Fabrication of NbTi Superconducting Joints for 400-MHz NMR Application

Abstract

NbTi superconducting joints (SJs) for a 400-MHz nuclear magnetic resonance (NMR) magnet system were fabricated using the superconducting solder matrix replacement in an open-air condition. A detection device for testing the resistance of SJ has been established. The results show that the overall resistance of SJs is 9.58 × 10 −12 Ω under the background field of 1 T by summation of individual joint resistance. The resistance of SJs and the capability for current load should meet the demands of the NMR system. The SJs are placed inside the cylindrical vessel above the magnet. The magnetic flux inside the top of the vessel is no more than 0.3 T to assure performance of joints. As results, there is only 0.0001 ppm for homogeneity deviation caused by SJs on this NMR system, and therefore, the negative effect is negligible.

High I c superconducting joint between Bi2223 tapes

“…T he superconducting joint technology has been well established for connecting metallic superconducting wires, such as Nb-Ti and Nb 3 Sn/Al, using superconducting solder thus far; [1][2][3][4][5] this is done in order to fabricate superconducting magnets for NMR and MRI systems equipped with a persistent current circuit, which provides a stable magnetic field. In the case of metallic superconductors, preparation of superconducting joints via solder is relatively easy because of their long superconducting coherence length and symmetric superconductivity.…”

Research on Fabrication Method of Low-Temperature Superconducting Joints

“…The superconducting properties are restored, and the outer ring is removed so that the superconducting loop of the inner loop can regain the induced current. The magnetic field of the superconducting loop is measured by the Hall sensor, and then the current and resistance in the loop are obtained [6][7].…”

“…The molten solder is finally injected into the copper tube and superconducting wire is stretched into it, waiting to solidify to form SJs. Experiments have shown that SJs prepared by this method have little adverse effect on the uniformity of the magnetic field [6].…”

Niobium-titanium (Nb-Ti) superconducting joints for persistent-mode operation

“…They achieved joint resistances of <1 × 10 −11 Ω in 1.5 T at 4.2 K. Cheng et al . also reported results on several Nb-Ti joints for a 400 MHz nuclear magnetic resonance magnet 4 . One of their joints in a closed-loop achieved a critical current ( I c ) of 89.5 A and joint resistance of 1.8 × 10 −13 Ω in 1 T at 4.2 K. In addition, Liu et al .…”