Magnetic box shielding and corresponding magnetic box shielding application method
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- ROSLER WOLFGANG
- Filing Date
- 2026-01-28
- Publication Date
- 2026-08-06
Smart Images
Figure DE2026100114_06082026_PF_FP_ABST
Abstract
Description
[0001] MAGNETIC BOX SHIELDING AND ASSOCIATED MAGNETIC BOX SHIELDING APPLICATION METHOD
[0002] The invention relates to a magnetic box shield with a number of flat elements, a DC power supply and a DC coil system.
[0003] Furthermore, the invention relates to a magnetic box shielding application method.
[0004] Shielding sensors and devices against magnetic fields is essential in many applications in physics, geophysics, space physics, and medical measurements and sensing, where small magnetic fields need to be measured or generated with high precision.
[0005] In recent years, a new type of optically pumped magnetometer (OPM) has been developed that operates at a “zero-field resonance” within a narrow range of approximately 5 nT (nanoTesla). Commercial OPMs with integrated field compensation systems require residual fields of less than 200 nT (TwinLeaf) or 50 nT (Qu-Spin). These new developments are driving a growing demand for cost-effective, room-sized magnetic shields with residual fields in the 0 to 200 nT range.
[0006] According to the current state of the art, the magnetic shielding of quasi-stationary fields can be achieved through two operating principles: flux diversion and field compensation. Flux diversion as a passive shielding method uses materials with high magnetic permeability. Materials with high magnetic permeability offer a clear path for magnetic field lines. The best available materials are NiFe alloys of the "Mumetal" class (or Permalloy; approximately 80% Ni, a few percent Mo, balance Fe) with extremely high permeability after thermal annealing. A shield (housing; enclosed volume; closed box, case) made of such a material can significantly reduce the residual field inside. The shielding factor describes the ratio of the magnetic field strength outside the shield to the field strength inside the shield. S depends, among other things, on the permeability as well as the geometry and dimensions of the shield.A single passive shield can significantly reduce the field within it, but never to zero. For shielding room-sized volumes, multiple shields (up to eight layers) spaced a certain distance apart can multiply the shielding factors of each individual shield and are the standard for high-performance passive magnetic shielding of larger volumes. Such room-sized passive, multi-layered shielding systems are often referred to as "magnetically shielded rooms" (MSRs). However, at very low fields, the remanent magnetization of the shield itself and its magnetic history become critical factors, and enormous efforts must be made to demagnetize the shielding material to improve shielding performance.
[0007] Field compensation can take place as active field compensation using coil systems and direct current to generate magnetic fields, or as passive field compensation using remanent magnetism.
[0008] Active field compensation generally uses three orthogonal DC coil systems to generate fields whose direction and intensity can be tuned to compensate for the magnetic field within a given volume. Such systems, for example Helmholtz coil systems, are widely used to generate zero fields in relatively small volumes, typically much smaller than 1 m³. 3For larger volumes, such coil systems are less suitable due to their very large dimensions relative to the limited volume of the usable homogeneous "zero field". However, active field compensation can be used to compensate for time-varying contributions to the quasi-stationary field.
[0009] Large coil systems are used in combination with passive shields to reduce the field outside of high-quality multilayer passive shields (Physikalisch-Technische Bundesanstalt Berlin, Germany; HUN-REN Zero Magnetic Field Laboratory Sopron, Hungary; Paul Scherrer Institute Villigen, Switzerland), and Helmholtz coil systems are used to compensate for small anomalies within MSRs to create an environment suitable for experiments in fundamental physics or medical sensor applications of zero-field OPMs. US 020240280657 A1 describes the development of more complex coil geometries to compensate for complex small magnetic anomalies within MSRs. All of these compensation coils are typically used either inside or outside traditional MSRs and require considerable additional space, thus significantly reducing the usable volume of the shield.Passive field compensation is achieved using remanent magnetization. Reference is made to Scott, G.R., & Frohlich, C. (1985). Large-volume, magnetically shielded room: A new design and material. In Magnetite Biomineralization and Magnetoreception in Organisms: A New Biomagnetism (pp. 197-220). Boston, MA: Springer US. In the paleomagnetic community, where room-sized shields with moderate residual fields are required, magnetic shielding systems (MSRs) made from relatively inexpensive electrical steel (“transformer steel”) have been successfully used for about 40 years, providing S-factors comparable to those of mumetal MSRs. Electrical steel has a relatively high magnetic permeability, about two orders of magnitude lower than that of mumetal, and can act as a strong permanent magnet. When a magnetic shield is magnetized as a whole in a particular direction, the field inside it is antiparallel to the magnetizing field.When an electrical tape shield is installed to compensate for the Earth's magnetic field (EMF), it must be magnetized in the EMF direction to utilize this effect. This is typically done with anhysteretic remanent magnetization (ARM), which means that the shielding material is subjected to alternating field demagnetization (AF) in the presence of a magnetic bias field (usually the EMF or the reduced ambient field within an external magnetic shield).
