Pulsed Magnetic Field Assisted Technique for Joining $ \hbox{MgB}_{2}$ Conductors for Persistent Mode MRI Magnets

Woźniak, Mariusz; Glowacki, B.A.; Setiadinata, S. B.; Thomas, Adrian

doi:10.1109/tasc.2012.2229093

Cited by 19 publications

(21 citation statements)

References 11 publications

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“…Several superconducting joint techniques for both in-situ and ex-situ MgB 2 conductors have been reported [13,[16][17][18][19][20][21][22][23] comparison of the critical current (I c ) of the joint with the wire, the closed-loop coil, and the microstructural analysis of the joints are presented in detail.…”

Section: Introductionmentioning

confidence: 99%

MgB₂superconducting joints for persistent current operation

Patel

Hossain

See

et al. 2015

Supercond. Sci. Technol.

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High-performance superconducting joints are essential for realizing persistent-mode magnets. Herein, we propose a concept and fabrication of such superconducting joints, which yielded reliable performance in the operating temperature range of 4.2-25 K. MgB 2 -MgB 2 joints in magnets are known to result in deterioration of localized electrical, thermal, and mechanical properties. To overcome these problems, the ends of the two wires are inserted into a pellet press, which is then filled with a mixture of unreacted magnesium and boron powders, followed by heat treatment. The critical current capacity and joint resistance were precisely evaluated by the standard four-probe method in open-circuit and by field-decay measurements in a closed-loop, respectively. These joints demonstrated up to 66% of the current-carrying capacity of unjoined wire at 20 K, 2 T and joint resistance of 1.4 x 10 −12 Ω at 4.2 K in self-field. AbstractHigh-performance superconducting joints are essential for realizing persistent-mode magnets.Herein, we propose a new process and fabrication of such superconducting joints, which yielded reliable performance in the operating temperature range of 4.2 K to 25 K. MgB 2 -MgB 2 joints in magnets, are known to result in deterioration of localized electrical, thermal, and mechanical properties. To overcome these problems, the ends of the two wires are inserted into a pellet press, which is then filled with a mixture of unreacted magnesium and boron powders, followed by heat treatment. The critical current capacity and joint resistance were precisely evaluated by the standard four-probe method in open-circuit and by fielddecay measurements in a closed-loop, respectively. These joints demonstrated up to 66% of the current-carrying capacity of unjoined wire at 20 K, 2 T and joint resistance of < 1.4 x 10 -12 Ω at 4.2 K in self-field.

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Section: Introductionmentioning

confidence: 99%

MgB₂superconducting joints for persistent current operation

Patel

Hossain

See

et al. 2015

Supercond. Sci. Technol.

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“…Therefore, for wide applicability of MgB 2 in MRI, more work still needs to be done on the joining process. So far, there have been several reports on joining both in situ and ex situ MgB 2 conductors [6,16,[20][21][22][23][24][25][26][27]. Comparison of our joint performance values with various literatures is summarized in table 1.…”

Section: Introductionmentioning

confidence: 95%

A new approach to a superconducting joining process for carbon-doped MgB₂conductor

Patel

Hossain

Maeda

et al. 2016

Supercond. Sci. Technol.

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We report a new approach to a superconducting joining process for unreacted in situ carbon (C)-doped magnesium diboride (MgB2) wires. To operate a magnetic resonance imaging (MRI) magnet in the persistent mode, the superconducting joints between two conductors are as critical as the other key components. In addition, a stable and reliable joining process enables the superconducting magnet to operate without an external power supply. However, joint results using unreacted in situ C-doped MgB2 wires, which are used for high-field operation, have been limited, and only very poor performance has been obtained. By controlling the pressure inside a joint part, in this study, we successfully obtained current carrying retention in the joint of up to 72% compared to wire without a joint. The closed-circuit resistance of our closed-loop coil was less than 1.8 × 10−13 Ω at 16.7 ± 4.7 K, as measured by the field-decay measurement method. These results indicate that MgB2 has a promising future in MRI application.

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“…1a in order to soften the cold-drawn copper. This sample (labelled OCD in Table 1) was electromagnetically densified with 200 J of energy and with forming coil as described in [16]. All three samples (Table 1) were finally heat-treated at 700 • C for 5 min with 20 • C min −1 heating rate and left in the furnace to naturally cool down to room temperature (Fig.…”

Section: Samplesmentioning

confidence: 99%

“…The resulting magnetic pressure acting uniformly on the surface of the wire sheath achieves its peak value of 712 MPa at 1.2 μs (Fig. 3) as calculated using finite element modelling [9,15,16]. …”

Section: Electromagnetic Compactionmentioning

confidence: 99%

Electromagnetically Assisted Densification of Copper-Sheeted in Situ MgB 2 /Cu Wires

Woźniak

Glowacki

2014

J Supercond Nov Magn

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This paper summarizes recent methods of improving critical current density of in situ Cu-sheathed MgB 2 wires. These methods include using optimum heat treatment schedule, adding copper powder to the wire core and electromagnetic densification of wire core. The large part of work reported here focuses on the latter method applied to the relatively low-density MgB 2 /Cu wire core. The packing density of unreacted, monofilament wire core was increased by 8 % with oscillating magnetic pressure, reaching a peak value above 700 MPa as calculated by finite element modelling of the forming process. The higher density of the MgB 2 core combined with copper powder addition resulted in a critical current density increase of more than fivefold in comparison to purely stoichiometric and cold-drawn-only wire.

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Pulsed Magnetic Field Assisted Technique for Joining $ \hbox{MgB}_{2}$ Conductors for Persistent Mode MRI Magnets

Cited by 19 publications

References 11 publications

MgB₂superconducting joints for persistent current operation

MgB₂superconducting joints for persistent current operation

A new approach to a superconducting joining process for carbon-doped MgB₂conductor

Electromagnetically Assisted Densification of Copper-Sheeted in Situ MgB 2 /Cu Wires

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Pulsed Magnetic Field Assisted Technique for Joining $ \hbox{MgB}_{2}$ Conductors for Persistent Mode MRI Magnets

Cited by 19 publications

References 11 publications

MgB2superconducting joints for persistent current operation

MgB2superconducting joints for persistent current operation

A new approach to a superconducting joining process for carbon-doped MgB2conductor

Electromagnetically Assisted Densification of Copper-Sheeted in Situ MgB 2 /Cu Wires

Contact Info

Product

Resources

About

MgB₂superconducting joints for persistent current operation

MgB₂superconducting joints for persistent current operation

A new approach to a superconducting joining process for carbon-doped MgB₂conductor