Quality Control of the CMS High Granularity Endcap Calorimeters

Abstract

The Compact Muon Solenoid (CMS) at CERN will be receiving upgrades to its data collection instrumentation in preparation for a larger number of collisions and proportional higher radiation upon resumed functionality in 2030. The endcap calorimeters, which are the sections of the calorimeters most affected by radiation, will be replaced with new high granularity calorimeters (HGCAL), which are composed of radiation-tolerant silicon modules and plastic scintillators installed on top of printed circuit boards (PCBs). The focus of this project is to test and calibrate the electronic components installed on the PCBs; the assembled PCBs are referred to as “tileboards”. The process of testing boards is split into two phases: a reception test and a functionality test. The reception test consists of a visual analysis to search for defects, which, if found, are photographed and reported to the manufacturer. The functionality test consists of a light detection phase and a calibration phase. The tileboards’ response to light was tested by flashing LEDs situated next to the photodetectors on the boards. The tileboards were injected with electric pulses to simulate photon detection to calibrate the turn-on points of the photosensors’ response. The full suite of tests is conducted at room temperature, while a truncated version is conducted at a temperature of -30 ℃ to simulate the operating temperature of the HGCAL detector. The testing process is still ongoing, and it is estimated to complete by the end of the first quarter of 2027.