[0010] As a result, the shield acquires a magnetic remanence that is parallel and proportional to the magnetizing bias field, with the resulting field inside being antiparallel to the external field and thus partially compensating for it. A magnetic shield made of ferromagnetic material magnetized parallel to the external field combines the effects of flux diversion, determined by its magnetic permeability and geometry, and the effect of passive field compensation, determined by its ferromagnetic properties, the efficiency of the anhysteretic magnetization process, and the direction and intensity of the bias field. Using this technology and an ARM in the presence of the Earth's magnetic field, many paleomagnetic laboratories worldwide achieve residual fields on the order of 300 nT or less in two- or three-stage large-scale MSRs.
[0011] Homogeneous magnetic fields can be generated between parallel magnetic poles.
[0012] Magnetic poles ideally consist of highly permeable materials such as electrical tape or mu-metal. The simplest example of such a magnet is a horseshoe magnet with parallel poles. The same principle is used to generate homogeneous magnetic fields of approximately 10⁻¹⁰ degrees. 3Tto create “magic boxes” the size of shoeboxes for experiments in fundamental physics (Petoukhov, AK et al. (2006). Compact magnetostatic cavity for polarized 3He neutron spin filter cells. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 560(2), 480-484), using permanent magnets or DC coils to generate a unidirectional magnetic field within the parallel walls, parallel to a principal axis of a rectangular box made of mu-metal. The surfaces of the box, which connect these paired magnets and are made of highly permeable materials, act as the poles of the (electro)magnet.The previously described ARM magnetization of magnetic shields utilizes the same physical effect, whereby paired opposite surfaces of the shield act as permanent magnets, and the respective connecting surfaces serve as the poles of these magnets in all three orthogonal spatial directions. Within the shield, ARMs are generated in all three orthogonal directions of the enclosure, parallel to the Earth's magnetic field, consequently producing a homogeneous field antiparallel to the (external) bias field within the shield.
[0013] DE 102014002067 A1 discloses a device for generating a magnetic field in a specified direction, comprising a container bounded by a soft magnetic wall, with windings (L) arranged in pairs one behind the other for each spatial axis (x, y, z). By applying different currents to the windings (L), a magnetic field with a specified gradient in the specified direction can be generated. Furthermore, the wall can be demagnetized by a specified interconnection of the windings (L).
[0014] The problems with the state of the art are essentially that, according to the state of the art, to shield larger volumes from magnetic fields with sufficient quality, considerable efforts in the form of expensive materials and complex compensation procedures are required.
[0015] The present invention is based on several problems.
[0016] One object of the invention is the design and optimization of an active, room-sized magnetic shielding system against static or quasi-stationary magnetic fields.
[0017] Furthermore, the invention aims to improve the performance of passive magnetic shielding.
[0018] Another task is the combination of passive magnetic shielding, active magnetic field compensation using DC coil systems, and passive magnetic field compensation using adjustable permanent magnetism in a single, formerly passive magnetic shield.
[0019] These problems are solved with a magnetic box shielding according to the main claim and a magnetic box shielding application method according to the subordinate claim.
[0020] A magnetic box shield comprising a number of flat elements, a DC power supply, and a DC coil system is characterized in that the flat elements are shielding elements.
