Magnet assembly

Abstract

An electromagnet comprising a ferromagnetic yoke which comprises a yoke. Mutually opposing first and second pole pieces are provided. The first pole piece is provided with a planar coil having a first side facing the yoke and a second side facing the yoke. A balancing member is arranged on the second side of the planar coil to counterbalance the attractive force between the planar coil and the yoke. The other pole piece may also be provided with a corresponding balancing member.

Description

FIELD OF THE INVENTION[0001]The present invention relates to an assembly for an electromagnet, particularly an electromagnet of the kind intended for producing a very high intensity magnetic field such as may be used in a magnetic resonance imaging (MRI) system. However, it is also applicable to other high field applications such as, but not limited to, nuclear magnetic resonance spectrometry (NMR), electron spin resonance spectroscopy (ESR) or general physics laboratory research.BACKGROUND OF THE INVENTION[0002]Traditionally, MRI machines are large expensive devices which have to be located in a specially constructed or adapted MRI room and require the operator to have a high degree of skill. These aspects preclude the use of MRI as a diagnostic tool in applications where space is at a premium and where it would be desirable for the machine to be operated by, for example, nursing staff with only a limited degree of training. An example of such an application would be in an accident...

AI Technical Summary

Benefits of technology

[0037]The balancing member may, for example, be in the form of one or more independently supported ferromagnetic rings. However, in one or more preferred embodiments, any or each balancing member is preferably constituted by part of a respective pole piece, i.e., is integral therewith. The pole pieces are ferromagnetic members extending towards each other from the yoke in the vicinity of, preferably passing through the coils. A particularly preferred configuration is wherein any or each pole piece is generally annular when viewed axially, although as will be explained in more detail hereinbelow, the outer circumferential surface and / or inner surface of the annulus may be provided with one or more projections and / or indentations and / or irregularities, preferably continuously around the annulus of the pole piece and / or in the yoke in the vicinity of the pole piece, to provide advantageous properties, in particular with regard to the functioning of the balancing member. Provision of shims to fine-line the magnetic field is also advantageous, e.g., to compensate for lack of axial symmetry in the yoke.

Problems solved by technology

Traditionally, MRI machines are large expensive devices which have to be located in a specially constructed or adapted MRI room and require the operator to have a high degree of skill.

These aspects preclude the use of MRI as a diagnostic tool in applications where space is at a premium and where it would be desirable for the machine to be operated by, for example, nursing staff with only a limited degree of training.

An impediment to such a design is the strong attractive force between the primary field coils and the magnet yoke which may severely limit the achievable performance and practicality of the magnet design.

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