Design of the Second Series of LHC Prototype Dipole Magnet Cryostats

Brunet, J.-C.; Parma, V.; Peón, G.; Poncet, A.; Rohmig, P.; Skoczen, B.; Williams, L. R.

doi:10.1007/978-1-4757-9047-4_52

Cited by 15 publications

(6 citation statements)

References 5 publications

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“…A full-scale thermal model, equipped with a dummy cold mass and heavily instrumented, confirmed the effectiveness of the multilayer system in degraded vacuum [14]. An experimental comparison of floating and thermalized multilayer systems at low boundary temperature [15] established the moderate potential gain of thermalization at 4.5 K. This solution was implemented in the second-series LHC prototype cryostats, 15-m long, which no longer housed the cryogenic distribution pipelines [16]. Trading moderate improvement of technical performance against complexity and cost, the 4.5 K thermalization of the multilayer system was finally not retained for the 1232 series cryostats [17].…”

Section: Development Of He II Cryostats For Accelerator Systemsmentioning

confidence: 88%

Does one need a 4.5 K screen in cryostats of superconducting accelerator devices operating in superfluid helium? lessons from the LHL

Lebrun¹,

Parma²,

Tavian³

2014

AIP Conference Proceedings

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Abstract. Superfluid helium is increasingly used as a coolant for superconducting devices in particle accelerators: the lower temperature enhances the performance of superconductors in high-field magnets and reduces BCS losses in RF acceleration cavities, while the excellent transport properties of superfluid helium can be put to work in efficient distributed cooling systems. The thermodynamic penalty of operating at lower temperature however requires careful management of the heat loads, achieved inter alia through proper design and construction of the cryostats. A recurrent question appears to be that of the need and practical feasibility of an additional screen cooled by normal helium at around 4.5 K surrounding the cold mass at about 2 K, in such cryostats equipped with a standard 80 K screen. We introduce the issue in terms of first principles applied to the configuration of the cryostats, discuss technical constraints and economical limitations, and illustrate the argumentation with examples taken from large projects confronted with this issue, i.e.

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Section: Development Of He II Cryostats For Accelerator Systemsmentioning

confidence: 88%

Does one need a 4.5 K screen in cryostats of superconducting accelerator devices operating in superfluid helium? lessons from the LHL

Lebrun¹,

Parma²,

Tavian³

2014

AIP Conference Proceedings

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“…The latter are mostly intercepted by the beam screens equipping the magnet apertures, cooled by circulation of supercritical helium between 5 and 20 K. In comparison with the above, the large transient heat loads produced by magnetic hysteresis and eddy current dissipation during current ramp and discharge can only be buffered by the heat capacity of the 15 l/m helium in the magnet cold mass. The cryostats [18] and cryogenic distribution line [7] combine several low-temperature insulation and heat interception techniques which will have to be reliably implemented on an industrial scale ( Figure 6). These include low-conduction support posts made of non-metallic glassfibre/epoxy composite [19], low-impedance thermal contacts under vacuum for heat intercepts and multi-layer reflective insulation wrapping the some 80'000 m 2 of cold surface area below 20 K [20].…”

Section: Superfluid-helium Magnet Cooling Schemementioning

confidence: 99%

Cryogenics for the Large Hadron Collider

Lebrun

2000

IEEE Trans. Appl. Supercond.

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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. 1 Abstract--The Large Hadron Collider (LHC), a 26.7 km circumference superconducting accelerator equipped with highfield 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 twophase saturated superfluid helium removes the heat load from the 36'000 ton cold mass, immersed in some 400 m 3 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.

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“…Two support points are sufficient for the shorter (6 m) and lighter (6,000 kg) cold mass of the SSS to keep the maximum vertical self weight sagitta below 0.25 mm. Further details on the cryostat assemblies can be found in Reference 7,8 .…”

Section: System Design Layoutmentioning

confidence: 99%

Supporting Systems from 293 K to 1.9 K for the Large Hadron Collider (LHC) Cryo-Magnets

Mathieu

Parma

Renaglia

et al. 1998

Advances in Cryogenic Engineering

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The LHC machine will incorporate some 2000 main ring super-conducting magnets cooled at 1.9 K by super-fluid pressurized helium, mainly 15m-long dipoles with their cryostats and 6m-long quadrupoles housed in the Short Straight Section (SSS) units. This paper presents the design of the support system of the LHC arc cryo-magnets between 1.9 K at the cold mass and 293 K at the cryostat vacuum vessel. The stringent positioning precision for magnet alignment and the high thermal performance for cryogenic efficiency are the main conflicting requirements, which have lead to a trade-off design. The systems retained for LHC are based on column-type supports positioned in the vertical plane of the magnets inside the cryostats. An ad-hoc design has been achieved both for cryo-dipoles and SSS. Each column is composed of a main tubular thin-walled structure in composite material (glass-fibre/epoxy resin, for its low thermal conductivity properties), interfaced to both magnet and cryostat via stainless steel flanges. The thermal performance of the support is improved by intercepting part of the conduction heat at two intermediate temperature levels (one at 50-75 K and the other at 4.5-20 K). These intercepts, on the composite column, are thermally connected to the helium gas cooled thermal shield and radiation screen of the cryomagnet. An overview of the design requirements is given, together with an appreciation of the system design. Particular attention is dedicated to the support system of the SSS where the positioning precision of the quadrupole magnet is the most critical.

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Design of the Second Series of LHC Prototype Dipole Magnet Cryostats

Cited by 15 publications

References 5 publications

Does one need a 4.5 K screen in cryostats of superconducting accelerator devices operating in superfluid helium? lessons from the LHL

Does one need a 4.5 K screen in cryostats of superconducting accelerator devices operating in superfluid helium? lessons from the LHL

Cryogenics for the Large Hadron Collider

Supporting Systems from 293 K to 1.9 K for the Large Hadron Collider (LHC) Cryo-Magnets

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