The CMS MTD Endcap Timing Layer: Precision Timing with Low Gain Avalanche Diode Sensors

The MIP Timing Detector (MTD) of the Compact Muon Solenoid (CMS) will provide precision timestamp for all charged particles up to a pseudorapidity of $|\eta|=3.0$. This upgrade will mitigate the effects of pile-up expected under the High-Luminosity LHC running conditions and bring new and unique capabilities to the CMS detector. The endcap region of the MTD, called the Endcap Timing Layer (ETL), will be instrumented with silicon low gain avalanche detectors (LGADs), covering the pseudorapidity region $1.6<|\eta|<3.0$. The LGADs will be read out with the ETROC read-out chip, which is being designed for precision timing measurements. We present recent progress in the characterization of LGAD sensors for the ETL and the development of ETROC, including test beam and bench measurements.