Magnetic shielding device and method for low-temperature current comparator

Abstract

The invention belongs to the technical field of shielding, and relates to a magnetic shielding device and shielding method for a low-temperature current comparator, the device comprises a shielding main body of a shell structure and an end cover, the first end part of the shielding main body is opened, and the end cover is arranged at the first end part of the shielding main body and is matched with the first end part to form a closed state; the second end part of the shielding main body is closed, and the second end part of the shielding main body and the end cover are both made of a high-permeability material; the side wall of the shielding main body is composed of at least one double-shielding layer, and when the side wall of the shielding main body is composed of multiple double-shielding layers, the multiple double-shielding layers are sequentially nested from inside to outside; each double-shielding layer comprises an outer shielding layer made of a high-permeability material and an inner shielding layer made of a superconducting material, the outer shielding layer and the inner shielding layer are in tooth-shaped occlusion connection, and tooth-shaped occlusion parts of the outer shielding layer and the inner shielding layer are periodically distributed to form superconducting regions and non-superconducting regions which are arranged at intervals. According to the invention, high-efficiency shielding effectiveness can be realized under low-temperature and different-frequency conditions.

Description

Technical Field

[0001] The invention belongs to the field of shielding technology, and relates to electromagnetic shielding technology, and in particular to a magnetic shielding device and method for a low-temperature current comparator. Background Art

[0002] Cryogenic Current Comparator (CCC) is a device used for high-precision current measurement, which is widely used in fields such as electrical metrology and superconducting quantum interferometer. The core of CCC is its ability to work in extremely low temperature environments and has extremely high measurement accuracy. Since the external magnetic field has a significant impact on the measurement accuracy of CCC, designing an efficient magnetic shielding structure is the key to ensuring the performance of CCC.

[0003] The cryogenic magnetic shielding technology developed by Amuneal uses a combination of internal and external shielding to provide extremely high magnetic shielding performance for high-precision measurement equipment such as superconducting quantum interference devices. This shielding method can reduce environmental noise to a very low level and is suitable for a variety of scientific research and experimental equipment. However, due to the combined design of internal and external shielding, this type of magnetic shielding structure is usually large and heavy, and its use is limited in certain experiments or applications. For example: when experiments need to be conducted in a limited space, this shielding structure design is not compact enough to reduce the volume while ensuring efficient shielding.

[0004] The research team of the Institute of Physics and Chemistry of the Chinese Academy of Sciences has achieved remarkable results in low-temperature magnetic shielding. They developed a multi-layer magnetic shielding structure specifically for testing superconducting single-flux quantum circuit chips (English: Superconducting Single-Flux-Quantum Circuit Chips), and conducted effective tests in liquid helium dewar flasks, achieving innovative results. This multi-layer magnetic shielding structure has a complex structure and high production cost. In addition, the ability to cope with interference from complex magnetic fields is weak, especially the shielding ability is reduced under higher frequency conditions.

[0005] The Chinese patent with the authorization announcement number CN 216250368U discloses a copper-magnetic composite shielding structure, which includes a copper shielding structure and a magnetic shielding structure. The multi-level shielding design effectively reduces the problems of local overheating and stray losses in the transformer tank. However, the shielding structure in the patent is mainly used for power transformer tanks, and its shielding performance decreases when dealing with complex magnetic field interference under low temperature conditions.

[0006] The Chinese patent with the authorization announcement number CN 115474424B discloses a magnetic shielding device and a shielding method for use in low-temperature environments. The magnetic shielding device includes a shielding body, and the shielding body includes at least two magnetic shielding units nested in sequence. The magnetic shielding unit includes a metal shell, and a superconducting layer and a high magnetic permeability material layer sequentially sleeved on the outer surface of the metal shell, and the superconducting critical temperatures of the superconducting layers of two adjacent magnetic shielding units are different. This patent improves the effect of magnetic shielding and ensures that it can be used in low or even ultra-low temperature environments. However, the shielding unit adopts a three-layer structure of an internal metal shell, an intermediate superconducting layer, and an external high magnetic permeability material layer, which has a complex structure and low manufacturing cost.

