Transverse pressure induced reduction of the critical current in BSCCO/Ag tapes

摘要

The transport critical current of different BSCCO/Ag superconductors can be reduced severely when a certain deformation is applied. The influence of a pressure acting transversely on the wide side of the tape is investigated at 77 K. An irreversible reduction in the critical current occurs above 10 MPa. The strain induced in the superconductor is considered in a two phase mechanical model for a multi-filamentary BSCCO tape. Because of the low yielding strength of the matrix material, and the small fraction of pressurised area besides the BSCCO filaments, only a relatively small pressure can be absorbed by the matrix. Based on this analysis it is concluded that the properties of the BSCCO itself mainly determine the transverse pressure dependence of these tapes at pressures above 30 MPa. Transverse pressure experiments are made on different types of BSCCO/Ag and AgMg tapes up to 150 MPa. The relative current change due to a pressure in a AgMg tape is large -3 GPa~(-1), compared to the value of -2 GPa~(-1) that is measured in Ag tapes. This observation supports the model that predicts a very limited role for the matrix strength in the case when a large transverse pressure is applied.