Lebrun, P Superconductivity and Cryogenics for Future High-Energy Accelerators High-energy particle accelerators are used to create new forms of matter, probe its structure at very small scales, reproduce in the laboratory very high temperature conditions naturally present in astronomical or cosmological objects, and generate high-brilliance electromagnetic radiation. To accelerate, guide and focus beams of charged particles, they produce electrical and magnetic fields in RF cavities and electromagnets. Economically attaining higher fields is an essential condition for sustaining development of performance while containing increase in size, capital and operating costs. Superconductivity and cryogenics have therefore become and will remain enabling technologies for high-energy accelerators. After discussing the rationale for their use, we present several projects of future machines, under construction or under study, with emphasis on their specific requirements, constraints and adopted solutions. eng 2007

http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=at-2007-004; http://cds.cern.ch/record/1026936/files/at-2007-004.pdf;

Imported from Invenio. Lebrun, P Cryogénie et supraconductivité pour le grand collisionneur de hadrons (LHC) du CERN Rev. Gén. Froid The Large Hadron Collider (LHC), presently in construction at CERN, the European Organization for Nuclear Research near Geneva (Switzerland), will be the most advanced research instrument of the world’s high-energy physics community, providing access to the structure of matter at an unprecedentedly fine scale. Reusing the 26.7 km circumference tunnel and infrastructure of the past LEP electron-positron collider, the LHC makes use of advanced technology: high-field superconducting magnets based on niobium-titanium alloy conductors operating in superfluid helium at 1.9 K will guide and bring into collision intense beams of protons and ions. After some ten years of focussed R&D, the LHC components are being series-built by specialized industry in CERN member states and procured through world-wide collaborations. After briefly recalling the physics goals, performance challenges and design choices, we present main aspects of cryogenics and superconductivity as key technologies for the LHC and report on its construction progress. Résumé Le Grand Collisionneur de Hadrons (Large Hadron Collider ou LHC) en construction au CERN, l´Organisation Européenne pour la Recherche Nucléaire située près de Genève (Suisse), constituera l´instrument le plus avancé de recherche en physique des particules, permettant d´explorer la matière à une échelle sans précédent. Le LHC, qui réutilisera le tunnel circulaire de 26,7 km de circonférence et l´infrastructure technique du collisionneur d´électrons et de positons LEP, est basé sur la cryogénie et la supraconductivité avancées : des aimants supraconducteurs à champ élevé utilisant des conducteurs en alliage de niobium et de titane, fonctionnant dans l´hélium superfluide à 1,9 K permettront de faire circuler et entrer en collision des faisceaux intenses de protons et d´ions de haute énergie. Après une décennie de développement ciblé, les composants du LHC sont produits en série par l´industrie spécialisée, dans les états membres du CERN ainsi qu'à travers des collaborations internationales avec d'autres régions du monde. Un bref rappel des buts de recherche, des défis et des choix techniques permettra de présenter les aspects principaux des technologies clés que constituent la cryogénie et la supraconductivité, et de mentionner l’état d’avancement du projet. eng 2004

http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhcproj-2004-802; http://cds.cern.ch/record/811057/files/lhc-project-report-802.pdf;

