Development and characterization of modules for the CMS Endcap Timing Layer for High-Luminosity LHC.

The Compact Muon Solenoid (CMS) detector at the CERN Large Hadron Collider (LHC) is undergoing an extensive upgrade program to prepare for the challenging conditions of the High-Luminosity LHC (HL-LHC). A new timing detector in CMS will measure minimum ionizing particles (MIPs) with a time resolution of ~40-50 ps per hit and coverage up to |η|=3. The precision time information from this MIP Timing Detector (MTD) will reduce the effects of the high levels of pileup expected at the HL-LHC and will bring new and unique capabilities to the CMS detector. The endcap region of the MTD, called the endcap timing layer (ETL), must endure high fluences, motivating the use of thin, radiation tolerant silicon sensors with fast charge collection. As such, the ETL will be instrumented with silicon low-gain avalanche diodes (LGADs), covering the high-radiation pseudo-rapidity region 1.6 < |η| < 3.0. The LGADs will be read out with the Endcap Timing Read Out Chip (ETROC), which is designed for precision timing measurements. We will present the extensive developments and progress made for the detector, particularly focusing on electrical tests of the first full-size modules, their performance within a complete system integrated with power and readout boards and connected to the backend data acquisition system (DAQ).