Cryogenics for the Large Hadron Collider

The Large Hadron Collider (LHC), a 26.7 km circumference superconducting accelerator equipped with high-field magnets operating in superfluid helium below 1.9 K, has now fully entered construction at CERN, the European Laboratory for Particle Physics. The heart of the LHC cryogenic system is the quasi-isothermal magnet cooling scheme, in which flowing two-phase saturated superfluid helium removes the heat load from the 36'000 ton cold mass, immersed in some 400 m3 static pressurised superfluid helium. The LHC also makes use of supercritical helium for non-isothermal cooling of the beam screens which intercept most of the dynamic heat loads at higher temperature. Although not used in normal operation, liquid nitrogen will provide the source of refrigeration for precooling the machine. Refrigeration for the LHC is produced in eight large refrigerators, each with an equivalent capacity of about 18 kW at 4.5 K, completed by 1.8 K refrigeration units making use of several stages of hydrodynamic cold compressors. The cryogenic fluids are distributed to the cryomagnet strings by a compound cryogenic distribution line circling the tunnel. Procurement contracts for the major components of the LHC cryogenic system have been adjudicated to industry, and their progress will be briefly reported. Besides construction proper, the study and development of cryogenics for the LHC has resulted in salient advances in several fields of cryogenic engineering, which we shall also review

An Introduction to Cryogenics

This paper aims at introducing cryogenics to non-specialists. It is not a cryogenics course, for which there exists several excellent textbooks mentioned in the bibliography. Rather, it tries to convey in a synthetic form the essential features of cryogenic engineering and to raise awareness on key design and construction issues of cryogenic devices and systems. The presentation of basic processes, implementation techniques and typical values for physical and engineering parameters is illustrated by applications to helium cryogenics

Operating at 1.8 K: the technology of superfluid helium

The technical properties of helium II ("superfluid" helium) are presented from the user point of view. Its applications to the cooling of superconducting devices, particularly in accelerators and colliders are discussed in terms of heat transfer capability and limitations in conductive and convective modes. Large-capacity refrigeration techniques below 2 K are reviewed, as concerns thermodynamic cycles as well as process machinery. Examples drawn from existing or planned projects illustrate the presentation

Superconductivity and Cryogenics for the Large Hadron Collider

Key technologies to the Large Hadron Collider (LHC), the 26.7 km circumference high-energy, high-luminosity particle collider under construction at CERN, are high-field superconducting magnets and superfluid helium cryogenics. After recalling the main challenges of the project, we present the rationale for applying these technologies on an unprecedented scale and briefly indicate the status of their implementation

Advances in Cryogenics at the Large Hadron Collider

After a decade of intensive R&D in the key technologies of high-field superconducting accelerator magnets and superfluid helium cryogenics, the Large Hadron Collider (LHC) has now fully entered its co nstruction phase, with the adjudication of major procurement contracts to industry. As concerns cryogenic engineering, this R&D program has resulted in significant developments in several fields, amon g which thermo-hydraulics of two-phase saturated superfluid helium, efficient cycles and machinery for large-capacity refrigeration at 1.8 K, insulation techniques for series-produced cryostats and mu lti-kilometre long distribution lines, large-current leads using high-temperature superconductors, industrial precision thermometry below 4 K, and novel control techniques applied to strongly non-line ar processes. We review the most salient advances in these domains

Advanced Superconducting Technology for Global Science: The Large Hadron Collider at CERN

The Large Hadron Collider (LHC), presently in construction at CERN, the European Organisation for Nuclear Research near Geneva (Switzerland), will be, upon its completion in 2005 and for the next twenty years, the most advanced research instrument of the world's high-energy physics community, providing access to the energy frontier above 1 TeV per elementary constituent. Re-using the 26.7-km circumference tunnel and infrastructure of the past LEP electron-positon collider, operated until 2000, the LHC will make use of advanced superconducting technology - high-field Nb-Ti superconducting magnets operated in superfluid helium and a cryogenic ultra-high vacuum system - to bring into collision intense beams of protons and ions at unprecedented values of center-of-mass energy and luminosity (14 TeV and 1034 cm-2.s-1, respectively with protons). After some ten years of focussed R&D, the LHC components are presently series-built in industry and procured through world-wide collaboration. After briefly recalling the physics goals, performance challenges and design choices of the machine, we describe its major technical systems, with particular emphasis on relevant advances in the key technologies of superconductivity and cryogenics, and report on its construction progress

Large Cryogenic Helium Refrigeration System for the LHC

In the framework of the Large Hadron Collider (LHC) project, CERN is presently building a large distributed cryogenic system to operate the high-field superconducting magnets of the 26.7 km accelerator in superfluid helium at 1.9 K. Refrigeration will be produced at several temperature levels down to 1.8 K, by eight cryogenic plants with a capacity of 18 kW @ 4.5 K (four of which recovered from the former LEP collider and suitably upgraded), feeding eight 2.4 kW @ 1.8 K refrigeration units using several stages of cold hydrodynamic compressors. After recalling the basics of LHC cryogenics, this paper gives an overview of the refrigeration system, from specification to design and production in industry, as well as status of the project

Helium cryogenic systems for the LEP2 and LHC projects at CERN

CERN is presently operating a large distributed 4.5 K helium cryogenic system (48 [email protected] K equivalent) for cooling the superconducting acceleration cavities of the 26.7 km circumference LEP2 lepton collider. This also constitutes the first part of the 1.8 K cryogenic system (about 150 [email protected] K equivalent) for the future Large Hadron Collider (LHC), the high-field superconducting magnets of which will operate in superfluid helium. We briefly describe the main features of each system, and review the progress of their development, construction and operation

The Large Hadron Collider, A Megascience Project

The Large Hadron Collider (LHC) will be the next particle accelerator built to serve the world's high-energy physics community at CERN, the European Organisation for Nuclear Research. Reusing the 26.7-km circumference tunnel and infrastructure of the existing LEP collider, the LHC will make use of advanced technology - high-field superconducting magnets operated in superfluid helium - to push the energy frontier up by an order of magnitude, while remaining economically feasible. The LHC demonstrates on a grand scale several typical features of megascience projects, such as the need for international funding, world-wide co-operation and integration in the local environment, which we review in the following