Speaker
Description
The High-Luminosity LHC will expose vertex detectors to unprecedented radiation levels, requiring sensors capable of withstanding high fluences in the $10^{16}-10^{17}\ \text{n}_{\text{eq}}/\text{cm}^2$ range while maintaining excellent spatial and temporal resolution. This work presents the development of 3D silicon pixel sensors for the second upgrade of the LHCb Vertex Locator (VELO), leveraging their intrinsically short charge-collection distances to achieve enhanced radiation tolerance and fast timing.
To identify optimal 3D sensor geometries, a simulation pipeline is being developed to explore a large parameter space. Design parameters under study include column diameter and spacing, sensor thickness, isolation structures (p-stop vs.\ p-spray), and electrode configurations for both single- and double-sided devices, with current efforts primarily focused on single-sided sensors due to an ongoing production run. Initial device-simulation studies have focused on breakdown voltage, capacitance, and electric-field behaviour, particularly in view of timing performance when coupled to the PicoPix fast-timing ASIC.
Following the device-simulation studies, the next step in the pipeline is a Monte Carlo track generator, which is now operational and provides charge-deposition patterns for arbitrary track angles, enabling a first systematic study of signal-formation dependence on the incidence angle, enabling comparisons between test-beam data and simulation results.The simulation pipeline is currently midway through integration, linking sensor-geometry optimisation, charge-transport modelling, and readout-electronics response. Experimental validation is being carried out through laboratory measurements and test-beam campaigns at the CERN SPS using a discrete electronic setup integrated with the Timepix4 telescope.