The CMS Electromagnetic Calorimeter Upgrade: Automated Tests of the Very Front End and Vertical Integration with Test Beam

The High Luminosity Large Hadron Collider (HL-LHC) is a planned upgrade to deliver unprecedented instantaneous luminosity of proton-proton collisions. The Compact Muon Solenoid (CMS) experiment at the LHC will be upgraded for the highly challenging environment of the HL-LHC; the HL-LHC will have a much higher rate of overlapping proton-proton collisions events, called pile-up, and also increased radiation levels. In particular, the electromagnetic calorimeter (ECAL) barrel electronics will be upgraded to meet the specifications required at HL-LHC and to improve the time resolution, which will aid in distinguishing pile-up and anomalous signals from signals of interest for physics analysis. The current working readout chain of the ECAL barrel upgrade consists of scintillating lead-tungstate crystals followed by avalanche photodiodes read out by very-front end (VFE) cards with custom ASICs to amplify and digitize signal, then front end (FE) cards which transmit data off detector to barrel calorimeter processors (BCP). We present an overview of the upgrade of the ECAL barrel electronics and describe automated testing procedures applied to 50 VFEs, as well as VFE performance at varying temperature. We also present test beam data from a vertical integration test, which included the full upgraded ECAL readout chain, from crystals to VFE and FE, to BCPs.