Stress dependence of the critical currents in neutron irradiated (RE)BCO coated conductors

The application of HTS coated conductors in future fusion or accelerator magnets is currently of increasing interest. High Lorentz forces and therefore high hoop stresses act on the conductors in large coils. The conductor is furthermore exposed to neutron radiation in fusion or accelerator magnets. The expected neutron fluence over the desired lifetime of such magnets can be simulated by irradiation experiments in a fission reactor. The coated conductors were characterized in the pristine state and after irradiation to a fast neutron fluence of 1 × 10 22 m −2 (ITER design fluence). The sensitivity of the critical currents to applied stress was measured in liquid nitrogen. The cold part of the setup was positioned within a rotatable split coil electro-magnet to assess the I c -anisotropy up to 1.4 T under maximum Lorentz force configuration. The I c -sensitivity to applied stress changed significantly in the GdBCO/IBAD conductor after irradiation, whereas nearly no change was observed in the YBCO/RABiTS conductor. Furthermore, I c and T c were strongly reduced in the GdBCO/IBAD sample after irradiation. The angular dependence of I c changed for both samples in different ways after the irradiation, but no change in the angular dependence was observed upon applying stress. The high neutron capture cross-section of Gd and the resulting strong reduction of T c seem to be responsible for the different stress dependences of I c in irradiated Gd-123 coated conductors.