VFAT Temperature Monitoring on a ME0 GEM Module

With the CMS experiment at the Large Hadron Collider undergoing the High Luminosity upgrade, new detectors are being added to the muon endcaps. One such detector is the ME0 Gas Electron Multiplier (GEM). To function reliably in the very forward region of CMS, new front-end electronics are being developed and tested, including thermal tests and temperature monitoring. The "VFAT" readout chips come equipped with two temperature sensors, an internal sensor in the ASIC, and an external sensor on the VFAT PCB. However, neither of these two sensors come calibrated. We show how these sensors can be calibrated on the detector using the Opto-Hybrid (OH) temperature sensors and cross-checked with a Koolance temperature sensor. The VFATs are cooled with water flowing through a cooling circuit chilled by a CW-5200 Industrial chiller. The Koolance sensor shows that with this method of temperature calibration, the VFATs internal temperature sensor can be off by ±2.5°C. When cooled the VFATs in contact with the cooling circuit operate at 30°C and those uncooled operate at 32°C. A "Cooling Failure" test was also performed where the temperatures were monitored after water cooling had been turned off. This test shows that the most cooled VFATs become the hottest, reaching up to 41.5°C.