Magnet device for producing a homogeneous magnetic field and magnetometer having same

Abstract

The invention relates to a magnet device (1) for producing a homogeneous magnetic field in a particular spatial region (6). To this end, the magnet device (1) has a plurality of individual magnets (2). These individual magnets (2) are spatially distributed such that they lie at least substantially on the surface of an imaginary sphere (3) enclosing the spatial region (6). The individual magnets (2) are magnetised and oriented such that in sphere coordinates the magnetisation of the i-th individual magnet (2) points in the direction (Mi, 2θi, φi) at its centre of gravity. The invention also relates to a method for producing a magnet device (1) of this type. The invention also relates to an NV magnetometer which has such a magnet device (1) or a plurality of individual magnets (2) with are arranged in a plurality of Halbach rings with different radii such that the individual magnets (2) are at least substantially distributed over the surface of the imaginary sphere (3).

Description

[0001] MAGNETIC DEVICE FOR GENERATING A HOMOGENEOUS MAGNETIC FIELD AND MAGNOTOMETER THEREFOR

[0002] The present invention relates to a magnetic device for generating a homogeneous magnetic field in a specific spatial region and to a method for manufacturing such a magnetic device. The invention further relates to a corresponding magnetometer.

[0003] Magnetic fields can be used for a wide variety of technical purposes and applications, for example, in data storage technology as well as in measurement technology. It is often advantageous to generate a particularly homogeneous magnetic field, at least in a specific area. Various approaches already exist for this purpose, such as different coil types or ring-shaped Halbach arrays. However, these approaches are not practical for all applications or can lead to noticeable edge effects, i.e., limited homogeneity of the magnetic field, or be associated with considerable cost and space requirements. Therefore, there is a need for further improvements.

[0004] The object of the present invention is to enable a particularly simple and cost-effective generation of a homogeneous magnetic field, for example for magnetometry.

[0005] The problem is solved by the subject matter of the independent claims. Further possible embodiments of the invention are specified in the subclaims, the description, and the drawings. Features, advantages, and possible embodiments presented in the description for one of the subject matter of the independent claims are to be regarded at least analogously as features, advantages, and possible embodiments of the respective subject matter of the other independent claims, as well as any possible combination of the subject matter of the independent claims, optionally in conjunction with one or more of the subclaims.

[0006] The magnetic device according to the invention is designed to generate a homogeneous magnetic field in a specific spatial region. For this purpose, the magnetic device has a plurality of individual magnets. These individual magnets are spatially distributed such that they, in particular their centers of gravity, lie at least substantially on the surface of an imaginary sphere that surrounds the spatial region. The spatial region or field region with the homogeneous magnetic field therefore lies inside this imaginary sphere. The fact that the individual magnets lie at least substantially on the surface of this imaginary sphere can, for example, mean that this is approximately the case except for manufacturing tolerances or restrictions imposed by the shape of the individual magnets and / or by the shape or internal magnet arrangement of a group or subgroup of a plurality of firmly connected individual magnets. According to the invention, the individual magnets are aligned ormagnetized that in spherical coordinates with a radius coordinate, the polar angle 0 and the azimuth angle (p shows the vectorial magnetization Mj of the i-th individual magnet at its center of gravity in the direction of the vector (|Mj|, (1 + 2 / p)0j, q>j), i serves here as an index that counts the individual magnets. With a total number of N individual magnets, i can therefore run from 1 to N, where N is a natural number or a positive integer. 0; and q>j are the polar angle and azimuth angle coordinates of the i-th magnet. The radius coordinate |Mi| indicates the amount or size of the magnetization.The center of gravity of the i-th individual magnet can have the coordinates (Ri, 0j, q>j), where all Rj can be the same for all individual magnets in the case of an ideal arrangement of the individual magnets on the surface of the imaginary sphere. p is a predetermined even natural number and specifies the polarity of the resulting magnetic field, i.e. the total magnetic field of the magnetic device or of the plurality of individual magnets. In one possible embodiment of the present invention, the magnetic device is set up or designed to generate a dipole field. In this case, p = 2 can apply and the magnetization directions can be (|Mj|, 2 0j, q>j). In general, however, fields of higher orders with polarities p = 4, 6, ... can also be generated using the magnetic device.

