CO2 to cool the Large Hadron Collider

The Large Hadron Collider (LHC) is a particle accelerator located at CERN in Geneva. It is 27 km long and is built 100 meters deep underground. The LHC along with its several detectors were built to help scientists learn more about the primordial universe and acquire new knowledge in subatomic particle physics. Components of the accelerator are 6 particle detectors, called ATLAS, CMS, ALICE, TOTEM, LHCf and LHCb. Especially ATLAS and CMS have been used in a variety of experiments, including the quest for the Higgs boson and the study of particles that may be constituents of the dark matter.

The detectors contain silicon cells which are to be maintained cold to minimize damage caused by radiation of the particles passing through them. Typically, sensors must be kept below -40 °C, which means that the cooling pipes must be kept at around -50 °C or less.

Most of the current refrigeration systems used by CERN contain synthetic refrigerants, with high global warming potential (GWP) but CERN wants to meet the environmental sustainability constraints imposed by the European F-Gas regulation and the Paris agreement.

For this reason, CERN will work in close collaboration with the Norwegian university NTNU on the CoolCERN project (2019-2023) to develop a cooling system for the two ATLAS and CMS detectors based on the natural refrigerant CO2 – R744 – which has zero ODP, negligible GWP and is not flammable. The required cooling capacity will be as high as 300 kW (ATLAS) and 600 kW (CMS) at evaporation temperatures below -50 °C, at 100 meters depth.

More information on the project HERE