Development of a IT cryocooler-cooled pulse coil with a Bi2223 superconducting parallel conductor for SMES

We designed and fabricated a IT cryocooler-cooled pulse coil operating at 40 K. A 4-strand interlayertransposed parallel conductor composed of Bi2223 rectangular cross-sectional multifilamentary wires was adopted to realize a uniform current distribution and to reduce the ac loss density down to the level of that of a single strand. The pulse coil is a 16-layer solenoidal one with an inner diameter of 52 mm, an outer diameter of 111 mm and a height of 120 mm. The heat drains of AIN plates, which are insulators, are arranged between layers for the cooling of the heat due to the ac loss by heat conduction. We could continuously operate the coil in a triangular waveform mode with an amplitude of IT and a frequency of 1 Hz. The ac loss was 10.6 W and the other thermal load was 13 W.