Theoretical Study of the Effect of Magnetic Field Sweep Rate and Temperature on Shielding Efficiency in a Bulk Tube-Shap
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ORIGINAL PAPER
Theoretical Study of the Effect of Magnetic Field Sweep Rate and Temperature on Shielding Efficiency in a Bulk Tube-Shaped HTS Ali Öztürk 1 & Alper Kara 1 Received: 2 June 2020 / Accepted: 25 July 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract In this paper, we have studied the shielding properties of a high temperature superconducting (HTS) bulk tube-shaped cylinder in varying magnetic fields. Within this scope, we have simulated the hollow cylinder geometry in axis-symmetric finite element method (FEM) in which the electromagnetic properties of a HTS are described by a nonlinear electric field-current density (E − J) power law including a critical current density depending on magnetic field. In the first stage, we have analyzed temperature dependence of shielding factor (SF), which is described as the ratio of the applied magnetic field to the magnetic field in the center of the hollow cylinder. In the second stage, the effect of magnetic field’s sweep rate (dBapp/dt) on the magnetic shielding was numerically examined. In the final stage, using the certain lines over the superconducting tube, we have worked out the shielding field (Bsz) of the HTS tube by subtracting the z-component of magnetic field (Bz) from applied magnetic field (Bapp). Our numerical investigations indicate that the superconducting tube can provide field and temperature-controlled magnetic shielding. Keywords High temperature superconductor (HTS) . Finite element method (FEM) . Magnetic shielding
1 Introduction Superconducting materials are famous for their high current transporting ability without any loss of energy compared with traditional conductors for current transmission cable. Bulk tube-shaped HTS materials are usually produced as current leads for magnets [1] or used as a part of fault current limiters [2]. Bulk HTSs play a significant role because of their shielding properties. Using the tubular form of HTS materials as a magnetic shield may also be advantageous [3, 4]. Magnetic shielding is generally used for two purposes. The first is so as to decrease the magnetic field produced by an electrical hardware which preserves the neighboring parts and the staff who operates very close to the magnetic field (for instance magnetic-resonance imaging (MRI) using medicine) [5, 6]. As for the second purpose, magnetic shielding helps to run oversensitive detectors correctly (for instance magnetoencephalography, magneto-cardiography device equipment) [7] to protect them from magnetic field turbulence given in
the environs. For the past few years, this feature has made them very attractive. But investigations of superconductivity properties experimentally are very costly and time-consuming. For this reason, many researchers have preferred to use the FEM in the simulations of shielding properties of HTS materials, instead of experimental study [8–10]. Simulations of a tube-shaped HTS have also been practical for calculating and understanding the shielding mechanism for either varying sweep r
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