Imported from Invenio. Lebrun, P Industrial Technology for Unprecented Energy and Luminosity: The Large Hadron Collider With over 3 billion Swiss francs procurement contracts under execution in industry and the installation of major technical systems in its first 3.3 km sector, the Large Hadron Collider (LHC) construction is now in full swing at CERN, the European Organization for Nuclear Research. The LHC is not only the most challenging particle accelerator, it is also the largest global project ever for a scientific instrument based on advanced technology. Starting from accelerator performance requirements, we recall how these can be met by an appropriate combination of technologies, such as high-field superconducting magnets, superfluid helium cryogenics, power electronics, with particular emphasis on developments required to meet demanding specifications, and industrialization issues which had to be solved for achieving series production of precision components under tight quality assurance and within limited resources. This provides the opportunity for reviewing the production status of the main systems and the progress of the project. eng 2004

http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhcproj-2004-745; http://cds.cern.ch/record/788536/files/lhc-project-report-745.pdf;

Imported from Invenio. Lebrun, P 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. eng 2007

http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=at-2007-001; http://cds.cern.ch/record/1012032/files/at-2007-001.pdf;

Imported from Invenio. Lebrun, P Cryogenics, Key to Advanced Science and Technology More than a complete overview of cryogenics today, this brief paper aims at presenting its continuing relation with advanced science and technology, not only as ancillary, but also in many instances as a central technique driving the development of ideas as much as the practical achievements. Its intellectually demanding and technically challenging nature in a variety of disciplines also make it an excellent training ground for technicians, engineers and applied physicists. eng 2003

http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=at-2003-005; http://cds.cern.ch/record/639631/files/at-2003-005.pdf; http://cds.cern.ch/record/639631/files/at-2003-005.ps.gz;

Imported from Invenio. Lebrun, Ph Leroy, D Morpurgo, M Perin, R Schmid, J Preliminary cost estimate of LHC magnet and cryogenics system eng CERN-LHC; superconducting-magnets; costs; 1987

http://cds.cern.ch/record/68632/files/INTERNAL-NOTE-EMA-87-14.pdf;

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Imported from Invenio. Lebrun, P Accelerator Technology Division, AT: AT Divisional Reports, 1990-1992 fre
https://library.web.cern.ch/archives/CERN_archive/guide/accelerators/LHC/isalhc;
Imported from Invenio. Bézaguet, Alain-Arthur Dauvergne, J P Knoops, S Lebrun, P Pezzetti, M Pirotte, O Bret, J L Chabaud, B Garde, G Guttin, C Hébral, B Pietropinto, S Roche, P Barbier-Neyret, J P Baudet, C Gagne, Y Poulain, C Castaing, B Ladam, Y Vittoz, F A Cryogenic High-Reynolds Turbulence Experiment at CERN AIP Conf. Proc. 1399-1406 613 The potential of cryogenic helium flows for studying high-Reynolds number turbulence in the laboratory has been recognised for a long time and implemented in several small-scale hydrodynamic experiments. With its large superconducting particle accelerators and detector magnets, CERN, the European Laboratory for Particle Physics, has become a major world center in helium cryogenics, with several large helium refrigerators having capacities up to 18 kW @ 4.5 K. Combining a small fraction of these resources with the expertise of three laboratories at the forefront of turbulence research, has led to the design, swift implementation, and successful operation of GReC (Grands Reynolds Cryogéniques) a large axisymmetric turbulent-jet experiment. With flow-rates up to 260 g/s of gaseous helium at ~ 5 K and atmospheric pressure, Reynolds numbers up to 107 have been achieved in a 4.6 m high, 1.4 m diameter cryostat. This paper presents the results of the first runs and describes the experimental set-up comprehensively equipped with "hot" wire micro-anemometers, acoustic scattering vorticity measurements and a large-bandwidth data acquisition system. eng 2002
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-2001-006; http://cds.cern.ch/record/525104/files/lhc-2001-006.pdf; http://cds.cern.ch/record/525104/files/lhc-2001-006.ps.gz;
Imported from Invenio. Lebrun, P Superconducting Technology for Particle Accelerators eng 2001 2001 ed.
