Effect of composition on the melting behaviour of Bi2212-Ag conductors

Rikel, M.O.; Arsac, S.; Soileux, E.; Ehrenberg, J.; Böck, J.; Marken, K.R.; Miao, Hanping; Bruzek, Christian-Éric; Pavard, S.; Matsumoto, Akiyoshi; Hellstrom, E. E.; Motowidlo, L.R.

doi:10.1088/1742-6596/43/1/013

Cited by 18 publications

(22 citation statements)

References 10 publications

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“…Indeed it is commonly observed that a full melting is needed to develop significant J c in Bi-2212 [21,24]. The tomogram of figure 8(a) makes it clear that melting is needed to avoid the non-uniform, physical separation of the filament powder structures by the transverse voids that completely interrupt the filament connectivity at many points.…”

Section: Discussionmentioning

confidence: 98%

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Void and phase evolution during the processing of Bi-2212 superconducting wires monitored by combined fast synchrotron micro-tomography and x-ray diffraction

Scheuerlein

Michiel

Scheel

et al. 2011

Supercond. Sci. Technol.

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Recent study of the current-limiting mechanisms in Bi-2212 round wires has suggested that agglomeration of the residual Bi-2212 powder porosity into bubbles of filament-diameter size occurs on melting the Bi-2212 filaments.These pores introduce a major obstacle to current flow, which greatly reduces the critical current density (J c ). Here we present an in situ non-destructive tomographic and diffraction study of the changes occurring during the heat treatment of wires and starting powder, as well as a room temperature study of ex situ processed wires. The in situ through-process study shows that the agglomeration of residual porosity is more complex than previously seen.Filament changes start with coalescence of the quasi-uniform and finely divided powder porosity into lens-shaped defects at about 850 0 C when the Bi-2201 impurity phase decomposes before the Bi-2212 starts to melt. These lens-shaped voids grow to bubbles of a filament diameter on melting of the Bi-2212 and continue to lengthen and then to agglomerate across multiple filaments while the filaments are in the liquid state. The experiment makes clear why melt processing is vital to developing high J c and also shows how rearrangement of the residual filament porosity on melting imposes a strong longitudinal inhomogeneity in each filament. Reducing the bubble density is clearly an important path to reaching much higher J c values in Bi-2212 round wires. Synchrotron micro-tomography is an exceptionally powerful technique for studying the spatial extent of the porosity on a scale of about 2 m and larger.Published in Superconductor Science and Technology (2011) Geneva, Switzerland CERN-ATS-2011-243December 2011 AbstractRecent study of the current-limiting mechanisms in Bi-2212 round wires has suggested that agglomeration of the residual Bi-2212 powder porosity into bubbles of filament-diameter size occurs on melting the Bi-2212 filaments. These pores introduce a major obstacle to current flow, which greatly reduces the critical current density (J c ). Here we present an in situ non-destructive tomographic and diffraction study of the changes occurring during the heat treatment of wires and starting powder, as well as a room temperature study of ex situ processed wires. The in situ through-process study shows that the agglomeration of residual porosity is more complex than previously seen. Filament changes start with coalescence of the quasi-uniform and finely divided powder porosity into lens-shaped defects at about 850 • C when the Bi-2201 impurity phase decomposes before the Bi-2212 starts to melt. These lens-shaped voids grow to bubbles of a filament diameter on melting of the Bi-2212 and continue to lengthen and then to agglomerate across multiple filaments while the filaments are in the liquid state. The experiment makes clear why melt processing is vital to developing high J c and also shows how rearrangement of the residual filament porosity on melting imposes a strong longitudinal inhomogeneity in each filament. Reducing the bubble density i...

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Section: Discussionmentioning

confidence: 98%

“…The precursor material used in this work reproduced the best material from composition optimization studies [20,21]. It was intended to be almost single-phase, but actually contained 2.8±0.5 wt% second phases including 1.2±0.2 wt% Bi-2201 [22].…”

Section: Discussionmentioning

confidence: 99%

Void and phase evolution during the processing of Bi-2212 superconducting wires monitored by combined fast synchrotron micro-tomography and x-ray diffraction

Scheuerlein

Michiel

Scheel

et al. 2011

Supercond. Sci. Technol.