[0007] In summary, the existing magnetic shielding structure has the problems of being bulky, high manufacturing cost and poor shielding performance stability. Summary of the invention

[0008] In view of the problems existing in the prior art, the present invention provides a magnetic shielding device and method for a low-temperature current comparator. The magnetic shielding device has a compact structure, a small size, a light weight, and a low manufacturing cost, and can achieve high-efficiency shielding performance under low-temperature and different frequency conditions.

[0009] In a first aspect, the present invention provides a magnetic shielding device for a low temperature current comparator, comprising:

[0010] It includes a shielding body and an end cover, wherein the shielding body is a shell structure;

[0011] The first end of the shielding body is open, and the end cover is arranged at the first end of the shielding body and cooperates with the first end to form a closed state;

[0012] The second end of the shielding body is closed, and the second end of the shielding body and the end cover are both made of high magnetic permeability material;

[0013] The side wall of the shielding body is composed of at least one double shielding layer. When the side wall of the shielding body is composed of multiple double shielding layers, the multiple double shielding layers are nested in sequence from inside to outside;

[0014] Each double shielding layer includes an outer shielding layer made of high magnetic permeability material and an inner shielding layer made of superconducting material. The outer shielding layer is connected to the inner shielding layer in a toothed manner. The toothed portions of the outer shielding layer and the inner shielding layer are periodically distributed to form superconducting areas and non-superconducting areas arranged at intervals.

[0015] In some embodiments, the period of the toothed engaging portion is 45°-90°, and the duty ratio of the tooth width of the toothed engaging portion is 50%-70%.

[0016] In some embodiments, the end cover has a connection hole for connecting a low-temperature current comparator.

[0017] In some embodiments, the connecting hole is a circular hole, and the diameter of the connecting hole is 26-30 mm.

[0018] In some embodiments, the thickness of the outer shielding layer is 1-2 mm, and the thickness of the inner shielding layer is 0.5-2 mm.

[0019] In some embodiments, the second end portion and the end cap have a thickness of 1-2 mm.

[0020] In some embodiments, when the side wall of the shielding body is composed of multiple double shielding layers, the spacing between two adjacent double shielding layers is 0-1 mm.

[0021] In a second aspect of the present invention, a magnetic shielding method for a low temperature current comparator is provided, using the magnetic shielding device for a low temperature current comparator described in the first aspect of the present invention, comprising the following steps:

[0022] A shielding body and an end cover are provided, wherein the side wall of the shielding body is composed of a single double shielding layer, wherein the double shielding layer comprises an outer shielding layer made of a high magnetic permeability material and an inner shielding layer made of a superconducting material, wherein the outer shielding layer is connected to the inner shielding layer in a toothed bite shape, and the toothed bite parts of the outer shielding layer and the inner shielding layer are periodically distributed to form superconducting areas and non-superconducting areas arranged at intervals;

[0023] Placing the sample to be tested in the shielding body, and cooling the shielding body to put the inner shielding layer of the shielding body in a superconducting state;

[0024] The shielding body and the end cover are used to shield the external magnetic field.

[0025] In a third aspect of the present invention, a magnetic shielding method for a low temperature current comparator is provided, using the magnetic shielding device for a low temperature current comparator described in the first aspect of the present invention, comprising the following steps:

[0026] A shielding body and an end cover are provided, wherein the side wall of the shielding body is composed of multiple double shielding layers, the multiple double shielding layers are nested in sequence from the inside to the outside, each double shielding layer comprises an outer shielding layer made of a high magnetic permeability material and an inner shielding layer made of a superconducting material, the outer shielding layer is connected with the inner shielding layer in a toothed bite shape, and the toothed bite parts of the outer shielding layer and the inner shielding layer are periodically distributed to form superconducting areas and non-superconducting areas arranged at intervals; a sample to be tested is placed in the shielding body, and the shielding body is cooled down to put the inner shielding layer of the shielding body in a superconducting state;

[0027] The shielding body and the end cover are used to shield the external magnetic field.