http://agenda.cern.ch/fullAgenda.php?ida=a034571; http://agenda.cern.ch/tools/SSLPdisplay.php?stdate=2001-07-01&nbweeks=7;
Imported from Invenio. Claudet, S Lebrun, P Tavian, L Towards Cost-To-Performance Optimisation of Large Superfluid Helium Refrigeration Systems The field range of superconducting devices may be extended by lowering their operating temperature, using superfluid helium refrigeration systems which have to deliver working pressures down to 1.6 kPa. The corresponding pressure ratio can be produced by integral cold compression or using a combination of cold compressors in series together with "warm" compressors at room temperature. The optimisation of such a system depends on the number, arrangement and characteristics of cold and warm machines as well as on the operating scenario and turndown capability. The aim of this paper is to compare relative investment and operating costs of different superfluid helium cryogenic systems, with the aim of optimising their cost-to-performance ratio within the constraints of their operating scenario. eng 2000
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-391; http://cds.cern.ch/record/449274/files/lhc-project-report-391.pdf; http://cds.cern.ch/record/449274/files/lhc-project-report-391.ps.gz;
Imported from Invenio. Vinen, W F Lebrun, Philippe Superfluid helium: physics and applications The behaviour of liquid helium is dominated by quantum effects, which give rise to superfluidity at low temperatures. An account will be given of the observed properties of the superfluid phase of liquid 4He, and of the way in which these properties can be described by a two-fluid model, supplemented by the requirement that motion of the superfluid component be irrotational with a hydrodynamic circulation that is quantized in units of h/m4. The existence of superfluidity and the quantization of circulation will be related to the presence of a Bose condensate. The description of excited states of the liquid in terms of weakly interacting thermal excitations (phonons and rotons will be discussed, and the relation between these excitations and the normal-fluid component will be explained. The existence and role of quantized vortex lines in the superfluid component will be discribed. A brief account will be included of topics of current research interest. eng academic training; superfluidity; helium; Academic training lecture; Superfluidity; Helium; CERN Geneva 1999
http://preprints.cern.ch/cgi-bin/setlink?base=AT&categ=Academic_Training&id=AT00000609; http://preprints.cern.ch/cgi-bin/setlink?base=AT&categ=Academic_Training&id=AT00000610; http://cds.cern.ch/record/385851/files/AT00000609.tif; http://cds.cern.ch/record/385851/files/AT00000610.tif; MP4; https://cern.ch/digital-memory/media-archive/video/open/mp4/385851-b.mp4; MP4; https://cern.ch/digital-memory/media-archive/video/open/mp4/385851-e.mp4; MP4; https://cern.ch/digital-memory/media-archive/video/open/mp4/385851-c.mp4; MP4; https://cern.ch/digital-memory/media-archive/video/open/mp4/385851-d.mp4;
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Imported from Invenio. Lebrun, P Advanced Superconducting Technology for Global Science: The Large Hadron Collider at CERN AIP Conf. Proc. 3-14 613 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. eng 2002
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-499; http://cds.cern.ch/record/517571/files/lhc-project-report-499.pdf; http://cds.cern.ch/record/517571/files/lhc-project-report-499.ps.gz;
Imported from Invenio. Lebrun, P 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. eng 2000
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-441; http://cds.cern.ch/record/473537/files/lhc-project-report-441.pdf; http://cds.cern.ch/record/473537/files/lhc-project-report-441.ps.gz;
Imported from Invenio. Saji, N Asakura, H Yoshinaga, S Itoh, K Nogaku, T Bézaguet, Alain-Arthur Casas-Cubillos, J Lebrun, P Tavian, L A one kPa centrifugal cold compressor for the 1.8 K helium refrigeration system of LHC CERN placed an order for a cold compressor prototype (CCP) with IHI for the LHC project. The CCP is supported by the oil-free magnetic bearings, driven by an induction motor. The compressor has the characteristics of high efficiency and wide operation range, thanks to the optimum design for the impeller and diffuser. The result of the performance tests at CERN showed that static heat in-leaks could be controlled at approx. 7.3 W, and an adiabatic efficiency is 75at a nominal flow of 18 g's with suction temperature of 4.4 K and suction pressure of 1 kPa. (4 refs). eng 1998
Imported from Invenio. Lebrun, P 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. eng 2001
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-374; http://cds.cern.ch/record/433552/files/lhc-project-report-374.pdf; http://cds.cern.ch/record/433552/files/lhc-project-report-374.ps.gz;
Imported from Invenio. Lebrun, P 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. eng 1999 1999 ed.
