Multifilamentary MgB2-based solenoidal and racetrack coils

• Published in: Physica. C, Superconductivity Superconductivity, 2007-07, Vol.458 (1-2), p.12-20
• Main Authors: SUMPTION, M. D, BHATIA, M, BUTA, F, BOHNENSTIEHL, S, TOMSIC, M, RINDFLEISCH, M, YUE, J, PHILLIPS, J, KAWABATA, S, COLLINGS, E. W
• Format: Article
• Language: English
• Subjects: Applied sciences; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electrical engineering. Electrical power engineering; Exact sciences and technology; Granular, melt-textured, amorphous and composite superconductors; Inhomogeneous superconductors and superconducting systems; Materials; Physics; Superconductivity
• ISSN: 0921-4534; 1873-2143
• DOI: 10.1016/j.physc.2007.03.001

In a continuation of a series of reports on the fabrication and properties of several demonstration coils and solenoids wound with MgB2 strand this paper describes the winding, testing, and load-line comparisons for a racetrack coil (R-4) and two solenoids (S-1 and S-2). Racetrack R-4 was wound with 19-filament strand, S-1 and S-2 with 7-filament strand. The filaments were clad in Nb-lined Cu and the restack bundle was enclosed in a monel sheath; some Cu stabilization was included. Transport Jc measurements were performed initially in liquid He, and then as a function of temperature up to 30K. Racetrack R-4 achieved 240A in self-field at 7.7K corresponding to a Jc of 240kA/cm2, leading to a strand Je of 43kA/cm2, and a winding Je,w of 22kA/cm2. At 4K, S-1 (310m of strand) achieved an Ic of 138A and a bore field of 3.4T; S-2 (742m of strand) an Ic of 85A and a bore field of 3.9T. The magnetic field profiles for all coils were calculated using a finite element approach in conjunction with the Biot-Savart equation. The windings were treated as a series of small segments, each tangential to the winding, numerical errors were estimated. These calculations were used to generate load-line comparisons for the coils.