Speaker
Description
As part of the CMS Phase-2 Upgrade project, a novel detector, the Endcap timing Layer (ETL), will be installed during LS3 with the goal of precisely measuring the production time of minimum ionizing particles (MIPs) during HL-LHC era which comes with increased number of collisions. To ensure optimal operating conditions, a two-phase CO2 cooling system is going to be used to extract the heat dissipated by detector’s electronics tiled on the 6.35 mm thick aluminium cooling plate. Sixteen cooling loops, in parallel connected to a single manifold and composed of a capillary and an evaporator, are responsible for distributing the coolant across the plate. A dedicated test stand has been designed and assembled at the CERN Tracker Integration Facility (TIF) to test the final prototype of the cooling plate and optimize the cooling system design. It is complemented by a SCADA system which provides both safety and environmental monitoring functions. The test stand is capable of generating up to 5 kW of power controlled by a programmable logic controller (PLC) with implemented interlock algorithm. Vital system parameters are monitored with a number of instrumentation such as absolute and differential pressure sensors, coriolis flow meter, in-flow temperature sensors, etc. Due to the specific design of the cooling system, obtaining accurate theoretical predictions of the evaporators’ pressure drop is difficult; therefore extensive tests have been performed in order to obtain these values experimentally. The crosstalk between the loops has been observed and temperature uniformity across the plate has also been investigated. Additionally, besides nominal operating conditions, the system has been tested under potential failure modes that could occur during detector operation. The system’s response has been evaluated in case of a single loop clogging or complete flow shut-off and margin to reaching dry-out conditions has been studied. In parallel to these studies, the behavior of the TIF CO2 plant has been evaluated since the CO2 parameters, such as vapor quality (VQ) and mass flow, are comparable with ones expected during final operation at P5. A significant pressure drop has been noticed on the return line to the plant’s accumulator, resulting in higher temperature at the setup’s outlet. These results emphasize once again the importance of proper sizing of detector transfer lines (DTLs) to ensure optimal CO2 conditions at the detector level. The presentation summarizes the results of thermal studies and shares lessons learned during the operation and testing process of the system.