Influence of strand surface condition on interstrand contact resistance and coupling loss in NbTi-wound Rutherford cables

Sumption, M.D.; Collings, E. W.; Scanlan, R.M.; Nijhuis, A.; Kate, H. Ten; Kim, S.W; Wake, M.; Shintomi, T.

doi:10.1016/s0011-2275(99)00021-1

Cited by 22 publications

(29 citation statements)

References 47 publications

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“…The bulk resistance of the Cu matrix in Cu-stabilised strands has a negligibly small influence on R C [8]. Hence, the outer strand surface layer plays a dominant role on R C .…”

Section: Discussionmentioning

confidence: 99%

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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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“…The bulk resistance of the Cu matrix in Cu-stabilised strands has a negligibly small influence on R C [8]. Hence, the outer strand surface layer plays a dominant role on R C .…”

Section: Discussionmentioning

confidence: 99%

“…Several researchers have studied the interstrand contact resistance in cables with different strand surfaces [6,7] and the contact resistance of heat-treated Sn-Ag coatings in particular [8]. For most heat-treated strand types it is concluded that it is the surface oxide that determines R C .…”

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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“…As is discussed extensively in [74], in most non-cored cables the electrical interstrand resistance is dominated by R oxide . The thickness of the metal-oxide layer depends on the coating, the heat treatment temperature and duration and the partial oxide pressure.…”

Section: Electrical Contactmentioning

confidence: 99%

“…On a bare copper surface stored at room temperature a layer of Cu 2 O grows slowly and is typically 1 -5 nm thick [74].…”

Section: Non-cored Cablementioning

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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Compact stranded superconducting conductors with both low ac loss and high stability II. Experiment to confirm fundamental performance

et al. 2004

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Influence of strand surface condition on interstrand contact resistance and coupling loss in NbTi-wound Rutherford cables

Cited by 22 publications

References 47 publications

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

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

Stability of superconducting Rutherford cables for accelerator magnets

Compact stranded superconducting conductors with both low ac loss and high stability II. Experiment to confirm fundamental performance

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