[0028] Compared with the prior art, the advantages and positive effects of the present invention are:

[0029] (1) The magnetic shielding device and method for low-temperature current comparator provided by the present invention, the shielding body is composed of at least one double shielding layer, each double shielding layer includes an outer shielding layer made of high magnetic permeability material and an inner shielding layer made of superconducting material, the outer shielding layer is connected with the inner shielding layer in a tooth-shaped bite, and the tooth-shaped bite part is distributed periodically to form a superconducting area and a non-superconducting area arranged at intervals. This tooth-shaped bite design, on the one hand, increases the contact area between the outer shielding layer and the inner shielding layer, optimizes the electromagnetic coupling effect by adjusting the tooth width and period, maximizes the material utilization rate and increases the shielding effect, and effectively improves the measurement accuracy of the low-temperature current comparator; on the other hand, it improves the shielding effectiveness without increasing the thickness, that is, under the same shielding effectiveness, compared with the shielding body of the existing shielding device, the shielding body has a small thickness, reduces the volume, saves space and cost.

[0030] (2) The magnetic shielding device and method for a low-temperature current comparator provided by the present invention not only have low-frequency and DC magnetic field shielding capabilities, but also have high-frequency shielding capabilities in a low-temperature environment by combining superconducting materials and high magnetic permeability materials, thereby achieving high magnetic shielding performance under different frequency conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a structural schematic diagram of a magnetic shielding device for a low-temperature current comparator according to an embodiment of the present invention;

[0032] Figure 2 It is a schematic diagram of the structure of the double shielding layer according to an embodiment of the present invention;

[0033] Figure 3 This is a schematic diagram of the top structure of the shielding body described in Example 1 of the present invention;

[0034] Figure 4 This is a diagram showing calculation results of the shielding effectiveness of the magnetic shielding device for a low-temperature current comparator according to Example 1 of the present invention;

[0035] Figure 5 It is a schematic diagram of the top view of the shielding body described in Example 2 of the present invention;

[0036] Figure 6 This is a diagram showing the calculation results of the shielding effectiveness of the magnetic shielding device for a low-temperature current comparator described in Example 2 of the present invention.

[0037] In the figure, 1, shielding body, 2, end cover, 21, connecting hole, 3, side wall, 4, outer shielding layer, 41, first outer shielding layer, 42, second outer shielding layer, 5, inner shielding layer, 51, first inner shielding layer, 52, second inner shielding layer, 6, central angle. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is described and illustrated below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Based on the embodiments provided by the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention.

[0039] Obviously, the drawings described below are only some examples or embodiments of the present invention. For ordinary technicians in this field, the present invention can also be applied to other similar scenarios based on these drawings without creative work. In addition, it can also be understood that although the efforts made in this development process may be complicated and lengthy, for ordinary technicians in this field related to the content disclosed by the present invention, some changes in design, manufacturing or production based on the technical content disclosed by the present invention are just conventional technical means, and should not be understood as insufficient content disclosed by the present invention.

[0040] Reference to "embodiments" in the present invention means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those of ordinary skill in the art that the embodiments described in the present invention may be combined with other embodiments without conflict.

[0041] Unless otherwise defined, the technical terms or scientific terms involved in the present invention shall have the usual meanings understood by persons with ordinary skills in the technical field to which the present invention belongs. The words "one", "a", "a", "the" and the like involved in the present invention do not indicate a quantity limitation and may indicate the singular or plural. The terms "include", "comprise", "have" and any of their variations involved in the present invention are intended to cover non-exclusive inclusions; for example, a process, method, system, product or device including a series of steps or modules (units) is not limited to the listed steps or units, but may also include steps or units that are not listed, or may also include other steps or units inherent to these processes, methods, products or devices. The words "connect", "connected", "coupled" and the like involved in the present invention are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The "multiple" involved in the present invention refers to two or more. "And / or" describes the association relationship of associated objects, indicating that there may be three relationships, for example, "A and / or B" may indicate: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the objects in the front and back relation are in an "or" relationship. The terms "first", "second", "third" and the like involved in the present invention are only used to distinguish similar objects and do not represent a specific ordering of the objects.

[0042] See also Figure 1 and Figure 2 According to a first aspect of the present invention, there is provided a magnetic shielding device for a low-temperature current comparator, comprising a shielding body 1 and an end cover 2, wherein the shielding body 1 is a shell structure.