http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=LHC-Project-Report-338; http://cds.cern.ch/record/411139/files/lhc-project-report-338.pdf; http://cds.cern.ch/record/411139/files/lhc-project-report-338.ps.gz;
Imported from Invenio. Chorowski, M Lebrun, P Riddone, G Preliminary Risk Analysis of the LHC Cryogenic System (CERN-LHC-Project-Report-324) The Large Hadron Collider (LHC), presently under construction at CERN, will require a helium cryogenic system unprecedented in size and capacity, with more than 1600 superconducting magnets operating in superfluid helium and a total inventory of almost 100 tonnes of helium. The objective of the Preliminary Risk Analysis (PRA) is to identify all risks to personnel, equipment or environment resulting from failures that may accidentally occur within the cryogenic system of LHC in any phase of the machine operation, and that could not be eliminated by design. Assigning a gravity coefficient and one analyzing physical processes that will follow any of the recognised failure modes allows to single out worst case scenarios. Recommendations concerning lines of preventive and corrective defence, as well as for further detailed studies, are formulated. eng 1999
http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=LHC-Project-Report-324; http://cds.cern.ch/record/410385/files/lhc-project-report-324.pdf; http://cds.cern.ch/record/410385/files/lhc-project-report-324.ps.gz;
Imported from Invenio. Claudet, S Gayet, P Lebrun, P Tavian, L Wagner, U Economics of Large Helium Cryogenic Systems: experience from Recent Projects at CERN Large projects based on applied superconductivity, such as particle accelerators, tokamaks or SMES, require powerful and complex helium cryogenic systems, the cost of which represents a significant, if not dominant fraction of the total capital and operational expenditure. It is therefore important to establish guidelines and scaling laws for costing such systems, based on synthetic estimators of their size and performance. Although such data has already been published for many years, the experience recently gathered at CERN with the LEP and LHC projects, which have de facto turned the laboratory into a major world cryogenic center, can be exploited to update this information and broaden the range of application of the scaling laws. We report on the economics of 4.5 K and 1.8 K refrigeration, cryogen distribution and storage systems, and indicate paths towards their cost-to-performance optimisation. eng 1999
http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=LHC-Project-Report-317; http://cds.cern.ch/record/410378/files/lhc-project-report-317.pdf; http://cds.cern.ch/record/410378/files/lhc-project-report-317.ps.gz;
Imported from Invenio. Byrns, R A Huang, Y Kerby, J S Lebrun, P Morrison, L Nicol, T H Peterson, T Trant, R Van Weelderen, R Zbasnik, J The Cryogenics of the LHC Interaction Region Final Focus Superconducting Magnets The LHC interaction region final focus magnets will include four superconducting quadrupoles cooled with pressurized, static superfluid helium at 1.9 K. The heat absorbed in pressurized He II, which m ay be more than 10 Watts per meter due to dynamic heating from the particle beam halo, will be transported to saturated He II at 1.8 K and removed by the 16 mbar vapor. This paper discusses the concep tual design for the cryogenics of the interaction region final focus superconducting magnets and the integration of this magnet system into the overall LHC cryogenic system. eng 1998
http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=LHC-PROJECT-REPORT-219; http://cds.cern.ch/record/365289/files/lhc-project-report-219.pdf; http://cds.cern.ch/record/365289/files/lhc-project-report-219.ps.gz;
Imported from Invenio. Lebrun, P Riddone, G Tavian, L Wagner, U Cooldown and Warmup Studies for the Large Hadron Collider The Large Hadron Collider (LHC), currently under construction at CERN, will make use of superconducting magnets operating in superfluid helium below 2 K. The LHC ring is divided in 8 sectors, each of them cooled by a refrigerator of 18 kW at 4.5 K equivalent cooling power. For the cooldown and warmup of a 3.3 km long LHC sector, the flow available above 80 K per refrigerator is 770 g/s and the cor responding capacity is 600 kW. This paper presents the results of cooldown and warmup simulations, as concerns time delays, temperature difference across magnets, available power and flow-rates, and estimates of energy and liquid nitrogen consumption. eng 1998
http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=LHC-PROJECT-REPORT-214; http://cds.cern.ch/record/365281/files/lhc-project-report-214.pdf; http://cds.cern.ch/record/365281/files/lhc-project-report-214.ps.gz;
Imported from Invenio. Lebrun, P 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. eng 2003
