work presents the development and test of the timing optimised 3D silicon, starting from the first computer aided design (CAD) sketch to the first test beam results obtained using the first prototype.