Magnetic shielding device based on permalloy-ferrite-superconducting coil with low magnetic noise and high shielding performance

Abstract

The magnetic shielding device based on the low magnetic noise and high shielding performance of the permalloy-ferrite-superconducting coil can provide a stable extremely low magnetic noise weak magnetic environment for an ultra-high sensitive SERF magnetic field and inertial measurement device, mainly composed of a permalloy magnetic shield, a ferrite magnetic shield, a superconducting coil magnetic shield support, a non-metallic dewar, a superconducting coil winding disc and an adjustable stud, etc., the ferrite magnetic shield is placed in the permalloy magnetic shield cavity, the superconducting coil magnetic shield support is placed in the ferrite cavity, the non-metallic dewar is placed on the superconducting coil magnetic shield support, and the superconducting coil winding disc is placed in the non-metallic dewar cavity, by combining the active magnetic shielding of the superconducting coil with the traditional passive magnetic shielding of the permalloy-ferrite, the problem that the magnetic noise of the traditional magnetic shielding material is difficult to further reduce is overcome, and the magnetic noise of the device is further reduced, and the sensitivity of the SERF magnetic field and inertial measurement device limited by the magnetic noise of the magnetic shielding itself can be greatly improved.

Description

TECHNICAL FIELD

[0001] The application relates to a magnetic shielding device based on a low magnetic noise and high shielding performance of a permalloy-ferrite-superconducting coil, and belongs to the technical field of electromagnetic shielding. BACKGROUND

[0002] The spin-exchange relaxation-free (SERF) based magnetic field and inertial measurement device has ultra-high sensitivity, and is widely applied to multiple fields such as frontier science, basic physics and biological medicine. Environmental magnetic interference will affect the realization of the high sensitivity of the SERF magnetic field and inertial measurement device, and therefore, multiple passive magnetic shields are often used to shield the magnetic field interference from the outside world, so as to provide a stable weak magnetic environment for the SERF magnetic field and inertial measurement device. Under the premise that there is no any external interference, the limit sensitivity only depends on the quantum noise thereof, but the magnetic shielding material itself will generate magnetic noise, which will directly affect the sensitivity of the SERF magnetic field and inertial measurement device, and therefore, the current magnetic shielding system often adopts the structure of outer multiple layers of permalloy and inner ferrite, so as to obtain a magnetic shielding system with high shielding coefficient and low magnetic noise, which can not only inhibit the environmental electromagnetic interference but also reduce the magnetic noise generated by the material. The current magnetic shielding system combined with multiple layers of high magnetic permeability permalloy and low magnetic noise manganese-zinc ferrite has realized a magnetic noise level of 0.7fT / Hz 1 / 2 @30Hz. However, the ferrite material is a dissipative material, and according to the fluctuation dissipation theorem, the magnetic noise thereof cannot be completely eliminated, and it is difficult to further reduce the magnetic noise level of the traditional magnetic shielding material, which restricts the further improvement of the sensitivity of the SERF magnetic field and inertial measurement device, and therefore, a new type of ultra-low magnetic noise magnetic shielding device needs to be designed to solve the above problems. The superconducting coil magnetic shielding method based on the anti-magnetic flux effect has low power loss, and the coil is a passive magnetic shield, is not affected by the current source noise, and the magnetic noise can reach the sub-aT level, but when the superconducting coil is used alone, the shielding coefficient is low and the direct current magnetic field cannot be shielded, and therefore, an external three-axis magnetic compensation coil is usually arranged to be actively compensated. The combination scheme of the three-axis magnetic compensation coil and the superconducting coil has a large volume, high power consumption and limited shielding effect, and therefore, it is difficult to meet the extreme requirements of the ultra-high sensitive magnetic field / inertial measurement. SUMMARY