[0021] - the flat elements form a box with at least four flat elements as a magnetically shielded space,
[0022] - the flat elements are magnetically highly permeable and are magnetically conductively connected to each other at their connection points;
[0023] - the DC power supply provides a DC current I for input into the DC coil system;
[0024] - the windings of the DC coil system are wound around at least two opposing flat elements of the box and are electrically insulated, wherein the DC current in the coil system generates a magnetic flux in the respective flat element which runs parallel to one of its dimensions and parallel to the magnetic flux in the opposing flat element, wherein the shielding is closed by flat elements in the direction of the magnetic flux;
[0025] where
[0026] The magnetic flux in the shielded area generates a magnetic field that is antiparallel to the flux direction in the shielding elements.
[0027] As previously described, the direct current induces a magnetic flux in the coil system within each flat element, which runs parallel to one of its dimensions and parallel to the magnetic flux in the opposite flat element. This means that the magnetic flux is oriented perpendicular to the plane of the coil / loop.
[0028] The box can be open or closed.
[0029] In addition, a device for demagnetization by alternating current (AF) and ARM magnetization may be present.
[0030] The device for demagnetization by alternating current (AF) and ARM magnetization may preferably consist of an alternating current source and a mopping coil.
[0031] With the DC power supply, the DC current I and the resulting magnetic flux in the shielding can be adjusted proportionally to the number of DC coil turns N ■ I.
[0032] A magnetic sensor may also be present to measure the direction and intensity of the magnetic field within the shielded area.
[0033] The magnetic sensor can be a magnetometer, in particular a commercially available magnetometer such as a 3-axis fluxgate or Squid magnetometer.
[0034] The magnetic box shielding application method with a magnetic box shield includes at least the following step:
[0035] Switching on the DC power supply, which supplies the DC coil system with DC current, thereby generating a magnetic flux in the flat elements wound with DC coils, which runs parallel to one of the element dimensions and parallel to the magnetic flux in the opposite flat element, wherein the shielding by flat elements is closed in the flux direction of the magnetic flux, wherein the magnetic flux in the shielded area generates a magnetic field that is antiparallel to the flux direction in the shielding elements.
[0036] A magnetic sensor can be used to measure the direction and intensity of the magnetic field within the shielded area.
[0037] In a preferred embodiment, the adjustment of the direct current I and the resulting magnetic flux in the shield can be proportional to the number of direct current coil turns N ■ direct current I with the direct current supply.
[0038] The present invention relates to passive magnetic shielding, active magnetic field compensation using DC coil systems, passive magnetic field compensation using tunable permanent magnetism, and the combination of all these effects in a single, formerly passive magnetic shield. The magnetic box shield enables a significant improvement in the performance of passive magnetic shields that utilize the field compensation effect of magnetic remanence. With the present invention, a formerly passive shield itself functions as a 2D or 3D electromagnet with high field homogeneity, which can be tuned to zero field or to preferred field values in any direction by small DC currents in two or three orthogonal spatial directions.
[0039] As previously described, direct current coils are used, wound around the walls of a box-shaped magnetic shield, transforming the previously passive shield into an adjustable active electromagnetic system. This generates largely homogeneous fields inside the magnetic box shield and makes it possible to directly compensate residual fields to zero within a large field area and within a large homogeneous volume. In contrast to existing active compensation systems, which are generally installed either outside or inside passive shields, the magnetic box shield according to the invention is installed on top of the existing shield, requires no significant additional space, and does not generate any significant additional magnetic anomalies within the shielded area.In contrast to existing multi-stage, high-performance passive shielding systems, the present invention allows for the simple compensation of small residual fields without the need for expensive additional layers of shielding materials or special demagnetization processes for the shielding. Depending on the local installation conditions, one embodiment of the invention enables 3D field compensation suitable for zero-field OPM operation in an "open box" configuration with open E and W ends of the shielding, thereby creating a user-friendly and non-claustrophobic environment for medical sensor applications.