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhcproj-2003-629; http://cds.cern.ch/record/605468/files/lhc-project-report-629.pdf; http://cds.cern.ch/record/605468/files/lhc-project-report-629.ps.gz;
Imported from Invenio. Bézaguet, Alain-Arthur Lebrun, P Tavian, L Performance Assessment of Industrial Prototype Cryogenic Helium Compressors for the Large Hadron Collider In order to develop the technology of large-capacity refrigeration at superfluid helium temperature, essential for the LHC project, CERN has procured from industry three prototype single-stage hydrody namic cryogenic helium compressors, based on different construction choices, and tested them in the laboratory. After recalling the common functional specification, as well as the main design features of the three machines, we present comparative performance results, and draw conclusions as concerns future full-scale machines for the LHC. eng 1998
http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=LHC-PROJECT-REPORT-213; http://cds.cern.ch/record/364735/files/lhc-project-report-213.pdf; http://cds.cern.ch/record/364735/files/lhc-project-report-213.ps.gz;
Imported from Invenio. Hatchadourian, E Lebrun, P Tavian, L Supercritical Helium Cooling of the LHC Beam Screens The cold mass of the LHC superconducting magnets, operating in pressurised superfluid helium at 1.9 K, must be shielded from the dynamic heat loads induced by the circulating particle beams, by means of beam screens maintained at higher temperature. The beam screens are cooled between 5 and 20 K by forced flow of weakly supercritical helium, a solution which avoids two-phase flow in the long, narr ow cooling channels, but still presents a potential risk of thermohydraulic instabilities. This problem has been studied by theoretical modelling and experiments performed on a full-scale dedicated te st loop. eng 1998
http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=LHC-PROJECT-REPORT-212; http://cds.cern.ch/record/364733/files/lhc-project-report-212.pdf; http://cds.cern.ch/record/364733/files/lhc-project-report-212.ps.gz;
Imported from Invenio. Lebrun, P 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. eng 1998
http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=LHC-PROJECT-REPORT-211; http://cds.cern.ch/record/364732/files/lhc-project-report-211.pdf; http://cds.cern.ch/record/364732/files/lhc-project-report-211.ps.gz;
Imported from Invenio. Chorowski, M Lebrun, P Serio, L Van Weelderen, R Thermohydraulics of Quenches and Helium Recovery in the LHC Magnet Strings Cryogenics 533-543 38 In preparation for the Large Hadron Collider project, a 42.5 m-long prototype superconducting magnet string, representing a half-cell of the machine lattice, has been built and operated. A series of tests was performed to assess the thermohydraulics of resistive transitions (quenches) of the superconducting magnets. These measurements provide the necessary foundation for describing the observed evolution of the helium in the cold mass and formulating a mathematical model based on energy conservation. The evolution of helium after a quench simulated with the model reproduces the observations. We then extend the simulations to a full LHC cell, and finally analyse the recovery of helium discharged from the cold mass. eng 1997
http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=LHC-PROJECT-REPORT-154; http://cds.cern.ch/record/341094/files/lhc-project-report-154.pdf; http://cds.cern.ch/record/341094/files/lhc-project-report-154.ps.gz;
Imported from Invenio. Decker, L Kündig, A Löhlein, K Purtschert, W Ziegler, B L Lebrun, P Tavian, L Brunovsky, I Tucek, L Operational Experience with a Cryogenic Axial-Centrifugal Compressor Adv. Cryog. Eng., A 637-641 43 The Large Hadron Collider (LHC), presently under construction at CERN, requires large refrigeration capacity at 1.8 K. Compression of gaseous helium at cryogenic temperatures is therefore inevitable. Together with subcontractors, Linde Kryotechnik has developed a prototype machine. This unit is based on a cryogenic axial-centrifugal compressor, running on ceramic ball bearings and driven by a variable-frequency electrical motor operating at ambient temperature. Integrated in a test facility for superconducting magnets the machine has been commissioned without major problems and successfully gone through the acceptance test in autumn 1995. Subsequent steps were initiated to improve efficiency of this prototype. This paper describes operating experience gained so far and reports on measured performance prior to and after constructional modifications. eng 1998
http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=LHC-PROJECT-REPORT-161; http://cds.cern.ch/record/340506/files/lhc-project-report-161.pdf; http://cds.cern.ch/record/340506/files/lhc-project-report-161.ps.gz;
