Abstract
In part I of this paper, the critical size of Y1Ba2Cu3O7-x (YBCO) has been determined from the magnetic stability criterion. Based on the result, composite conductors of YBCO and copper are designed assuming critical current density of 1.0×109A/m2 at 77K and 1.0×1010A/m2 at 20K. A multifilamentary composite of 4mm in diameter can be operated up to the critical current at 77K but, at lower temperatures, the self-field instability limits the maximum current. A composite tape conductor is also designed: the thickness of YBCO is 25μm and the total thickness of copper is 100μm. The analysis shows that the tape conductor is quite stable when the wide face is exposed to the coolant. A tape of 20mm width can attain its critical currents of 500A at 77K and 5, 000A at 20K without suffering from magnetic instability.
