Examination of contacts between strands by electrical measurement and topographical analysis

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

doi:10.1109/77.614622

Cited by 17 publications

(18 citation statements)

References 2 publications

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“…**The hardness for the eutectoid Sn-3.5Ag (wt.%) alloy has been determined in a solder joint by nanoindentation using a Berkovitch indenter and an indent depth in the order of 100 nm. ***For Cu 3 …”

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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Section: Discussionmentioning

confidence: 99%

“…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 contact between crossing strands has the form of a stretched ellipse with a long to short axes ratio of about 3, and an average surface of 1.25 mm 2 for Cable 1 [8]. Two regions can be distinguished by visual observation: the peripheral zone and the central zone.…”

Section: Evolution Of Contacts In the Sn 95wt Ag 5wt Coated Cablesmentioning

confidence: 99%

“…For c) we cut several samples of a cable and we heat treat them in 200 °C dry air for 4,8,12, and 16 h respectively. Then we trace the curves (see Fig.…”

Section: The Sequence Of Measurementsmentioning

confidence: 99%

Strand coating for the superconducting cables of the LHC main magnets

Richter

Adam

Leroy

et al. 1999

IEEE Trans. Appl. Supercond.

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The electrical resistance of contacts between strands in the Rutherford type superconducting cables has a major effect on the eddy current loss in cables, and on the dynamic magnetic field error in the LHC main magnets. In order to guarantee the value and constancy of the contact resistance, various metallic coatings were studied from the electrical and mechanical points of view in the past.We report on the molten bath Sn 95wt. Ag 5wt. coating, oxidized thermally in air after the cabling is completed, that we adopted for the cables of the LHC main magnets. The value of the con-tact resistance is determined by the strand coating and cabling procedures, oxidation heat treatment, and the magnet coil cu-ring and handling. Chemical analysis helps to understand the evolution of the contacts.We also mention results on two electrolytic coatings resulting in higher contact resistance. Abstract  The electrical resistance of contacts between strands in the Rutherford type superconducting cables has a major effect on the eddy current loss in cables, and on the dynamic magnetic field error in the LHC main magnets. In order to guarantee the value and constancy of the contact resistance, various metallic coatings were studied from the electrical and mechanical points of view in the past.We report on the molten bath Sn 95wt. Ag 5wt. coating, oxidized thermally in air after the cabling is completed, that we adopted for the cables of the LHC main magnets. The value of the contact resistance is determined by the strand coating and cabling procedures, oxidation heat treatment, and the magnet coil curing and handling. Chemical analysis helps to understand the evolution of the contacts.We also mention results on two electrolytic coatings resulting in higher contact resistance.

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“…The contact surfaces A adj and A cross are a function of the cable geometry and vary over the width of the cable due to the cable keystone. Empirical data are available [18] on a few cables which are used to scale to other type of Rutherford cables. A given helium volume (V He ) is attributed to each strand section, which is for typical insulated cables about 5-10% of the strand volume V s .…”

Section: The Thermal Modelmentioning

confidence: 99%

CUDI: A model for calculation of electrodynamic and thermal behaviour of superconducting Rutherford cables

Verweij

2006

Cryogenics

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CUDI is the extended Fortran code to calculate the electrodynamic and thermal behaviour of any type of Rutherford cable subject to global and/or local variations in field, transport current, and external heat release. The internal parameters of the cable can be freely varied along the length and across the width, such as contact resistances, critical current, cooling rates etc. In this way, all the typical non-uniformities occurring in a cable, e.g. broken filaments, strand welds, cable joints, and edge degradation can be simulated. Also the characteristics of the strands in the cable can be varied from strand to strand. Heat flows through the matrix, through the interstrand contacts, and to the helium are incorporated, as well as the self-field and selfand mutual inductances between the strands. The main features and structure of the program will be discussed.

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Examination of contacts between strands by electrical measurement and topographical analysis

Cited by 17 publications

References 2 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

Strand coating for the superconducting cables of the LHC main magnets

CUDI: A model for calculation of electrodynamic and thermal behaviour of superconducting Rutherford cables

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