[0003] The application provides a magnetic shielding device with low magnetic noise and high shielding performance based on a permalloy-ferriet superconducting coil, which is innovative in that traditional permalloy-ferriet passive magnetic shielding is combined with superconducting coil active magnetic shielding, so that the problem that the magnetic noise of traditional permalloy-ferriet passive magnetic shielding material cannot be further reduced can be solved, and the superconducting coil active magnetic shielding inside the ferriet magnetic shielding can further shield the ferriet magnetic noise, the remaining permalloy magnetic noise and the remaining environmental magnetic noise. The superconducting coil active magnetic shielding can further reduce the overall shielding device magnetic noise without introducing new magnetic noise, so that the magnetic noise that cannot be eliminated by traditional magnetic shielding material can be effectively suppressed. Meanwhile, the introduction of the superconducting coil active magnetic shielding further increases the shielding coefficient of the overall magnetic shielding device, so that the shielding performance of the permalloy-ferriet superconducting coil magnetic shielding device is higher. The magnetic shielding device with low noise and high shielding performance based on the permalloy-ferriet superconducting coil has great significance for improving the sensitivity of SERF magnetic field and inertial measurement device. In addition, the application can establish a theoretical model based on the analysis and decomposition of the specific source of magnetic noise, which has important significance for the magnetic noise analysis of the combined magnetic shielding device.

[0004] The technical solution of the application is as follows:

[0005] The magnetic shielding device with low magnetic noise and high shielding performance based on the permalloy-ferriet superconducting coil is characterized in that it comprises a first central cavity formed by a ferriet barrel body, a ferriet lower cover and a ferriet upper cover, the ferriet magnetic shielding is located in a permalloy magnetic shielding, the permalloy magnetic shielding is formed by a permalloy barrel body, a permalloy lower cover and a permalloy upper cover, a superconducting coil magnetic shielding support is arranged in the first central cavity, the superconducting coil magnetic shielding support comprises a lower disc, a support cylinder and an upper disc, the lower disc is located at the bottom of the first central cavity, the upper disc extends upward to form a second central cavity, a non-metallic Dewar is arranged around the outer periphery of the upper disc, the non-metallic Dewar comprises two annular disc cakes with the same structure connected by adjustable studs, an upper annular disc cake is arranged in the upper annular disc of the superconducting coil spool, and a lower annular disc cake is arranged in the lower annular disc of the superconducting coil spool, the second central cavity has left and right through holes, front and rear through holes and upper and lower through holes which are connected to the outside of the magnetic shielding device.

[0006] The permalloy magnetic shielding is a multi-layer structure, and there are spacers between each layer to control the gap between the layers.

[0007] There are spacers between the innermost layer of the ferriet magnetic shielding and the permalloy magnetic shielding to ensure that the ferriet is located in the center of the innermost layer of the permalloy magnetic shielding.

[0008] The material of the non-metal Dewar is ethylene-vinyl acetate copolymer, and exhaust ports are left on the annular covers of each annular disc for timely exhausting the vaporized liquid nitrogen.

[0009] Four adjustable studs are evenly distributed between the two annular discs.

[0010] The material of the superconducting coil winding disc is polytetrafluoroethylene, and arc-shaped protrusions are arranged at the center and the edge of the annular disc for winding the superconducting tape, wherein the arc-shaped protrusion at the center is a complete circular edge, and the arc-shaped protrusion at the edge is two arc-shaped protrusions with a gap, and the gap is used for arranging the connecting section of the inner and outer superconducting tapes, and six circular holes are evenly distributed between the arc-shaped protrusions at the center and the edge of the winding disc to reduce the weight.

[0011] The superconducting tape used in the superconducting coil is a superconducting tape without copper cladding.

[0012] The total magnetic noise of the magnetic shielding device is composed of the environmental magnetic noise remaining after the magnetic shielding of the permalloy, the ferrite and the superconducting coil, the magnetic noise of the permalloy itself remaining after the magnetic shielding of the ferrite and the superconducting coil, and the magnetic noise of the ferrite itself remaining after the magnetic shielding of the superconducting coil.