[0007] If 0 = 0, the magnetization at the upper pole of the imaginary sphere can, for example, point upwards, i.e. along the direction from the center of the sphere through this pole, i.e. along the polar axis. The polar axis can then define the direction of the resulting magnetic field. By appropriately adjusting the magnetizations and / or orientations of the individual magnets, the polar axis as well as the axis or axes that define the azimuth angle can be freely defined. In this way, with at least essentially the same spatial arrangement of the individual magnets, different magnetic field directions of the resulting overall magnetic field of the magnetic device can be realized. The polar axis can be free of individual magnets, or one or more individual magnets can be arranged on the polar axis. With an arrangement of the individual magnets in rings or rings, as described elsewhere, the magnetization orThe magnetization axis of the magnetic device can, for example, run parallel to the axis of the rings or in any other direction relative to it. The axis of the rings can run through their centers and perpendicular to their main planes of extension.

[0008] A typically somewhat less homogeneous resulting magnetic field can also be achieved if all individual magnets have the same cp component in their magnetizations, for example, q>j = 0.

[0009] The magnetic device according to the invention can, for example, also have a frame or a holder to which the individual magnets are attached or held.

[0010] The magnetic device according to the invention can generate a magnetic field inside the imaginary sphere that results from the superposition or combination of the individual magnetic fields of the individual magnets. This resulting magnetic field can exhibit better homogeneity than, for example, a magnetic field inside a cylindrically stacked arrangement of Halbach rings, i.e., ring-shaped Halbach arrays. In particular, the edge effects occurring in such an arrangement can be avoided or reduced by the design of the magnetic device proposed according to the invention. In order to utilize the homogeneous magnetic field inside the magnetic device according to the invention for practical purposes or arrangements, a respective object or material or the like that is to be exposed to the homogeneous magnetic field can be introduced into the interior of the imaginary sphere, for example, through a gap between the individual magnets.Alternatively, the magnetic device or a frame or holder for the individual magnets of the magnetic device can also consist of two sphere halves, which are closed after the object or material has been inserted into the interior of the sphere. The at least substantially spherical design of the magnetic device according to the invention can enable particularly simple and flexible rotation, so that different directions of the homogeneous magnetic field can be set. In particular, no additional installation space is required in the vicinity of the magnetic device to enable such rotation of the magnetic device at any angle or about any axes. This can enable a particularly compact design of the magnetic device itself and / or a device comprising it, such as a magnetometer or the like.Furthermore, it has been shown that with the magnetic device designed according to the invention, a good homogeneity of the magnetic field can be achieved even with a very small number of individual magnets. This can save costs and facilitate the selection or tuning of the individual magnets, as well as the accessibility of the area of ​​the homogeneous magnetic field.

[0011] The magnetic device can also have at least one flux concentrator. This can be arranged, in particular, inside the imaginary sphere. It has been shown that the homogeneity of the overall magnetic field of the magnetic device can be increased by additionally arranging a flux concentrator inside the imaginary sphere. Alternatively, by additionally arranging a flux concentrator inside the imaginary sphere, smaller or less powerful individual magnets can be used than without the use of a flux concentrator, while maintaining the same and constant homogeneity. The flux concentrator can, for example, be designed as two counter-rotating truncated cones, for example, made of a highly permeable material such as soft iron or the like.

[0012] In one possible embodiment of the present invention, the individual magnets have the same shape and magnetization. In other words, the individual magnets are designed to be identical to one another in terms of their external shape and magnetization—except for manufacturing tolerances, for example. This can enable a particularly simple and cost-effective construction of the magnetic device and easily achieve particularly good homogeneity of the magnetic field.

[0013] In a further possible embodiment of the present invention, the individual magnets are designed as permanent magnets. Thus, the magnetic device does not require, for example, an electrical power supply or the like to generate the homogeneous magnetic field. This not only makes it possible to achieve a particularly simple and cost-effective design of the magnetic device, but also to avoid disturbance or influence of the magnetic field, for example by electromagnetic fields emitted by connecting cables or electrical connections or the like. In a possible further development of the present invention, the permanent magnets each have a homogeneous magnetization. This allows the individual magnets to be manufactured particularly simply and cost-effectively and to be spatially arranged and / or replaced flexibly, while still achieving good homogeneity of the resulting magnetic field inside the imaginary sphere.

