阅读说明：本技术 一种大型磁屏蔽系统及其消磁装置、消磁方法 (Large-scale magnetic shielding system and demagnetization device and demagnetization method thereof ) 是由 王帆 卓彦 杨思嘉 吴顺子 于 2020-01-08 设计创作，主要内容包括：本发明涉及一种大型磁屏蔽系统及其消磁装置、消磁方法,所述消磁装置包括：线圈,布置在磁屏蔽室的磁屏蔽材料层上,并与所述磁屏蔽材料层形成闭合磁路；磁场检测装置,检测所述磁屏蔽室内的磁场强度及梯度；控制系统,所述控制系统接收表示所述磁场检测装置检测到的磁场强度大小的信号,并产生控制信号；以及驱动装置,所述驱动装置在所述控制系统的控制下向所述线圈施加驱动信号。本发明实施例公开的消磁装置可以自动化对大型磁屏蔽室/磁屏蔽筒等进行快速消磁操作,从而在其内部获得良好的低静磁场(消磁)和低梯度场(匀场)环境。(The invention relates to a large-scale magnetic shielding system and a demagnetizing device and a demagnetizing method thereof, wherein the demagnetizing device comprises: a coil disposed on a magnetic shield material layer of a magnetic shield room and forming a closed magnetic path with the magnetic shield material layer; a magnetic field detection device for detecting the magnetic field intensity and gradient in the magnetic shielding room; a control system which receives a signal representing the magnitude of the magnetic field intensity detected by the magnetic field detection device and generates a control signal; and a driving device that applies a driving signal to the coil under the control of the control system. The demagnetizing device disclosed by the embodiment of the invention can automatically carry out rapid demagnetizing operation on a large magnetic shielding room/magnetic shielding cylinder and the like, thereby obtaining good low static magnetic field (demagnetizing) and low gradient field (shimming) environments in the demagnetizing device.)

1. A demagnetizing device, comprising:

a coil disposed on a magnetic shield material layer of a magnetic shield room and forming a closed magnetic path with the magnetic shield material layer;

a magnetic field detection device that detects a magnetic field intensity in the magnetic shield room;

a control system which receives a signal representing the magnitude of the magnetic field intensity detected by the magnetic field detection device and generates a control signal; and

a drive device that applies a drive signal to the coil under control of the control system.

2. The demagnetizing device of claim 1, wherein the magnetic field strength comprises a static magnetic field strength and a gradient magnetic field strength.

3. The demagnetizing device of claim 1 or 2, wherein the driving signal comprises a connection signal for controlling a connection manner between the coils and a current signal for controlling a magnitude of a magnetic field generated by the coils.

4. The demagnetizing device of claim 3, wherein the magnetic shielding material layers of the magnetic shielding compartment comprise at least one inner magnetic shielding material layer and/or at least one outer magnetic shielding material layer, and the coil is disposed on at least one of the inner and outer magnetic shielding material layers, respectively.

5. The demagnetizing device of claim 4, wherein the magnetic shielding compartment is in the form of a polyhedron comprising edges, and the coil comprises a first coil and/or a second coil, the first coil being arranged on the inner and outer surfaces of the at least one layer of magnetic shielding material, and the second coil being arranged on the edges of the at least one layer of magnetic shielding material.

6. The demagnetizing device of claim 4, wherein the magnetic shielding chamber is in the form of a cylinder, and the coil comprises a first coil and/or a second coil, the first coil being disposed on the inner and outer surfaces of the at least one magnetic shielding material layer in a circumferential direction of the at least one magnetic shielding material layer, and the second coil being disposed on the inner and outer surfaces of the at least one magnetic shielding material layer in an axial direction of the magnetic shielding material layer.

7. The demagnetizing device of claim 3, wherein the driving device is configured to apply a connection signal to the coils such that the coils are connected in series in a demagnetizing operation.

8. The demagnetizing device of claim 3, wherein the current signal is an alternating signal that decays in a pattern.

9. The demagnetizing device of claim 8, wherein the current signal is a sinusoidal signal that decays logarithmically with time.

10. The demagnetizing device of claim 3, wherein a maximum power of the current signal is not lower than a minimum power required to magnetize the magnetically shielded room to a saturated state.

11. The demagnetizing device of any one of claims 1 to 10, wherein the control device is configured to provide feedback control during demagnetization.

