Performance studies of AC-LGAD silicon detectors

A new class of silicon detectors, the Low-Gain Avalanche Diode (LGAD), has already shown excellent timing performances O(30-40 ps) and is being considered for several applications in the most diverse fields, ranging from timing in high energy physics experiments to medical imaging. LGADs typically exhibit a low to moderate gain (5 - 100), short rise time and high signal-to-noise ratio. Fine pixelization of LGADs is difficult to achieve, and to provide fine spatial resolution the AC-coupled LGAD (AC-LGAD) approach was introduced. In this type of device, the signal is capacitively induced on fine-pitched electrodes placed over an insulator. LGAD and AC-LGAD prototypes have been designed and fabricated at Brookhaven National Laboratory and segmented in both pixel matrices and strips. These prototypes are characterized via Transient Current Technique (TCT) using a fast-pulsed IR laser. The timing resolution is measured by studying the time coincidence between signals generated by a beta particle beam from a 90Sr source in two sensors or by using a collimated proton beam. Additional studies of the sensor's performance have been carried out, including the induced signal in neighbouring pixels and strips.