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    Experimental and numerical investigation of flux trapping in bulk YBCO under different permanent magnet configurations
    (Elsevier Science Sa, 2025) Uzun, Oguzhan; Abdioglu, Murat; Ozturk, U. Kemal
    This study investigates flux trapping in bulk YBaCuOx (YBCO) high-temperature superconductors (HTS) under various permanent magnet configurations (PMCs) through both experimental and numerical methods. A finite element method (FEM) based on the H-formulation of Maxwell's equations is employed to simulate the HTS-PM interaction, showing good agreement with experimental results in peak trapped flux density values. The maximum trapped flux densities for PMC-1, PMC-2, PMC-3, and PMC-4 were measured as 207 mT, 359 mT, 392 mT, and 478 mT, respectively, demonstrating the significance of PMC design in optimising flux trapping in HTS materials. Enhanced flux trapping was observed with configurations including additional permanent magnets, such as PMC-2 and PMC-4, yielding trapped flux efficiencies of 77.5 % and 55.0 %, respectively. Obtained results in trapped flux efficiency are very impressive as compared to a value of 23 % trapped flux efficiency in literature in which a solenoid magnet with a 3 T peak value of magnetic flux density is used to trap a magnetic field in the HTS. The magnetic flux trapping methodology of this research is very effective for magnetic bearing applications with self-stabilisation in which high magnetic fields are not needed since it doesn't need any magnetic field sources with complex structures, such as coils, to facilitate the magnetic field trapping in the HTSs.
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    Investigation of interior seed effects on levitation force in Melt-Grown YBCO superconductors by experimental and numerical methods
    (Elsevier Sci Ltd, 2025) Ozturk, Ufuk Kemal; Abderrahmane, Babe Cheikh; Uzun, Oguzhan; Abdioglu, Murat; Guner, Sait Baris; Queval, Loic
    This study introduces a novel Top-Interior Multi-Seeding Melt Growth (TI-MSMG) technique for fabricating highperformance YBCO bulk superconductors and explanations some physical background based on FEM modelling. The depth of the interior seed was gradually changed as 0, 2 and 4 mm (samples S0, S2 and S4, respectively) from the upper surface of the samples. By incorporating an interior seed into the precursor pellet, the TI-MSMG method enables systematic control over grain morphology and critical current density distribution. Magnetic levitation and guidance forces were measured using a three-axis force measurement system, and a twodimensional finite element method (FEM) model based on the H-formulation of Maxwell's equations was developed to simulate the electromagnetic behaviour of the superconductors with different seed positions. Experimental and modelling results reveal that samples incorporating an interior seed (S2) exhibit significantly enhanced levitation and guidance forces compared to S0 and S4, attributable to improved inter-domain interactions and morphological consistency, so a better current coupling. The numerical simulations accurately reproduced the experimental findings, confirming the validity of the modelling approach. These findings indicate that the TI-MSMG process not only addresses some limitations of conventional top-seeding methods but also enhances levitation force performance through optimization of interior seed depth, thereby enabling more efficient and tailored designs for high-temperature superconducting systems such as magnetic levitation, energy storage, and superconducting motors.