12. The demagnetizing device of claim 4, wherein the coil comprises a shield coil disposed on an inner surface of the inner magnetic shielding material layer, the connection signal causes the shield coil to be controlled independently of other coils in an active shielding mode, and the current signal is an active shielding/shimming signal that actively shields the interior changing magnetic field and gradient of the magnetic shielding compartment.

13. The demagnetizing device of claim 12, wherein the current signal is a weak current signal, a magnitude of which varies based on the internal magnetic field strength and/or gradient measured by the magnetic field detection device.

14. A large magnetic shielding system comprising:

a magnetic shield room configured in the form of a polyhedron or a cylinder, the magnetic shield room including at least one layer of a magnetic shield material; and

the demagnetizing device of any one of claims 1 to 13, wherein the control system and the driving device are disposed outside the magnetically shielded room, and the magnetic field detection device is disposed inside the magnetically shielded room and connected to the control system via a cable.

15. Large magnetic shield system according to claim 14, in which the magnetic shield material layer comprises permalloy or high permeability magnetic materials containing nickel, iron using other names.

16. The large magnetic shield system of claim 14, wherein said magnetic shield room further comprises: a push-pull or rotary opening and closing shield door and a plurality of waveguides for arranging cables.

17. Large magnetic shielding system according to claim 14, wherein the magnetic shielding compartment comprises at least two layers of magnetic shielding material, which are spaced apart and interconnected by a support structure.

18. A degaussing method for a large magnetic shielding system, comprising:

receiving a subject or a sample to be tested in a working area of a magnetic shielding room;

detecting the magnetic field intensity in the magnetic shielding room, and comparing the magnetic field intensity in the magnetic shielding room with a preset threshold value; and

and when the magnetic field intensity or gradient in the magnetic shielding room is larger than the threshold value, carrying out degaussing operation.

19. The demagnetization method of claim 18, wherein the demagnetization operation comprises:

generating a drive signal that attenuates in a pattern;

applying a drive signal to the coil causing the magnetically shielded cells to be magnetized to a saturated state; and

attenuating the drive signal to zero or near zero;

wherein the magnetic shield room includes at least one magnetic shield material layer, the coils are arranged on the inner surface and the outer surface of at least one of the magnetic shield material layers and form a closed magnetic circuit with the at least one magnetic shield material layer, and the driving signal includes a connection signal controlling the connection manner between the coils and a current signal controlling the magnitude of a magnetic field generated by the coils.

20. The demagnetization method of claim 19, wherein a connection signal is applied to the coils in the demagnetization operation so that the coils are connected in series.

21. The demagnetizing method of claim 19, wherein the coil is disposed on an inner surface and an outer surface of each of the layers of the magnetic shielding material layer.

22. The demagnetization method of claim 19, wherein the current signal is a sinusoidal signal that decays logarithmically over time.

23. The demagnetizing method of claim 18, further comprising:

when the magnetic shield room is operated, it is operated in an active shield mode.

24. The demagnetizing method of claim 23, wherein operating in the active shielding mode comprises:

applying a connection signal to a shield coil such that the coils are independently controlled; and

applying an active shielding/shimming signal to a shielding coil to actively shield the interior varying magnetic field and gradient of the magnetically shielded room, wherein the shielding coil is one of the coils that is disposed on an interior surface of an innermost one of the layers of the magnetically shielding material.

25. The method of claim 24, wherein the shield signal is a low current signal and the shield coil is controlled independently of the other coils in the active shield mode.

Technical Field

The invention relates to a large-scale magnetic shielding system, a demagnetizing device and a demagnetizing method thereof.

Background

Magnetoencephalography (MEG), Magnetocardiography (MCG) devices, superconducting rock magnetometers and the like are the main devices used in large magnetic shielding devices at present. Most of the devices are sensitive magnetic detection devices based on superconducting magnetic quantum interferometers (SQUIDs), because the superconducting magnetic quantum interferometers measure the relative strength of the magnetic flux change of the acquisition coils, the dynamic range is large, and the recording of a first-order gradiometer to a high-order gradiometer can be realized through different windings of the acquisition coils, the superconducting magnetic quantum interferometers can work in a strong static magnetic field environment and have no strict requirement on a low static magnetic field environment.

