Multifilament V3Ga and Nb3Sn superconductors produced by the ECN-technique

Multifilament V3Ga and Nb3Sn have been produced using the ECN-technique. Composites of vanadium or niobium tubes, containing a powder of intermetallic compounds and embedded in pure unalloyed copper are reduced to wires of 1-0.5 mm diameter. V3Ga is formed at reaction temperatures between 550°C and 650°C and Nb3Sn between 600°C and 700°C. During the isothermal heat treatments intermediate formation of V6Ga5and Nb6Sn5occurs. Tcvalues increase during progression of the reactions from 10 K to 15 K for V3Ga and from 14 K to 18 K for Nb3Sn. The Jc(H) curves between 2 T and 11 T for V3Ga show that the field dependence is strongly related to the degree of chemical reaction. After complete formation of the V3Ga layer the decay of the almost exponential Jc(H) curves is weakest, indicating that these samples are superior at higher field values, in spite of lower values at low fields. The Jcvalues at 10 T of completely reacted V3Ga samples are found to be strongly dependent on layer thickness, ranging from 1×10⁸A/m²for a layer of 12 μm to 7×10⁸A/m²for a layer of 6 μm.