[0043] The first end of the shielding body 1 is open, and the end cover 2 is arranged at the first end of the shielding body, and cooperates with the first end to form a closed state. The second end of the shielding body 1 is closed, and the second end of the shielding body 1 and the end cover 2 are both made of high magnetic permeability materials (for example: Permalloy, Iron-Nickel alloy, Iron-Silicon alloy, etc.). The side wall of the shielding body 1 is composed of a single-layer double shielding layer. When the side wall of the shielding body is composed of multiple layers of double shielding layers, the multiple layers of double shielding layers are nested in sequence from the inside to the outside. Each double shielding layer includes an outer shielding layer 4 made of high magnetic permeability material (for example: Permalloy, Iron-Nickel alloy, Iron-Silicon alloy, etc.) and an inner shielding layer 5 made of superconducting material (for example: Niobium, Yttrium Barium Copper Oxide, etc.), and the outer shielding layer 4 is connected with the inner shielding layer 5 in a toothed bite shape, and the toothed bite parts of the outer shielding layer 4 and the inner shielding layer 5 are periodically distributed to form superconducting areas and non-superconducting areas arranged at intervals.

[0044] Specifically, the edge of the end cover is tightly matched with the first end of the shielding body to ensure that during the use of the magnetic shielding device, the end cover and the shielding body are closed without obvious gaps to prevent external magnetic fields from penetrating from the connection. When the magnetic shielding device is working, the inner shielding layer made of superconducting material shields low-frequency and DC magnetic fields under low temperature conditions, and the outer shielding layer made of high magnetic permeability material effectively shields high-frequency magnetic fields. By combining the inner shielding layer with the outer shielding layer, different shielding layers are periodically arranged through tooth-like bites, so that the superconducting area and the non-superconducting area are alternately arranged to form a multi-level combined shielding device to achieve more efficient shielding effectiveness. In some embodiments, the period of the tooth-like bite portion is 45°-90°, and the tooth width duty ratio of the tooth-like bite portion is 50%-70% to ensure a higher magnetic shielding efficiency.

[0045] In some embodiments, see Figure 1 The end cover 2 is provided with a connection hole 21 for connecting a low-temperature current comparator.

[0046] In some embodiments, the connection hole 21 is a circular hole, and the diameter of the connection hole is 26-30 mm. It should be noted that the diameter of the connection hole is not less than 26 mm, in order to facilitate effective connection with the low-temperature current comparator, and the diameter of the connection hole is not more than 30 mm, in order to ensure that there is no obvious gap when the low-temperature current comparator is connected through the connection hole during the use of the magnetic shielding device, so as to prevent the external magnetic field from penetrating from the connection hole, and ensure effective connection without affecting the shielding effect.

[0047] In some embodiments, the thickness of the outer shielding layer is 1-2 mm to ensure that the outer shielding layer maintains efficient magnetic shielding performance while reducing the thickness of the side wall of the shielding body. The thickness of the inner shielding layer is 0.5-2 mm to ensure that the inner shielding layer has superconducting performance while reducing the thickness of the side wall of the shielding body.

[0048] In some embodiments, the thickness of the second end portion and the end cap is 1-2 mm to ensure that the second end portion and the end cap of the shielding body maintain efficient magnetic shielding performance while reducing the thickness of the second end portion and the end cap.

[0049] In some embodiments, when the side wall of the shielding body is composed of multiple double shielding layers, the spacing between two adjacent double shielding layers is 0-1 mm.

[0050] In the magnetic shielding device for a low-temperature current comparator in the embodiment of the present invention, the side wall of the shielding body adopts at least one double shielding layer, and the inner shielding layer and the outer shielding layer in the double shielding layer are connected by a periodic tooth-like bite. The selection of shielding materials and the multi-layer structure are combined to enhance the synergy between high magnetic permeability materials and superconducting materials, thereby achieving a high-efficiency shielding effect that is difficult to achieve with traditional shielding structures. The device has a compact structure, small size, and light weight, and can reduce the structural thickness while improving the shielding effectiveness, thereby saving space and cost.

[0051] The second aspect of the present invention provides a magnetic shielding method for a low temperature current comparator, using the magnetic shielding device for a low temperature current comparator described in the first aspect of the present invention, comprising the following steps: Figure 1 and Figure 2 , providing a shielding body 1 and an end cover 2, the side wall of the shielding body 1 is composed of a single-layer double shielding layer, the double shielding layer includes an outer shielding layer 4 made of a high magnetic permeability material and an inner shielding layer 5 made of a superconducting material, the outer shielding layer 4 is connected to the inner shielding layer 5 in a toothed bite, and the toothed bite portion of the outer shielding layer 4 and the inner shielding layer 5 is periodically distributed to form a superconducting area and a non-superconducting area arranged at intervals;

[0052] The sample to be tested is placed in the shielding body 1, and the shielding body 1 is cooled down to put the inner shielding layer 5 of the shielding body 1 in a superconducting state;

[0053] The shielding body 1 and the end cover 2 are used to shield the external magnetic field.

