Mechanical and electrical characteristics of a reinforced Bi2Sr2CaCu2O8 tape coil in large hoop stress

We fabricated a strengthened silver-sheathed multifilamentary Bi2Sr2CaCu2O8 tape coil with parallel co-winding Ag-0.5wt%Mg tape between turns and an additional Cu-50wt%Ag tape on the outer coil surface. The reinforced double-pancake coil with a wide bore 280 mm in diameter was investigated in a large hoop stress state up to 240 MPa at an external magnetic field of 10 T and 4.2 K. It is found that good transport properties without degradation for the test coil are revealed under a successfully reduced strain of less than 0.2% at 240 MPa. Moreover, it is pointed out that thermal stability for the silver-sheathed Bi2Sr2CaCu2O8 tape is closely related to the current sharing characteristics as a result of cryogenic stabilization with heat transfer from the metal surface to liquid helium. (author)