[0013] The calculation formula of the total magnetic noise of the magnetic shielding device is as follows:

[0014] δB tot = δB0S tot + δB p S tc + δB t S c

[0015] Wherein, δB tot is the total magnetic noise, δB0 is the environmental magnetic noise, δB p is the magnetic noise generated by the magnetic shielding of the permalloy, δB t is the magnetic noise generated by the magnetic shielding of the ferrite, S tot is the total shielding coefficient, including the passive magnetic shielding shielding coefficient S pt of the permalloy and the active magnetic shielding shielding coefficient S c of the superconducting coil, S tot =S pt S c ; S tc is the shielding coefficient of the ferrite and the superconducting coil excluding the outer permalloy, including the passive magnetic shielding shielding coefficient S t of the ferrite and the active magnetic shielding shielding coefficient S c of the superconducting coil, S tc =S t S c; The calculation time because of the permalloy and ferrite magnetic shielding is passive magnetic shielding, and the coupling between layers needs to be considered when used together; and the superconducting coil magnetic shielding is active magnetic shielding, and there is no coupling between the permalloy and the ferrite, so it is considered separately.

[0016] The technical effects of the present application are as follows: the magnetic shielding device based on the low magnetic noise and high shielding performance of the permalloy-ferrite-superconducting coil can overcome the problem that the further reduction of the magnetic noise of the existing traditional magnetic shielding material limits the further improvement of the sensitivity of the ultra-high sensitive SERF magnetic field and inertial measurement device. The present application first places the pad in the bottom of the innermost layer of the permalloy magnetic shielding, then places the ferrite magnetic shielding in the center cavity of the innermost layer of the permalloy, ensures that the pumping light holes on the upper and lower covers of the ferrite are aligned with the pumping light holes of the permalloy magnetic shielding, and the detection light holes of the side wall are aligned with the detection light holes of the permalloy magnetic shielding. Then the superconducting coil magnetic shielding support is placed in the center cavity of the ferrite, and the corresponding pumping and detection light holes on the superconducting coil magnetic shielding support are also aligned with the corresponding pumping and detection light holes of the ferrite. Then the two superconducting coil spools wound with superconducting tapes are respectively placed in two non-metal Dewars, liquid nitrogen is poured into the non-metal Dewars until the liquid nitrogen fills the entire cavity of the non-metal Dewar, and then the lid is closed. First, place one annular circular cake of the non-metal Dewar on the upper disc of the superconducting coil magnetic shielding support, then install four adjustable studs on the lid of the placed non-metal Dewar annular circular cake, and place the second annular circular cake of the non-metal Dewar on the circular pad. Finally, cover the upper cover of the ferrite and permalloy, and ensure that the corresponding pumping light holes on the upper cover are aligned. The superconducting coil magnetic shielding shields the ferrite magnetic noise that cannot be further reduced, and can also further reduce the environmental magnetic noise and the permalloy magnetic noise. The material of the non-metal Dewar is ethylene-vinyl acetate copolymer, which does not introduce the magnetic noise caused by the Johnson current in the metal Dewar. The material of the superconducting coil spool is polytetrafluoroethylene, which is resistant to low temperature and also serves as a plastic material with high impedance, and does not introduce additional magnetic noise. The superconducting coil magnetic shielding theoretically does not generate magnetic noise, but the outer layer of the superconducting tape is plated with a copper layer for protection of the superconducting material, so it will introduce magnetic noise caused by Johnson current. In order to avoid this magnetic noise, the superconducting tape used in the superconducting coil needs to use superconducting tape without copper wrapping.

[0017] Compared with the prior art, the traditional permalloy-ferrite magnetic shielding material itself has magnetic noise, and the material magnetic noise is difficult to further reduce, which cannot meet the further improvement of the sensitivity of the ultra-high sensitive SERF magnetic field and inertial measurement device. The present application combines the active magnetic shielding of the superconducting coil with the passive magnetic shielding of the traditional permalloy-ferrite, overcomes the problem that the magnetic noise of the traditional magnetic shielding material is difficult to further reduce, reduces the magnetic noise of the magnetic shielding device, and solves the application demand of low magnetic field noise. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a schematic diagram of the structure of a magnetic shielding device based on the low magnetic noise and high shielding performance of the permalloy-ferrite-superconducting coil according to the present application.