[0054] The third embodiment of the present invention provides a magnetic shielding device for a low-temperature current comparator. Different from the first embodiment of the present invention, in this embodiment, the side wall of the shielding body 1 is composed of multiple layers of double shielding layers, and the multiple layers of double shielding layers are nested in sequence from the inside to the outside. For example: the side wall of the shielding body is composed of three layers of double shielding layers, and the three layers of double shielding layers are nested in sequence from the inside to the outside. The first double shielding layer can be located in the innermost layer, the second double shielding layer is located in the middle layer, and the third double shielding layer is located in the outermost layer. Alternatively, the third double shielding layer can be located in the innermost layer, the second double shielding layer is located in the middle layer, and the first double shielding layer is located in the outermost layer. It can be set according to the specific situation.

[0055] It should be noted that the number of double shielding layers can be reasonably increased or decreased according to actual shielding requirements. It can be two double shielding layers, three double shielding layers, or four or five double shielding layers.

[0056] A fourth aspect of the present invention provides a magnetic shielding method for a low temperature current comparator, using the magnetic shielding device for a low temperature current comparator described in the third aspect of the present invention, comprising the following steps: Figure 1 and Figure 2 , providing a shielding body 1 and an end cover 2, the side wall of the shielding body 1 is composed of multiple layers of double shielding layers, the multiple layers of double shielding layers are nested in sequence from the inside to the outside, each double shielding layer includes an outer shielding layer 4 made of a high magnetic permeability material and an inner shielding layer 5 made of a superconducting material, the outer shielding layer 4 is connected to the inner shielding layer 5 in a toothed bite, and the toothed bite portion of the outer shielding layer 4 and the inner shielding layer 5 is periodically distributed to form superconducting areas and non-superconducting areas arranged at intervals;

[0057] The sample to be tested is placed in the shielding body 1, and the shielding body 1 is cooled down to put the inner shielding layer 5 of the shielding body 1 in a superconducting state;

[0058] The shielding body 1 and the end cover shield 2 are used to shield the external magnetic field.

[0059] In order to verify the effectiveness of the magnetic shielding device and method for a low-temperature current comparator described in the above embodiments of the present invention, the following specific embodiments are used for description.

[0060] Example 1: See Figures 1 to 3 The present embodiment provides a magnetic shielding device for a low-temperature current comparator, including a shielding body 1 and an end cover 2. The shielding body 1 is a cylindrical shell structure, and the end cover 2 is a circular cover with a thickness of 1.5 mm. A circular connection hole 21 is provided on the surface of the end cover 2, and the diameter of the connection hole 21 is 28 mm, so as to be connected to the low-temperature current comparator. The edge of the end cover 2 is tightly matched with the shielding body 1 to ensure that there is no obvious gap in the magnetic shielding device during use to prevent the external magnetic field from penetrating from the connection.

[0061] The shielding body comprises a side wall, a first end portion which is opened, and a second end portion which is closed. The end cover 2 is arranged at the first end portion of the shielding body 1 and cooperates with the first end portion to form a closed state.

[0062] The second end of the shielding body 1 and the end cover 2 are both made of Permalloy, and the thickness of the second end of the shielding body is 1.5 mm. The second end of the shielding body 1 is connected to the side wall by welding.

[0063] The side wall of the shielding body 1 is composed of a single double shielding layer. The double shielding layer includes an outer shielding layer 4 made of Permalloy and an inner shielding layer 5 made of superconducting material niobium. The outer shielding layer 4 is connected to the inner shielding layer 5 in a toothed bite. The toothed bite portion of the outer shielding layer 4 and the inner shielding layer 5 is distributed in a 90° periodicity, that is, a toothed period is arranged every 90° on the circumference. The duty ratio of the outer shielding layer 4 and the inner shielding layer 5 in each period is 50%, that is, on each 90° circumference, the outer shielding layer 4 and the inner shielding layer 5 each cover half of the tooth width, and the central angle of each circle is 45°, forming superconducting areas and non-superconducting areas arranged at intervals.

