Experimental Research of the New Developed High-J c Nb 3 Sn Superconducting Strand for 14 T MRI Magnet

The Institute of Plasma Physics Chinese Academy of Sciences (ASIPP) has announced a project to design and manufacture a high field MRI magnet with a 900 mm warm bore and comprised of Nb3Sn Rutherford cables in 2017. The maximum magnetic induction of magnet system is 14.3 T and magnetic field homogeneity in a spherical volume with 22 cm diameter is better than 0.5 ppm. The high performance Nb3Sn strand is the potential options to use for such high field magnet system. ASIPP cooperates with Western Superconducting Technologies Company (WST) to develop high performance Nb3Sn strand whose critical current density Jc is higher than 2000 A/mm2 at 4.2 K, 12 T. To obtain the actual performance of WST high performance Nb3Sn strand, three short samples are prepared with different non-copper ratio or different heat treatment, the critical current Ic or quench current of all sample is measured at different field by the voltage-current (V-I) method, the residual resistivity ratio (RRR) of all sample is also measured. To study the strand whether it will be affected by low field instability, a small coil is built with WST strand, and the experimental result is presented and discussed in this paper.