[0040] One embodiment of the invention makes it possible to improve and manipulate the ARM in passive ferromagnetic shields by generating a tailored additional bias field for ARM generation (for example, for electrical steel or iron shielding material), thereby significantly improving the passive shielding factor of such shields.
[0041] The magnetic box shielding according to the invention relates to various embodiments of systems and associated application methods that combine the passive shielding (flux diversion) of highly permeable magnetic shields with an active system of direct current coils (DC coils), thereby controlling the magnetic flux in the shielding material and transforming the shield itself into an electromagnet. This DC coil system can be used in a variety of embodiments for the direct active compensation of magnetic fields inside the shield. In other embodiments, it can be used to generate a controlled and directed magnetic flux in the shielding material to produce a controlled anhysteretic remanence of the shield, which significantly improves the passive shielding performance of ferromagnetic shields made of remanent materials such as electrical steel or iron.
[0042] One embodiment of the magnetic box shield enables the direct compensation of residual fields in up to three spatial directions, for example, within the inner stage(s) of a multi-stage magnetic shield. In the prior art, the cost of additional shielding increases immensely as very small fields are approached. Improved shielding generally requires additional layers of expensive shielding materials, which reduce the usable interior space and necessitate special demagnetization protocols for the shielding. With the present invention, small residual fields on the order of 1000 nT or less can be directly compensated in room-sized shields using very small currents (e.g., N = up to 10 turns of the current coils in each orthogonal spatial direction, currents of less than 100 mA for mu-metal shielding material in room-sized shields).
[0043] A second embodiment of the magnetic box shield enables the compensation of residual fields in an arrangement according to the invention with an open box in two spatial directions ("2D+" compensation). An open-box shield, as shown in Figures 2 and 3, with open E and W ends, is mechanically rotated about its vertical (z) axis until the EW (x) component of the residual field in the center of the box is zero. The remaining horizontal (y) and vertical (z) components of the residual field can be compensated by active compensation using the y and z DC coil sets. This design enables a user-friendly environment (no enclosed, confined space) combined with a very lightweight, cost-effective, and high-performance shielding solution, e.g., for medical sensor applications.
[0044] A third embodiment of the magnetic box shield allows for the compensation of gradient fields by operating the paired current coils with slightly different currents. Instead of a homogeneous field, the active shield now generates a controlled gradient field powered by the asymmetrical electromagnets. A combination of up to three orthogonal pairs of DC coils operating in gradient mode makes it possible to compensate for all unidirectional field gradients within the shield.
[0045] Another embodiment of the magnetic box shielding enables the generation of ARMs in any direction and with a much higher intensity compared to the prior art. Conventionally, the Earth's magnetic field or the ambient field within an external magnetic shield is used as a bias field to generate ARMs. This is particularly relevant when using highly permeable shielding materials with strong remanent magnetization, such as electrical steel or iron, but also for mu-metal, which has a much lower remanence, a factor that becomes relevant at very low residual fields.
[0046] To generate an ARM, the magnetic shield is demagnetized in the presence of a bias field (conventionally the Earth's magnetic field) using AC coils with decreasing amplitude currents. Due to the size of MSRs, the ARM is typically generated in a process where the MSR's surfaces are "wiped" with a much smaller, high-power AC coil. The decreasing amplitude is often achieved by using a constant AC current and removing the "wiping coils" from the already treated area. The intensity of the ARM is proportional to the intensity of the bias field and depends on the magnetic properties of the shielding material and the intensity of the AC field. If the intensity of the bias field in the shielding material can be increased, the intensity of the ARM, and thus its contribution to the shielding factor S, can be improved.The present invention enables the generation of controlled bias fields. Bias fields parallel to the Earth's magnetic field with higher intensity generate greater ARM magnetization of the shielding and improve the contribution of remanent magnetization to field compensation. Thus, the invention allows for a significant improvement in the shielding effectiveness of ferromagnetic shielding with remanent magnetism. During the ARM generation process, typically only parts of the shielding are magnetized simultaneously. Local field anomalies can be compensated for by applying ARMs adapted in intensity and direction to different parts of the shielding.
