POLYHEDRAL COIL SYSTEMS HAVING A LARGE HOMOGENEITY VOLUME AND LARGE ACCESS ZONE

Abstract

A coil system (30, 40, 50) for generating a homogeneous magnetic field, includes a coil assembly (2), each assembly having at least two coils (S1, S2, S3), the respective windings (W1, W-2, W3) of which span. rotationally symmetrical faces lying plane-parallel to one another having different sizes and a common axis of rotation running perpendicularly to the faces, forming a coil axis (4), wherein a current can flow in the opposite direction through at least one of the coils (S1, S2, S3), and having at least two coil assemblies (2), wherein the coils (S1, S2, S3) of each coil assembly (2) are located within and oriented plane-parallel to the base of a generating pyramid, the tip of which coincides with the centre of a regular convex polyhedron and the base surface of which is identical to one such face of the convex polyhedron, on which the projection of the pyramid tip onto the pyramid base surface coincides with the centre of the pyramid base surface.

Claims

1. A coil system (30, 40, 50) for generating a homogeneous magnetic field, the coil system (30, 40, 50) comprising a coil assembly (2), each coil assembly (2) being composed of at least two coils (S1, S2, S3), the respective windings (W1, W2, W3) of said coils (S1, S2, S3) forming plane-parallel, rotationally symmetrical surfaces having different sizes and a common axis of rotation as a coil axis (4) running perpendicular to the surfaces, a current flowing in the opposite direction in relation to another one of said coils through at least one of said coils (S1, S2, S3), further comprising at least three coil assemblies (2), the coils (S1, S2, S3) of each coil assembly (2) being located inside and oriented plane-parallel to the base surface of a generating pyramid, the apex of which coincides with the center of a regular, convex polyhedron and the base surface of which is identical to a surface of the convex polyhedron in which the projection of the pyramid apex onto the pyramid base surface coincides with the center of the pyramid base surface, wherein the polyhedron is a tetrahedron, a hexahedron, an octahedron, a dodecahedron or an icosahedron which has n surfaces can be composed of n generating pyramids in a volume-filling manner.

2. The coil system according to claim 1, wherein the rotationally symmetrical surface formed by the respective windings (W1, W2, W3) of the respective coils (S1, S2, S3) is a combination of polygonal surface segments and circular surface segments.

3. The coil system according to claim 1, wherein the rotationally symmetrical surface formed by the respective windings (W1, W2, W3) of one of the coils (S1, S2, S3) is realized in a spiral shape.

4. The coil system according to claim 1, wherein a winding shape of one of the windings (W1, W2, W3) has, in sections, a component in the direction of the axis of rotation.

5. A use of the coil system (30, 40, 50) according to claim 1 in a system for calibrating magnetic field sensors and magnetic compasses, for generating and simulating magnetic conditions on satellites and space probes, for compensating magnetic fields, for reducing or neutralizing magnetic signatures on ship components, for testing and controlling the quality of permanent magnets, for measuring magnetic properties in materials research and geophysics and for generating magnetic fields and magnetic field gradients in medical technology and magnetic resonance imaging.

6. (canceled).

7. The coil system according to claim 2, wherein the rotationally symmetrical surface formed by the respective windings (W1, W2, W3) of one of the coils (S1, S2, S3) is realized in a spiral shape.

8. The coil system according to claim 2, wherein a winding shape of one of the windings (W1, W2, W3) has, in sections, a component in the direction of the axis of rotation.

9. The coil system according to claim 3, wherein a winding shape of one of the windings (W1, W2, W3) has, in sections, a component in the direction of the axis of rotation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Further advantageous embodiment features are apparent from the following description and from the drawings, which outline a preferred embodiment of the invention by means of examples. In the drawings,

[0033] FIG. 1 shows coil assemblies nested in one another from the state of the art,

[0034] FIG. 2 shows a schematic view of a coil assembly according to the invention which has three coils,

[0035] FIG. 3 shows a schematic, spatial representation of a one-dimensional symmetric coil system,

[0036] FIG. 4 shows a schematic, spatial representation of a three-dimensional symmetric coil system disposed as a cube,

[0037] FIG. 5 shows a schematic, spatial representation of a three-dimensional symmetric coil system disposed as a tetrahedron,

[0038] FIG. 6 shows a model of another three-dimensional, symmetric coil system.

