Cryogenics for the Large Hadron Collider Experiments

High Energy Physics experiments have frequently adopted cryogenic versions of their apparatus to achieve the desired performance. Among the four new experiments for the CERN Large Hadron Collider (LHC) the two largest, ATLAS and CMS, include spectrometers using 4.5 K superconducting magnets and detectors filled with liquid argon at 87 K, respectively for particle momentum and energy measurements. These detectors are of unprecedented size and complexity and the definition of the associated cryogenic systems is the result of a collaboration between CERN and several external institutes all around the world. A review of the various systems is presented with particular emphasis to the basic cooling principles, the special cryogenic features and the operation scenarios.