[0047] In a feasibility study for the magnetic box shielding, controlled ARMs were successfully generated. This involved the use of an outer 2 mm thick magnetic box shielding with an open box made of electrical tape with a volume of approximately 93 m³.3 (approx. 7.15 x 4.10 x 3.20 m) was used. This achieved a shielding factor S of approx. 20 with an ARM generated in the Earth's magnetic field and an S-value of approx. 30 using the present invention with current coils in a vertical direction (strongest component of the EMF; 10 loops with a current of approx. 0.52 A).
[0048] By 2026, two MSRs (Mass Rapid Reaction Systems) incorporating the technology according to the invention had already been completed and were ready for operation. In the larger MSR, the now-closed electromagnet shielding has an S-factor of approximately 40 with a tuned ARM (approximately 25 with a ground-field ARM). The inner mu-metal shielding can be actively adjusted to zero in two spatial directions. The internal volume of this shielding is approximately 6.60 x 3.60 x 2.70 m, which is gigantic for comparable magnetic shielding.
[0049] The second MSR, completed in 2026 (internal dimensions approx. 3.80 x 3.05 x 2.15 m), is intended to remain without any installations and be available for experiments. Its ARM-tuned external shielding with electrostatic bands has an S-value of >50, and within the active mu-metal internal shielding, the fields can be compensated to zero at any point. What remains are small anomalies of 10 nT in the rest of the interior, which ultimately result from the "conventional" construction of the surrounding building (steel mesh in the floor screed, steel reinforcement in the walls, etc.).
[0050] The invention is described below with reference to the accompanying illustrations in the description of the figures, which are intended to explain the invention and are not to be considered limiting.
[0051] They show:
[0052] Fig. 1 shows an exemplary schematic representation of the magnetic flux in a box-shaped electromagnet and the magnetic field inside the box according to the state of the art in cross-section;
[0053] Fig. 2 shows an exemplary schematic representation of a magnetic box shield according to the invention in the form of an open box shield in perspective view with a z-coil system; Fig. 3 shows an exemplary schematic representation of a magnetic box shield according to the invention in the form of an open box shield with y- and z-coil systems 3 in perspective view;
[0054] Fig. 4 shows an exemplary schematic representation of a magnetic box shield according to the invention in the form of a closed box shield with a) separate views of the coil systems 3 for the z, y and x directions and b) in perspective view;
[0055] Fig. 5 exemplary photographic representations of a magnetic box shield according to the invention in the form of an open box shield equipped with a Z-coil system and a Y-coil system;
[0056] Fig. 6 two implemented MSRs;
[0057] Fig. 7 Exterior view of the smaller MSR;
[0058] Fig. 8 z- and y-coils;
[0059] Figs. 9 and 10 Field mapping of the electrical band shielding with ARM in EMF;
[0060] Fig. 11 Measured values inside the MSR.
[0061] Fig. 1 shows a cross-section of the magnetic flux 4 in a box-shaped electromagnet and the magnetic field inside the box. The magnet consists of a frame made of highly permeable material 2 and direct current (DC) coils 3 wound around two opposite walls of the box-shaped frame and energized, generating a magnetic flux 4 of the same direction and intensity in both walls. This magnetic flux 4 transforms the frame 2 into an electromagnet, with the top and bottom surfaces of the box, connecting the coil-equipped walls, becoming magnetic poles. Inside the box, the magnetic field lines 5 connecting the poles describe a largely homogeneous magnetic field that is oriented antiparallel to the magnetic flux 4 in the shielding material generated by the DC coil system 3.
[0062] Fig. 2 shows a perspective view of a magnetic box shield 1 according to the invention in the form of an open box shield equipped with a set of z-direct current coils 3, 3.3, and the magnetic field inside the open box 6, 6.1. Similar to Fig. 1, the magnetic fields inside the box 6.1 along the z-axis can be adjusted and / or compensated by adjusting the polarity and intensity of the direct current. The term "open box 6.1" refers to a shield with two open sides, here in the x-direction. Fig. 3 shows a perspective view of an open magnetic shield 1 according to the invention with y-coil systems 3, 3.2 and z-coil systems 3, 3.3, which enables two-dimensional (2D) magnetic field adjustment in the y- and z-directions inside the open box 6.1.One embodiment of such 2D field compensation systems in an open-box arrangement can be used as an active 3D field compensation system (2D+) if the shield is designed to be mechanically rotated about its vertical axis: The EW component (x) of the magnetic field can be compensated by mechanically adjusting the shield direction in the magnetic NS direction, with the field being measured by a sensor at the center of the shield and the shield being adjusted by rotating it about its vertical axis until the x component is zero. The y component of the shield is now parallel to the magnetic N. The horizontal y and vertical z components of the residual fields within the open-box shield can now be compensated to zero by the y and z DC coil systems 3.2, 3.3.
