New Precision Timing Prototype Enhances CMS Detector Capabilities

The ETL Readout Chip version 1 (ETROC1) has been developed as the first full chain precision timing prototype for the CMS MTD endcap timing layer upgrade. This advancement utilizes Low Gain Avalanche Diode (LGAD) sensors to detect charged particles, aiming for a time resolution of 40 to 50 picoseconds (ps) per hit, and 30 to 40 ps per track when combining hits from two detector layers.

The ETROC1 features a 5 x 5 pixel array, which includes a 4 x 4 active pixel array. Each active pixel is equipped with essential components such as a bump pad, charge injection circuit, pre-amplifier, discriminator, digital-to-analog converter, and time-to-digital converter. These components are crucial for processing LGAD signals and measuring timing-related information. The peripheral circuits provide necessary clock signals and readout functionalities.

The chip measures 7 mm x 9 mm and has been fabricated using a 65 nm CMOS process. Extensive testing has been conducted using charge injection, infrared laser, and proton beam stimuli. The results indicate that the time resolution of the bump-bonded ETROC1 combined with LGAD chipsets achieves a range of 42 to 46 ps per hit during beam tests.

This development is significant as it enhances the capabilities of the CMS detector at the Large Hadron Collider, allowing for more precise measurements in high-energy physics experiments. The findings are detailed in the paper titled "ETROC1: The First Full Chain Precision Timing Prototype ASIC for CMS MTD Endcap Timing Layer Upgrade" by Xing Huang and 18 other authors, available on arXiv under the identifier arXiv:2404.14207.