In recent years, with the development of optical pump atomic detection technology, especially since 2003, human beings began to be able to manipulate atomic spins to achieve a Spin Exchange Free Relaxation (SERF) state, research on ultra-high-sensitivity magnetic field measurement based on precession of atomic spins in the SERF state began to be spotlighted. The method can greatly surpass the sensitivity realized by the prior related measuring means, so that the human obtains a new tool for understanding the world. An atomic magnetometer (namely, an atomic magnetic detector) based on the optical pumping detection technology can work in a room temperature environment, does not need liquid helium for cooling, has small volume and light weight, can realize low-cost mass production through a semiconductor process, and brings new eosin for magnetoencephalography, magnetocardiography and other weak magnetic detection in the fields of medicine, biology and materials.

However, the current optical pump atomic magnetometer based on the SERF effect requires extremely low background magnetic field (usually <20nT) and low dynamic range to reach the ideal working condition, so that a good magnetic shielding working environment is required.

Disclosure of Invention

An embodiment of the present invention provides a demagnetizing device, including: a coil disposed on a magnetic shield material layer of a magnetic shield room and forming a closed magnetic path with the magnetic shield material layer; a magnetic field detection device that detects a magnetic field intensity in the magnetic shield room; the control system receives a signal representing the magnitude of the magnetic field intensity detected by the magnetic field detection device, compares the magnetic field intensity with a preset threshold value and generates a control signal; and a driving device that applies a driving signal to the coil under the control of the control system.

An embodiment of the present invention provides a large-sized magnetic shield system including: a magnetic shield room configured in the form of a polyhedron or a cylinder, the magnetic shield room including at least one layer of a magnetic shield material; and the demagnetizing device as described above, wherein the control system and the driving device are disposed outside the magnetic shielding room, and the magnetic field detection device is disposed inside the magnetic shielding room and connected to the control system through a cable.

An embodiment of the present invention provides a demagnetization method for a large magnetic shield system, the method including: receiving a subject or a sample to be tested in a working area of a magnetic shielding room; detecting the magnetic field intensity in the magnetic shielding room, and comparing the magnetic field intensity in the magnetic shielding room with a preset threshold value; and when the magnetic field intensity in the magnetic shielding room is larger than the threshold value, carrying out degaussing operation.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments of the present invention will be briefly described below. Wherein the drawings are only for purposes of illustrating some embodiments of the invention and are not to be construed as limiting the invention to all embodiments thereof.

FIG. 1 shows a perspective view of a large magnetic shield system comprising a degaussing device according to an embodiment of the invention;

FIG. 2 shows a schematic view of a demagnetization device according to an embodiment of the invention;

FIG. 3 shows a perspective view of a large magnetic shield system comprising a demagnetization device according to another embodiment of the invention; and

FIG. 4 shows a flow chart of a degaussing method according to an embodiment of the invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of specific embodiments of the present invention. Like reference symbols in the various drawings indicate like elements. It should be noted that the described embodiments are only some embodiments of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the invention without any inventive step, are within the scope of protection of the invention.

Unless defined otherwise, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs. The use of "first," "second," and similar terms in the description and claims of the present application do not denote any order, quantity, or importance, but rather the terms are used to distinguish one element from another. Also, the use of the terms "a" or "an" and the like do not necessarily denote a limitation of quantity. The word "comprising" or "comprises", and the like, means that the element or item preceding the word comprises the element or item listed after the word and the equivalent thereof, but does not exclude other elements or items. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships may also be changed accordingly.

In the following description and in the appended claims, the directional terms "inner" and "outer" are used, wherein the inner, inner surface refers to the surface facing the working area surrounded by the "magnetic shielding compartment" and the outer, outer surface refers to the surface opposite to said inner, inner surface.

Known multi-layer large magnetic shielding systems typically employ layers of high permeability magnetic shielding material to shield the external magnetic field, the residual magnetism of the high permeability material itself for shielding can seriously affect the static magnetic field in the magnetic shielding device, and these magnetic shield systems usually only arrange demagnetizing coils (shielding chambers) on the outer shielding layer along the edges, wind demagnetizing coils (large magnetic shield cylinders) on the outer shielding layer or temporarily arrange demagnetizing coils (large magnetic shield cylinders) by using an axial threading method, therefore, the magnetic shielding systems are difficult to effectively eliminate the residual magnetism of the inner magnetic shielding material, and the demagnetizing devices can only perform demagnetizing operation during equipment installation or regular maintenance, so that the time consumption is long, manual control is mostly adopted, the demagnetizing effect is poor, the demagnetizing efficiency is low, and the internal static magnetic field caused by the operation of a shielding system switch and internal equipment cannot be demagnetized in real time during daily use. This set of problems makes sensitive magnetic detectors such as atomic magnetometers based on the SERF effect sensitive to static magnetic fields difficult to work effectively directly on common large magnetic shielding systems.

