Picosecond timing resolution with 3D trench silicon sensors.

In the high-luminosity LHC phase the collider will operate at $1.5 \times 10^{34}/{cm}/{s}$ and strict requirements will be posed on subdetectors capabilities. Concerning the LHCb Upgrade2 VELO, to guarantee a good detector performance the additional information of the hit time stamping with an accuracy of at least $50 {ps}$ is needed. A very promising option today to achieve this level of timing precision is the 3D trench silicon pixel, developed by the INFN TimeSPOT Collaboration. This kind of sensor would allow to build a 4D tracker, capable of excellent resolution in both space and time measurements. The latest beam test with the 3D trench sensors has been performed at SPS/H8 in 2021. By means of low-noise custom electronics boards featuring a two-stage transimpedance amplifier it was possible to test silicon pixels and strips made with the 3D trench technology. To extrapolate the sensor time resolution, the crossing time of a particle was estimated using two MCP-PMTs as time tag, with an accuracy of approximately $7 {ps}$. Preliminary results show that the standard deviation of the core of the pixels time distribution is about $10 {ps}$ and the tilted sensor has shown an efficiency close to $100%$.