Speaker
Description
Future experiments at hadron colliders require an evolution of the tracking sensor technologies to ensure sufficient radiation hardness and timing resolution to cope with unprecedented fluxes of charged particles.
3D diamond sensors with laser-graphitized electrodes, featuring strong binding energy, small atomic number and high carrier mobility, could provide an appealing option. However, currently the high resistance of the engraved electrodes delays the propagation of the induced signals towards the readout, deteriorating the precision of the timing measurements.
Historically, the contribution to the uncertainty on diamond sensors' timing measurements due to the signal propagation through the electrodes was largely dominant, allowing to neglect contributions from field inhomogeneities and electronics jitter. Recent technological advancements in graphitization technology, however, call for a renewed effort in modeling signal generation in these devices, where all the components are considered in a comprehensive way. To this purpose, we apply an extended version of the Ramo-Shockley theorem representing the effect of signal propagation as a time-dependent weighting potential, obtained by solving numerically the Maxwell equations in a quasi-static approximation, with appropriate boundary conditions.
To this end, we developed a custom solver leveraging spectral methods and validated it against the solution obtained with the Finite Element Method implemented by the commercial software COMSOL MultiPhysics. The response of the modeled sensor to a beam of particles is then simulated using Garfiel++ and compared to the data acquired with a 3D diamond sensor in a beam test carried on in 2021 by the TimeSPOT Collaboration at the SPS, at CERN. After validation on data, the simulation pipeline is used to study the different contributions to time resolution and to draw conclusions on further sensor developments to improve their time resolution.
Reducing the resistivity of the columns remains the first priority, while improving the readout electronics design, e.g. by shortening the shaping time, appears to be at least as important as optimizing the sensor geometry.
