Speaker
Description
With the innovation of accelerator magnet technology, the design of superconducting magnets is also changing and put forward high requirements on the performance of NbTi superconducting wire, which requires high critical current density and ultra low loss. A new type of superconducting wire with high critical current density, fine filament, ultra low loss NbTi/Cu5Ni/Cu has been developed in this paper. The wire uses high purity Cu5Ni alloy instead of conventional high purity oxygen-free copper as the matrix, which prevents the coupling between every filament at low temperature and reduces the AC loss effectively. Meanwhile, the Cu5Ni matrix and NbTi filament are separated by high purity Nb. Nb as a barrier layer could isolate the diffusion reaction between Cu and Ti in the process of high temperature and long time aging heat treatment, and reduce the number of wire breakage effectively. In order to reduce the hysteresis loss of the wire, the filament of the wire is increased to 75276, the filament diameter is reduced to 1.9μm, and the Cu/Sc ratio is 1.3. The filament diameter of Φ1.2mm wire is 2.9μm, Jc(4.2K, 5T) is 2710A/mm2, and the ‘n’ value is 35. When the filament diameter further decreases, the filament diameter of Φ0.82mm wire is 1.9μm, Jc(4.2K, 5T) is 2410A/mm2, and ‘n’ value is only 18. The Jc and ‘n’ value of the wire are all reduced. The reason may be due to the breakage of some filaments. Finally, the wire with Φ0.82mm, 75276 filaments and Cu/Sc ratio of 1.3 was prepared. The hysteresis loss (4.2K,±3T) was 20.1mJ/cm3, which reached a new low in history.