[0014] In a possible development of the present invention, in addition to the individual magnets designed as permanent magnets, the magnetic device has at least one electromagnet for generating a magnetic field superimposed on the magnetic field or the individual magnetic fields of the permanent magnets. This magnetic field generated by means of the at least one electromagnet can also be referred to here as a superimposed magnetic field for better differentiation. Such an additional electromagnet can increase the flexibility of the magnetic device, thus opening up additional application possibilities, and / or enabling particularly precise setting or adaptation of the homogeneous magnetic field inside the imaginary sphere with particularly low energy expenditure. For example, the superimposed magnetic field or corresponding control of the at least one electromagnet can modulate the magnetic field of one or more of the permanent magnets orof the magnetic field inside the imaginary sphere or a fine adjustment of the strength of the homogeneous magnetic field can be achieved with relatively low current or electrical energy input. For this purpose, the at least one electromagnet does not have to generate or cause the entire field strength, but only the change in the magnetic field of the permanent magnets. Such an electromagnet can, for example, be designed as a coil surrounding the individual magnets, or several electromagnets can be arranged, in particular evenly, around the spherical arrangement of the individual magnets, or the like.

[0015] In a further possible embodiment of the present invention, the individual magnets are spatially spaced from one another so that they only cover part of the surface of the imaginary sphere, and therefore not the entire solid angle. The individual magnets are therefore arranged in such a way and are only so large that there is a gap or distance between every two adjacent individual magnets. This means that correspondingly few and small individual magnets, for example a maximum of 20 individual magnets, can be used. This can enable a particularly good homogeneity of the magnetic field inside the imaginary sphere in a particularly simple and practical way. In addition, such a reduced orThe particularly small total area covered by the individual magnets, for example, when using the magnetic device for magnetic field measurement, such as in an NV magnetometer (NV: Nitrogen Vacancy), reduces the influence or disturbance of the magnetic field to be measured, for example, compared to conventional designs or compared to an at least almost complete, i.e., closed, spherical arrangement of the individual magnets. This can thus enable magnetic field measurement with particularly high sensitivity and accuracy.

[0016] In a further possible embodiment of the present invention, the individual magnets are distributed as evenly as possible, i.e. equidistantly, over the surface of the imaginary sphere. Whether an exactly even distribution is possible can depend, for example, on the number and / or shape of the individual magnets. The precise arrangement of the individual magnets to optimize or maximize the evenness of the distribution can be determined, for example, using a corresponding predefined optimization algorithm. For example, an algorithm can be used in which the individual magnets are represented as charged or repelling particles or elements that can move freely on the surface of the imaginary sphere. This would automatically distribute these particles or elements as evenly as possible. By appropriate calculation or simulation of the repulsion or repulsion, the exact arrangement of the individual magnets can be determined.The interactions or the corresponding movements of the individual magnets can ultimately be used to determine their positions for the most even distribution of the individual magnets possible. Likewise, for example, a mapping of a Fibonacci grid or a Fibonacci spiral onto the surface of the imaginary sphere can be used to determine evenly distributed points, i.e. positions for the individual magnets. Other algorithms can also be used. Particularly when the individual magnets are so small that they do not touch or abut one another, an exactly even distribution can be achieved, for example for 2 or 4 or 6 or 8 or 12 or 20 individual magnets. The even arrangement or distribution of the individual magnets can lead to or contribute to a particularly good homogeneity of the magnetic field inside the imaginary sphere.

[0017] In addition, to achieve a certain homogeneity of the magnetic field inside the imaginary sphere, very few individual magnets are required and particularly small individual magnets can be used. In a further possible embodiment of the present invention, the individual magnets, in particular their centers of gravity, are arranged at some or all of the vertices of an imaginary Platonic solid, for which the imaginary sphere forms its circumsphere. For example, when using 12 individual magnets, these can be arranged at the vertices of an icosahedron, and when using 20 individual magnets, these can be arranged at the vertices of an imaginary dodecahedron. In the embodiment of the present invention proposed here, in particular 4 or 6 or 8 or 12 or 20 individual magnets can be used.It has been shown that the arrangement of the individual magnets proposed here allows a particularly good homogeneity of the magnetic field inside the imaginary sphere or the imaginary Platonic solid in all three Cartesian axes or spatial directions to be achieved, in particular without significant losses in the magnetic field strength compared to other arrangements.

[0018] In one possible embodiment of the present invention, the magnetic device has exactly 12 individual magnets or exactly 20 individual magnets. As described elsewhere, this enables the arrangement of the individual magnets at the vertices of an imaginary icosahedron or dodecahedron. It has been shown that this makes it possible to achieve improved homogeneity of the magnetic field inside the imaginary sphere, for example, compared to a conventional Halbach ring arrangement of individual magnets. This is particularly true when more individual magnets are used in the conventional Halbach ring arrangement than in the magnetic device according to the invention. The relatively small number of individual magnets proposed here can also facilitate the manufacture of the magnetic device because, for example, fewer, as identical as possible, individual magnets need to be selected and positioned relative to one another.