Furthermore, since the atomic magnetic detector can perform mobile recording, the presence of the gradient field in the shielded room can introduce a lot of noise during its movement. Although the static and gradient fields can be compensated for proper operation by active compensation devices located in the detector or shield system, the currents in the active compensation system introduce additional noise.

Aiming at the problems, the invention provides an automatic rapid demagnetizing device for a large magnetic shielding system, the large magnetic shielding system comprising the demagnetizing device and a demagnetizing method, which can effectively reduce the remanence inside the large magnetic shielding system and continuously maintain the favorable low static magnetic field (demagnetizing) and low gradient field (shimming) environment inside the large magnetic shielding system in long-term use, thereby reducing the magnetic field intensity required by an active compensation device or completely separating from the active compensation device, further reducing or eliminating the noise introduced by the active compensation device and further improving the signal-to-noise ratio of the whole magnetic detection system. Further, the shield coil disposed on the inner surface of the inner layer of the magnetic shield material layer can be switched to the active shield mode as needed to compensate for the internal varying magnetic field of the magnetic shield room in the operating state without additionally providing an active compensation device.

Exemplary embodiments of the present invention will now be described more fully hereinafter with reference to the accompanying drawings.

The demagnetizing device for a large magnetic shield room according to an embodiment of the present invention comprises: a coil disposed on a magnetic shield material layer of a magnetic shield room and forming a closed magnetic path with the magnetic shield material layer; a magnetic field detection device that detects a magnetic field intensity in the magnetic shield room; the control system receives a signal representing the magnitude of the magnetic field intensity detected by the magnetic field detection device, compares the magnetic field intensity with a preset threshold value, and generates a control signal when the magnetic field intensity is greater than the preset threshold value; and a driving device that applies a driving signal to the coil under the control of the control system.

Fig. 1 shows a perspective view of a large magnetic shield system including a demagnetizing device according to an embodiment of the present invention, and fig. 2 shows a schematic view of a demagnetizing device according to an embodiment of the present invention.

According to an embodiment of the invention, the demagnetizing device can be disposed on a large shielding room, for example, as shown in fig. 1, and comprises: an inner magnetic shield material layer 6 and an outer magnetic shield material layer 7 disposed outside the inner magnetic shield material layer 6, a coil 1 disposed on the inner magnetic shield material layer 6 and the outer magnetic shield material layer, respectively, a magnetic field detection device 4 disposed in the inner magnetic shield material layer 6 to detect the magnitude of a magnetic field within a working area 8 surrounded by the inner magnetic shield material layer 6, a control system 2 connected with the magnetic field detection device 4 to receive a signal indicating the magnitude of the magnetic field within the working area, and a drive device 3 driving the coil under the control of the control system 2 to eliminate residual magnetism, wherein the coil 1 is disposed on the magnetic shield material layers 6, 7 of the magnetic shield room 100 and forms a closed magnetic circuit with the magnetic shield room 100, more specifically, with at least one magnetic shield material layer of the magnetic shield room 100. The arrangement of the coil 1 and the layers 6, 7 of magnetic shielding material can be made by winding, with the edge extending between the vertices of the shielding compartment through the seams or openings in the shielding material. The present invention is not limited thereto, and the magnetic shield material layer of the magnetic shield room may include only one magnetic shield material layer, or include a plurality of inner magnetic shield material layers and a plurality of outer magnetic shield material layers. Further, the coil 1 may be arranged on the magnetic shield material layers 6, 7 in other manners, and the present invention is mainly limited to the arrangement position of the coil on the magnetic shield material layers, and the arrangement manner is not particularly limited.

In the present embodiment, the magnetic shield room 100 is constituted as a cubic structure, as shown in fig. 1. Alternatively, the magnetic shield room may be configured in other polyhedral or cylindrical forms as shown in fig. 3.