[0019] Figure 2 is a schematic diagram of the structure of a multi-layer permalloy-ferrite magnetic shielding according to the present application. Figure 1

[0020] Figure 3 is a schematic diagram of the structure of a superconducting magnetic shielding support according to the present application. Figure 1

[0021] Figure 4 is a schematic diagram of the structure of a non-metal Dewar according to the present application. Figure 1

[0022] Figure 5 is a schematic diagram of the structure of a superconducting coil winding reel according to the present application. Figure 1 The reference signs are explained as follows: 1 - permalloy barrel; 2 - ferrite barrel; 3 - non-metal Dewar; 4 - superconducting coil winding reel; 5 - ferrite lower cover; 6 - permalloy lower cover; 7 - superconducting coil magnetic shielding support; 8 - adjustable stud; 9 - ferrite upper cover; 10 - permalloy upper cover.

[0023] DETAILED DESCRIPTION

[0024] The present application will be described below in conjunction with the accompanying drawings Figures 1-5 and examples.

[0025] Figure 1 is a schematic diagram of the structure of a magnetic shielding device based on the low magnetic noise and high shielding performance of the permalloy-ferrite-superconducting coil according to the present application. Figure 2 is a schematic diagram of the structure of a multi-layer permalloy-ferrite magnetic shielding according to the present application. Figure 1 is a schematic diagram of the structure of a superconducting magnetic shielding support according to the present application. Figure 3 is a schematic diagram of the structure of a non-metal Dewar according to the present application. Figure 1 is a schematic diagram of the structure of a superconducting coil winding reel according to the present application. Reference Figure 4 Figure 1 Figure 5 Figure 1 Figures 1-5 ​​​​​​​​As shown, a magnetic shielding device based on permalloy-ferrite-superconducting coils, exhibiting low magnetic noise and high shielding performance, includes a first central cavity forming a ferrite magnetic shield through a ferrite barrel body 2, a ferrite lower cover 5, and a ferrite upper cover 9. The ferrite magnetic shield is located within a permalloy magnetic shield, which is formed by the permalloy barrel body 1, the permalloy lower cover 6, and the permalloy upper cover 10. A superconducting coil magnetic shielding support 7 is disposed within the first central cavity. The superconducting coil magnetic shielding support 7 includes a lower disk, a supporting cylinder, and a... The upper disk and the lower disk are located at the bottom of the first central cavity. The upper disk extends upward with a cylindrical wall to form a second central cavity. The outer periphery of the cylindrical wall of the upper disk is provided with a non-metallic Dewar 3. The non-metallic Dewar 3 includes two annular discs with the same structure connected vertically by an adjustable stud 8. The upper annular disc has a superconducting coil winding disk 4 built into the upper annular disc, and the lower annular disc has a superconducting coil winding disk 4 built into the lower annular disc. The second central cavity has left and right through holes, front and back through holes and upper and lower through holes that connect to the outside of the magnetic shielding device.

[0026] This invention combines active magnetic shielding of a superconducting coil as the innermost layer with traditional passive magnetic shielding of permalloy-ferrite, resulting in a total shielding coefficient S. tot And the shielding coefficient S excluding the outer permalloy layer tc The overall shielding performance is enhanced compared to traditional permalloy-ferrite passive magnetic shielding; simultaneously, the environmental magnetic noise δB0 and the magnetic noise δB generated by the permalloy magnetic shielding are reduced. p Magnetic noise δB generated by ferrite magnetic shielding t All of these can be further shielded by the innermost layer of superconducting coil active magnetic shielding. This is especially true for the magnetic noise δB generated by the ferrite in traditional permalloy-ferrite passive magnetic shielding. t Directly affecting the SERF magnetic field and the sensitivity of the core components inside the inertial measurement device, this invention proposes to combine active magnetic shielding of the superconducting coil with passive magnetic shielding of traditional permalloy-ferrite, which effectively improves the shielding coefficient of the overall magnetic shielding device and reduces the total magnetic noise of the device.

