Patent ID: 8565845

Claim:
A superconducting coil, having the shape of a pancake formed by winding a superconducting conductor; the superconducting conductor comprising a tape-shaped (Bi, Pb)2223-based superconducting wire and a tape-shaped thin-film RE123-based superconducting wire that are electrically connected in parallel with each other; wherein: (a) the tape-shaped (Bi, Pb)2223-based superconducting wire has a first critical-current value at an operating temperature and magnetic field; (b) the tape-shaped thin-film RE123-based superconducting wire has a second critical-current value at the operating temperature and magnetic field; and (c) a ratio of the first critical-current value to the second critical-current value is at least 0.8 and at most 1.25, and a ratio of an n-value of the tape-shaped (Bi, Pb)2223-based superconducting wire to that of the tape-shaped thin-film RE123-based superconducting wire is at least ⅙ and at most ⅔, wherein the n-value is a coefficient value of current in a current-voltage characteristic which is expressed as V∝I n , V-voltage and I-current.