Dc Magnetic Concentrator and Omnidirectional Cascaded Cloak by Using Only One or Two Homogeneous Anisotropic Materials of Positive Permeability

Abstract

Abstract-A novel concentrator for static magnetic field enhancement is proposed and designed utilizing transformation optics. Compared with other devices for static magnetic field enhancement, our device has many good features: first, our concentrator can achieve a DC magnetic field enhancement in a relatively large free space with high uniformity. Secondly, our concentrator is composed by only one or two homogenous anisotropic materials with principal value greater than zero (without any infinitely large or zero value), which can be achieved by using currently available materials. Thirdly, the geometrical shape of the proposed device determines the enhancement factor and the permeability of the device. After choosing suitable geometrical parameters, we can obtain a concentration with a suitable enhancement factor and a material requirement that is easily achievable. The proposed concentrator will have many important applications in many areas (e.g., magnetic resonance imaging and magnetic sensors). Based on the same theoretical model, we also proposed a cascaded shielding device cloak for static magnetic fields. The proposed DC magnetic shielding device can be realized without using any material of zero permeability, and will have potential applications in, e.g., hiding a metallic object from being detected by a metal locator.

Transformation Inside a Null-Space Region and a Dc Magnetic Funnel for Achieving an Enhanced Magnetic Flux With a Large Gradient

“…Next, we will show that if we choose a null-space slab inserted in free space as the reference space, the required permeability of our compressor can be greatly reduced under some approximations. As the permeability tensor in Equation (7) is symmetrical, we can always diagonalize it [13]. Before we undertake diagonalization, we first make an approximation: considering ∆ d is a very small quantity, and thus Note that the field gradient is slightly asymmetrical about the arrows in (a), (c), (e), and (g).…”

“…based on transformation optics in [11][12][13][14] 1. Can achieve an enhanced DC magnetic field with high uniformity.…”

“…Our design is based on transformation optics [17,18], which has been widely used to design DC magnetic devices [9][10][11][12][13][14][15][16]. The basic idea is that we can control the DC magnetic field by using magnetic materials with some special permeability.…”

“…In recent years, many novel devices for DC magnetic fields have been designed or even verified experimentally, including cloaking for DC magnetic fields [9,10], DC magnetic concentrators [11][12][13][14], DC magnetic lenses [15] and DC magnetic hoses [16] by using a new theory called transformation optics (TO) [17,18]. These novel DC magnetic devices can perform excellently in some special applications.…”

“…These novel DC magnetic devices can perform excellently in some special applications. For example, DC magnetic concentrators based on TO can provide an enhanced DC magnetic field with high uniformity in a large free space region [11][12][13][14], which may be used to improve the imaging quality in MRI. Many of these (superconductor-based or mostly TO-based) magnetic lenses are closed structures, which mean they can only provide a good magnetic field enhancement in the free space region inside the lenses.…”