[0019] In a further possible embodiment of the present invention, the individual magnets, or at least some of the individual magnets, are arranged in a plurality of rings with different radii. The rings can in particular be constructed and arranged relative to one another in such a way that all adjacent individual magnets have at least substantially the same or at least similar distances from one another, for example, differing by a maximum of 50%, or a maximum of 20%, or a maximum of 10%, or a maximum of 5%. Different arrangements or angular positions of the individual rings can be possible. This can depend, for example, on the number of rings and / or the number of individual magnets per ring. Different rings can have different numbers of individual magnets.For example, starting from a circle or equator of the imaginary sphere outward, i.e., toward the poles of the imaginary sphere, i.e., toward smaller polar angles, rings with smaller radii can be used. This allows the individual magnets to remain at least substantially aligned on the surface of the imaginary sphere. This also allows improved magnetic field homogeneity to be achieved, for example, compared to a cylindrically stacked arrangement of several rings of the same diameter.To achieve the same homogeneity with such a cylindrical arrangement of rings of the same diameter as with the magnetic device according to the invention in a similar spatial volume, many more rings would have to be used. This could result in correspondingly higher costs and greater installation space requirements, as well as a greater susceptibility to errors or deviations or differences between the individual magnets that could disrupt the magnetic field homogeneity. The individual rings can, for example, be prefabricated separately from one another, which can enable correspondingly simpler production of the individual rings and particularly simple assembly, as well as simplifying the precise alignment of the individual magnets relative to one another.

[0020] In a possible refinement of the present invention, the multiple rings are arranged parallel to one another. In other words, the planes in which the diameters of the rings run can be arranged parallel to one another. This allows for a particularly simple arrangement of the rings and thus also for the manufacture of the magnetic device, as well as a particularly simple and even distribution of the individual magnets across the surface of the imaginary sphere, since no rings need to cross each other.

[0021] In an alternative possible embodiment of the present invention, the individual magnets are arranged in several groups, wherein the different groups have different cp coordinates, i.e. are arranged at different azimuth angle positions. Within the different groups, their individual magnets have the same cp coordinates, but different © coordinates. Illustratively, the several groups can therefore be shaped or arranged similarly to orange slices, for example. The groups can be spaced from one another, as described elsewhere. The embodiment of the present invention proposed here can also enable a simplified arrangement of the individual magnets or a simplified manufacture of the magnetic device, for example compared to the individual, free positioning of all individual magnets.For example, similar to what was described elsewhere in connection with rings made up of several individual magnets, the individual groups of individual magnets can be prefabricated separately from one another and then assembled to form the magnetic device. Because the individual magnets within a group ultimately have the same cp coordinates, the individual groups can be prefabricated particularly easily and precisely, meaning the individual magnets within a group can be arranged and aligned relative to one another particularly easily and precisely.

[0022] The present invention also relates to a method for producing the or a magnetic device according to the invention. In this method, a framework is first provided. In a first variant, the individual magnets are then initially arranged in a holder in a movable manner, in particular individually movable, and aligned using an external magnetic field. In the alignment thus achieved, the individual magnets are then fixed in the holder. The holder with the correspondingly fixed individual magnets is then attached to the framework. In a second variant, the individual magnets are arranged and attached directly to attachment points or in receptacles in the framework. The orientations of the individual magnets are predetermined by these attachment points or receptacles.For this purpose, the fastening points or receptacles can, for example, be shaped or designed in such a way that the respective individual magnet can only be arranged or fastened on or in them in a single predetermined orientation. This second variant can, for example, be particularly advantageous if the magnetizations of the individual magnets are aligned along a geometrically defined direction or axis of the individual magnets or are clearly defined relative to it. In the case of cylindrical individual magnets, such a geometrically defined direction or axis can be, for example, their cylinder axis or, in the case of cuboid individual magnets, a direction parallel or perpendicular to a side surface. Since the separate holder and the additional external magnetic field for aligning the individual magnets can be dispensed with here, a particularly simple and cost-effective production of the magnetic device is possible.Preferably, both the frame and the mounts are made of a material with as little magnetic potential as possible. In the first variant, the external magnetic field can be generated, for example, with a surrounding coil or coil arrangement or one or more permanent magnets. The self-alignment of each individual magnet in this external magnetic field can then be exploited. This can be particularly advantageous for round or cylindrical individual magnets, or for individual magnets whose magnetization is not defined in a simple or clear manner relative to a geometrically distinct direction or axis, in order to achieve reliable and precise alignment of the individual magnets.

