Abstract
Understanding how irradiation degrades superconductivity in REBCO coated conductor is a pressing field of research for the development of compact fusion devices. Here, defect formation in GdBa2Cu3O7−δ coated conductor is studied using a high dose of 2 MeV He+ ion irradiation. While laboratory based X-ray diffraction and magnetometry measurements show that the crystal structure becomes less well ordered with the loss of superconductivity in the material, transmission electron microscopy reveals a complex landscape of structural defects within the as-manufactured tape which complicate the identification and characterisation of irradiation induced structural changes. To resolve this, three sets of polarisation dependent extended X-ray absorption fine structure (EXAFS) spectroscopy experiments were carried out to map the local structure of the Gd, Ba, and Cu atomic sites within the material, providing three independent probes for studying irradiation defects within the structurally anisotropic REBCO unit cell. Here the Ba and Cu environments were the more sensitive to the irradiation treatment, with only small changes to the Gd local structure observed. Both the Ba and Cu local structures retained much of the pristine structure in the a/b-plane following irradiation, with greater shifts evident in the c-axis aligned measurements. In the irradiated Cu K edge EXAFS analysis, a shifted peak in the c-axis aligned measurements is observed that is not compatible with the REBCO local structure. This is attributed to an O site irradiation defect motif consistent with a Frenkel defect.