An industrial R&D programme is ongoing at SuperOx, aimed at improving 2G HTS wire performance in magnetic field. We introduce perovskite artificial pinning centres (APC) into the HTS layer matrix. In contrast to most studies described in the literature, we use the high rate production processing parameters and PLD equipment at SuperOx. This paper reports the results of Phase I of this programme. We fabricated 2G HTS wires by pulsed laser deposition of GdBCO films doped with 6%, 12% and 18% (molar) of BaSnO ₃ and 6% (molar) of BaZrO ₃ , and compared their performance with an undoped reference sample. The depositions were carried out at production growth rates of 375, 560 and 750 nm min ⁻¹ by varying laser pulse frequency. BaZrO ₃ and BaSnO ₃ formed columnar semi-coherent nanoinclusions in the GdBCO film matrix. The average transverse size of the nanocolumns was about 5 nm, and their volume density correlated with the dopant concentration. All doped samples exhibited much lower angular anisotropy of in-field critical current and higher lift-factors than the undoped sample. Samples containing 6% BaSnO ₃ and deposited at the lower growth rates, had higher I _c than the undoped sample in the entire temperature range, in a wide range of magnetic field ( B // c ). The sample containing 6% BaZrO ₃ had higher I _c than the undoped sample at 20 and 4.2 K. These results are an encouraging start of our programme, as they show a positive impact of APC introduced into 2G HTS wires fabricated at production throughput. Phase II work will be focussed on maximising the improvements in specific temperature and field conditions, as well as on the verification of reproducibility of the improvements in production wires.

The morphology and structure of damaged regions (tracks) produced by swift heavy 167, 77, and 46 MeV ¹³²Xe²³⁺ ions in YBCO-based second generation industrial high temperature superconductors wires (2G HTS) were studied using transmission electron microscopy. It was shown that ions produce tracks aligned along the ion trajectory but of morphology depending on their energy: continuous, nearly continuous, or discontinuous tracks like prolate ellipsoids of 10–15 nm in length and spheroids of 5 nm in diameter. The damaged regions of about 5 nm in diameter contain an amorphous material with a lower density compared to the pristine YBCO. The material density drops from 6300 kg m⁻³ for YBCO matrix to 3600 kg m⁻³ inside the tracks. Barium enrichment was found in the vicinity of the track at a distance of about 10 nm from the center of the defect. Ion damage tracks with different morphologies showed different effectivenesses as pinning centers. Tracks composed of discontinuous pinning centers—spheroids of about 5 nm in diameter—bring the best enhancement of the critical current density. It occurs for the lowest ion energy (46 MeV) in the range of energy loss of 8.9 keV/nm–4.7 keV/nm for Xe ions. The samples showed highest critical current densities of 56 MA/cm² (4.2 K) and 3 MA/cm² (77 K) in self-field, while in magnetic fields of 8 T, the values of 17 MA/cm² (4.2 K) and 1.6 MA/cm² (77 K) were achieved. The reduction of the superconducting volume corresponding to the amorphous radiation defects did not exceed 4% from the total sample volume.

Nb ₃ Sn platelets with thicknesses between 0.12 and 0.20 mm produced by a high isostatic pressure process at 1250 °C were irradiated at 300 K with 12 MeV protons. The effects of irradiation on the lattice parameter a , the atomic order parameter S and the transition temperature T _c were measured as a function of proton fluence. In view of the presence of multiple energy radiation sources in future accelerators, the present proton data are compared with neutron irradiation data from the literature. The fluences for both types of radiation were replaced by the dpa number, the ‘ displacements per atom ’, calculated using the FLUKA code, which is proportional to the number of radiation induced Frenkel defects. It was found that the variation of both a and S for Nb ₃ Sn after proton and neutron irradiation as a function of dpa fall almost on the same curve, in analogy to the recently reported correlation between T _c and the dpa number. By a simultaneous irradiation of two adjacent thin Nb ₃ Sn platelets, we have shown that this correlation is not only valid for the state of ‘steady energy loss’ (protons traveling through the first platelet) but also for the state of higher damage at the Bragg peak (second platelet). It follows that the number of radiation induced Frenkel defects in the A15 grains, calculated via the dpa number, can be considered as a ‘universal’ parameter, allowing the calculation of the variation of T _c , a and S of Nb ₃ Sn under the effect of multiple high energy radiation sources, as in future superconducting accelerators.

Design versions of HTS three-phase cables consisting of 2G HTS tapes have been investigated by the numerical simulation method with the aim of AC losses minimization. Two design versions of cables with the coaxial and extended rectangular cross-section shape are considered – the non-sectioned and sectioned one. In the latter each cable phase consists of sections connected in parallel. The optimal dimensions of sections and order of their alteration are chosen by appropriate calculations. The model used takes into account the current distribution between the sections and its non-uniformity within each single HTS tape as well. The following characteristics are varied: design version, dimension, positioning of extra copper layer in a cable, design of HTS tapes themselves and their mutual position. The dependence of AC losses on the latter two characteristics is considered in details, and the examples of cable designs optimized by the total set of characteristics for the medium class of voltages (10 – 60 kV) are given. At the critical current JC=5.1 кA per phase and current amplitudes lower than 0.85JC, the level of total AC losses does not exceed the natural cryostat heat losses.

This paper presents the results of calculation of ac HTS cables designs optimized by the values of hysteresis and eddy current losses. The superconducting elements of the cables are 2G HTS tapes. The program we developed and used allowed the variation of both the cable shape and its internal structure. There have been considered nonsectioned and sectioned cables having two variants of geometry-the axially symmetrical coaxial and extended rectangular cross-sectional shape. It has been shown that the internal structure optimization allows decreasing of ac losses in several times for both cross-sectional shapes. Due to the compensation of the perpendicular magnetic field component, the characteristics of flat three-phase cables turn out to be close of those with the axially symmetrical cross-sectional shape. In this case, the rectangular cross-sectional shape allows obtaining better mass, dimensional, and mechanical parameters and better cooling conditions of phases. The cables sectioning allows an essential reduction of ac losses. But, the latter is possible only when there is a uniform current distribution over the sections, i.e., at a very exact design calculation.

In the present work, dynamics of vortex structure in the type-II superconductors with defects under a transport current has been studied using the time dependent Ginzburg-Landau equations. The vortex interactions with the pining centers in two-dimensional cases have been investigated. The model has been solved using ψU-method and finite element method. The defects are normal regions and it size was greater-than through influence of proximity effect. In our simulation, we have considered that using model agree well for description of vortices behavior in inhomogeneous sample under a transport current. We have considered defects influence and relative position on dynamics of vortices. Also we have calculated the values of critical current density at various configuration of sample.