Simulation Research Of Magnetic Shielding Efficiency Of Superconducting/Ferromagnetic/Copper Systems

Development of science and technology is accompanied by electromagnetic radiation of computers, mobile phone, radar, satellite and supergrid, which is harmful to human health, economic construction and national defense construction. The electromagnetic shielding has become an important issue of attention, which has a twofold purpose, it is indeed required in order to reduce the magnetic field produced by a device, protecting the neighboring equipment and the personnel operating very near to it, on the other side, magnetic shielding allows the correct operation of sensitive detectors protecting them from the electromagnetic noise emitted in the surroundings. This is conventionally accomplished using metal shields such as iron, copper or aluminium. In recent years, The high temperature superconducting magnetic shielding technology play an important role in biological detection, magnetic resonance imaging(MRI) scanners and magnetic levitation train, etc, the high temperature superconductors should shield electromagnetic fields completely and exclude magnetic fields of any frequency down to d.c. by their Meissner effect, as long as the field intensity is below the critical field Hc. This paper investigates the possibility of using the superconducting materials, iron, and copper as passive magnetic shields.The superconductor's basic characteristic of magnetic shielding is introduced in the paper, and a three-dimensional finite element method(FEM) analysis by Ansoft Maxwell 3D is performed to evaluate the magnetic characteristics of the hollow cylindrical shell immersed in a steady uniform magnetic field generating by the copper coil depending on the mutual complementarity of the ferromagnetic materials such as iron and nickle, high conductivity conductor such as copper and aluminum and HTS magnetic shielding materials. The paper deals with the magnetic shielding efficiency of a hollow cylinder of superconducting material depending on the magnetic field strengths, and investigate the potential of magnetic shielding of systems in a hybrid YBCO/Fe and YBCO/Cu structure consisting of two coaxial hollow cylinders in a magnetic field applied parallel to their axis, and the YBCO/Fe/Cu of three coaxial hollow cylinders in a magnetic field applied parallel to their axis, the height of each cylinder are chosen of similar values in order to analyze the shielding potential of the materials in alternating magnetic field, the magnetic shielding characteristics for different external magnetic fields strengths is discussed too.The results of simulation indicate the hybrid YBCO/Fe structure gives shielding factors up to more than three times higher than those of the YBCO cylinders alone in the low frequency, the hybrid YBCO/Cu structure gives shielding factors up to more than two times higher than those of the YBCO cylinders alone in the high frequency, and the YBCO/Fe/Cu structure gives shielding factors up to more than four times higher than those of the YBCO cylinders alone in any frequency down to d.c. The most ideal one of such structures is the YBCO/Fe/Cu structure, which has the highest shielding factors. The research of high temperature superconducting magnetic shielding has important theoretical and applied significance for the electromagnetic radiation problem to be solved.