1993 年 28 巻 9 号 p. 526-532
We applied Bi-based superconducting bulk for current leads in a cryocooler cooled superconducting magnet using no liquid helium: The bulk has a composition of (Bi+Pb):Sr:Ca:Cu=2:2:2:3 and is utilized in the form of thin-walled sintered cylindrical tube. Critical current and critical current density of the bulk under self magnetic field at 77K are at 1, 100A and 1, 200A/cm2, respectively. At a current of 400A, this magnet can generate a steady magnetic field of 4T in a room temperature 38mm bore. Heat leakage through Bi (2223) bulk leads when passing a current of 400A is slight at about 0.2W. Thereby, the resulting total heat load on the coil is less than 0.4W, within cooling capacity of the G-M cryocooler.