Exemplarily, the coil 1 can be arranged not only at the edge of the magnetic shielding room, but also uniformly on each surface of the magnetic shielding room, and through the specific coil arrangement and the selection of the winding number, the magnetic field distribution on each surface of the shielding room is as uniform as possible in the demagnetization process, so that the optimal demagnetization effect is obtained. Due to the large magnetic shielding device, the space inside is ample and the magnetic detector (e.g., atomic magnetometer) typically needs to be arranged at a distance from the inner wall of the magnetic shield room to reduce the influence of the residual magnetism of the shielding material. Preferably, the coils can be arranged on both the inner and outer sides of the layers of the magnetic shield, especially the inner surface of the inner layer, to achieve an optimal demagnetization effect.

As shown in fig. 1, the coil 1 includes a first coil 11 and a second coil 12, the first coil 11 being disposed on the inner and outer surfaces of the inner magnetic shield material layer 6, and the second coil 12 being disposed on the edges of the inner magnetic shield material layer 6. For the outer magnetic shield layer 7, a coil (not shown) can also be provided as well.

Alternatively, in other embodiments, particularly when the magnetic shield room is in the form of a cylinder (magnetic shield cylinder), as shown in fig. 3, the first coil 11 'is arranged on the inner surface of the inner layer magnetic shield material layer 6' in the circumferential direction of the magnetic shield material layer, and the second coil 12 'is arranged on the inner surface of the inner layer magnetic shield material layer 6' in the axial direction of the inner layer magnetic shield material layer. Also in a similar manner, a coil (not shown) can be provided on the outer magnetic shield layer 7'.

It is noted that the coils arranged on the inner surface of the inner layer of magnetic shielding material 6 may also be referred to as active shielding/shimming coils, since the driving means 3 apply an active shielding/shimming signal to the shielding coils under the control of the control system 2 to actively shield the inner varying magnetic field and/or gradient of the magnetic shielding compartment 100 in the operational state. At this time, the driving signals may further include active shielding/shimming signals calculated from the internal magnetic field/gradient change of the magnetic shield room 100.

The "operating state" described in the present invention refers to an operating state in which the magnetic detector in the magnetic shielding room 100 is in a magnetic field detection state, and at this time, due to the movement of the object to be measured or the influence of the geomagnetic field, a changing internal magnetic field and/or gradient field is generated in the magnetic shielding room with time. In this case, an active shielding device is required to further reduce the magnetic field strength and gradient in the magnetically shielded room.

Alternatively, the shielding signal is a weak current signal, and the magnitude thereof may vary based on the internal magnetic field strength and/or gradient detected by the magnetic field detection device 4, which is not limited by the present invention.

For example, a magnetic shield room can include at least one layer of magnetic shield material. Alternatively, the magnetic shield room may comprise at least two layers of magnetic shield material, the different layers of magnetic shield material being spaced apart and interconnected by a support structure. In the present embodiment, as described above, the magnetic shield room 100 includes two magnetic shield material layers, the inner magnetic shield material layer 6 and the outer magnetic shield material layer 7, respectively, in which the inner magnetic shield material layer 6 is disposed inside the outer magnetic shield material layer 7. Further, for example, as shown in fig. 2, the first coil 11 may include a first inner coil 111, a second inner coil 113, and a first outer coil 112, a second outer coil 114, the first inner coil 111 being disposed at an outer surface of the inner magnetic shield material layer 6, the second inner coil 113 being disposed at an inner surface of the inner magnetic shield material layer 6; the first outer coil 112 is disposed on the outer surface of the outer magnetic shield material layer 7, and the second outer coil 114 is disposed on the inner surface of the outer magnetic shield material layer 7.

Alternatively, the control system 2 may control the connection between different sets of coils 1, for example, in parallel, in series, independently or disconnected. Specifically, the driving signal includes a connection signal for controlling a connection mode between the coils and a current signal for controlling a magnitude of a magnetic field generated by the coils, and the connection signal may control the connection mode between the coils, for example, by controlling on/off of an electrical switch such as a relay.

