Positron Annihilation Lifetime Spectroscopy Study of Neutron Irradiated High Temperature Superconductors YBa2Cu3O7-δ for Application in Fusion Facilities
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This study focuses on the crystallographic defects introduced by neutron irradiation and the resulting changes of the superconducting properties in the high temperature superconductor YBa2Cu3O7-δ. This material is considered to be most promising for magnet systems in future fusion reactors. Two different bulk samples, pure non-doped YBa2Cu3O7-δ (YBCO) and multi-seed YBa2Cu3O7-δ doped by platinum (MS2F) were studied prior to and after irradiation in the TRIGA MARK II reactor in Vienna. Neutron irradiation is responsible for a significant enhancement of the critical current densities as well as for a reduction in critical temperature. The accumulation of small open volume defects (<0.5 nm) partially causes those changes. These defects were studied by positron annihilation lifetime spectroscopy at room temperature. A high concentration of Cu–O di-vacancies was found in both samples, which increased with neutron fluence. The defect concentration was significantly reduced after a heat treatment.
KeywordsYBa2Cu3O7-δ Fast neutron irradiation Positron annihilation spectroscopy Critical current density
N. Hari Babu, Brunel Centre for Advanced Solidification Technology (BCAST), Brunel University, and P. Diko from the Slovak Academy of Sciences (SAV) are acknowledged for the preparation of the investigated materials. The Nano Engineered Superconductors for Power Applications (NESPA) and VEGA 01/0129/09 grants are also acknowledged.
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