4D-Share - DC-coupled resistive readout in silicon sensors with internal gain: signal sharing for ultimate time and space resolution in future 4D tracking

Breakthroughs in understanding nature are made possible by developing increasingly accurate experimental apparatuses, such as silicon-based tracking systems able to measure the direction of particles generated in the collisions. Since their first appearance, silicon tracking detectors underwent a remarkably fast evolution. Recent developments in sensor design are opening the way to 4D-tracking detectors, able to measure concurrently position and time of passage of a charged particle using the same sensitive device. The ongoing R&D path based on the innovative Low Gain Avalanche Diode (LGAD) technology, delivered sensors with excellent time resolution (~30 ps), the standard LGADs, and more recently TI-LGADs, and AC-coupled resistive LGADs [1], addressing the feasibility of pixels arrays with an 100% active area and micron-level spatial resolutions. This proposal brings a new paradigm in high accuracy particle tracking, by introducing controlled signal sharing in the principles of operation of silicon sensors, exploited by innovative signal reconstruction methods. The sensor is designed as a thin LGAD with a resistive DC-coupled read-out, also called DC-coupled Resistive Silicon Detector (DC-RSD). The spatial resolution of a silicon detector is typically proportional to the pixel size of the sensor: resolution of the order of 5-10 microns can be achieved with millions of tiny pixels (25x25 square microns). This is technically difficult to implement and leads to very limited space for the electronics devoted to signal processing. In the , a single large resistive layer with an uniform response replaces the array of separate DC-RSD design implants. Similarly to the AC-LGADs, the pixelation of the sensor is determined by the layout of the read-out metallic pads. The built-in signal sharing, typical of a resistive read-out, is combined with the internal gain of LGADs, to achieve micron-level position resolution with large pixels (200x200 square microns). The DC-coupled read-out aims to achieve controlled sharing of the signals The DC-RSD design breaks the relationship between pixel size and spatial resolution, allowing to keep the same resolution with 100 times larger area pixels. The pixel size is determined by the particle density. The main goals of the project are: - Fully develop the concept of DC-coupled resistive read-out; optimize the design using analytic modeling, TCAD and SPICE - Design and produce thin silicon sensors that combine built-in sharing with internal gain (one prototype run of DC-RSD) - Perform full characterization of the production, with static and dynamic measurements in the laboratory (new and irradiated devices) - Develop analytic and machine learning reconstruction codes for the estimate of hit position and time The DC-RSD sensors will benefit all fields of science that make use of particle localization.