Investigation of multifilament MgB2 superconducting joint technique for development of MRI magnets

Abstract

This study presents the investigation of superconducting joints fabricated using multifilament magnesium diboride (MgB2) wires for the development of persistent-current mode magnetic resonance imaging (MRI) magnets. The critical current of the jointed samples decreased with increasing cutting angle because the smaller cutting angle allowed greater exposure of the MgB2 filament, thereby increasing the contact area for the wire-bulk-wire connection. In addition, an appropriate pressing pressure (300 MPa) was necessary to establish the multifilament MgB2 joint without significant degradation of superconducting properties. The resistance of the optimal MgB2 joint, measured using the field-decay technique, was <1.5 × 10−14 Ω. Therefore, the proposed joint technique can be employed for developing multifilament MgB2 MRI magnets operating in the persistent-current mode.

Tailored joint fabrication process derived ultra-low resistance MgB2 superconducting joint

“…The Ic performance of our joint at 10 K in self-field is comparable to the joint results reported by Yao et al [21]. However, it is lower at 20 K in self-field compared with Ic of the joint recently reported by Yoo et al [33]. Therefore, we further need to improve the transport Ic of our joint.…”

“…Further tailoring of compaction pressure around 20 kN force might reduce the cracks in the joint part. These cracks can be attributed to somewhat lowering Ic of our joint compared with Yoo et al [33]. The interface between the MgB2 filament and bulk appeared very good with some half pores on the edge.…”

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

“…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 . The reason for this performance variation is still unknown.…”

Optimized superconducting MgB2 joint made by IMD technique

“…IMD MgB 2 wires have much higher J c than that of powderin-tube processed MgB 2 wires [16]. The IMD process has another advantage, due to its ability to produce highly dense MgB 2 core structures without porosity, making for better connections in the joints [17][18][19][20][21]. An ultra-stable magnetic field is required for high-resolution magnetic resonance imaging (MRI) and thus, superconducting joints are required to operate MRI MgB 2 magnets in a persistent current (PC) mode.…”