Three solenoids were wound with MgB2 strands and tested for their transport properties. One of the coils was wound with a Cu-sheathed monofilamentary strand and the others with a 7-filament strand with Nb-reaction barriers, Cu stabilization and an outer Monel sheath. The wires were first S-glass insulated, then wound onto an OFHC Cu former. The coils were then heat-treated (675C, 0.5h, monofilamentary strand and 700C, 20min, multifilamentary strand). Smaller (1m) segments of representative strand were also wound into barrel-form samples and heat-treated together with the coils. After heat-treatment, the coils were epoxy-impregnated. Transport JC measurements were performed at various taps along the coil lengths. Measurements were initially made in liquid He, and then as a function of temperatures of up to 30K. The homogeneity of response along the coils was investigated, and a comparison with the short-sample results was made. Each coil contained more than 100m of 0.84–1.01mm OD strands. One of the 7-strand coils attained 222A at 4.2K, self-field, with a JC of 300kA/cm2 in the SC and a winding pack Je of 23kA/cm2. At 20K, these values were 175 and 13.4kA/cm2. Magnet bore fields of 1.5 and 0.87T were achieved at 4.2 and 20K, respectively. The other multifilamentary coil gave similar results.

Solenoidal Coils Made from Monofilamentary and Multifilamentary MgB2 Strands. M.D.Sumption, M.Bhatia, F.Buta, S.Bohnenstiehl, M.Tomsic, M.Rindfleisch, J.Yue, J.Phillips, S.Kawabata, E.W.Collings: Superconductor Science and Technology, 2005, 18, 961-5