NTNU and CERN work in close cooperation to develop a full CO2 refrigeration circuit for the ATLAS and CMS particle detectors with cooling capacities up to 300kW (ATLAS) and 600kW (CMS) at evaporating temperatures below -50℃.

Preventing deteroriation

The silicon cells of the detectors, once cooled down, should be kept at low temperature to prevent their deterioration. These detectors have a total cost of about 1 billion NOK, and this is why we need a primary cooling system complying with stability and reliability to keep the detectors in continuous operation, without any interruption.

More environmentally friendly cooling

There is an increasing concern in CERN to meet the environmental sustainability constraints due to the European F-gas regulation and a global consensus (Paris COP and Kigali agreement).

For this reason, the scope of the project is to develop a primary cooling system applying a natural working fluid. Carbon dioxide (CO2), also called R744 in refrigeration, has been used by NTNU and SINTEF during the past 30 years and been adapted to various R744 systems for all kinds of applications. In this case, the system will be designed for operation close to CO2 triple point (-56.56°C), with a capacity up to 0.6 MW, cooling down the oil-free R744 loop that reaches the detectors. In addition to pumped circulation, an application of a R744 turbo compressor technology for high elevation differences will be evaluated for a future evolution of the system.

The large ring illustrates the 27 km long HLC tunnel. Photo: Maximilien Brice, CERN