Temperature Measurements for Improved HCAL Barrel Readout Box Cooling at the CMS Experiment

Over the summer of 2024, Baylor University had the opportunity to test a prototype upgrade to the cooling system for the Hadron Calorimeter (HCAL) at the Compact Muon Solenoid (CMS) experiment at CERN. The silicon photomultipliers (SiPMs) within the HCAL Barrel readout boxes need to be kept as cool as possible in order to maintain sensitivity and data quality. The current chilled-water cooling system can accommodate a SiPM temperature of five degrees Celsius, but with improvements to the cooling flow it should be able to reach SiPM temperatures between minus 10 to minus 15 degrees Celsius. This presentation is about temperature data taken from various points on the readout box both before and after the upgrade, which indicates areas of significant improvement over the current cooling scheme as well as items that warrant further refinement. Funding comes from the U.S. Department of Energy award DE-SC0007861.