Testing the Cooling and Readout Chain of the Barrel MTD Detector for the HL-LHC Upgrade

The MIP Timing Detector (MTD) is a new subdetector that will be installed in the Compact Muon Solenoid (CMS) experiment. Its implementation will help mitigate the difficult conditions of the planned High Luminosity LHC (HL-LHC) upgrade. Placed in a 40mm gap between the final layer of the CMS pixel tracker and electromagnetic calorimeter is the Barrel Timing Layer (BTL) of the MTD. The BTL is segmented into 72 independent trays, housing LYSO crystals, SiPM arrays, CO₂ cooling, and data-transfer electronics. Numerous tests are ongoing to validate the current design of the detector. One full-scale tray with integrated CO₂ cooling is currently being tested from 20°C to -35°C, the full range of operating temperatures at CMS. Resistive strips simulating the heat load of full BTL readout units are attached to the tray during the cooling tests to gather data on the temperature response of the system under operation conditions. Data from these initial tests provide critical information about necessary adjustments and precautions for the final implementation of BTL, and act as a roadmap for more complex testing using complete BTL readout units as they become available. The results of validation of the BTL readout with the HL-LHC data acquisition system are also presented.