Characteristics of Round and Extracted Strands of Nb3Al Rutherford Cable

Long Nb{sub 3}Al strands with copper stabilizer are promising for future high field accelerator magnets. A 1.2 kilometer Nb{sub 3}Al strand with Cu stabilizer was fabricated at the National Institute for Materials Science in Japan. Using this strand a 30 meter Cu stabilized Nb{sub 3}Al Rutherford cable was made for the first time by a collaboration of NIMS and Fermilab. The Nb{sub 3}Al strands extracted from cable with a relatively low packing factor showed almost no J{sub c} degradation. But the extracted strands from the highly compacted cable showed some degradation in both J{sub c} and n value, which may be caused by local separation of the copper stabilizer. Still, its J{sub c} degradation is lower than that of typical Nb{sub 3}Sn strands. The current limit due to magnetic instability in low field is about 500 A at 4.2 K. The magnetization of the strands, which was measured with balanced coils at 4.2 K, showed large flux jumps, usually around 1.5 T. This value is much larger than the B{sub c2} (4.2 K) of the Nb matrix, which is around 0.4 Tesla. The magnetic instability of the Nb{sub 3}Al strand at low field is not completely understood, but it might be explained by the superconducting coupling current through the Nb matrix.