Abstract
The cooling systems of the future tracking detectors of the ATLAS and CMS experiments at the Large Hadron Collider (LHC) at CERN will be entirely based on CO2 refrigeration technology. The system is a booster refrigeration system, composed of a two stage primary part with transcritical R744 equipment and a low temperature secondary CO2 pumped loop. The primary refrigeration sub-system installed on surface provides cold R744 at −53∘C to the CO2 pumped loops installed 100 m underground and rejects the heat exchanged. The process must be reliable and remain stable regardless of the amount of heat exchanged, which will amount to hundreds of kilowatts and is expected to vary throughout the lifetime of the detectors. The paper discusses the concept adopted for the innovative transcritical R744 cycle and describes the technical details of the first prototype built.
Highlights
R744 equipment and a low temperature secondary CO2 pumped loop
The silicon detectors used to reconstruct the tracks of charged particles in collider experiments need to operate at stable temperature to maximise the signal to noise ratio
The Large Hadron Collider at CERN is undergoing an upgrade preparing it for the High Luminostiy programme (HL-HLC) starting in 2026 [2]
Summary
R744 equipment and a low temperature secondary CO2 pumped loop. The primary refrigeration sub-system installed on surface provides cold R744 at −53 °C to the CO2 pumped loops installed. The Large Hadron Collider at CERN is undergoing an upgrade preparing it for the High Luminostiy programme (HL-HLC) starting in 2026 [2] This upgrade is planned to increase by a factor of 10 the luminosity, i.e., the density of the particles created by the collision. The two largest particle detectors in the world, ATLAS and CMS installed at LHC, are going through major upgrades to get ready for a 10 year-long operation along with the High Luminosity version of the accelerator. Such upgrades involve the replacement of the present particle trackers with large silicon detectors of new generation, capable of coping with the increased density of tracks
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