Toshinori Ozaki1,Satoshi Semboshi2,Hiroyuki Okazaki3,Hiroshi Koshikawa3,Shunya Yamamoto3,Tetsuya Yamaki3,Atsushi Yabuuchi4,Tetsuro Sueyoshi5,Hitoshi Sakane6
Kwansei Gakuin University1,Tohoku University2,National Institutes for Quantum and Radiological Science and Technology3,Kyoto University4,Kyushu Sangyo University5,SHI-ATEX Co., Ltd.6
Toshinori Ozaki1,Satoshi Semboshi2,Hiroyuki Okazaki3,Hiroshi Koshikawa3,Shunya Yamamoto3,Tetsuya Yamaki3,Atsushi Yabuuchi4,Tetsuro Sueyoshi5,Hitoshi Sakane6
Kwansei Gakuin University1,Tohoku University2,National Institutes for Quantum and Radiological Science and Technology3,Kyoto University4,Kyushu Sangyo University5,SHI-ATEX Co., Ltd.6
High-temperature superconductors (HTS) based on REBa2Cu3Oy (REBCO, RE = rare earth) have become powerful materials for high field applications such as rotation machines, generators for wind turbine and magnet use in medical imaging machines. Optimizing the critical current density <i>J</i><sub>c</sub> of REBCO coated conductors (CCs) at a given temperature and magnetic field is particularly important for these applications. The in-field <i>J</i><sub>c</sub> can be enhanced by the introduction of precipitates and defects with nano-meter size, which can pin the vortices. The desirable pinning structures could be provided by ion irradiation which enable the creation of a variety of defects, such as points, clusters and tracks, by choosing appropriate ion species and energy. Therefore, ion irradiation would be a promising approach to realize high performance CCs by engineering the vortex pinning landscape for the specific needs of each application. Recently, ion irradiation in a low energy range has been revisited as a practically feasible approach to improve in-field <i>J</i><sub>c</sub>, due to compact accelerator, less radioactivation and less expensive to operate. We demonstrated an enhancement of <i>J</i><sub>c</sub> by using proton and Au-ion irradiation with low-energy in iron-chalcogenide FeSe<sub>0.5</sub>Se<sub>0.5</sub> superconducting films.[1] In this presentation, we present systematically the effect of low-energy ion irradiation on flux pinning and microstructure in REBCO CCs. Upon 10 MeV Au ion irradiation (10 MeV Au ions would penetrate through the GdBCO layer), over 70% <i>J</i><sub>c</sub> enhancement was achieved around 3 T at 30 K, indicative of effective pinning defects by the irradiation. In the case of 2 MeV Au ion irradiation (2 MeV Au ions would stop in the GdBCO layer), a nearly 50% increase in <i>J</i><sub>c</sub> is observed over 3 T at 30 K. The superconducting transition temperature <i>T</i><sub>c</sub>’s of the GdBCO CCs irradiated by both 2 and 10 MeV Au ions decrease gradually with increasing flucence up to around 8.0×10<sup>11</sup> /cm<sup>–2</sup> and then significantly started to drop. Positron annihilation measurements reveal that irradiation-induced vacancy-type defects caused a reduction in <i>T</i><sub>c</sub> [2]. We will also report superconducting properties and flux pinning in GdBCO CCs irradiated by various doses and ion species.<br/>We would like to thank Sumitomo Electric Industries, Ltd. for providing the GdBCO CCs.<br/>1) T. Ozaki et al., Supercond. Sci. Technol. 33, 094008 (2020).<br/>2) A. Yabuuchi et al., Appl. Phys. Express 13, 123004 (2020).