Nbの人工層状ピンニングセンターを有するNbTi超電導多層圧延板の製造

抄録

NbTi superconducting multilayer rolled sheet with Nb layers for artificial pinning centers can be manufactured using Cu alloy hardened by precipitation as intermittent layers. The total number of Nb layers is 580, that of NbTi layers is 551, that of Cu-3Ni-0.6Si-0.2Zn intermittent layers is 28 and that of Cu layers is 2 (only outside). The global pinning force F_p value of the multilayer sheet 40μm in total thickness cut widthwise is about 15GN/m³, while the magnetic field is 1T. This value is comparable with those of superconducting multifilamentary wires with artificial pinning centers. But F_p values when the magnetic field is above 3T are almost the same as those of conventionally aged sheets. The Nb layers for artificial pinning centers are effective at 3T and below 3T in a comparatively low magnetic field. According to the relationship between F_p values and the measured thicknesses of Nb and NbTi layers, Nb layers do not have much effect as artificial pinning centers until their thickness is less than 100nm. When the mean thickness of the Nb layers is 95 to 33nm, the magnetic field where the F_p value reaches the maximum is kept around 1T. The maximum F_p value is obtained when the mean thickness of the Nb layers is 39nm. The restacked multilayer sheet, 80μm in total thickness and 29nm in mean thickness of the Nb and NbTi layers, is manufactured by combining the former two multilayer sheets. The magnetic field where the F_p value reaches the maximum in this restacked multilayer sheet is shifted by 0.5T to 1.5T from 1T going toward the higher magnetic field range, and the F_p value at 3T also increases to about 10GN/m³, which is considerably high compared with that of the conventional sheets. According to this result the large-size multilayer sheet with a strong pinning force in higher magnetic fields could be manufactured by the rolling method if the final total thickness of the sheet and the thicknesses of Nb and NbTi layers are optimized.