Performance of an over-pressure processed Bi-2223/Ag/SUS tape and a small layer-winding coil

We have successfully demonstrated the utility and potential of Bi-2223/Ag tapes fabricated by a CT-OP (controlled-overpressure) process. In this paper, we report the I c – B – T performance of a short tape with stainless steel lamination and energizing-test results of a small layer-winding coil in an external magnetic field ranging from 0 to 12 T and at temperatures ranging from 4.2 to 90 K. The coil is a solenoid layer-winding of a 135 m piece of Bi-2223/Ag tape with stainless steel lamination on both sides. The dimensions of the conductor are 2.7 mm in width and 0.25 mm in thickness, including a 0.02 mm thick stainless steel lamination on both sides. A short sample cut from the same tape has critical currents exceeding 76 A, 307 A and 438 A at 77 K, 30 K and 4.2 K, respectively, in self-field. The winding was performed using a 'react & wind' technique and the resultant coil had 597 turns and dimensions of 65 mm (inner diameter), 83 mm (outer diameter) and 60 mm (winding height). In 12 T, 4.2 K, the coil- I c is 191 A, which adds 1.42 T to the external field. In the present coil, the coil- I c is controlled by the field component in the coil's radial direction generated by the coil itself. The I c values of the coil agree very well with those estimated from the short sample's performance and field distribution. The results indicate that the homogeneity of the Bi-2223 conductor is very good throughout its whole 135 m length.