[0023] It should be noted that the individual magnets used in the present invention may themselves be subject to manufacturing tolerances. Accordingly, permissible tolerances for the individual magnets can be determined or specified, for example, depending on the intended application of the magnetic device. The individual magnets can then be measured in a standardized manner, particularly with regard to their magnetic field strength and / or their magnetization.

[0024] Magnetization direction. Based on this, individual magnets to be used for the respective magnetic device to be manufactured can then be selected in a corresponding process step, for example, which are identical to one another within the specified tolerances. In particular, if not enough similar individual magnets can be found, it is possible, for example, to use the measurement results for the available individual magnets and a corresponding computer-aided simulation to determine which selection of individual magnets and / or which arrangement of the available individual magnets offers or enables the best result, i.e. in particular the best homogeneity of the resulting magnetic field inside the imaginary sphere. The correspondingly selected individual magnets can then be assembled to form the magnetic device as described.

[0025] The present invention also relates to an NV magnetometer. In a first variant, the NV magnetometer according to the invention can have the or a magnetic device according to the invention. In a second variant, the NV magnetometer according to the invention has several individual magnets arranged in several rings with different radii. In the second variant, the rings are arranged relative to one another such that all individual magnets are distributed at least substantially over the surface of an imaginary sphere. The magnetization of the individual rings can each point in the direction (|Mj| , 20, 0), where the index i here denotes the i-th ring. In the NV magnetometer according to the invention, the magnetic device or the arrangement of the individual magnets can generate a homogeneous magnetic field that serves as an offset magnetic field, i.e., to split the electron energy levels.Compared to conventional magnetometers, the NV magnetometer according to the invention can have a relatively small magnet or permanent magnet volume and total volume, thus requiring a correspondingly small installation space. The reduction in the magnet volume, and in particular also in the total solid angle range covered by the individual magnets, as well as the reduction in the number of individual magnets made possible by the present invention, can reduce the influence of the magnetic field to be measured and thus enable more precise measurements. Furthermore, the improved homogeneity of the offset magnetic field allows for particularly high sensitivity and measurement accuracy.

[0026] Further features of the invention can be derived from the following description of the figures and from the drawings. The features and combinations of features mentioned above in the description, as well as the features and combinations of features shown below in the description of the figures and / or in the figures alone, can be used not only in the respective combinations specified, but also in other combinations or on their own, without departing from the scope of the invention.

[0027] The drawing shows in the only figure a partial schematic representation of a magnetic device for generating a homogeneous magnetic field for an NV magnetometer.

[0028] Fig. 1 shows a partial schematic representation of a magnetic device 1, for example as part of an NV magnetometer. The magnetic device 1 comprises several – here, for example, 12 – individual magnets 2. These individual magnets 2 are spatially distributed over the surface or on the surface of an imaginary sphere 3. Specifically, the individual magnets 2 are arranged at vertices 5 of a Platonic solid, in the present example a twelve-sided icosahedron. The imaginary sphere 3 forms the circumsphere of this icosahedron. The icosahedron can merely serve to illustrate the possible arrangement for the individual magnets 2 shown here as an example. In the present case, however, the icosahedron can also serve as an actual physical framework 4 to which the individual magnets 2 are attached. Such a framework 4 can, however, also be designed differently if the positions of the individual magnets 2 are identical.

[0029] Although the individual magnets 2 are arranged on the surface of the imaginary sphere 3, they do not completely cover this surface, so that the individual magnets 2 are spaced apart from one another. The individual magnets 2 can be designed, in particular, as permanent magnets. By appropriately magnetizing the individual magnets 2 and aligning them, a homogeneous magnetic field can be generated in an inner region surrounded by the sphere 3 or the individual magnets 2, which is referred to here as field region 6.

[0030] To generate this homogeneous magnetic field in the field region 6, an electromagnet is not necessarily required due to the design of the individual magnets 2 as permanent magnets. Accordingly, a correspondingly complex, low-noise, shielded power source or energy supply is not required to generate the homogeneous magnetic field in the field region 6. This can be particularly advantageous when using the magnetic device 1 in a magnetometer, especially in an NV magnetometer.