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“…A dramatically increased critical current (peak effect) within a few tenth of a degree at the beginning of melting the 2212 phase as was found by Matsumoto et al [3] is only weakly pronounced. Rikel et al [13] confirmed this behavior but, however, it is in contrast to earlier papers in which a pronounced peak effect was shown [2,3]. For a better comparison with literature data and to see the influence of different wire diameters, the critical current density is shown via T max in figure 2.…”

Section: Single Wiresmentioning

confidence: 75%

The influence of the maximum heat treatment temperature on the performance of thin reinforced multifilament Bi-2212 wires for cables

Nast¹,

Ringsdorf²,

Runtsch³

et al. 2010

J. Phys.: Conf. Ser.

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Abstract. For high field applications and applications operated at 20-30 K round Bi-2212 wires are still very interesting. For accelerator magnets or the future generation of fusion magnets operation currents up to 10 kA or even several 10 kA are required. For this purpose cabling of BSCCO wires in a low AC loss arrangement is necessary. With Bi-2212 wires optimized on J c and T c cabling to 3x3 and 7x7 strands was the goal, in order to demonstrate the feasibility of a cable-in-conduit concept. To reach the necessary mechanical stability for a cabling process a AgMg (2 at% Mg) outer sheath was used with a reinforcement twice of usual material. However, this sheath affects strongly the reaction kinetics, which leads to a decrease of the critical current density in comparison to a pure silver sheath. 7, 19 and 37 filament wires were fabricated by the powder-in-tube (PIT) and partial melting process, treated in pure oxygen. The current carrying capacity of the Bi-2212 wires essentially depends on the maximum heat treatment temperature T max and the filament diameter. The best average J c of 90 kA/cm² (4.2 K, self-field) was reached in 37 filament wires with filament sizes of 29 µm, treated at the maximum temperature between 879°C and 884°C. We realized stranded conductors and report first results of their superconducting properties.

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“…The new powder eclipses the previous melt-cast [47] granulate powder, produced by Nexans LLC and used by the wire industry between 2005 and 2017 [48], raising the J c of wires by ~80% [49,50]. The new powder has the same optimized W521 composition Bi2.17Sr1.94Ca0.90Cu1.98Ox established by the Nexans Superconductors, Germany and the OI-ST [51][52][53].…”

Section: The Development Of Bi-2212 Into a Magnet-grade Conductor: Ma...mentioning

confidence: 94%

Superconducting Accelerator Magnets Based on High-Temperature Superconducting Bi-2212 Round Wires

Shen

Fajardo

2020

Instruments

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Superconducting magnets are an invaluable tool for scientific discovery, energy research, and medical diagnosis. To date, virtually all superconducting magnets have been made from two Nb-based low-temperature superconductors (Nb-Ti with a superconducting transition temperature Tc of 9.2 K and Nb3Sn with a Tc of 18.3 K). The 8.33 T Nb-Ti accelerator dipole magnets of the large hadron collider (LHC) at CERN enabled the discovery of the Higgs Boson and the ongoing search for physics beyond the standard model of high energy physics. The 12 T class Nb3Sn magnets are key to the International Thermonuclear Experimental Reactor (ITER) Tokamak and to the high-luminosity upgrade of the LHC that aims to increase the luminosity by a factor of 5–10. In this paper, we discuss opportunities with a high-temperature superconducting material Bi-2212 with a Tc of 80–92 K for building more powerful magnets for high energy circular colliders. The development of a superconducting accelerator magnet could not succeed without a parallel development of a high performance conductor. We will review triumphs of developing Bi-2212 round wires into a magnet grade conductor and technologies that enable them. Then, we will discuss the challenges associated with constructing a high-field accelerator magnet using Bi-2212 wires, especially those dipoles of 15–20 T class with a significant value for future physics colliders, potential technology paths forward, and progress made so far with subscale magnet development based on racetrack coils and a canted-cosine-theta magnet design that uniquely addresses the mechanical weaknesses of Bi-2212 cables. Additionally, a roadmap being implemented by the US Magnet Development Program for demonstrating high-field Bi-2212 accelerator dipole technologies is presented.

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Effect of composition on the melting behaviour of Bi2212-Ag conductors

Cited by 18 publications

References 10 publications

Void and phase evolution during the processing of Bi-2212 superconducting wires monitored by combined fast synchrotron micro-tomography and x-ray diffraction

Void and phase evolution during the processing of Bi-2212 superconducting wires monitored by combined fast synchrotron micro-tomography and x-ray diffraction

The influence of the maximum heat treatment temperature on the performance of thin reinforced multifilament Bi-2212 wires for cables

Superconducting Accelerator Magnets Based on High-Temperature Superconducting Bi-2212 Round Wires

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