Degradation of a REBCO Coil Due to Cleavage and Peeling Originating From an Electromagnetic Force

Kajita, Kentaro; Iguchi, Seiya; Xu, Yi; Nawa, Masato; Hamada, Mamoru; Takao, T.; Nakagome, Hideki; Matsumoto, Shinji; Nishijima, G.; Suematsu, H.; Takahashi, Masato; Yanagisawa, Yoshinori

doi:10.1109/tasc.2016.2515564

Cited by 58 publications

(40 citation statements)

References 23 publications

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“…The baseline magnet technology for future high energy proton colliders is the 12-16 T wind-and-react, A vital concern for any HTS magnet is the need to detect quench so that active protection can be Important concerns with REBCO conductors, despite their high stability, are that they contain localized defects either pre-existing 15 or created during coil winding or during magnet operation 22 , that their critical current is anisotropic in magnetic field, and that this anisotropy depends on flux pinning and therefore REBCO processing conditions; these uncertainties mean that quench is often localized, unpredictable, unexpected, and catastrophic [21][22][23]27 . This is illustrated by a single-layer coil wound from a 2 m long REBCO single tape (2 mm wide, 100 µm in thickness with 40 µm Cu) with a known defected 2 cm section (I c = 48 A versus ~55 A for other sections at 77 K).…”

Section: Discussionmentioning

confidence: 99%

“…However, the paradox for HTS magnets is that, when quench does occur, it is a much bigger threat than in LTS magnets because normal zones are smaller, quench velocities much smaller, with the consequence of much higher energy density in much smaller normal zones. Several REBCO and Bi-2223 magnet systems have been degraded during quench [21][22][23][24][25][26][27] , likely when small normal zones generated too little voltage for warning, making active quench protection unable to prevent local overheating as magnetic energy turned into very localized heating. A key challenge of HTS magnets is thus the timely detection of small hot spots that grow only at several cm/s, rather than the two orders of magnitude larger rate in Nb-Ti and Nb 3 Sn magnets.…”

mentioning

confidence: 99%

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Stable, predictable and training-free operation of superconducting Bi-2212 Rutherford cable racetrack coils at the wire current density of 1000 A/mm2

Shen

Bosque

Davis

et al. 2019

Sci Rep

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High-temperature superconductors (HTS) could enable high-field magnets stronger than is possible with Nb-Ti and Nb 3 Sn, but two challenges have so far been the low engineering critical current density J E , especially in high-current cables, and the danger of quenches. Most HTS magnets made so far have been made out of REBCO coated conductor. Here we demonstrate stable, reliable and training-quench-free performance of Bi-2212 racetrack coils wound with a Rutherford cable fabricated from wires made with a new precursor powder. These round multifilamentary wires exhibited a record J E up to 950 A/mm 2 at 30 T at 4.2 K. These coils carried up to 8.6 kA while generating 3.5 T at 4.2 K at a J E of 1020 A/mm 2 . Different from the unpredictable training performance of Nb-Ti and Nb 3 Sn magnets, these Bi-2212 magnets showed no training quenches and entered the flux flow state in a stable manner before thermal runaway and quench occurred. Also different from Nb-Ti, Nb 3 Sn, and REBCO magnets for which localized thermal runaways occur at unpredictable locations, the quenches of Bi-2212 magnets consistently occurred in the high field regions over a long conductor length. These characteristics make quench detection simple, enabling safe protection, and suggest a new paradigm of constructing quench-predictable superconducting magnets from Bi-2212.

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Stable, predictable and training-free operation of superconducting Bi-2212 Rutherford cable racetrack coils at the wire current density of 1000 A/mm2

Shen

Bosque

Davis

et al. 2019

Sci Rep

View full text Add to dashboard Cite

show abstract

“…As explained above, the large currents in the circumferential direction are induced in the SP coils next to a quenched SP coil. It is well known that a large current in a strong magnetic field deteriorates the critical current of SP coil, due to peeling the REBCO layer from the Hastelloy substrate [13]. In general, the threshold of REBCO layer peeling is 0.4 -0.5% in strain.…”

Section: Mechanical Stress and Strainmentioning

confidence: 99%

Electromagnetic, Thermal, and Mechanical Quench Simulation of NI REBCO Pancake Coils for High Magnetic Field Generation

Noguchi

2019

IEEE Trans. Appl. Supercond.

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The no-insulation (NI) winding technique drastically enhances the thermal stability of REBa2Cu30y (REBCO) coils. Even if a larger current than a critical current carried in NI REBCO pancake coils, the coils would not burn out. So far, many NI REBCO pancake coils showed a "self-protecting" characteristic in experiments. However, most of these experiments have been done under a low magnetic field or cooled by liquid nitrogen. Under these conditions, a huge electromagnetic force does not occur after an NI REBCO pancake coil transitions into a normal state.Recently, the NI winding technique has been applied to high field magnets, such as NMR and accelerators. Under a high magnetic field, a huge hoop stress are generated after one NI REBCO pancake coil constituting a high field magnet by stacking reaches to quench. The huge hoop stress causes the delamination of REBCO coated conductors. That is, the quench protection condition of high field NI REBCO magnets is decided according to the mechanical condition, even though the magnets show a high thermal stability. In this paper, 3 simulation models for NI REBCO pancake coils are compared, and then the mechanical condition is discussed for a quench protection through an electromagnetic, thermal, and mechanical simulation of multistacked NI REBCO pancake coils for high field generation.

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“…Although the exact mechanism for the observed degradation and its impact on the magnet long-term performance remain to be clarified [137,139], observations from recent REBCO pancake coils in high background fields provide relevant insights. First, Lorentz forces can cause deformation and stress concentration in tapes and joints that are not well supported and lead to I c degradation [140,141]. One solution is to fully impregnate the coil [141], consistent with the significantly improved resilience to the transverse pressure in impregnated Roebel cables [37,111,112].…”

Section: What Is the Long-term Performance Of Rebco Magnets Under Lormentioning

confidence: 99%

Dipole Magnets above 20 Tesla: Research Needs for a Path via High-Temperature Superconducting REBCO Conductors

2019

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To enable the physics research that continues to deepen our understanding of the Universe, future circular colliders will require a critical and unique instrument—magnets that can generate a dipole field of 20 T and above. However, today’s maturing magnet technology for low-temperature superconductors (Nb-Ti and Nb 3 Sn) can lead to a maximum dipole field of around 16 T. High-temperature superconductors such as REBCO can, in principle, generate higher dipole fields but significant challenges exist for both conductor and magnet technology. To address these challenges, several critical research needs, including direct needs on instrumentation and measurements, are identified to push for the maximum dipole fields a REBCO accelerator magnet can generate. We discuss the research needs by reviewing the current results and outlining the perspectives for future technology development, followed by a brief update on the status of the technology development at Lawrence Berkeley National Laboratory. We present a roadmap for the next decade to develop 20 T-class REBCO accelerator magnets as an enabling instrument for future energy-frontier accelerator complex.

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Degradation of a REBCO Coil Due to Cleavage and Peeling Originating From an Electromagnetic Force

Cited by 58 publications

References 23 publications

Stable, predictable and training-free operation of superconducting Bi-2212 Rutherford cable racetrack coils at the wire current density of 1000 A/mm2

Stable, predictable and training-free operation of superconducting Bi-2212 Rutherford cable racetrack coils at the wire current density of 1000 A/mm2

Electromagnetic, Thermal, and Mechanical Quench Simulation of NI REBCO Pancake Coils for High Magnetic Field Generation

Dipole Magnets above 20 Tesla: Research Needs for a Path via High-Temperature Superconducting REBCO Conductors

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