Effect of Ion Irradiation on the Superconducting Properties of HTS Composites in a Helical Cable

In next-generation Megascience facilities (tokamaks, synchrotrons, and accelerators), strong magnetic fields generated by HTS-based magnetic systems are required to confine plasma and charged particles. The transport and magnetic properties of HTS tapes, which form the basis of these magnetic systems, are sensitive to the type and concentration of defects in the superconducting layer. This paper investigates the effect of ion irradiation on the superconducting properties of HTS tapes in helical cables. The dependence of the critical current of HTS tapes subjected to preliminary ion irradiation on the external magnetic field is studied. Irradiation is performed with Fe2+ ions at an energy of 5.6 MeV and various fluences at room temperature. The samples consist of 4 mm wide HTS tapes with an exposed superconducting layer, wound on a 5 mm diameter cupronickel tube, as well as undeformed tapes. At a fluence of 5 × 1012 cm–2, the critical current density increases at temperatures below 30 K over the entire measured magnetic field range for undeformed tapes. Further increase in fluence leads to degradation of the superconducting properties. For tapes subjected to bending deformation, the highest critical current density corresponds to a fluence of 1 × 1013 cm–2, although it does not exceed the value for the undeformed, unirradiated sample.