Fabrication of$rm Cu$Stabilizer into Long-Length RHQT-Processed$rm Nb_3rm Al$Round Wire

For the practical conductors with large current capacity, the Cu stabilizer is necessary in order to obtain their fully performance. The most important issue remaining for producing the RHQT (rapid-heating/quenching and transformation)-processed Nb₃Al round wire was how to fabricate the Cu stabilizer after the RHQ treatment. We successfully solved this problem and developed the Cu ion-plating technique for fabricating the Cu stabilizer into the RHQT-processed Nb₃Al round wires. Although stable Nb oxide layer is formed on the wire surface, the Cu ion-plating can continuously remove them and cover the Cu seed-layer of 1 mum in thickness. Then, the Cu stabilizer can be also fabricated by the Cu electroplating with an appropriate of Cu ratio. The reel-to-reel apparatus of both the Cu ion-plating and electroplating for km-class long-wire have been set up. It was possible to apply the wire drawing by conventional die after the Cu electroplating due to the good bonding between the Cu stabilizer and Nb₃Al round wire. This is very attractive advantage for obtaining the severe homogeneity of the wire diameter in long-length. Moreover, in order to obtain large enough RRR, it may be suitable to carry out the following techniques before fabricating the Cu stabilizer, which are an anode-oxidization of wire surface, normal die drawing and easy chemical etching of Nb oxide layer. This additional process is very effective to get much clean and homogeneous surface of the Nb₃Al round wires with Nb matrix, and then it has been fabricated the Cu stabilizer without degradation of RRR. RRR of about 200 and non-Cu Jc (4.2K, 15T) of about 1,000 A/mm² were obtained on the present Cu-stabilized RHQT-processed Nb₃Al round wires having 1.0 mm in diameter and about 1.0 of Cu/non-Cu ratio. Nb₃Al filament diameter is 30-50 mum at present. These results must be very attractive for application of the high energy physics conductors