Variation of Quench Propagation Velocities in YBCO Cables

Haro, E.; Järvelä, Joonas; Stenvall, Antti

doi:10.1007/s10948-015-2976-y

Cited by 17 publications

(9 citation statements)

References 21 publications

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“…Bi-2212 is investigated at the conductor level, by contributing to the powder improvement [46]. Among other issues, protection is going to be very challenging because of slow voltage raise, as in any HTS coil, and is under careful investigation [47], [48]. The recent CERN innovation for enhanced protection, CLIQ [49] may be very useful in this respect.…”

Section: B Magnets (Task 103): Targets and Resultsmentioning

confidence: 99%

The EuCARD-2 Future Magnets European Collaboration for Accelerator-Quality HTS Magnets

Rossi

Badel

Bajko

et al. 2015

IEEE Trans. Appl. Supercond.

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114

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Abstract-EuCARD-2 is a project supported by FP7-European Commission that includes, inter alia, a work-package (WP10) called "Future Magnets". This project is part of the long term development that CERN is launching to explore magnet technology at 16 T to 20 T dipole operating field, within the scope of a study on Future Circular Colliders. The EuCARD2 collaboration is closely liaising with similar programs for high field accelerator magnets in the USA and Japan. The main focus of EuCARD2 WP10 is the development of a 10 kA-class superconducting, high current density cable suitable for accelerator magnets, The cable will be used to wind a stand-alone magnet 500 mm long and with an aperture of 40 mm. This magnet should yield 5 T, when stand-alone, and will enable to reach a 15 to 18 T dipole field by placing it in a large bore background dipole of 12-15 T. REBCO based Roebel cables is the baseline. Various magnet configurations with HTS tapes are under investigation and also use of Bi-2212 round wire based cables is considered. The paper presents the structure of the collaboration and describes the main choices made in the first year of the program, which has a breadth of five to six years of which four are covered by the FP7 frame.

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Section: B Magnets (Task 103): Targets and Resultsmentioning

confidence: 99%

The EuCARD-2 Future Magnets European Collaboration for Accelerator-Quality HTS Magnets

Rossi

Badel

Bajko

et al. 2015

IEEE Trans. Appl. Supercond.

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114

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“…Finally, it would be interesting to check whether the propagation velocity of a normal zone in YBaCuO cables as reported in [23], in relation to a propagation of the temperature front, both calculated with a finite element method, can be explained by a similar correlation analysis as presented above, and whether inhomogeneities and current percolation have been observed. This will be investigated in a separate paper.…”

Section: Correlation Of Stability With Current Limitingmentioning

confidence: 89%

Superconductor Stability Against Quench and Its Correlation with Current Propagation and Limiting

Reiss

2015

J Supercond Nov Magn

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This paper presents a numerical (finite element) analysis of superconductor stability and current propagation under random variations of critical superconductor parameters. Instead of using singular (homogeneous) values, random variations potentially are appropriate to take into account any conductor inhomogeneity that can be considered as an obstacle to current propagation. Traditional assumptions like homogeneous current distribution, critical temperature, critical current density and critical magnetic fields are not justified in general; a local disturbance (for example, release of mechanical stress energy), if not immediately distributed by solid conduction, would generate a transient increase of local conductor temperature. Local critical current density and magnetic field then will be reduced, and current distribution will change. Disturbances may arise also from transport currents that locally exceed the critical current of the superconductor. Disturbances of all kinds may increase the conductor temperature above its critical value. A local analysis of all superconductor states thus is mandatory to safely avoid a quench. As an extension of standard stability models, also flux flow resistive states are taken into account. We will try to find a possibly existing correlation between current propagation and superconductor stability. Fault current limiting is discussed as a special case of current propagation. The analysis is applied to a bundle of high-temperature superconductor (HTSC) filaments. As will be shown, temperature profiles in a superconductor do not allow a clear distinction between Ohmic resistive or flux flow resistive fault current limiting. Though frequently made in the literature, this separation is highly questionable, because Ohmic resistive and flux flow resistive states may locally coexist, side by side, but are not very stable in the superconductor volume.

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“…For the normal region the critical current is computed from the cable critical current surface, which takes into account the angular dependency of the magnetic field. However, for the hot spot we assign a critical current which is lower than the operation current, thus, effectively quenching the magnet slowly, as in our previous work [31]- [33]. The hot spot region, which is located in the area with the highest magnetic field density, is shown in Fig.…”

Section: Modelling Domainmentioning

confidence: 99%

Hot Spot Temperature in an HTS Coil: Simulations With MIITs and Finite Element Method

Haro

Stenvall

Nugteren

et al. 2015

IEEE Trans. Appl. Supercond.

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Abstract-MIITs, a zero-dimensional concept to study hot spot temperature, has been previously used to estimate hot spot temperatures and quench heater delays in NbTi and Nb3Sn magnets. However, quench behaviour is completely different in high temperature superconducting (HTS) magnets due to the slow normal zone propagation velocity and high temperature margin. Because MIITs concept does not take into account thermal diffusion in the magnet, opposite to the finite element method (FEM) analysis, the difference of these concepts is studied in this paper. Here we have taken the approach to compute the hot spot temperatures for a future HTS magnet, designed to be built from REBCO Roebel cable, with MIITs and FEM simulations. The magnet protection is accomplished with a dump resistor, and the effect of quench detection threshold voltage on the hot spot temperature has been studied. Furthermore, the inductance of the magnet increases with the magnet length. Thus, there exists a maximum inductance of the magnet which should not be exceeded to be able to protect the magnet only with a dump resistor. The hot spot temperatures with different values of inductance are also studied in this paper. Our simulations show, that the hot spot temperatures computed with MIITs are from 60 K to 150 K higher than those of FEM analysis. Thus, MIITs concept seems unreliable when considering hot spot temperatures in HTS magnets protected with only dump resistors. However, MIITs concept might be a usable tool when comparing different magnet designs. If 400 K is the upper limit for the hot spot temperature and the protection scheme includes only a dump resistor, the length of the investigated magnet can be increased to only such value that the magnet inductance is at most 50 mH.

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Variation of Quench Propagation Velocities in YBCO Cables

Cited by 17 publications

References 21 publications

The EuCARD-2 Future Magnets European Collaboration for Accelerator-Quality HTS Magnets

The EuCARD-2 Future Magnets European Collaboration for Accelerator-Quality HTS Magnets

Superconductor Stability Against Quench and Its Correlation with Current Propagation and Limiting

Hot Spot Temperature in an HTS Coil: Simulations With MIITs and Finite Element Method

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