$rm Nb_3rm Al$ Wire Development for Future Accelerator Magnets

Recent developments in RHQ Nb 3 Al wire for accelerator magnets are presented and discussed. The main items of the development are to increase the critical current density (J c ) and to find a good stabilization method. For the former item, test wires with different Nb-matrix/filament ratios were made, and the effect of the ratio on J c was investigated in correlation with the heat treatment and the area reduction after the RHQ process. For the latter item, a special copper electroplating technique was developed to deposit a thick Cu layer on the surface of the wire. The mechanical bonding strength and the electrical characteristics of the Cu layer were studied by bending and drawing the wire, and by measuring the resistance. Although the present piece length of the Cu stabilized Nb 3 Al wire is about 40 cm, we can draw and reduce the wire down to 60% of the original diameter, without breaking the wire or damaging the bonding of the Cu stabilizer. The highest noncopper J c achieved during this study was 2156 A/mm 2 at 10T and 4.2 K