Current progress in the superconducting wires production and further improvement of their performance have accelerated the development of the superconducting applications for power transmission and infrastructure, rotation machines, magnets and other devices using strong magnetic field. Such applications require superconducting wires with excellent performance under high magnetic fields, and what is crucial, their properties should be consistent and reproducible. Fabrication of the pinning center in superconducting materials is one of the means to improve their performance under high magnetic fields. In most of the cases such pinning centers are introduced by variation of chemical composition and conditions of the HTS phase formation leading to the formation of the correlated or random inclusions of the nonsuperconducting nanoparticles intergrown into the superconducting material. Another interesting approach based on the ion-irradiation of thin films was proposed almost immediately after discovery of HTS materials, however its potential for the large scale applications has not been fully investigated. Irradiation of superconducting wires by Au+5 and Cu+2 ions was demonstrated to be promising by [1-2]. However, we are not aware of further commercial application of this method.

In this study, we investigated the influence of the ion-irradiation on 2G-HTS wires of various compositions to gain further knowledge about feasibility and practical potential of this method for the large-volume wire production system. We also investigated how the top metal layer may influence the efficiency of ion beam for modification of the 2G-HTS wires properties.

Several types of HTS samples with REBaCuO(RE= Gd, Y,Eu and Nd/Eu/Gd) composition were deposited by pulse laser deposition (PLD) on buffer substrates with Hastelloy/IBAD-MgO/LaMnO3 architecture. Irradiation experiments employing 18MeV Au ions and 12MeV Ni ions were carried with such HTS thin films with different thickness, irradiation angle and etc. The typical irradiation doses varied in the range of 10^10 – 10^13 ions/cm2 to find optimal irradiation conditions and estimate the impact of this method on the total cost of 2G-HTS wires. Superconducting properties and their field dependence for the obtained samples were measurements using PPMS at 77, 65, 50 40K as well as by direct measurements of Ic(B,Q) dependences using the high field magnet facilities at Tohoku University.

It was found that in general ion-irradiation results in the improvement of the tapes critical current (Ic) as a function of magnetic field for the optimal does. However, the degree of such enhancement depends on the composition of the superconducting material, being rather weak for the conventional YBaCuO and the most pronounced for the multilayered wires with (Nd/Eu/Gd)BaCuO/EuBaCuO+BaHfO3 structure. The improvement was the strongest for the operating temperatures of 40-70K and moderate field range of 1-7T, which corresponds to the range of the operating conditions of motors and magnetic levitation (MagLev) applications. Considering such practical applications, the best result obtained in this work correspond to 100A/4mm width at 77K, 1T, and 200A/4mm at 65K, 2T and 400A/4mm at 40K and 5T.

1. M.W. Rupich et al., IEEE Trans. Appl. Supercond. 26 (2016) 6601904
2. N.M. Strickland et al., IEEE Trans. Appl. Supercond. 17 (2007) 3306

Keywords: coated conductors, ion-irradiation, critical current, REBCO