Experimental Study on Quasi-Isotropic Critical Current of an HTS Conductor With High Engineering Current Density

It is well known that the critical current of the second generation (2G) high temperature superconducting (HTS) wire strongly depends on magnetic field and its orientation. An HTS conductor with high engineering current density considering the effect of quasi-anisotropy of critical current has been proposed, and its configuration is a combination of a quasi-isotropic strand (Q-IS) on which winding HTS wires similar with winding method of cable layer. In this paper, the dependence of the critical current density of inner Q-IS on twisting pitch of Q-IS and winding pitch of cable layer was analyzed by both of simulation and experiment. Experimental results are good agreement with the simulation ones, and show that the critical current density of Q-IS increases as decreasing winding pitch of cable layer and twisting pitch of Q-IS. The achieved maximum critical current density is about 7% more than the one of Q-IS in self-field. It is predicted that the critical current density of inner Q-IS will increase further if the 2G HTS wire is narrower or the current in outer cable layer bigger. The variation of n-value of inner Q-IS with winding pitch of cable layer and twisting pitch of Q-IS is also measured, and the trend of n-value is similar to the trend of critical current density.