Study of the Readout of AC-LGAD Sensor and ALTIROC Chip Assemblies

The development of detectors that provide high resolution in four dimensions has attracted wide-spread interest in the scientific community for a wide variety of applications. This can be achieved by leveraging new sensor designs, such as the AC-coupled Low Gain Avalanche Diode (AC-LGAD). This type of silicon detector has already shown excellent timing performances while also providing high spatial resolution and is therefore considered a promising candidate for future detectors to provide 4-dimensional measurements of particle interactions. While previous works detailed the possibility to readout these sensors using chips designed for standard (DC-)LGAD sensors, here we focus on the study of the operational specification of a complete AC-LGAD based detector. Fundamental readout parameters such as the minimum charge sensitivity, noise level, and signal jitter have been evaluated for AC-LGAD sensors designed and fabricated at the Brookhaven National Laboratory (USA). These sensors have been coupled to a fast-time ASIC, the ATLAS LGAD Timing Integrated Read-Out Chip (ALTIROC), developed by Omega/IJCLab (France) for the ATLAS timing detector at the HL-LHC. The studies shown are used as a basis for the creation and optimization of a dedicated AC-LGAD readout ASIC.