Performance of USTC first batch resistive AC-LGAD sensor

In this paper, the design and characterization of AC-LGAD sensors at the University of Science and Technology of China is introduced. The sensors are characterized with an infrared laser Transient Current Technique (TCT) system for evaluating signal response characteristics and spatial resolution. The temporal resolution was quantified with electrons emitted by a Sr-90 radioactive source. The spatial resolution can reach 4 μm and a temporal resolution of 48 ps is achieved

💡 Research Summary

This paper presents the successful design, fabrication, and performance characterization of the first batch of AC-coupled Low-Gain Avalanche Detector (AC-LGAD) sensors developed by the University of Science and Technology of China (USTC). As high-luminosity particle colliders, such as the High-Luminosity LHC (HL-LHC), demand unprecedented precision in particle tracking, the development of sensors capable of “4D tracking”—simultaneously providing high-precision spatial and temporal information—has become a critical frontier in experimental particle physics.

The core innovation of the AC-LGAD architecture discussed in this study lies in the integration of a resistive layer. Unlike conventional LGADs, which are limited by pixel size for spatial resolution, AC-LGADs utilize an AC-coupling mechanism. This allows the charge signal induced by an incident particle to spread across adjacent electrodes via the resistive layer. By analyzing the signal sharing pattern among multiple electrodes, the sensor can interpolate the hit position with much higher precision than the physical pixel pitch, effectively overcoming the traditional trade-off between pixel size and readout complexity.

To evaluate the performance of this new sensor batch, the researchers employed two sophisticated characterization methodologies. First, an infrared laser-based Transient Current Technique (TCT) system was utilized. By scanning the sensor surface with a laser, the team could precisely simulate particle-induced currents to assess signal response characteristics and charge collection efficiency. This experimental setup demonstrated that the AC-LGAD can achieve an extraordinary spatial resolution of 4 μm, which is vital for distinguishing closely spaced particle tracks.

Second, the temporal resolution was rigorously tested using a Sr-90 radioactive source. By utilizing the electrons emitted from the beta decay of Sr-90, the researchers were able to simulate real-world particle-matter interactions. The results revealed a remarkable temporal resolution of 48 ps. This level of precision is essential for the “time-stamping” of particles in high-density collision environments, enabling the separation of overlapping events in the time domain.

In conclusion, the study provides a robust demonstration of the high-performance capabilities of the USTC-developed AC-LGAD sensors. The achievement of 4 μm spatial resolution and 48 ps temporal resolution marks a significant milestone in semiconductor detector technology. These advancements provide a foundational technological leap for the next generation of high-energy physics experiments, offering the precision necessary to explore the fundamental laws of the universe through high-precision 4D particle tracking.