[0031] In such a magnetometer, the magnetic device 1 can be used, for example, in a magnetic field sensor head. Due to the at least substantially spherical arrangement of the individual magnets 2 provided here, this head can be particularly small, for example, compared to a cylindrical stack of Halbach rings, since the spherical or spherical arrangement of the individual magnets 2 eliminates edge effects along the cylinder axis of such a cylindrical stack of Halbach rings.

[0032] Likewise, when using the magnetic device 1 in an NV magnetometer, it can be particularly advantageous that it makes it particularly easy to rotate or align the homogeneous offset magnetic field generated in the field region 6 in a desired direction. Likewise, due to the distances provided here between the individual magnets 2 in various rotational positions of the magnetic device 1, a laser beam for magnetic field measurement can be easily irradiated into the field region 6. Thus, using the magnetic device 1, for example, a single-axis magnetometer operation can be converted or modified to a multi-axis or 3D magnetometer operation, in particular without changing any remaining structure of the magnetometer.

[0033] Overall, the examples described show how a particularly simple and cost-effective generation of a particularly homogeneous magnetic field can be enabled and applied.

[0034] LIST OF REFERENCE SYMBOLS

[0035] 1 magnetic device

[0036] 2 single magnets 3 ball

[0037] 4 Scaffolding

[0038] 5 key points

[0039] 6 Field area

Claims

PATENT CLAIMS 1. Magnetic device (1) for generating a homogeneous magnetic field in a specific spatial region (6), comprising a plurality of individual magnets (2) which are spatially distributed so that they lie at least substantially on the surface of an imaginary sphere (3) which surrounds the spatial region (6), wherein the individual magnets (2) are aligned such that, in spherical coordinates with a radius coordinate, the polar angle 0 and the azimuth angle (p), the magnetization Mj of the i-th individual magnet (2) at its center of gravity points in the direction (|Mj|, (1 + p / 2)0j, q>j), where p is a predetermined even natural number.

2. Magnetic device (1) according to claim 1, characterized in that p=2, i.e. the magnetization of the i-th individual magnet (2) at its center of gravity points in the direction (|Mi|, 20i, q>i).

3. Magnetic device (1) according to one of the preceding claims, characterized in that the individual magnets (2) have the same shape and magnetization.

4. Magnetic device (1) according to one of the preceding claims, characterized in that the individual magnets (2) are designed as permanent magnets.

5. Magnetic device (1) according to claim 4, characterized in that the permanent magnets each have a homogeneous magnetization.

6. Magnetic device (1) according to claim 4 or 5, characterized in that the magnetic device (1) comprises, in addition to the permanent magnets, an electromagnet for generating a magnetic field superimposed on the magnetic field of the permanent magnets.

7. Magnetic device (1) according to one of the preceding claims, characterized in that the individual magnets (2) are spaced apart from each other so that they only cover part of the surface of the imaginary sphere (3) and there is a gap between each two adjacent individual magnets (2).

8. Magnetic device (1) according to one of the preceding claims, characterized in that the individual magnets (2) are distributed as equidistantly as possible over the surface of the imaginary sphere (3).

9. Magnetic device (1) according to one of the preceding claims, characterized in that the individual magnets (2), in particular their centers of gravity, are arranged at corner points (5) of an imaginary Platonic body (4), for which the imaginary sphere (3) forms its circumsphere (3).

10. Magnetic device (1) according to one of the preceding claims, characterized in that the magnetic device (1) has exactly 12 individual magnets (2) or exactly 20 individual magnets (2).

11. Magnetic device (1) according to one of the preceding claims, characterized in that the individual magnets (2) are arranged in several rings with different radii.

12. Magnetic device (1) according to claim 11, characterized in that the plurality of rings are arranged parallel to one another.

13. Magnetic device (1) according to one of claims 1 to 10, characterized in that the individual magnets (2) are arranged in several groups, wherein the different groups have different cp coordinates and the individual magnets (2) within a group have the same cp coordinates but different 0 coordinates.

14. A method for producing a magnetic device (1) according to any one of the preceding claims, wherein a framework (4) is provided and - the individual magnets (2) are first arranged movably in a holder, aligned by means of an external magnetic field and fixed in the holder in this alignment, and then the holder with the fixed individual magnets (2) is attached to the frame, or - the individual magnets (2) are fastened directly in receptacles of the scaffold, by which the orientations of the individual magnets (2) are predetermined.

15. NV magnetometer, comprising - a magnetic device (1) according to one of claims 1 to 13, or - a plurality of individual magnets (2) arranged in a plurality of rings with different radii, so that the individual magnets (2) are distributed at least substantially over a surface of an imaginary sphere (3).

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