[0063] Fig. 4 shows coil configurations for magnetic box shields 1 with a closed box 6.2. The term closed box 6.2 refers to a shield with all 6 sides of the MSR installed. For each orthogonal spatial direction, coil systems 3 must be installed on all sides parallel to the respective spatial direction.
[0064] Example: For the z-component, all four vertical walls must be equipped with coils 3.
[0065] Fig. 4a shows separate views of the coil systems 3 for the z, y and x directions.
[0066] Fig. 4b shows a perspective view of an MSR equipped with all xyz coil systems 3 for magnetic compensation and / or field manipulation in three dimensions (3D).
[0067] In open boxes 6.1, the geometry of the coil system 3 is simpler and easier to install than in closed boxes 6.2 with fully enclosed shields. Fig. 5 shows photographs of a magnetic box shield 1 according to the invention in the form of a 2D+ open box shielding system, equipped with a Z-coil system (4 windings) 3.3 and a Y-coil system (2 windings) 3.2 (Fig. 5a). To measure the magnetic field within the shield 1, a precise 3-component fluxgate magnetometer 7 (magnetometer 7 readings, Fig. 5b) was placed in the center of the shield 1, and a precise power supply 8 (power supply 8 readings after adjusting the magnetic field to less than 0.2 nT, Fig. 5c) was used to adjust the currents for the Y and Z DC coil systems 3.2, 3.3. The mu-metal shield 9, with a thickness of 0.762 mm and dimensions of 750 mm x 770 mm x 770 mm (xyz), was placed in a large open box 6.1 with an electrical steel shield 2 mm thick and dimensions 7150 mm x 4150 mm x 3200 mm (xyz) with a residual field of approximately 1500 nT. The residual field within the small mu-metal shield 9 was approximately 50 nT without active field compensation (flux diversion). The shield 1 was mechanically aligned to magnetic N by rotating it about its z-axis until the x-component was zero at the center of the shield. The residual field could be reduced with small direct currents of approximately
[0068] The 3.7 mA at the z-DC coil system 3.3 and the 20.9 mA at the y-DC coil system 3.2 were compensated to zero (within the noise level and calibration accuracy of the magnetometer of approximately 0.05 nT). Despite the relatively short x-dimension (750 mm) of the open box 6.1, a relatively large volume with residual fields of less than 5 nT was achieved within approximately 100 mm x 100 mm x 100 mm in the center of the shield.
[0069] Fig. 6 shows both MSRs: in the foreground the large MSR (Palmag), external dimensions (electrical tape shielding) approx. 7.14 x 4.10 x 3.30 m3 internal dimensions (mu-metal shielding) approx.
[0070] 6.60 x 3.60 x 2.70 m³; on the right in the background, the smaller MSR (exp) external dimensions approx. 4.25 x 3.50 x 2.65 m³, internal dimensions approx. 3.81 x 3.05 x 2.15 m³. The z-coils of the external shielding are clearly visible on the large MSR.
[0071] Fig. 7 shows an external view of the smaller MSR.
[0072] Fig. 8 shows z- and y-coils (detail) made of enamelled copper wire on the mu-metal shielding inside the MSR.
[0073] Figures 9 and 10 show the field mapping of the electrical band shielding with ARM in EMF and tuned ARM in microtesla (pT).
