Progress in scale-up of RE BCO STAR™ wire for canted cosine theta coils and future strategies with enhanced flexibility

The width-bending behaviors for a rare earth barium copper oxide (REBCO) high-temperature superconducting (HTS) tape have been investigated. It has been found experimentally that the width-bending strain of a Yttrium Barium Copper Oxide (YBCO) tape does not degrade the critical current as much as is expected from the axial strain. The critical current is not directly affected by the width-bending strain but by the axial strain, which the width-bending strain generates by the Poisson effect. Since Poisson’s ratio is about 0.3, the axial strain effective on the critical current is about 30% of the width-bending strain. Therefore, the width-bending strain of even 1.5% degrades the critical current by only 15% if the REBCO layer side is bent inward. However, the critical current degraded by more than 70% when the REBCO layer is outward. The width-bending effects on the critical current have been further examined, considering Poisson’s ratio changes and the neutral plane shift of the REBCO tape substrate. Those changes would occur when the material yields due to severe width-bending. Based on the width-bending of REBCO tapes, flat-tape Rutherford-type cabling is discussed. A REBCO Rutherford-type cable can provide various advantages, especially for narrow-tape cabling. The flat-tape Rutherford-type cable has better characteristics against an electromagnetic transverse Lorentz force. Furthermore, the tape length of the cable can be approximately the same as the cable length allowing for excellent tape usage. REBCO Rutherford-type cabling will be a promising high-current, high-field cabling method using thin substrate REBCO tapes. It will be useful for AC ramp-field and pulse-field applications with low AC losses and low shield currents. It notes that the filaments in the cable are symmetrically distributed in parallel. Therefore, each filament’s inductance is uniform, and a uniform current distribution among the filaments can be obtained.

Section: Summary Of Width-bendingmentioning

confidence: 99%

Width-bending characteristic of REBCO HTS tape and flat-tape Rutherford-type cabling

Takayasu¹

2021

“…Although its fundamental geometry is similar to corc® conductors, the star® wire pushes the concept further with several distinctions. The thin substrate, 15-22 µm thick, and Cu of asymmetric thickness at each side of the tape, position the rebco layer near the neutral axis of the composite tape, improving the tape bending performance [21,23,24]. star® wires not only can use a Cu former as small as 0.7 mm diameter but also usually contain less than 15 rebco tapes.…”

Section: Introductionmentioning

confidence: 99%

“…Although the performance of star® wire progressed significantly in the past few years, there are few reports on using star® wires in magnets [24]. Here we report the fabrication and test of a subscale canted cos θ (CCT) dipole magnet called s0.…”

Section: Introductionmentioning

confidence: 99%

An initial magnet experiment using high-temperature superconducting STAR® wires

Wang

Bogdanof

Ferracin

et al. 2022

Self Cite

A dipole magnet generating 20 T and beyond will require high-temperature superconductors such as Bi2Sr2CaCu2O8-x and REBa2Cu3O7-x (RE = rare earth, REBCO). Symmetric tape round (STAR®) wires based on REBCO tapes are emerging as a potential conductor for such a magnet, demonstrating a whole-conductor current density of 580 A mm-2 at 20 T, 4.2 K, and at a bend radius of 15 mm. There are, however, few magnet developments using STAR® wires. Here we report a subscale canted cosθ dipole magnet as an initial experiment for two purposes: to evaluate the conductor performance in a magnet conﬁguration and to start developing the magnet technology, leveraging the small bend radius aﬀorded by STAR® wires. The magnet was wound with two STAR® wires, electrically in parallel and without transposition. We tested the magnet at 77 and 4.2 K. The magnet reached a peak current of 8.9 kA, 78% of the short-sample prediction at 4.2 K, and a whole-conductor current density of 1500 A mm-2. The experiment demonstrated a minimum viable concept for dipole magnet applications using STAR® wires. The results also allowed us to identify further development needs for STAR® conductors and associated magnet technology to enable high-ﬁeld REBCO magnets.

“…SuperPower SCS4030-AP 20. 16 SuperPower-AP, and Shanghai-AP-30 conductors are moderate with I c (B //c = 1 T)/I c (0 T) = 0.24-0.32.…”

Section: Transport Properties At 77 Kmentioning

confidence: 97%

“…The cable must be compact and flexible, while also featuring a high current density and a large currentcarrying capacity. To develop such a cable, various R&D works [14][15][16] are underway using conventional REBCO conductors. However, realizing a high-field accelerator magnet might require REBCO conductors with a significantly higher J c and high flexibility that allows for a small bending radius.…”

Section: Introductionmentioning

confidence: 99%

Superconducting properties of commercial REBCO-coated conductors with artificial pinning centers

Tsuchiya

Wang

Fujita

et al. 2021

Over the last 20 years, technologies for manufacturing rare-earth barium copper oxide (REBCO)-coated conductors have undergone a steady development. Currently, the properties of these conductors are reasonably stable owing to the intensive efforts of the manufacturers. However, for high-field magnet applications, such as the magnets used in nuclear magnetic resonance instruments, accelerators, and fusion reactors, further enhancements in the current-carrying capabilities and/or the current densities of the conductors under a high magnetic field are necessary. Recently, several conductors doped with artificial pinning centers (APCs) have become commercially available, primarily from four manufacturers: Fujikura, Shanghai ST, SuperOx, and SuperPower. In this study, we characterized these relatively new conductors from the viewpoint of a magnet designer. We measured the critical currents (I c) of full-size 4 mm wide conductors in a wide field range at 4.2 K and 77 K; we also measured the critical temperatures. The measurement results showed that the I c values at 4.2 K under perpendicular fields for these conductors are significantly greater than those of non-APC conductors; for the 4 mm wide conductors, the I c values are in the range of 300–740 A and 450–1000 A at 18 T and 12 T, respectively. Furthermore, we clarified that the non-Cu current density (J c) at 4.2 K for some of the investigated conductors is more than twice the J c of the recent Nb3Sn conductors in fields exceeding 15 T. In the investigated commercial REBCO-APC conductors, the highest layer J c of ∼60 kA mm−2 (at 18 T and 4.2 K) was noted. We also investigated the I c–B relationship at 4.2 K for the recent REBCO-APC conductors.