IDENTIFYING AND INVESTIGATING J[sub c] VARIATIONS IN COATED CONDUCTORS FABRICATED BY MOCVD∕IBAD

Coulter, J. Y.; Ugurlu, Ozan; Willis, J. O.; Holesinger, T. G.; Xie, Yiyuan

doi:10.1063/1.3402322

Cited by 7 publications

(1 citation statement)

References 7 publications

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“…It would simply state that a lower n, as well as the operating temperature providing a sufficient reserve with respect to T c , are the main factors for lowering the probability of a thermal runaway. Thus, if the weak spot is caused by an imperfection in the superconductor microstructure resulting in a reduced critical temperature or weaker flux pinning [42,102], the thermal runaway would appear sooner. However, improvements in the industrial production of CCs make macroscopic geometrical defects probable causes of weak spots.…”

Section: Triggering Of a Thermal Runawaymentioning

confidence: 99%

Stability of DC transport in HTS conductor with local critical current reduction

Gömöry

Šouc

2021

Supercond. Sci. Technol.

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A common feature of commercially available conductors based on high-temperature superconducting compounds is the fluctuation of critical current along the length. Fortunately, the practice adopted by manufacturers nowadays is to supply the detailed I c(x) data with the conductor. Compared to knowing just the average of critical current, this should also allow a much better prediction of the conductor performance. Statistical methods are suitable for this purpose in the case when the fluctuations are regular at the low end of critical current distribution. However, a different approach is necessary at the presence of ‘weak spots’ that drop out of any statistics. Because of the strong nonlinearity of the current–voltage curve, such a location could transform into a ‘hot spot’ at transporting direct current (DC), with an abrupt increase of temperature endangering the conductor operation. We present a set of analytical formulas including the prediction of the maximum DC that could be carried sustainably before the thermal runaway appears. It is necessary to know the cooling conditions as well as the properties of the conductor constituents and their architecture. A formula for the voltage appearing on a weak spot, and its dependence on the DC, is also proposed. For this purpose the result of previous theoretical work has been slightly modified after comparing it with numerical iterative computations and finite element modeling. We demonstrate that the derived model allows a powerful analysis of experimental data comprising an estimation of the weak spot parameters i.e. its critical current and the length of the defect zone.

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Section: Triggering Of a Thermal Runawaymentioning

confidence: 99%

Stability of DC transport in HTS conductor with local critical current reduction

Gömöry

Šouc

2021

Supercond. Sci. Technol.

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45.5-tesla direct-current magnetic field generated with a high-temperature superconducting magnet

Hahn

Kim

et al. 2019

Nature

569

277

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Evidence that transverse variability of critical current density can greatly mitigate screening current stress in high field REBCO magnets

Bang,

Lee,

Bradford

et al. 2024

Sci Rep

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Plastic damage of REBCO (REBa 2 Cu 3 O 7-x , where RE=rare earth) coated conductors by screening current stress (SCS) is a significant concern for ultra-high-field superconducting magnets. Indeed, the third Little Big Coil (LBC3), a REBCO magnet that generated a record, high field of 45.5 T, showed wavy plastic damage produced by excess SCS in all pancakes except two made with single-slit conductors having their slit edges pointing inward towards the magnet center. Reasons for this slit edge orientation-dependent damage mitigation having not yet been presented, we made it the central issue of this new Little Big Coil (LBC4). Accordingly, we constructed and tested LBC4 by replicating LBC3, except that only single-slit tapes were used and every slit edge pointed inward towards the magnet center. LBC4 reached 44.0 T without quench but with some dissipation. After a small lowering of the current without disappearance of the dissipation, the current was charged again, resulting in a quench at 43.5 T due to excess heating in one pancake-to-pancake joint. Indeed, LBC4 exhibited much less wavy conductor damage than LBC3, demonstrating significant SCS mitigation. Detailed post mortem showed a transverse variation of critical current density ( ) across the LBC4 conductor, being highest at the slit edge and lowest at the not-slit edge. Our computed screening current stresses were markedly lowered by this gradient. This paper shows the importance of considering such transverse variability, which has not previously been considered, in the precise stress analysis of ultra-high-field REBCO magnets.

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IDENTIFYING AND INVESTIGATING J[sub c] VARIATIONS IN COATED CONDUCTORS FABRICATED BY MOCVD∕IBAD

Cited by 7 publications

References 7 publications

Stability of DC transport in HTS conductor with local critical current reduction

Stability of DC transport in HTS conductor with local critical current reduction

45.5-tesla direct-current magnetic field generated with a high-temperature superconducting magnet

Evidence that transverse variability of critical current density can greatly mitigate screening current stress in high field REBCO magnets

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