Preferably, the driving device 3 is configured to apply a connection signal to the coils 1 during the degaussing operation so that the coils 1 are connected in series to ensure consistency of current intensity and phase through each coil during degaussing to ensure good degaussing effect. Furthermore, different coils may be connected differently as desired to achieve optimal degaussing of a particular section. Alternatively, the shield coil is connected in series with the other coils in a degaussing operation and is controlled independently or disconnected from the other coils in an active shield operation. Because the control system 2 of the demagnetizing device provided by the embodiment of the invention can adopt different connection modes among the coils 1, the arrangement paradigm of the coils is relatively flexible, and the arrangement paradigm can take into account the magnetic field intensity change and/or gradient change which can generate a linear or other standard mode under weak current, namely, the demagnetizing operation and the active shielding operation can be considered at the same time.

Alternatively, the magnetic shielding material layer comprises permalloy, which is also known as iron-nickel alloy, a common soft magnetic material used for manufacturing the magnetic shielding material layer, and has a very high permeability of a weak magnetic field. The present invention is not limited thereto, and those skilled in the art can also adopt other common high-permeability or low-remanence materials as the magnetic shielding material layer. In addition, different materials can be used for different magnetic shielding material layers to form a composite magnetic shielding room.

The magnetic field detection device 4 is provided in the magnetic shield room 100 to detect the static magnetic field and the gradient field strength in the magnetic shield room 100. Illustratively, the magnetic field detection means 4 is further configured to compare the detection result with a threshold value, to control the degaussing process or to provide feedback control during the degaussing process. In the present embodiment, the magnetic field detection device 4 is disposed in or near the working area of the magnetic shield room 100.

It should be noted that the "working area" of the present invention refers to the area where the magnetic detection system is located, and the subject or the sample to be tested is accommodated in the working area when the magnetic detection system is in operation. The static or gradient field strength in or near the working region needs to meet certain requirements to ensure proper operation of the magnetic detector (e.g. an atomic magnetometer), e.g. a very low and spatially uniformly distributed background magnetic field (typically <20 nT).

The control system 2 may comprise a circuit configured to receive a signal generated by the magnetic detection system, the signal being indicative of the static magnetic field strength or gradient magnetic field strength in the operating region, and to compare the detected static magnetic field strength or gradient magnetic field strength with a predetermined threshold value, the control system 2 generating a control signal to control the drive means 3 to generate a drive signal (e.g. a drive current) to drive the coil 1 when the detected static magnetic field strength or gradient magnetic field strength is greater than the threshold value.

The control system 2 may also include a processor for controlling the operation of the demagnetizing device based on a built-in software program or a programmable hardware system or user instructions. The processor may be a Micro Controller Unit (MCU), a Field Programmable Gate Array (FPGA), a digital signal processor, a CPU, a desktop computer, a workstation, or other processor with data receiving and processing capabilities.

The drive device 3 includes, for example, a power amplifier, and the drive device 3 receives a control signal of the control system 2 and drives the coil 1 through the power amplifier.

The current signal of the drive signal may be, for example, an alternating signal that is attenuated in a certain pattern. In this embodiment, the current signal is a sinusoidal signal that decays logarithmically with time.

Illustratively, the maximum power that the driving device 3 applies to the coil 1 (i.e., the current signal) is not lower than the minimum power required for the magnetic shield room 100 to be magnetized to the saturation state.

As shown in fig. 1, a large magnetic shield system according to an embodiment of the present invention includes: a magnetic shield room configured in the form of a polyhedron or a cylinder, the magnetic shield room including at least one layer of a magnetic shield material; and the demagnetizing device as described above, wherein the control system and the driving device are disposed outside the magnetic shielding room, and the magnetic field detection device is disposed inside the magnetic shielding room and connected to the control system through a cable.

Illustratively, the spacing between the different layers includes air or an insulator sound barrier material for shielding electrical or acoustic signals. A radio frequency shielding layer (not shown) may also be included in the compartment to shield radio frequency signals.

Exemplarily, the magnetic shield room includes a shield door which is opened and closed by a push-pull type or a rotation type and a plurality of waveguides for arranging cables.

Fig. 3 shows a perspective view of a large magnetic shield system comprising a degaussing device according to another embodiment of the invention. This embodiment will be described below in conjunction with fig. 3, and for the sake of brevity, only differences from the previous embodiment will be described below.

In the embodiment shown in fig. 3, the magnetic shield room 200 is configured in a cylindrical form, and includes a shield door that is rotatably opened and closed and a plurality of waveguides (neither shown) for arranging cables.

