Abstract
Superconducting joints are essential for persistent-mode operation in a superconducting magnet system to produce an ultra-stable magnetic field. Herein, we report rationally designed niobium-titanium (Nb-Ti) superconducting joints and their evaluation results in detail. For practical applications, superconducting joints were fabricated by using a solder matrix replacement method with two types of lead-bismuth (Pb-Bi) solder, including Pb42Bi58 as a new composition. All the joints attained a critical current of >200 A below 1.43 T at 4.2 K. Our optimized superconducting joining method was tested in a closed-loop coil, obtaining a total circuit resistance of 3.25 × 10−14 Ω at 4.2 K in self-field. Finally, persistent-mode operation was demonstrated in an Nb-Ti solenoid coil with a persistent-current switch. This work will pave the way to developing high-performance Nb-Ti superconducting joints for practical applications.
Highlights
Superconducting magnets are used to produce a strong magnetic field in a compact system, which otherwise cannot be attained using conventional copper (Cu) based magnets
We checked the element composition using energy dispersive X-ray spectroscopy (EDS) because the superconductivity of Pb-Bi at 4.2 K is very sensitive to its composition and the age of the solder from the time of its manufecturing[14,15]
Beyond certain Bi concentration in the Pb-Bi alloys, Bi precipitates can act as impurities, which would have eventually reduced Jc of the Pb42Bi58 under magnetic field compared with the Pb44.5Bi55.514
Summary
Superconducting magnets are used to produce a strong magnetic field in a compact system, which otherwise cannot be attained using conventional copper (Cu) based magnets. To precisely estimate the joint resistance, a single-turn Nb-Ti closed-loop coil was fabricated and evaluated by using the field-decay measurement method. The Sn coated Nb-Ti wires were immersed in a molten Pb-Bi bath at 350 °C for 80 min (Fig. 3c)[13].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
