Speaker
Description
In preparation for the high-luminosity LHC phase, the ATLAS detector will be upgraded with a new silicon inner tracker, the ITk, relying on a cooling system based on carbon dioxide (CO2) evaporative properties.
In order to test the key aspect of the cooling, a prototype for the ITk Outer Endcap Layer 4 Half-Shell cooling system was built in Milan and tested at the CERN CO2 BabyDEMO cooling plant. The facility is able to provide a CO2 flow of 150 g/s with a temperature as low as -45 C.
The presentation will illustrate the mechanical construction of the prototype and the use of 3D-printed titanium parts. The thermal load of the detector (expected to be 1kW on the Layer 4 Half-Shell during normal operation) was also simulated. The sizing of the capillary present in the system, required to reach the design pressure drop 8 bar_a and to trigger the CO2 evaporation, will also be discussed. The pressure and temperature sensors installed in the prototype and the data acquisition will be described: the system includes in-flow sensors for pressure and temperature (8 of each type), a DeltaBar for the capillary pressure drop measurement and the external temperature sensors for each of the 9 evaporator pipes.
The measurement performed at the BabyDEMO cooling plant, both at the nominal ATLAS operating condition and in more extreme scenarios, will be described. The system was proved to be stable under all the conditions tested, and the total pressure drop was within the 10 bar required by the system specification. The results obtained from the prototype will also be compared to thermos-fluidic simulation.