Imported from Invenio. Lebrun, P Serio, L Tavian, L Van Weelderen, R Cooling Strings of Superconducting Devices below 2 K: the Helium II Bayonet Heat Exchanger Adv. Cryog. Eng., A 419-426 43 High-energy particle accelerators and colliders contain long strings of superconducting devices - acceleration RF cavities and magnets - operating at high field, which may require cooling in helium II below 2 K. In order to maintain adequate operating conditions, the applied or generated heat loads must be extracted and transported with minimum temperature difference. Conventional cooling schemes based on conductive or convective heat transport in pressurized helium II very soon reach their intrinsic limits of thermal impedance over extended lengths. We present the concept of helium II bayonet heat exchanger, which has been developed at CERN for the magnet cooling scheme of the Large Hadron Collider (LHC), and describe its specific advantages as a slim, quasi-isothermal heat sink. Experimental results obtained on several test set-ups, and a prototype magnet string have permitted to validate its performance and sizing rules, for transporting linear heat loads in the W.m-1 range over distances of several tens of meters. eng 1998
http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=LHC-PROJECT-REPORT-144; http://cds.cern.ch/record/336315/files/lhc-project-report-144.pdf; http://cds.cern.ch/record/336315/files/lhc-project-report-144.ps.gz;
Imported from Invenio. Chorowski, M Erdt, W K Lebrun, P Riddone, G Serio, L Tavian, L Wagner, U Van Weelderen, R A Simplified Cryogenic Distribution Scheme for the Large Hadron Collider Adv. Cryog. Eng., A 395-402 43 The Large Hadron Collider (LHC), currently under construction at CERN, will make use of superconducting magnets operating in superfluid helium below 2 K. The reference cryogenic distribution scheme was based, in each 3.3 km sector served by a cryogenic plant, on a separate cryogenic distribution line which feeds elementary cooling loops corresponding to the length of a half-cell (53 m). In order to decrease the number of active components, cryogenic modules and jumper connections between distribution line and magnet strings a simplified cryogenic scheme is now implemented, based on cooling loops corresponding to the length of a full-cell (107 m) and compatible with the LHC requirements. Performance and redundancy limitations are discussed with respect to the previous scheme and balanced against potential cost savings. eng 1998
http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=LHC-PROJECT-REPORT-143; http://cds.cern.ch/record/336314/files/lhc-project-report-143.pdf; http://cds.cern.ch/record/336314/files/lhc-project-report-143.ps.gz;
Imported from Invenio. Lebrun, P Superfluid helium as a technical coolant The characteristics of superfluid helium as a technical coolant, which derive from its specific transport properties, are presented with particular reference to the working area in the phase diagram (saturated or pressurised helium II). We then review the principles and scaling laws of heat transport by equivalent conduction and by forced convection in pressurised helium II, thus revealing intrinsic limitations as well as technological shortcomings of these cooling methods. Once properly implemented, two-phase flow of saturated helium II presents overwhelming advantages over the previous solutions, which dictated its choice for cooling below 1.9 K the long strings of superconducting magnets in the Large Hadron Collider (LHC), a 26.7 km circumference particle collider now under construction at CERN, the European Laboratory for Particle Physics near Geneva (Switzerland). We report on recent results from the ongoing research and development programme conducted on thermohydraulics of two-phase saturated helium II flows, and on the validation of design choices for the LHC cooling system. eng 1997
http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=LHC-PROJECT-REPORT-125; http://cds.cern.ch/record/330851/files/lhc-project-report-125.pdf;
Imported from Invenio. Benda, V Dauvergne, J P Haug, F Knoops, S Lebrun, P Momal, F Sergo, S Tavian, L Vullierme, B Upgrade of the CERN Cryogenic Station for Superfluid Helium Testing of Prototype LHC Superconducting Magnets eng 1997
http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=LHC-PROJECT-REPORT-20; http://cds.cern.ch/record/326937/files/lhc-project-report-20.pdf;
Imported from Invenio. Lebrun, P Riddone, G Tavian, L Wagner, U Demands in refrigeration capacity for the Large Hadron Collider eng 1997
http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=.&id=CERN-LHC-PROJECT-REPORT-18; http://cds.cern.ch/record/315773/files/lhc-project-report-18.pdf; http://cds.cern.ch/record/315773/files/lhc-project-report-18.ps.gz; http://cds.cern.ch/record/315773/files/lhc-project-report-18.tif;
