Measurements on Subscale Y-Ba-Cu-O Racetrack Coils at 77 K and Self-Field

Wang, Xiaorong; Caspi, S.; Cheng, D.; Dietderich, D.R.; Félice, H.; Ferracin, P.; Godeke, A.; Joseph, J.; Lizarazo, J.; Prestemon, S.; Sabbi, G.

doi:10.1109/tasc.2010.2043349

Cited by 14 publications

(6 citation statements)

References 21 publications

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“…Although several practical cable and magnet schemes were presented here, it can be less trivial to obtain the explicit base curve as required by the constant-perimeter method for some winding cases, e.g., the continuous ramp between the two layers of pancake or racetrack coils where the strain in the tapes can limit the critical current [15,16,54]. This can be a challenge to apply the constant-perimeter method.…”

Section: Discussionmentioning

confidence: 99%

Strain Distribution in REBCO-Coated Conductors Bent With the Constant-Perimeter Geometry

Wang

Arbelaez

Caspi

et al. 2017

IEEE Trans. Appl. Supercond.

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Abstract-Cable and magnet applications require bending REBa2Cu3O 7−δ (REBCO, RE = Rare Earth) tapes around a former to carry high current or generate specific magnetic fields. With a high aspect ratio, REBCO tapes favor the bending along their broad surfaces (easy way) than their thin edges (hard way). The easy-way bending forms can be effectively determined by the constant-perimeter method that was developed in the 1970s to fabricate accelerator magnets with flat thin conductors. The method, however, does not consider the strain distribution in the REBCO layer that can result from bending. Therefore, the REBCO layer can be over-strained and damaged even if it is bent in an easy way as determined by the constant-perimeter method.To address this issue, we developed a numerical approach to determine the strain in the REBCO layer using the local curvatures of the tape neutral plane. Two orthogonal strain components are determined: the axial component along the tape length and the transverse component along the tape width. These two components can be used to determine the conductor critical current after bending. The approach is demonstrated with four examples relevant for applications: a helical form for cables, forms for canted cos θ dipole and quadrupole magnets, and a form for the coil end design. The approach allows to optimize the design of REBCO cables and magnets based on the constantperimeter geometry and to reduce the strain-induced critical current degradation.

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Section: Discussionmentioning

confidence: 99%

Strain Distribution in REBCO-Coated Conductors Bent With the Constant-Perimeter Geometry

Wang

Arbelaez

Caspi

et al. 2017

IEEE Trans. Appl. Supercond.

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“…Their advantages as compared to low T c superconductor (LTS) magnets include easy cooling without liquid helium by using a cryocooler, potentially improved thermal stability or larger temperature marginespecially when operated at a higher temperature where the specific heats of materials are larger-and the generation of very high magnetic fields when operated at a low temperature because of their high critical current densities, even in high magnetic fields. In particle accelerators for physics research, very high magnetic field generation or large temperature margins are attractive when compared with LTS magnets [1][2][3][4][5][6][7][8]. In particle accelerators for cancer therapy, higher magnetic field generation reducing the size of a facility and reduced power consumption are attractive when compared with copper magnets [9][10][11][12][13][14][15]; their easy cooling and improved thermal stability are attractive in comparison with LTS magnets.…”

Section: Introductionmentioning

confidence: 99%

Temporal behaviour of multipole components of the magnetic field in a small dipole magnet wound with coated conductors

Amemiya

Otake

Sano

et al. 2015

Supercond. Sci. Technol.

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To study the influence of coated-conductor magnetization on the field quality of accelerator magnets, we made a small dipole magnet consisting of four racetrack coils wound with GdBCO coated conductors and measured its magnetic field in liquid nitrogen by using rotating pick-up coils. We focused on the dipole and sextupole components (coefficients) of the magnetic field, which vary with time owing to the decay of the magnetization of the coated conductors. About 50 min (3055 s) after the current was ramped up to 50 A, the dipole coefficient normalized by the design value of the dipole component, i.e., the value calculated with the designed coil shape and the uniform current distribution in the coated conductors, increased by 7.4 × 10 −4 , and the sextupole coefficient normalized by the design value of the dipole component increased by 1.8 × 10 −4 . The magnitudes of the dipole and sextupole components depended on the excitation history of the magnet. Electromagnetic field analyses were carried out to calculate the current distributions in coated conductors, considering their superconducting properties; the dipole and sextupole coefficients were then determined from the calculated current distributions. Although the analyses were based on the two-dimensional approximation of the cross-section of the magnet, the temporal behaviours as well as the hysteretic characteristics of the calculated dipole and sextupole coefficients agree qualitatively with those of the dipole and sextupole coefficients measured in the magnet.

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“…YBa 2 Cu 3 O 7−δ (YBCO)-coated conductors [1] are promising for many applications such as nuclear magnetic resonance (NMR) [2], high field magnets [3] and accelerators [4] etc, due to their high axial tensile strength (>700 MPa) [1,5] and high critical current density at a high magnetic field. If we take advantage of the attractive properties of YBCO-coated conductors, we can increase the current density in superconducting coils and thus dramatically reduce the coil size [6].…”

Section: Introductionmentioning

confidence: 99%

The mechanism of thermal runaway due to continuous local disturbances in the YBCO-coated conductor coil winding

Yanagisawa

Okuyama

Nakagome

et al. 2012

Supercond. Sci. Technol.

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Though YBCO coils are stable against transient disturbances such as conductor motion, they suffer from thermal runaway at a current below the coil critical current due to continuous local disturbances attributed to partial degradation of the conductor in the coil winding. Continuous heat generation in the degraded layer induces thermal runaway in adjacent layers; thermal runaway does not occur in the degraded layer spontaneously due to the small n index of the degraded YBCO-coated conductor. The thermal runaway current depends on the cooling conditions of the winding. For a paraffin-impregnated YBCO coil under quasi-adiabatic conditions, the thermal runaway current is far below the coil critical current, while it is close to the coil critical current in the case of a dry-wound coil. The permissible temperature rise following a thermal runaway for YBCO conductors in the degraded layer is demonstrated to be 340 K. If the YBCO coils are operated at a temperature below 20 K, the current density, typically 600-800 A mm −2 , is much higher than that at 77 K. Therefore, the time interval between thermal runaway initiation and the melting temperature becomes less than 0.5 s, posing a difficult problem for protection; i.e., thermal runaway due to continuous local disturbances is hazardous to the safe operation of high current density YBCO coils.

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Measurements on Subscale Y-Ba-Cu-O Racetrack Coils at 77 K and Self-Field

Cited by 14 publications

References 21 publications

Strain Distribution in REBCO-Coated Conductors Bent With the Constant-Perimeter Geometry

Strain Distribution in REBCO-Coated Conductors Bent With the Constant-Perimeter Geometry

Temporal behaviour of multipole components of the magnetic field in a small dipole magnet wound with coated conductors

The mechanism of thermal runaway due to continuous local disturbances in the YBCO-coated conductor coil winding

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