[0064] It should be noted that in this embodiment, the selection of a 90° period and a 50% outer shielding layer tooth width was obtained through multiple simulation debugging and optimization. During the debugging process, when the outer shielding layer tooth width was 50%, simulation tests were performed for different periodic designs, such as 30°, 45°, 60°, 90° and other angle distributions. After calculating the magnetic flux density value obtained by simulation, the shielding effectiveness results were obtained. Figure 4. Through comparative analysis, it is found that the magnetic shielding device described in this embodiment is superior to the conventional double shielding layer structure in terms of material proportion and shielding efficiency. Specifically, under the premise of 90° period and 50% outer shielding layer tooth width bite, without increasing the material thickness, it can more effectively reduce the penetration of the external magnetic field and achieve a shielding effectiveness greater than 110dB, thereby improving the overall magnetic shielding efficiency. Moreover, under the condition of 50% outer shielding layer tooth width bite, when other different period designs are used, the shielding effectiveness is no less than 105dB, which has great practical significance.

[0065] Example 2: See Figure 1 , Figure 2 The present embodiment provides a magnetic shielding device for a low-temperature current comparator, including a shielding body 1 and an end cover 2. The shielding body 1 is a cylindrical shell structure, and the end cover 2 is a circular cover with a thickness of 2 mm. A circular connection hole 21 is provided on the surface of the end cover 2, and the diameter of the connection hole 21 is 27 mm, so as to be connected to the low-temperature current comparator. The edge of the end cover 2 is tightly matched with the shielding body 1 to ensure that there is no obvious gap in the magnetic shielding device during use to prevent the external magnetic field from penetrating from the connection.

[0066] The shielding body comprises a side wall, a first end portion which is opened, and a second end portion which is closed. The end cover 2 is arranged at the first end portion of the shielding body 1 and cooperates with the first end portion to form a closed state.

[0067] The second end of the shielding body 1 and the end cover 2 are both made of Permalloy, and the thickness of the second end of the shielding body is 2 mm. The second end of the shielding body 1 is connected to the side wall by welding.

[0068] See also Figure 5The side wall of the shielding body 1 is composed of two double shielding layers, which are the first double shielding layer and the second double shielding layer, respectively. The second double shielding layer is nested in the first double shielding layer. The first double shielding layer includes a first outer shielding layer 41 made of Permalloy and a first inner shielding layer 51 made of superconducting material niobium. The first outer shielding layer 41 is connected with the first inner shielding layer 51 in a toothed bite. The toothed bite portion of the first outer shielding layer 41 and the first inner shielding layer 51 is distributed in a 60° periodicity, that is, a toothed period is arranged every 60° on the circumference. The duty ratio of the first outer shielding layer 41 and the first inner shielding layer 51 in each period is 50%, that is, on each 60° circumference, the first outer shielding layer 41 and the first inner shielding layer 51 each cover half of the tooth width, and the center angle of each occupies 30°, forming a superconducting area and a non-superconducting area arranged at intervals. The second double shielding layer includes a second outer shielding layer 42 made of Permalloy and a second inner shielding layer 52 made of superconducting material niobium, and the second outer shielding layer 42 is connected with the second inner shielding layer 52 in a toothed bite. The toothed bite portion of the second outer shielding layer 42 and the second inner shielding layer 52 is distributed in a 60° periodicity, that is, a toothed period is arranged every 60° on the circumference. The duty ratio of the second outer shielding layer 42 and the second inner shielding layer 52 in each period is 50%, that is, on each 60° circumference, the second outer shielding layer 42 and the second inner shielding layer 52 each cover half of the tooth width, and the center angle 6 of the outer shielding layer and the center angle of the inner shielding layer each account for 30°, forming a superconducting area and a non-superconducting area arranged at intervals.

