Identification of Material Properties and Optimal Design of Magnetically Shielded Rooms

Aldo Canova,Luigi Solimene,Luca Giaccone,Fabio Freschi,Maurizio Repetto

doi:10.3390/magnetochemistry7020023

Aldo Canova, Luigi Solimene + Show 3 more

Open Access

https://doi.org/10.3390/magnetochemistry7020023

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Abstract

In this paper, we propose an optimal design procedure for magnetically shielded rooms. Focusing on multi-layer ferromagnetic structures, where inner layers operate at very low magnetic field, we propose an identification method of the magnetic material characteristic in the Rayleigh region. A numerical model to simulate the shielding efficiency of a multi-layer ferromagnetic structure is presented and experimentally tested on different geometries and layer configurations. The fixed point iterative method is adopted to handle the nonlinearity of the magnetic material. In conclusion, the optimization of the design parameters of a MSR is discussed, using the Vector Immune System algorithm to minimize the magnetic field inside the room and the cost of the structure. The results highlight that a linear magnetic characteristic for the material is sufficient to identify the suitable geometry of the shield, but the nonlinear model in the Rayleigh region is of fundamental importance to determine a realistic shielding factor.

Highlights

Shielded Rooms (MSRs) are closed spaces employed for the magnetic field mitigation in environments where sensitive electronic equipment is used [1,2,3,4,5]
This paper aims to define an identification procedure for the B( H ) curve of the shielding material in the Rayleigh region, to define a design strategy based on a numerical simulation of the ferromagnetic shield able to handle the nonlinearity of the material, and to evaluate the design parameters of a Magnetically Shielded Rooms (MSRs) through a multi-objective optimization strategy, based on the Vector Immune System algorithm [12]
An effective design procedure requires the accurate evaluation of the material characteristic in the Rayleigh region of the B( H )

Summary

Introduction

Shielded Rooms (MSRs) are closed spaces employed for the magnetic field mitigation in environments where sensitive electronic equipment is used (e.g., electronic microscopes and medical imaging devices) [1,2,3,4,5]. An effective design strategy for a MSR is the adoption of multiple closed ferromagnetic layers, not in contact with each other. The inner layer shields the residual field passing through the outer ones. A qualitative representation of the flux lines obtained using one layer and three layers is shown in Figure 1b,c, respectively. The aim is to minimize the magnetic field in a target region that often coincides with the center of the room [6,7]

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