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

The MIP Timing Detector of the CMS will provide precision timestamp for all charged particles up to a pseudorapidity of vertical bar eta vertical bar = 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, will be instrumented with silicon Low-Gain Avalanche Diodes, covering the pseudorapidity region 1. 6 < vertical bar eta vertical bar < 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.