The coil includes a first coil 11 'and a second coil 12', the first coil 11 'being arranged in the circumferential direction of the magnetic shield material layer on the inner and outer surfaces of the inner shield material layer 6, the second coil 12' being arranged in the axial direction of the magnetic shield material layer on the inner and outer surfaces of the inner shield material layer 6; in addition, coils (not shown) may be similarly provided on the inner and outer surfaces of the outer shielding material layer 7.

FIG. 4 shows a flow chart of a degaussing method according to an embodiment of the invention. An embodiment of the degaussing method will be described below in connection with fig. 4.

An exemplary embodiment of the present invention provides a demagnetization method for a large magnetic shield system, including: receiving a subject or a sample to be tested in a working area of a magnetic shielding room; detecting the static magnetic field and the gradient field strength in the magnetic shielding room through a magnetic field detection device, and comparing the magnetic field in the magnetic shielding room with a threshold value; and when the magnetic field in the magnetic shielding room is larger than a threshold value, carrying out degaussing operation.

Illustratively, the demagnetization method may further include: the shield door of the magnetic shield room is closed after receiving the subject or the sample to be tested.

Illustratively, the degaussing operation includes: generating a drive signal that attenuates in a pattern; generating a drive signal that attenuates in a pattern; applying a drive signal to the coil causing the magnetically shielded cells to be magnetized to a saturated state; and attenuating the drive signal to zero or near zero.

The drive signal (in particular, the current signal) is, for example, a sinusoidal signal that decays logarithmically with time. At the initial stage of the application of the drive signal, since the maximum power applied to the coil by the drive means is not lower than the minimum power required for magnetizing the magnetic shield room to the saturation state, the magnetic shield room is magnetized to the saturation state at this time. Then, as the drive signal decays to zero or close to zero, the magnetic field strength of the magnetization of the magnetic shielding room also decays to zero or close to zero, and at this time, the demagnetization operation is completed.

During degaussing, the magnetic field detection means can detect the static magnetic field and the gradient field strength in the magnetically shielded room continuously or at certain time intervals and compare them with preset threshold values. When the magnetic field in the magnetic shielding room is larger than the threshold value, the demagnetization operation is continued, and when the magnetic field in the magnetic shielding room is smaller than or equal to the threshold value, the demagnetization operation is finished.

The set value of the threshold value can be selected according to the requirements of practical application so as to ensure the demagnetization efficiency and better demagnetization effect.

In addition, a plurality of demagnetization modes may be set, including, for example, a fast demagnetization mode in which the power and/or the decay rate of the drive signal is larger than those in the normal demagnetization mode, and a normal demagnetization mode. Alternatively, the fast degaussing mode may be performed first, and then the normal degaussing mode may be performed.

Optionally, the embodiment of the present invention may further work in an active shielding mode, where the method in the active shielding mode includes: when the magnetic shield room is operated, it is operated in an active shield mode.

Illustratively, operating in the active mask mode includes: applying connection signals to the coils to configure each coil into an independent control form; an active shielding/shimming signal is applied to the shielding coils disposed on the inner shielding layer to actively shield the interior varying magnetic field and gradient of the magnetically shielded room. Illustratively, the mask signal is a weak current signal.

In summary, the present invention provides an automatic fast degaussing device for a large magnetic shielding system, a large magnetic shielding system including the degaussing device, and a degaussing method, which can effectively reduce the remanence inside the large magnetic shielding system, maintain a good low static magnetic field (degaussing) and low gradient field (shimming) environment, reduce the magnetic field strength required to be provided by an active compensation device or completely separate from the active compensation device, and further reduce or eliminate the noise introduced by the active compensation device, thereby further improving the signal-to-noise ratio of the whole magnetic detection system. Further, the shield coil disposed on the inner surface of the inner layer of the magnetic shield material layer can be switched to the active shield mode as needed to compensate for the internal varying magnetic field of the magnetic shield room in the operating state without additionally providing an active compensation device.

Exemplary embodiments of the large magnetic shield system and the demagnetizing device and demagnetizing method thereof proposed in the present invention are described above in detail with reference to preferred embodiments, however, it will be understood by those skilled in the art that various modifications and variations can be made to the above specific embodiments without departing from the concept of the present invention. Furthermore, various combinations of the features and structures presented in the various aspects of the invention may be made without departing from the scope of the invention, which is defined in the appended claims.