Eddy currents in superconducting Rutherford cables

Mallick, G. T.; Carr, W. J.; Toms, Jan; Kovachev, V.

doi:10.1016/s0011-2275(99)80006-x

Cited by 5 publications

(7 citation statements)

References 6 publications

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“…We have made considerable efforts to find out what was the reason for that kind of behavior and what shall be done to avoid such magnet characteristics. [10][11][12][13][14][15][16][17][18] It was found at first that the basic reasons for the very high experimental loss were Rutherford cable characteristics and not individual strand properties (strand RRR for instance). Then it was also found that coil curing at high pressure and temperature could lead to a very low interstrand resistance in cables.…”

Section: Interstrand Resistancementioning

confidence: 99%

“…Solid lines represent fitted resistance from field quality measurements for the same positions of the magnet coil. We also found that low interstrand resistance in Rutherford cables is a basic reason for the type A and the type B characteristics of the quench current behavior of magnets, 9,[15][16][17] Briefly the A type is due to low crossover resistance all over the dipole coil which causes high interstrand coupling dissipation and quenching at locations which move from the dipole pole to the midplane with a ramp rate increase. The type B quench behavior is due to some "weak" spots in the coil having a low crossover resistance of the cable.…”

Section: Interstrand Resistancementioning

confidence: 99%

“…22 It can be seen in Figs. 15 recover faster with temperature than quarter hard copper (Q) This probably has to do with the stronger dislocation field of full hard Cu and can play an important practical role. For instance, at about 170 • C which can be the magnet coil curing temperature the hardness i.e.…”

Section: Interstrand Resistancementioning

confidence: 99%

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Ac Losses of Superconducting Accelerator Magnets

Kovachev

2003

Mod. Phys. Lett. B

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We are focusing on the uncertainties of analytical and numerical analysis of AC losses in superconducting accelerator magnets working at a relatively high ramp rate. The loss experimental techniques are discussed as well as the source of error in the measurements. The correlation between the interstrand resistance of Rutherford cables and quench current behavior of superconducting magnets is addressed. The control of the critical current of full Rutherford cables by measuring the strands extracted from such cables is illustrated. The importance of cables curing temperature on microhardness and RRR of Cu-matrix of multifilamentary NbTi is pointed out.

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Section: Interstrand Resistancementioning

confidence: 99%

Section: Interstrand Resistancementioning

confidence: 99%

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Ac Losses of Superconducting Accelerator Magnets

Kovachev

2003

Mod. Phys. Lett. B

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“…Therefore, the proposal of a 'low loss-high stability type' cable with an added normal matrix layer at the cable edges, as proposed recently (Gohda et al 1999), seems to be surprising. Up until now, the contribution of the edge layer to the coupling losses was not or only insufficiently treated (Morgan 1973, Ries and Takács 1981, Carr 1983, Sytnikov et al 1989, Mallick et al 1995, Takács 1997, although it was generally accepted that such a layer increases the coupling losses.…”

Section: Introductionmentioning

confidence: 99%

The design of flat superconducting cables with considerable edge currents between the strands: coupling losses between opposite strands

Takács

2001

Supercond. Sci. Technol.

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The decreased contact resistance of strands close to the edges of a cable is usually unavoidable. One has therefore to include this influence on the coupling losses, mainly for flat structures. In addition, the concept of a cable with higher stability is a challenging opportunity to design more reliable cables using a practical approach. Namely, some additional conducting edge layer (occurring naturally or included artificially at the cable edges) increases the amount of current, which can be transferred from one strand to another, thus increasing the stability of the cable against electromagnetic perturbations. Therefore, we calculate the total losses of such structures by including all contributions to the coupling losses. We show that, in spite of the increased coupling losses, by introducing the additional well conducting layer close to the edges, one can compensate for the losses by producing a much higher increase in the current transfer factor between the strands. This can lead to a more stable cable design for ac fields and currents. However, it seems that the well conducting edge layer should be cut into segments whose lengths do not exceed the cabling or twist pitch. Otherwise, the increased edge losses would be too high and detrimental to the stability. The crucial question for cables with such segmented edge layers is whether the increased coupling loss density close to the edges (about four times the maximum loss density in cables without edge sheath) is still tolerable from the cooling point of view.

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“…In order to study this problem further, a program was initiated between the SSC and Westinghouse Corporation (WEC), the designated contractor for the HEB dipole manufacture. A considerable enhancement in the understanding of ramp rate behavior has resulted [2,3,4].…”

Section: Ramp Rate Studiesmentioning

confidence: 99%