The outer diameter of this wire is 0" 52 mm and the ratio of A1 to NbTi is 1"0. The current field characteristic of the wire, for instance, heat treated at 300 C for 80 hours, is presented in Figure 2. With these results, the mean current density in the wire is 30 000 A cm -2 at 50 kG. Figure 3 shows the voltage-current characteristics, when little hysteresis effects are present.
In addition to the advantages presented above, the problem of the aluminium's softness against electromagnetic forces is improved by the use of a drawing technique of coaxial NbTi, pure A1, and duralumin. The thickness of the outer duralumin may be increased according to the electromagnetic forces in the coil. The material used as an insulator, anode oxide, which has heat conductivity of the order 2 to 3 better than conventional organic insulation can be also electrolysed on the surface of duralumin. Then, with the development of the new drawing technique, the advantages of aluminium stabilizer can be completely exploited.
A solenoid magnet is being constructed with 2 000 m of this wire in which the over-all current density will be more than 15 000 A cm -2 at 50 kG. A better self-protection at quenching is expected for this A1 stabilized coll. ~I~ALL, ~/UL Current l ~. . ~5OOpV JSA Figure 3. Voltage current characteristic of the AI stabilized wire with the magnetic field as a parameter
On the other hand, the drawing of fine multifilament NbTi wires with high purity A1 is now being tried by this method.