Imported from Invenio. Benda, V Bézaguet, Alain-Arthur Casas-Cubillos, J Claudet, S Erdt, W K Lebrun, P Riddone, G Sergo, V Serio, L Tavian, L Vullierme, B Van Weelderen, R Wagner, U Conceptual design of the cryogenic system for the Large Hadron Collider (LHC) eng 1996
http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=CERN-LHC-PROJECT-REPORT-12; https://accelconf.web.cern.ch/e96/abstracts/leb4165.pdf; https://accelconf.web.cern.ch/e96/PAPERS/ORALS/THO04A.PDF; http://cds.cern.ch/record/310033/files/lhc-project-report-12.pdf; http://cds.cern.ch/record/310033/files/lhc-project-report-12.ps.gz;
Imported from Invenio. Ferlin, G Jenninger, B Lebrun, P Peón-Hernández, G Riddone, G Szeless, Balázs Comparison of floating and thermalized multilayer insulation systems at low boundary temperature The Large Hadron Collider (LHC) is 26.7 km circumference particle collider using high-field superconducting magnets operating in superfluid helium. An efficient and robust thermal insulation system is therefore required to minimize the residual heat in leak to the large surface area at 1.9 K constituted by the stainless steel wall of the helium enclosure. The baseline solution uses "floating" multilayer reflective insulation. Moreover, an alternative consists of a combination of multilayer reflective films and a soft screen, partially thermalized to the 5 K level and supported away from the cold wall by net-type insulating spacers. This chapter establishes the improvement potential of the alternative over the baseline solution, and compares their insulation performance on the basis of measured characteristics of thermal contacts and spacers. eng 1997
http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=CERN-LHC-PROJECT-REPORT-21; http://cds.cern.ch/record/310032/files/lhc-project-report-21.pdf; http://cds.cern.ch/record/310032/files/lhc-project-report-21.ps.gz; http://cds.cern.ch/record/310032/files/lhc-project-report-21.tif;
Imported from Invenio. Bézaguet, Alain-Arthur Casas-Cubillos, J Guinaudeau, H Hilbert, B Lebrun, P Serio, L Suraci, A Van Weelderen, R Cryogenic operation and testing of the extended LHC prototype magnet string After the assembly, commissioning and successful first operation of a full-scale superconducting magnet string, and as a new prototype dipole magnet was added to approach final configuration, the cryogenic system has been slightly modified to allow the verification of the performance of the superfluid helium cooling loop in counter-current two-phase flow. At the same time the control system strategies have been updated and only two quench relief valves have been installed, one at each end of the string. We report on the cryogenic operation of the extended version of the string and the response of the system to transients. eng 1997
http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=CERN-LHC-PROJECT-REPORT-23; http://cds.cern.ch/record/308240/files/lhc-project-report-23.pdf; http://cds.cern.ch/record/308240/files/lhc-project-report-23.ps.gz; http://cds.cern.ch/record/308240/files/lhc-project-report-235.cover_LHCpr235.ps.gz;
Imported from Invenio. Decker, L Löhlein, K Schustr, P Vins, M Brunovsky, I Lebrun, P Tavian, L A cryogenic axial-centrifugal compressor for superfluid helium refrigeration CERN's new project, the Large Hadron Collider (LHC), will use superfluid helium as coolant for its high-field superconducting magnets and therefore require large capacity refrigeration at 1.8 K. This may only be achieved by subatmospheric compression of gaseous helium at cryogenic temperature. To stimulate development of this technology, CERN has procured from industry prototype Cold Compressor Units (CCU). This unit is based on a cryogenic axial-centrifugal compressor, running on ceramic ball bearings and driven by a variable-frequency electrical motor operating under low-pressure helium at ambient temperature. The machine has been commissioned and is now in operation. After describing basic constructional features of the compressor, we report on measured performance. eng 1997
http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=CERN-LHC-PROJECT-REPORT-22; http://cds.cern.ch/record/308239/files/lhc-project-report-22.pdf; http://cds.cern.ch/record/308239/files/lhc-project-report-22.ps.gz;
