Development of Round Multifilament Bi-2212/Ag Wires for High Field Magnet Applications

Miao, Hanping; Marken, K.R.; Meinesz, M.; Czabaj, B.; Hong, Seung Pyo

doi:10.1109/tasc.2005.847648

Cited by 140 publications

(102 citation statements)

References 14 publications

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“…We tried to measure the average dimensions of the filaments and we estimated their size around 20 m for the rectangular wire and 14 m for the square sample. This explains the better performances of the square sample in terms of Jc, as previous studies have shown how 15 m is the value for the optimum Jc performance [11,12].…”

Section: Figure2 Jc (Left Axis) and Je (Right Axis) For The A) Rectamentioning

confidence: 63%

New concept for the development of Bi-2212 wires for high-field applications

Leveratto

Braccini

Contarino

et al. 2016

Supercond. Sci. Technol.

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The first step towards high critical currents in Bi-2212 wires was the comprehension that the supercurrent is blocked over long lengths by filament-diameter bubbles grown during the melt stage, which cause expansion of the wire diameter and dedensification of the superconducting filaments.Whereas the previous successful approach to reduce the problem of voids related to bubbles was based on the application of a high overpressure during the heat treatment, we fabricated Bi-2212 wires by applying a new concept of suitably alternating groove-rolling and drawing techniques with the aim of densifying the phase already during the working procedure prior to the heat treatment.We here for the first time were able to reach in wires reacted with closed ends -i.e. with gas trapped in the wire as it happens in long-length wires -the very same values of critical current shown in short wires reacted with open ends. This is the irrefutable evidence that, only by acting on the deformation technique, we were able to raise the critical current by properly densifying the superconducting powder inside the filaments already before the melt stage. Whole-conductor current densities in our long length simulation wires already reach 400 A/mm 2 at 4.2 K and 5 T, which can be still easily increased through architecture optimization. The actual breakthrough is that the densification is optimized without further complex treatments through a technique which can be straightforwardly applied to long-lengths wires.

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Section: Figure2 Jc (Left Axis) and Je (Right Axis) For The A) Rectamentioning

confidence: 63%

New concept for the development of Bi-2212 wires for high-field applications

Leveratto

Braccini

Contarino

et al. 2016

Supercond. Sci. Technol.

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“…Future efforts will focus on adding maximum field using these Bi-2212 wires. As prior measurements have shown, this wire is capable of J E values over 250 A/mm 2 at 45 T and over 400 A/mm 2 at 25 T [6]. Such J E performance coupled with the now demonstrated techniques for wind-and-react coils make this a promising material for continued high field coil development.…”

Section: Small Coil Developmentmentioning

confidence: 77%

Cost Effective Open Geometry HTS MRI System amended to BSCCO 2212 Wire for High Field Magnets

Marken¹

2006

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BackgroundThe original goal of this Phase II Superconductivity Partnership Initiative project was to build and operate a prototype Magnetic Resonance Imaging (MRI) system using HTS coils wound from continuously processed dip-coated BSCCO 2212 tape conductor. MRI is the largest existing commercial application of superconductors. In 1999 -2000 a business opportunity was perceived for competitively priced, superconducting MRI systems having an open architecture to allow patient comfort and easy access by medical personnel. At that time, open architecture MRI was the fastest growing segment of the market. Most open geometry systems of the time were not superconducting, because of the complex cryogenic systems needed for liquid helium cooling of low temperature superconducting (LTS) magnets, while still allowing open access to the high field region. However, superconducting systems offer distinct advantages in terms of field quality and field strength, and therefore obtainable image quality. Although the feasibility of making conduction cooled HTS MRI coils from multifilamentary BSCCO-2223 conductors had already been shown at that time, the price of the 2223 tape was (and remains) too high. However, BSCCO-2212 can be melt processed and thus can be made as an inexpensive slurry coated conductor, without the need for labor intensive powder-in-tube deformation processing.Cost estimates showed that dip-coated 2212 tape would have labor and materials costs that are between 10 and 25% of those for multifilamentary 2223 tape. In addition, capital costs are significantly lower. Thus there were compelling reasons to explore the possibility of using dip-coated tape. The melt processing of 2212, which is not feasible with 2223, is what makes the lower cost, coated conductor format a possibility; however, the technical methods for continuously melt processing long lengths needed to be established. One of this program's original aims was to verify that uniform properties, including current density, physical dimensions, and mechanical strength, could be achieved in long lengths of this tape.Using dip-coated tape, the plan was for MRI magnet coils to be wound to fit an established commercial open geometry, 0.2 Tesla permanent magnet system. New electronics and imaging software for a prototype higher field superconducting system would have added significantly to the cost. However, the use of the 0.2 T platform would allow the technical feasibility and the cost issues for HTS systems to be fully established. Also it would establish the energy efficiency and savings of HTS open MRI compared with resistive and permanent magnet systems. The commercial goal was an open geometry HTS MRI running at 0.5 T and 20 K.It was expected that success with this prototype system would lead to lower costs and increased performance for open geometry MRI. This progress was expected to result in a greatly expanded market for the low cost end of MRI applications. This could have very

