DC measurement of electrical contacts between strands in superconducting cables for the LHC main magnets

Richter, David H.; Adam, J.; Depond, J.M.; Leroy, D.; Oberli, L.

doi:10.1109/77.614621

Cited by 39 publications

(37 citation statements)

References 9 publications

(11 reference statements)

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“…It is assumed that the surface layer of the strand is sealed of from air. Therefore the oxygen from the oxide layer will dissolve in the underlying Cu bulk [76], resulting in a much thinner oxide barrier as compared to a heat treatment without pressure.…”

Section: Non-cored Cablementioning

confidence: 99%

“…The interstrand resistances are measured according to a DC electrical method: Two opposite strands of a cable are connected to a power supply, while the voltage between one strand and all the other strands are measured [76]. Most reports on interstrand resistance of non-cored cables only comprise R c , since it is easier to measure than R a .…”

Section: Interstrand Electrical Resistancementioning

confidence: 99%

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Stability of superconducting Rutherford cables for accelerator magnets

Willering

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f c e e r g s o r a c l r a t o m a n e t Gerard Willering S t a b i l i t y o f S u p e r c o n d u c t i n g r C b l e R u t h e f o r d a s PrefaceThe work described in this thesis results from an extensive collaboration between the special chair for Industrial Application of Superconductors in the Low Temperature Division at the University of Twente and the Magnets, Superconductors and Cryostats group at CERN. The research has been carried out at CERN as well as at the University of Twente and it is funded by both institutes. Part of the cable samples were prepared by GSI in the frame of research collaboration on cable stability.I am very grateful to the members of these groups for giving me the opportunity to perform the research, for their interest and useful discussions.i ContentsPreface i Chapter 1 IntroductionAfter the discovery of superconductivity in the beginning of the 20 th century the understanding of the phenomenon has grown. Practical conductors are produced for various magnet applications. Although the number of superconducting materials is high, only a few can be used in high-field and high-current density applications. This thesis deals with cable stability, with the focus on application in accelerator magnets.In this chapter a brief overview of the existing and near future accelerators and their superconducting magnets is presented. The most recent superconducting accelerator, the lhc and the near future superconducting accelerator sis 300 are described.The phenomenon of superconductivity is shortly discussed and practical superconductors are introduced with an emphasis on strands and cables. Different types of cables are presented and the relevance of this thesis for in particular the Rutherford type of cable is discussed.The terms quench and recovery are introduced. The importance of research on stability is illustrated by the large number of training quenches in the lhc main dipole magnets. Superconducting accelerator magnetsIn High Energy Physics the interaction of elementary particles is being studied. Many particle accelerators have been constructed to accelerate particles and collide them at high energy. Synchrotron accelerators provide a circular track with RFcavities to accelerate bunches of particles each cycle.Synchrotron accelerators require dipole magnets to bend the particle beam and keep it in its circular track. Quadrupole magnets are used to focus and defocus the beam and higher-order magnets correct field distortions and chromaticity. The collision energy depends on the magnetic field in the aperture of the dipole B a (T) and the bending radius of the dipole magnets r d (km) following E ≈ 0.3B a r d (TeV). The limitation in the track circumference is strongly dictated by the amount of material and the costs involved. In normal conducting magnets iron is applied to enhance the electromagnetic field produced with copper windings. The magnetic field in iron saturates at about 2 T, therefore the needed amount of copper windings and the costs involved increase strongly for hig...

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Section: Non-cored Cablementioning

confidence: 99%

Section: Interstrand Electrical Resistancementioning

confidence: 99%

Stability of superconducting Rutherford cables for accelerator magnets

Willering

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“…At present measurements of ICR are performed in several laboratories using the electric method [4][5][6] or the calorimetric method [7], both well described in [8]. Measurements on Nb 3 Sn samples have been performed at CEA-Saclay [5] and at Twente University in collaboration with Ohio State University [7].…”

Section: Introductionmentioning

confidence: 99%

Measurement of Inter-Strand Contact Resistance in Epoxy Impregnated Nb3Sn Rutherford Cables

Ambrosio¹,

Barzi²,

Chichili³

et al. 2004

AIP Conference Proceedings

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An apparatus for the measurement, under transverse pressure, of the inter-strand contact resistance in epoxy-impregnated Nb 3 Sn Rutherford cables has been recently assembled at Fermilab. Procedures have been developed to instrument and measure samples extracted from Nb 3 Sn coils. Samples were extracted from coils fabricated with the Wind-and-React and the React-and-Wind technology, both presently under development at Fermilab. A ceramic binder is used to improve the insulation and to simplify the fabrication of coils using the Wind-and-React technology. Synthetic oil is used to prevent sintering during the heat treatment of coils to be wound after reaction. In order to evaluate the effects of the ceramic binder and of the synthetic oil on the inter-strand resistance, measurements of samples extracted from coils were compared with measurements of cable stacks with varying characteristics. In this paper we describe the apparatus, the sample preparation, the measurement procedure, and the results of the first series of tests.

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“…For this purpose a Sn-Ag coating is applied onto the copper matrix of the strands, which is subsequently submitted to a 200 °C heattreatment in air, lasting typically a few hours. The Sn-Ag coating is applied by a continuous hot-dip process [3,4,5].…”

Section: Introductionmentioning

confidence: 99%

The effect of CuSn intermetallics on the interstrand contact resistance in superconducting cables for the large hadron collider

Scheuerlein

Gasser

Jacob

et al. 2005

Journal of Applied Physics

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The LHC superconducting cables are submitted to a 200°C heat-treatment in air in order to increase the resistance between the crossing strands (R C ) within the cable. During this treatment the as-applied Sn-Ag alloy strand coating is transformed into a CuSn intermetallic compound layer. The microstructure, the surface topography and the surface chemistry of the non-reacted and reacted coatings have been characterised by different techniques, notably focused ion beam (FIB), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). Based on the results obtained by these techniques the different influences that the intermetallics have on R C are discussed. The desired R C is obtained only when a continuous Cu 3 Sn layer is formed, i.e. a sufficient wetting of the Cu substrate by the tinning alloy is crucial. Among other effects the formation of the comparatively hard intermetallics roughens the surface and, thus, reduces the true contact area and it strongly affects the oxide growth on the strand surface. The oxide formed on the fully reacted coatings, which may contain essentially Cu-oxides, appears to be more stable, both mechanically and thermally, as compared to the oxide formed on the tinning alloy.

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DC measurement of electrical contacts between strands in superconducting cables for the LHC main magnets

Cited by 39 publications

References 9 publications

Stability of superconducting Rutherford cables for accelerator magnets

Stability of superconducting Rutherford cables for accelerator magnets

Measurement of Inter-Strand Contact Resistance in Epoxy Impregnated Nb3Sn Rutherford Cables

The effect of CuSn intermetallics on the interstrand contact resistance in superconducting cables for the large hadron collider

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