DETAILED DESCRIPTION

[0039] In FIG. 1, examples of coil assemblies nested in one another for generating a three-dimensional magnetic field are shown. The left representation shows Helmholtz coils nested in one another triaxially, the representation in the middle shows a Maxwell coil system which has three coils per axis, and the right representation shows a Braunbek coil system which has four coils per axis. In all three representations, the coil axes are orthogonal to one another.

[0040] In FIG. 2, a schematic view of a coil assembly 2 according to the invention which has three coils S1, S2, S3 is shown. Coils S1, S2, S3 are disposed in such a manner that the surfaces formed by their respective windings W1, W2, W3 are plane-parallel to one another and have a common axis of rotation as a coil axis 4 which runs perpendicular to the surfaces.

[0041] According to the invention, coils S1, S2, S3 are dimensioned in such a manner that coils S1, S2, S3 and their outer dimensions can be positioned inside a generating pyramid which has a surface line 6—in the present case shown in a projection.

[0042] FIG. 3 shows a schematic, spatial representation of a one-dimensional symmetric coil system 20 in which two coil assemblies 2 of FIG. 1 are disposed symmetrically as a basis assembly in such a manner that their coil axes 4 (FIG. 2) are located on a common straight line, the pyramid apices of the pyramids pointing to one another and coinciding with the center of a polyhedron realized as a cube.

[0043] As an enhancement of a one-dimensional symmetric coil system, a schematic, spatial representation of a three-dimensional symmetric coil system 30 according to the invention which is disposed as a cube is shown in FIG. 4. Corresponding to the number of sides of the convex polyhedron as a cube, coil system 30 is composed of six coil assemblies according to the invention.

[0044] Said representation shows that the geometric condition according to the invention that the coils be disposed inside an outer surface of a generating pyramid having an opening angle of 90° must be satisfied in order to be able dispose any number of coils in the external shape of a cube without overlap.

[0045] The cubic assembly can be composed of six of such generating pyramids, the base surface of said pyramid corresponding to a lateral surface of the cube.

[0046] It is not possible to realize such an orthogonal triaxial assembly on the basis of three identical pairs of Helmholtz coils since the coils would penetrate one another because of the defined ratio of coil size to coil distance of the Helmholtz assembly. For this reason, the aforementioned pairs of coils nested in one another, i.e., pairs of coils having different sizes, have been suggested by the state of the art. However, said assemblies limit the available experimental space and the charging opening in a disadvantageous manner.

[0047] By contrast, the realization according to the invention allows a larger experimental space having a larger charging opening compared to the state of the art and therefore a more favorable ratio of the outer dimensions of the coil system to the usable experimental volume.

[0048] FIG. 5 shows a schematic, spatial representation of a three-dimensional symmetric coil system disposed as a tetrahedron. Corresponding to the four surfaces of the tetrahedron, said tetrahedron can be composed of four identical generating pyramids in a volume-filling manner, the respective base surface of the pyramids being an equilateral triangle. Said coil system in the form of a tetrahedron is therefore composed of four identical sub-tetrahedrons (triangle pyramids) within each of which two coils S1, S2 are located.

[0049] FIG. 6 shows a model 50 of a three-dimensional symmetric coil system disposed as a cube. In the model, two coils S1, S2 which represent a coil assembly according to the invention are disposed on each side of the cube. Pairs of coils S1, S2 are dimensioned in such a manner that they can be disposed inside the generating pyramids which fill the volume of the cube. The larger experimental space and its good accessibility in contrast to a nested Helmholtz assembly are clearly identifiable.