The LHCb Vertex Detector Upgrade. The prototypes study with the Timepix3 Telescope

A dedicated irradiation programme with a particle beam followed by detailed studies are essential for proper evaluation of detector prototypes and predict their performance after accumulating the predicted particle fluence at the end of their lifetime. In order to perform precise measurements with the LHCb VELO (Vertex Locator) detector prototypes a dedicated high-resolution pixel beam telescope was developed based on 8 Timepix3 detector planes. This telescope has been taking data at CERN in the PS and SPS facilities since 2014. The Timepix3 can operate in a trigger less mode (data driven readout) with very precise timestamps. The data produced by the telescope can easily incorporate the signals from the Device Under Test (DUT) and in particular for Timepix3 devices the analysis is straight forward. The offline analysis compares the performance after irradiation with several fluences of protons or neutrons from 2 to 8 $\times 10^{15}$ 1-MeV $n_{eq}/cm^2$ ; different silicon substrates (n-on-p or n-on-n), distances from last pixel to the edge, guard rings designs and different vendors. Charge collection efficiencies, track resolution, eta correction are of particular interest as function of fluence. The presentation will describe the detailed LHCb VELO upgrade design choices as well as with some highlights of the Timepix3 Telescope operational performance.