The CMS ECAL Phase-2 Upgrade for High Precision Timing and Energy Measurements

Abstract

The electromagnetic calorimeter of the Compact Muon Solenoid Experiment (CMS) will be upgraded for the High-Luminosity phase of the LHC, where an unprecedented number of pile-up events (up to 200 simultaneous proton-proton collisions) and a challenging increase in data rate are expected. The current lead tungstate crystals and avalanche photodiode detectors will remain, while the upgrade will address the front-end and off-detector read-out electronics of the barrel region of the calorimeter. The new electronics will have to comply with the requirements of the upgraded Level 1 hardware trigger system, in terms of increased latency and data bandwidth, in order to preserve detector performance despite the increased instantaneous luminosity (above 5 × 1034cm−2s−1). A pivotal characteristic of the new design will be the capability to provide precision timing measurements, of the order of 30 ps for photons and electrons above 30 GeV. This excellent time resolution will improve the overall CMS physics performance under the expected pile-up conditions. The chosen solution for the front-end electronics includes a custom dual gain trans-impedance amplifier implemented in a 130nm CMOS processor. The new front-end will also include an ASIC providing two 160 MHz ADC channels (one for each gain), gain selection, and data compression, in 65nm CMOS technology. The upgrade will provide single crystal granularity for the hardware trigger and will enable a full read out of the detector. The status of the ongoing R&D activities will be presented, together with the latest beam test results with prototypes, and the development plan for the project up to installation.