[WB8] Evaluation & Flux Pinning II

9:30 AM - 9:45 AM JST(12:30 AM - 12:45 AM UTC)

[WB8-02] Influence of disorder on fundamental superconducting properties

*Michael Eisterer¹, Alexander Bodenseher¹, Morteza Asiyaban¹, Raphael Unterrainer¹ (1. Atominstitut, TU Wien (Austria))

Keywords:

Neuron Irradiaton,Radiation Damage,Coated Conductors,Nb3Sn Wires,Nuclear Fusion

Superconductivity arises in the electronic system of regular crystal lattices. However, a certain degree of lattice disorder is often favorable for some superconducting properties, such as the upper critical field or critical current density. High disorder levels on the other hand, harm all superconducting properties. This becomes potentially problematic for applications in radiation environments, such as fusion or accelerator magnets.Any defect breaks the lattice symmetry and hence increases scattering of the charge carriers, which manifests by an increase in normal state resistivity. In single band superconductors with isotropic energy gap (most conventional superconductors), scattering does not break the cooper pairs and the transition temperature remains constant. Efficient impurity scattering relies on a high density of small defects and decreases the superconducting coherence length, leading to an increase of the upper critical field. Defects are also necessary for flux pinning although most efficient with a size comparable to the coherence length. The only negative effect of defect introduction in conventional superconductors is a decrease in superfluid density, which influences important parameters, such as the condensation and pinning energy and consequently the critical current and flux creep.The order parameter in the cuprate superconductors is anisotropic and scattering becomes pair breaking. This leads to a decrease in transition temperature and accelerates the loss in superfluid density; thus, radiation affects this class of materials stronger than conventional superconductors.High-fluence neutron irradiation was performed in a TRIGA research reactor to investigate the resulting degradation of the superconducting transition temperature and critical currents in REBCO coated conductors and Nb₃Sn wires. Both materials are candidates for conductors in fusion magnets. The results confirm the harmful effect of pair breaking scattering. A predictive model without any free parameters can describe the behavior of both materials.