[0074] The measured values inside the MSR (passive and active) are shown in Fig. 11. The field mapping measurements inside the MSR are shown in nanotesla (nT) at half-meter intervals (the height is indicated below the field map; the top row shows the active shielding and the bottom row shows the passive shielding of the mu-metal). The height of 1.31 m corresponds to the center of the inner shielding. All measurement points along the walls, as well as in the lowest (0.31 m) and highest (2.31 m) levels, are located in the immediate vicinity of the mu-metal shielding and the current coils, so that seemingly "worse" values may occur there with active shielding compared to passive shielding. It can be seen that overall better values are achieved with active shielding than with passive shielding (possibly...).Isolated instances of poorer readings along the walls, floor (0.31 m) and ceiling (2.31 m) are due to the fact that the measuring points may be located only a few centimeters away from the xyz current coils, and the field may be slightly distorted there. Reference symbol list:
[0075] 1 Magnetic box shielding
[0076] 2 magnetic frames
[0077] 3 DC coil system, DC coil 3.1 x-DC coil system
[0078] 3.2 y-DC coil system
[0079] 3.3 z-DC coil system
[0080] 4 Magnetic flux
[0081] 5 magnetic field lines
[0082] 6 boxes
[0083] 6.1 open box
[0084] 6.2 closed box
[0085] 7 Magnetometer
[0086] 8 DC power supply
[0087] 9 Mumetal shielding
Claims
REQUIREMENTS 1. Magnetic box shielding (1) with a number of flat elements, a DC power supply (8) and a DC coil system (3), characterized by the fact that - the flat elements are shielding elements; - the flat elements form a box (6) with at least four flat elements as a magnetically shielded space; - the flat elements are highly magnetically permeable and are magnetically conductively connected to each other at their connection points; - the DC power supply (8) provides a DC current I for input into the DC coil system (3); - the windings of the DC coil system (3) are wound around at least two opposing flat elements of the box (6) and are electrically insulated, wherein the DC current in the coil system (3) generates a magnetic flux (4) in the respective flat element, which runs parallel to one of its dimensions and parallel to the magnetic flux (4) in the opposing flat element, wherein the shielding is closed by flat elements in the direction of the magnetic flux (4); where The magnetic flux (4) in the shielded area generates a magnetic field that is antiparallel to the flux direction in the shielding elements.
2. Magnetic box shielding (1) according to claim 1, characterized by the fact that the box (6) is open or closed.
3. Magnetic box shielding (1) according to claim 1 or 2, characterized by the fact that A device for demagnetization by alternating current (AF) and ARM magnetization is available.
4. Magnetic box shielding (1) according to the preceding claim, characterized in that The device for demagnetization by alternating current (AF) and ARM magnetization consists of an alternating current source and a mopping coil.
5. Magnetic box shielding (1) according to one of the preceding claims, characterized in that with the DC supply (8) the DC current I and the resulting magnetic flux (3) in the shielding are adjustable proportionally to the number of DC coil turns N ■ I.
6. Magnetic box shielding (1) according to one of the preceding claims, characterized in that A magnetic sensor is present for measuring the direction and intensity of the magnetic field within the shielded area.
7. Magnetic box shielding (1) according to the preceding claim, characterized in that the magnetic sensor is a magnetometer (7).
8. Magnetic box shielding application method with a magnetic box shield (1) according to any one of claims 1 to 7, at least comprising the step: Switching on the DC power supply (8), which supplies the DC coil system (3) with DC current, thereby generating a magnetic flux (4) in the flat elements wound with DC coils (3), which runs parallel to one of the element dimensions and parallel to the magnetic flux (4) in the opposite flat element, wherein the shielding by flat elements is closed in the flux direction of the magnetic flux (4), wherein the magnetic flux (4) generates a magnetic field in the shielded area which is antiparallel to the flux direction in the shielding elements.
9. Magnetic box shielding application method according to the preceding claim, characterized by the fact that The direction and intensity of the magnetic field within the shielded area are measured using a magnetic sensor.
10. Magnetic box shielding application method according to one of the two preceding claims, characterized by the fact that an adjustment of direct current I and the resulting magnetic flux (4) in the shield proportional to the number of direct current coil turns N ■ direct current I with the direct current supply (8) is carried out.