[0069] It should be noted that in this embodiment, the selection of a 60° period and a 50% outer shielding layer tooth width was obtained through multiple simulation debugging and optimization. During the debugging process, when the outer shielding layer tooth width was 50%, simulation tests were performed for different periodic designs, such as 30°, 45°, 60°, 90° and other angle distributions. After calculating the magnetic flux density value obtained by simulation, the shielding effectiveness results were obtained. Figure 6 . Through comparative analysis, it is found that the magnetic shielding device described in this embodiment is superior to the conventional double shielding layer structure in terms of material proportion and shielding efficiency. Specifically, under the premise of not increasing the material thickness, with a period of 96° and a tooth width of 50% of the outer shielding layer, it can more effectively reduce the penetration of the external magnetic field and achieve a shielding effectiveness greater than 120dB, thereby improving the overall magnetic shielding efficiency. Moreover, under a tooth width of 50% of the outer shielding layer, when other different period designs are used, the shielding effectiveness is no less than 118dB, which has great practical significance.

[0070] The above embodiments are used to explain the present invention rather than to limit the present invention. Any modification and change made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A magnetic shielding device for a low temperature current comparator, characterized in that: It includes a shielding body and an end cover, wherein the shielding body is a shell structure; The first end of the shielding body is open, and the end cover is arranged at the first end of the shielding body and cooperates with the first end to form a closed state; The second end of the shielding body is closed, and the second end of the shielding body and the end cover are both made of high magnetic permeability material; The side wall of the shielding body is composed of at least one double shielding layer. When the side wall of the shielding body is composed of multiple double shielding layers, the multiple double shielding layers are nested in sequence from inside to outside; Each double shielding layer includes an outer shielding layer made of high magnetic permeability material and an inner shielding layer made of superconducting material. The outer shielding layer is connected to the inner shielding layer in a toothed manner. The toothed portions of the outer shielding layer and the inner shielding layer are periodically distributed to form superconducting areas and non-superconducting areas arranged at intervals.

2. The magnetic shielding device for a low temperature current comparator according to claim 1, characterized in that: The period of the tooth-shaped biting part is 45°-90°, and the tooth width duty ratio of the tooth-shaped biting part is 50%-70%.

3. The magnetic shielding device for a low temperature current comparator according to claim 1, characterized in that: The end cover is provided with a connection hole for connecting a low-temperature current comparator.

4. The magnetic shielding device for a low temperature current comparator according to claim 2, characterized in that: The connecting hole is a round hole, and the diameter of the connecting hole is 26-30 mm.

5. The magnetic shielding device for a low temperature current comparator according to claim 1, characterized in that: The thickness of the outer shielding layer is 1-2 mm, and the thickness of the inner shielding layer is 0.5-2 mm.

6. The magnetic shielding device for a low temperature current comparator according to claim 1, characterized in that: The thickness of the second end portion and the end cap is 1-2 mm.

7. The magnetic shielding device for a low temperature current comparator according to claim 1, characterized in that: When the side wall of the shielding body is composed of multiple double shielding layers, the spacing between two adjacent double shielding layers is 0-1 mm.

8. A magnetic shielding method for a low temperature current comparator, using the magnetic shielding device for a low temperature current comparator as claimed in any one of claims 1 to 7, characterized in that: The steps are: A shielding body and an end cover are provided, wherein the side wall of the shielding body is composed of a single double shielding layer, wherein the double shielding layer comprises an outer shielding layer made of a high magnetic permeability material and an inner shielding layer made of a superconducting material, wherein the outer shielding layer is connected to the inner shielding layer in a toothed bite shape, and the toothed bite parts of the outer shielding layer and the inner shielding layer are periodically distributed to form superconducting areas and non-superconducting areas arranged at intervals; Placing the sample to be tested in the shielding body, and cooling the shielding body to put the inner shielding layer of the shielding body in a superconducting state; The shielding body and the end cover are used to shield the external magnetic field.

9. A magnetic shielding method for a low temperature current comparator, using the magnetic shielding device for a low temperature current comparator as claimed in any one of claims 1 to 7, characterized in that: The steps are: A shielding body and an end cover are provided, wherein the side wall of the shielding body is composed of multiple double shielding layers, which are nested in sequence from the inside to the outside, each double shielding layer comprises an outer shielding layer made of a high magnetic permeability material and an inner shielding layer made of a superconducting material, the outer shielding layer is connected to the inner shielding layer in a toothed bite shape, and the toothed bite parts of the outer shielding layer and the inner shielding layer are periodically distributed to form superconducting areas and non-superconducting areas arranged at intervals; Placing the sample to be tested in the shielding body, and cooling the shielding body to put the inner shielding layer of the shielding body in a superconducting state; The shielding body and the end cover are used to shield the external magnetic field.

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