Imported from Invenio. Bézaguet, Alain-Arthur Brahy, D Casas-Cubillos, J Coull, L Cruikshank, P Dahlerup-Petersen, K Faugeras, Paul E Flemsæter, B Guinaudeau, H Hagedorn, Dietrich Hilbert, B Krainz, G Kos, N Lavielle, D Lebrun, P Leo, G Mathewson, A G Missiaen, D Momal, F Parma, Vittorio Quesnel, Jean Pierre Richter, D Riddone, G Rijllart, A Rodríguez-Mateos, F Rohmig, P Saban, R I Schmidt, R Serio, L Skiadelli, M Suraci, A Tavian, L Walckiers, L Wallén, E Van Weelderen, R Williams, L McInturff, A The LHC test string: first operational experience CERN operates the first version of the LHC Test String which consists of one quadrupole and three 10-m twin aperture dipole magnets. An experimental programme aiming at the validation of the LHC systems started in February 1995. During this programme the string has been powered 100 times 35 of which at 12.4 kA or above. The experiments have yielded a number of results some of which, like quench recovery for cryogenics, have modified the design of subsystems of LHC. Others, like controlled helium leaks in the cold bore and quench propagation bewteen magnets, have given a better understanding on the evolution of the phenomena inside a string of superconducting magnets cooled at superfluid helium temperatures. Following the experimental programme, the string will be powered up and powered down in one hour cycles as a fatigue test of the structure thus simulating 20 years of operation of LHC. eng 1996
http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=CERN-LHC-PROJECT-REPORT-32; https://accelconf.web.cern.ch/e96/abstracts/sab2197.pdf; https://accelconf.web.cern.ch/e96/PAPERS/ORALS/WEO07A.PDF; http://cds.cern.ch/record/307374/files/lhc-project-report-32.pdf; http://cds.cern.ch/record/307374/files/lhc-project-report-32.ps.gz; http://cds.cern.ch/record/307374/files/WEO07A.PDF;
Imported from Invenio. Pietropinto, S Baudet, C Castaing, B Chabaud, B Gagne, Y Hébral, B Ladam, Y Lebrun, P Pirotte, O Poulain, C Roche, P E Low Temperature Gaseous Helium and very High Turbulence Experiments Cryogenic gaseous helium gives access to extreme turbulent experimental conditions. The very high cooling helium flow rates available at CERN have been used to reach Reynolds numbers up to Re ~ 10**7 in a round jet experiment. First results are discussed. eng 2002
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-2002-014; http://cds.cern.ch/record/593265/files/lhc-2002-014.pdf; http://cds.cern.ch/record/593265/files/lhc-2002-014.ps.gz;
Imported from Invenio. Lebrun, P Tavian, L Vandoni, Giovanna Wagner, U Cryogenics for Particle Accelerators and Detectors Cryogenics has become a key ancillary technology of particle accelerators and detectors, contributing to their sustained development over the last fifty years. Conversely, this development has produced new challenges and markets for cryogenics, resulting in a fruitful symbiotic relation which materialized in significant technology transfer and technical progress. This began with the use of liquid hydrogen and deuterium in the targets and bubble chambers of the 1950s, 1960s and 1970s. It developed more recently with increasing amounts of liquefied noble gases - mainly argon, but also krypton and even today xenon - in calorimeters. In parallel with these applications, the availability of practical type II superconductors from the early 1960s triggered the use of superconductivity in large spectrometer magnets - mostly driven by considerations of energy savings - and the corresponding development of helium cryogenics. It is however the generalized application of superconductivity in particle accelerators - RF acceleration cavities and high-field bending and focusing magnets - which has led to the present expansion of cryogenics, with kilometer-long strings of helium-cooled devices, powerful and efficient refrigerators and superfluid helium used in high tonnage as cooling medium. This situation was well reflected over the last decades by the topical courses of the CERN Accelerator School (CAS). In 1988, CAS and DESY jointly organized the first school on Superconductivity in Particle Accelerators, held at Haus Rissen in Hamburg, where I shared the h. and duty of lecturing on cryogenics with Professor J.L. Olsen of ETH Z rich, while P. Seyfert of CEA Grenoble delivered an evening seminar on superfluidity. This successful school was reiterated in 1995, with cryogenics being addressed by Professor W.F. Vinen of University of Birmingham (superfluidity), as well as J. Schmid (thermodynamics and refrigeration) and myself (superfluid helium technology) of CERN. In the CAS School on Superconductivity and Cryogenics for Particle Accelerators and Detectors held in May 2002 in Erice, Sicily, I am particularly pleased to see a more complete syllabus in cryogenics, most of which is covered by CERN colleagues and published in this report. This is in my view, another sign of the development and vitality of this discipline at CERN, primarily in the LHC division which, by virtue of its mandate and competence, is presently building the largest helium cryogenic system in the world for the Large Hadron Collider and its experiments. I hope this report constitutes a useful source of information and updated reference for our staff dedicated to this formidable endeavour. eng 2002
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-2002-011; http://cds.cern.ch/record/592467/files/lhc-2002-011.pdf; http://cds.cern.ch/record/592467/files/lhc-2002-011.ps.gz;
Imported from Invenio.