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“…Conductor E is a Bi-2212 round wire produced by OST [61]. Its 7×85 filament architecture makes it the only double-stacked conductor and results in a fine filamentary structure with ~ 14 μm diameter filaments before heat treatment, as shown in Figure 2-3.…”

Section: Conductor Ementioning

confidence: 99%

“…Bend-and release experiments 61 allow the determination of the maximum tensile strain in the ceramic filaments for conductors that are not straight when unrestrained (the curvature is mostly determined by the conductor diameter during heat treatment), and that show partially plastic deformation during bending. For conductors A, D, H, and I a limited set of data points is obtained, but sufficient to estimate bending strain in the coils wound from these conductors that are discussed later in this chapter.…”

Section: Bend-and-releasementioning

confidence: 99%

“…For comparison, two other types of conductor are investigated that can be considered extreme cases of grain misalignment: Bi-2212 round wire [61] and YBCO coated conductor [80]. This provides an opportunity to determine to what degree equations and parameters that describe the magnetic field dependence and anisotropy of the critical current density in BSCCO tapes are applicable to HTS conductors with a different architecture.…”

Section: Introductionmentioning

confidence: 99%

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High-temperature superconductors in high-field magnets

Weijers

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Preface and acknowledgementThis thesis deals with selected topics out of a wide research and development effort on HTS insert coil technology. Its origin goes back to the founding charter of the NHMFL in the year 1988 which listed the goal of realizing a 25 T superconducting magnet as one of the milestones the NHMFL was to achieve. High-temperature superconductors had only just been discovered and the required technology was non-existent. The path to where we are now has been eventful and a real learning experience. From the early days in the mid-1990-ies of the 'Wind and Pray" approach when coil testing relentlessly pointed out the shortcomings of both conductor and coil technologies at the time to the first successful "mini-coils" (around coil number 70) to the successive 1 T, 3 T and 5 T inserts (the latter reaching 25 T and bringing the total of numbered coils over 300 a decade later) to the promise of 30 + T superconducting user magnets with coated conductors in the not-toodistant future.Lacking the funds to buy the very expensive conductors, a collaboration was established with industry. This approach has served us well and resulted in a wide assortment of conductors to work with. New superconductors were donated in exchange for feedback on its performance as observed in our magnet technology development program. We also tested complete coils built by ourselves or by partners, in background magnetic field, a task for which the NHMFL facilities are well suited.This work is centered on the 5T insert coil for a total magnetic field of 25 T, but the research and development effort is interwoven with and inseparable from the broader HTS insert coil technology development program. Therefore discussions on a wider range of conductors and coils in line with the broader scope of this thesis are presented.While I take full responsibility for the described NHMFL insert coil designs, analysis and interpretation of the data on coils and conductors, having executed or been directly involved with all experiments described and having wound many a coil, this work has had the benefit of many direct and indirect contributions of a large number of people inside and outside the NHMFL. In contrast, developing this thesis itself has been the loneliest work I have ever done, but ultimately just as rewarding. There are many people that I would like to thank for their contributions to the HTS insert program in general and this thesis in particular.

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Development of Round Multifilament Bi-2212/Ag Wires for High Field Magnet Applications

Cited by 140 publications

References 14 publications

New concept for the development of Bi-2212 wires for high-field applications

New concept for the development of Bi-2212 wires for high-field applications

Cost Effective Open Geometry HTS MRI System amended to BSCCO 2212 Wire for High Field Magnets

High-temperature superconductors in high-field magnets

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