Critical current anisotropy in NbTi cables

Abstract

The short sample critical current of multifilamentary NbTi cables is usually measured in a magnetic field which is oriented perpendicular to the broad face of the cable. This is the same orientation that occurs at the equatorial turns of a cos theta type dipole magnet and is, therefore, usually specified in quality control short sample tests. It is generally found that the current density in cables is less than in wires. This degradation, as it is commonly called, may be as large as 15%. The effect is illustrated in a statistical way, which shows the distribution of wire and cable results for the Colliding Beam Accelerator Project at BNL. The current densities were calculated using geometrical data. Some 200 cable and 750 wire tests are included in the normal curve distributions shown. The mean cable Jc is 14% lower than that of the wire. Similar results were obtained in previous work.