Measurement and Analysis of Thermal Performance of LHC Prototype Cryostats

Benda, V.; Dufay, L.; Ferlin, G.; Lebrun, Philippe; Rieubland, J. M.; Riddone, G.; Szeless, B.; Tavian, L.; Williams, L. R.

doi:10.1007/978-1-4613-0373-2_101

Cited by 8 publications

(9 citation statements)

References 1 publication

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“…The heat inleak from the thermal shield was also reduced by cooling it with gaseous helium at 50-70 K instead of liquid nitrogen [13]. 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].…”

Section: Development Of He II Cryostats For Accelerator Systemsmentioning

confidence: 89%

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: 89%

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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“…Applying this model to a 15-m long LHC dipole cryostat, we can find the range of validity of values of R cp and r cm for which a thermalized system performs better than floating multilayer insulation. Figure 3 shows the break-even lines comparing with the 10-layer system of type B in reference [4], which presently equips the LHC prototype cryomagnets [6][7][8], assuming an emissivity of the soft screen of 0.05 in the 5 to 30 K range. The surface covered by the spacers has been considered equivalent to 25 % of the total cold mass area.…”

Section: Potential Of a Thermalized Multilayer Insulation Systemmentioning

confidence: 99%

“…At 10 -4 Pa the residual heat flux to the cold mass as low as 30 mW/m2 can in principle be achieved. An actively cooled screen will be mounted in a full-scale thermal model [7,8] and heat inleak measurements will be carried out in order to confirm sample measurements and predicted performance. …”

Section: Comparative Performancementioning

confidence: 99%

“…First results [4] confirmed the advantage of multilayer systems over single reflective surfaces for coping with degraded insulation vacuum, a situation bound to happen locally over the circumference of the machine, and further tests [5] sought to improve the performance of "floating" multilayer systems by limiting parasitic conduction between layers. Cryostats for prototype cryomagnets [6] and a full-size thermal model [7] were built in industry and operated with such an insulation system, bringing a real-scale verification of the thermal performance measured on samples and thus validating thermal budget estimates for the LHC [8]. In view of the importance of this source of heat inleak to the 1.9 K level, we investigate in the following the potential of improvement presented by an alternative combining multilayer reflective films and a soft screen, actively thermalized to the 5 K level and supported away from the cold wall by net-type insulating spacers.…”

Section: Introductionmentioning

confidence: 99%

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Comparison of Floating and Thermalized Multilayer Insulation Systems at Low Boundary Temperature

Ferlin

Jenninger

Lebrun

et al. 1997

Proceedings of the Sixteenth International Cryogenic Engineering Conference/International Cryogenic Materials Conference

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The Large Hadron Collider (LHC) will be a 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 minimise the residual heat inleak 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. 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. We establish the improvement potential of the alternative over the baseline solution, and compare their insulation performance on the basis of measured characteristics of thermal contacts and spacers. The Large Hadron Collider (LHC) will be a 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 minimise the residual heat inleak 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. 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. We establish the improvement potential of the alternative over the baseline solution, and compare their insulation performance on the basis of measured characteristics of thermal contacts and spacers.

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“…The expected static loads of the main elements in the half cells has been assessed with good confidence and experimentally verified through several independent, yet converging approaches [4][5][6][7]. Parallel to the magnet cryostats in the arc runs the cryogenic distribution line from which each halfcell is supplied with cryogenic fluids.…”

Section: The Arcsmentioning

confidence: 99%

Demands in Refrigeration Capacity for the Large Hadron Collider

Lebrun¹,

Riddone²,

Tavian³

et al. 1997

Proceedings of the Sixteenth International Cryogenic Engineering Conference/International Cryogenic Materials Conference

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The capacity demands on the cryogenic installations for the Large Hadron Collider (LHC) at CERN have been recently updated [1]. Unlike the LEP energy upgrade using superconducting acceleration cavities LHC will require high power refrigeration at 1.9 K, as well as non-isothermal cooling at 4.5 K to 20 K and at 50 K to 75 K. This paper presents the assessment of cryogenic capacity that has to be supplied by the eight refrigerators for LHC in relation with the foreseen operating modes of the machine. The capacity demands on the cryogenic installations for the Large Hadron Collider (LHC) at CERN have been recently updated [2]. Unlike the LEP energy upgrade using superconducting acceleration cavities LHC will require high power refrigeration at 1.9 K, as well as non-isothermal cooling at 4.5 K to 20 K and at 50 K to 75 K. This paper presents the assessment of cryogenic capacity that has to be supplied by the eight refrigerators for LHC in relation with the foreseen operating modes of the machine.

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Measurement and Analysis of Thermal Performance of LHC Prototype Cryostats

Cited by 8 publications

References 1 publication

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

Comparison of Floating and Thermalized Multilayer Insulation Systems at Low Boundary Temperature

Demands in Refrigeration Capacity for the Large Hadron Collider

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