Screening of magnetic fields by superconducting and hybrid shields with a circular cross-section

• Published in: Superconductor science & technology Vol. 35; no. 4; pp. 44002 - 44010
• Main Authors: Gozzelino, Laura, Fracasso, Michela, Solovyov, Mykola, Gömöry, Fedor, Napolitano, Andrea, Gerbaldo, Roberto, Ghigo, Gianluca, Laviano, Francesco, Torsello, Daniele, Grigoroscuta, Mihai A, Aldica, Gheorghe, Burdusel, Mihail, Badica, Petre
• Format: Journal Article
• Language: English
• Published: IOP Publishing 01.04.2022
• Subjects: bulk superconductors; magnetic shielding; MgB; superconductor modelling
• ISSN: 0953-2048; 1361-6668
• DOI: 10.1088/1361-6668/ac4ad0

Abstract The use of superconducting (SC) materials is crucial for shielding quasi-static magnetic fields. However, the need for space-saving solutions with high shielding performance requires the development of a three-dimensional (3D) modelling procedure capable of predicting the screening properties for different orientations of the applied field. In this paper, we use a 3D numerical model based on a vector potential formulation to investigate the shielding ability of SC screens with cylindrical symmetry and a height/diameter aspect ratio close to unity, without and with the superimposition of a ferromagnetic (FM) circular shell. The chosen materials were MgB 2 and soft iron. First, the outcomes of the calculations were compared with the experimental data obtained with different shielding arrangements, achieving a notable agreement in both axial field (AF) and transverse field (TF) orientations. Then, we used this validated modelling approach to investigate how the magnetic mitigation properties of a cup-shaped SC bulk can be improved by the superimposition of a coaxial FM cup. Calculations highlighted that the FM addition is very efficient in enhancing the shielding factors (SFs) in the TF orientation. Assuming a working temperature of 30 K and using a layout with the FM cup protruding over the SC one, SFs up to eight times greater than those with a single SC cup were attained at applied field up to 0.15 T, reaching values equal to or higher than 10 2 in the inner half of the shield. In the AF orientation, the addition of the same FM cup incurs a modest worsening at low fields, but at the same time it widens the applied field range where SF ⩾ 10 4 occurs near the close extremity of the shield to over 1 T.