Persistent Mode MgB$_{2}$ Short Windings

The authors have reported the results of low n-value from a MgB 2 test coil developed a year ago. A second test coil has been developed with wire of different structure and manufacturing process. Although the n-value related voltage of the second test coil was lower than the first test coil at designed current, it still showed low n-value. A third test coil has been wound with reduced mechanical stress. It also showed very similar n-value related voltage and n-value. Investigation of voltage distribution over the coil indicated that magnetic field was the major factor causing degradation of the n-value and resulting in n-value related voltages. Since the n-value related coil voltages were on the order of 0.1 μV/cm, the usual short sample I c test (1 μV/cm was the definition of I c ) might not detect the n-value related voltage and might not be able to investigate the cause of low n-value. Therefore, the medium length (∼10 m) samples were tested and they showed the wire's lengthwise nonuniformity both on n-value and I c , which might be another potential cause of the low n-value of the coil. Along with the electrical investigation, the manufacturing process of the wire was carefully inspected for longitudinal uniformity. Some wire segment samples from the same batch exhibited nonuniformity in the particle size distribution resulting in nonuniform filaments. This might have occurred in the wire for the second and third test coils.

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“…Currently 100 A at 13 K was confirmed. It is the intention for future work to improve joint to have the full short sample critical current [10].…”

Section: Jointmentioning

confidence: 99%

Second Test Coil for the Development of a Compact 3 T $ \hbox{MgB}_{2}$ Magnet

Mine

Buresh

et al. 2013

IEEE Trans. Appl. Supercond.

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“…Superconducting joints for both monofilament ,,− and multifilament MgB 2 conductors ,,,− have been reported. The joints fabricated for multifilament MgB 2 conductors showed inferior performance compared with the joints fabricated for monofilament MgB 2 conductors owing to their finer filament size. ,,, Carbon (C)-doping is usually used in the MgB 2 material to improve its in-field performance. − However, the performance of the joints fabricated using C-doped MgB 2 conductors was found to be poorer compared with that of undoped MgB 2 conductors .…”

Section: Introductionmentioning

confidence: 99%

MgB₂ Superconducting Joint Architecture with the Functionality to Screen External Magnetic Fields for MRI Magnet Applications

Patel

Matsumoto

Kumakura

et al. 2022

ACS Appl. Mater. Interfaces

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A superconducting joint architecture to join unreacted carbon-doped multifilament magnesium diboride (MgB2) wires with the functionality to screen external magnetic fields for magnetic resonance imaging (MRI) magnet applications is proposed. The intrinsic diamagnetic property of a superconducting MgB2 bulk was exploited to produce a magnetic field screening effect around the current transfer path within the joint. Unprecedentedly, the joint fabricated using this novel architecture was able to screen magnetic fields up to 1.5 T at 20 K and up to 2 T at 15 K and thereby almost nullified the effect of the applied magnetic field by maintaining a constant critical current (I c). The joint showed an I c of 30.8 A in 1.5 T at 20 K and an ultralow resistance of about 3.32 × 10–14 Ω at 20 K in a self-field. The magnetic field screening effect shown by the MgB2 joint is expected to be extremely valuable for MRI magnet applications, where the I c of the joints is lower than the I c of the connected MgB2 wires in a given magnetic field and temperature.

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“…The first MRI models with MgB 2 coils [1,2] did not use superconducting joints, but it became clear that such joints would significantly improve their performance. Since then, several types of superconducting joints for connection of mono-and multifilamentary MgB 2 wires have been developed and tested [2][3][4][5][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

“…The simplicity of preparing bulk MgB 2 , its low mass density and the availability of raw materials could make it a major driving force of a future liquid hydrogen economy. The progress in MgB 2 joint design and fabrication [2][3][4][5][7][8][9][10] gives good reasons for optimism.…”

Section: Introductionmentioning

confidence: 99%

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Magneto-optical imaging of superconducting MgB₂joints

Mikheenko

Yurchenko

Johansen

2012

Supercond. Sci. Technol.

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A technique for joining superconducting MgB 2 pellets has been developed. For the first time, magneto-optical imaging has been used to visualize the superconducting behaviour of an MgB 2 joint. No significant difference was found between the penetration of the magnetic flux in the joint and in the bulk at low magnetic fields and at temperatures less than 35 K. The critical current density of the joint in high magnetic field was determined by measuring the transversal and longitudinal magnetic moment of a bar cut from the sample. A description was developed to extract the critical current density from magnetization measurements. The magnetization measurements reveal a critical current anisotropy in the pressed MgB 2 and a high critical current in the joint at low temperatures. A possibility to shape the superconductor by pressing, and the conditions preventing development and spread of fractures have been investigated. The joint technique, which utilizes high pressure, high temperature and high electrical current could be scaled up providing a basis for the wide use of superconductors at liquid hydrogen temperatures.

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Persistent Mode MgB$_{2}$ Short Windings

Cited by 29 publications

References 7 publications

Second Test Coil for the Development of a Compact 3 T $ \hbox{MgB}_{2}$ Magnet

Second Test Coil for the Development of a Compact 3 T $ \hbox{MgB}_{2}$ Magnet

MgB₂ Superconducting Joint Architecture with the Functionality to Screen External Magnetic Fields for MRI Magnet Applications

Magneto-optical imaging of superconducting MgB₂joints

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Persistent Mode MgB$_{2}$ Short Windings

Cited by 29 publications

References 7 publications

Second Test Coil for the Development of a Compact 3 T $ \hbox{MgB}_{2}$ Magnet

Second Test Coil for the Development of a Compact 3 T $ \hbox{MgB}_{2}$ Magnet

MgB2 Superconducting Joint Architecture with the Functionality to Screen External Magnetic Fields for MRI Magnet Applications

Magneto-optical imaging of superconducting MgB2joints

Contact Info

Product

Resources

About

MgB₂ Superconducting Joint Architecture with the Functionality to Screen External Magnetic Fields for MRI Magnet Applications

Magneto-optical imaging of superconducting MgB₂joints