Coupling Loss, Interstrand Contact Resistance, and Magnetization of Nb$_{3}$Sn Rutherford Cables With Cores of MgO Tape and S-Glass Ribbon

Abstract

Multistrand cables may exhibit two classes of parasitic magnetization both of which can distort the bore-field of an accelerator magnet: (1) a static magnetization ("hysteretic") resulting from intrastrand persistent currents, and (2) a dynamic magnetization produced by interstrand coupling currents generated during field ramping. The latter, which are moderated by the interstrand contact resistances (ICR), can be controlled by the presence of an insulating core inserted between the layers of the cable. Stainless steel ribbon (with its associated native oxide coating) is a frequently used core. Recently, however, MgO-paper tapes and woven s-glass ribbons have been suggested by LBNL (Lawrence Berkeley National Laboratory) as alternative core materials in the interests of improved flexibility and compatibility with the cabling process. This paper reports on the results of calorimetric AC loss (hence ICR) measurements on a set of four such cables and presents the results within the context of previously measured cored and uncored Nb 3 Sn cables. Also considered is a typical ramp-rate-induced coupling magnetization and its relationship to persistent-current magnetizations over the operating range of an accelerator magnet.

Multipoles Induced by Inter-Strand Coupling Currents in LARP <formula formulatype="inline"> <tex Notation="TeX">$\hbox{Nb}_{3}\hbox{Sn}$</tex></formula> Quadrupoles

“…No single physical R c exists if ISCC B 2 and B 6 are to be matched simultaneously, indicating that R c is not uniform across the magnet cross section. Nevertheless, this range is consistent with a R c = 0.33 μΩ measured on a prototype HQ cable without core [30].…”

Effects of Core Type, Placement, and Width on the Estimated Interstrand Coupling Properties of QXF-Type Nb₃Sn Rutherford Cables

“…Rc) values we have obtained for uncored Nb3Sn cables have been: 0.24 [9], <0.1 [17], 0.17, 0.37, 0.39 [18], 0.24 [19], 0.37 [20], 0.23 [21], 0.15, 0.36 [22], 0.4 [23], 0.37 [24], 0.22 [25], 0.10, 0.17. 0.25 [26], 0.33 [27] for an average of 0.26 ± 0.1 μΩ along with two "high" values of 1.76 [22] and 1.93 [18]. The sintering together of the Cu surfaces of the Nb3Sn/Cu strands during RHT under pressure is responsible for the very low Rc; clearly a core is needed to separate the Cu/Cu interfaces.…”

Transverse pressure effect on superconducting Nb3Sn Rutherford and ReBCO Roebel cables for accelerator magnets

“…The inter-strand resistance is a key parameter that influences the accelerator magnets' dynamic magnetic field quality. Many studies already reported relevant findings in Nb 3 Sn Rutherford cables [93][94][95][96][97][98][99]. However, only a few publications concern the investigation of the inter-strand contact resistance of ReBCO Roebel cables [100][101][102] performed on non-impregnated cables at 77 K. The AC loss performance of such cables is reported as well but mostly investigated at 77 K [50].…”