[0027] refer to Figures 1-5As shown, a magnetic shielding device based on permalloy-ferrite-superconducting coils, characterized by low magnetic noise and high shielding performance, comprises a permalloy magnetic shield (sidewall 1, upper cover 10, lower cover 6), a ferrite magnetic shield (sidewall 2, upper cover 9, lower cover 5), a superconducting coil magnetic shielding support 7, a non-metallic Dewar 3, and a superconducting coil winding disc 4. This invention innovatively combines traditional permalloy-ferrite passive magnetic shielding with superconducting coil active magnetic shielding, solving the problem that traditional permalloy-ferrite passive magnetic shielding materials cannot further reduce magnetic noise. By adding superconducting coil active magnetic shielding inside the ferrite magnetic shield, it shields ferrite magnetic noise, remaining permalloy magnetic noise, and remaining environmental magnetic noise. The superconducting coil active magnetic shield further reduces the overall magnetic noise of the shielding device without introducing new magnetic noise, thus effectively suppressing magnetic noise that traditional magnetic shielding materials cannot eliminate. Simultaneously, the introduction of superconducting coil active magnetic shielding further increases the shielding coefficient of the overall magnetic shielding device, resulting in higher shielding performance for the permalloy-ferrite-superconducting coil magnetic shielding device. The low-noise and high-shielding magnetic shielding device based on permalloy-ferrite-superconducting coils proposed in this invention is of great significance for improving the sensitivity of SERF magnetic fields and inertial measurement devices. The permalloy magnetic shielding is multi-layered, with each layer uniformly distributed. Each layer includes a sidewall 1, an upper cover 10, and a lower cover 6. The innermost layer of permalloy magnetic shielding forms a central cavity. Four orthogonal holes are evenly distributed at the center of the sidewall, and one hole is located at the center of the upper and lower covers. The ferrite is located at the center of the multi-layered permalloy magnetic shielding cavity and includes a sidewall 2, an upper cover 9, and a lower cover 5, forming a central cavity. Four orthogonal holes are evenly distributed at the center of the sidewall, and one hole is located at the center of the upper and lower covers. The holes on the sidewall, upper cover, and lower cover are aligned with the holes at the same positions on the multi-layered magnetic shielding. The superconducting coil magnetic shielding support 7 includes a lower disk, a supporting cylinder, and an upper disk. The lower disk is located at the bottom of the ferrite central cavity, and the upper disk extends upward with a cylindrical wall to form the central cavity. The cylindrical wall has four evenly distributed orthogonal holes at its center, and the upper and lower disks each have one hole at their center. The holes on the cylindrical wall, upper disk, and lower disk are aligned with the holes in the ferrite at the same positions. The non-metallic Dewar 3 is located on the upper disk of the superconducting coil magnetic shielding support, concentrically placed with the cylindrical wall extending from the upper disk. The non-metallic Dewar 3 consists of two identical annular discs. The base extends the annular wall to form a cavity, and an annular cover completely covers the cavity. Four evenly distributed adjustable studs are located between the two annular discs. The two annular discs are symmetrically distributed with respect to the holes on the cylindrical wall of the superconducting coil magnetic shielding support. The superconducting coil winding disk 4 is located inside the non-metallic Dewar cavity and has two identical annular discs.

[0028] The permalloy magnetic shield (side wall 1, upper cover 10, lower cover 6) has pads between each layer to control the gap between layers.

[0029] The ferrite magnetic shield (side wall 2, upper cover 9, lower cover 5) and the permalloy magnetic shield (side wall 1, upper cover 10, lower cover 6) have a spacer between the innermost layers to ensure that the ferrite is located at the center of the innermost layer of the permalloy magnetic shield.

[0030] The non-metallic Dewar 3 is made of ethylene-vinyl acetate copolymer, and each annular cover of the annular disc has an exhaust port for timely exhaust of the vaporized liquid nitrogen.

[0031] The contact area of each adjustable stud 8 is large enough to ensure that the annular disc of the non-metallic Dewar 3 placed thereon can be placed stably. The adjustable stud can adjust the spacing between the upper and lower discs by changing the height, thereby optimizing the shielding performance of the superconducting coil magnetic shield and making the use of the superconducting coil magnetic shield more flexible.

[0032] The superconducting coil spool 4 is made of polytetrafluoroethylene, and the center and edge of the annular disc have circular arc protrusions for winding the superconducting tape. The circular arc protrusion at the center is a complete circular edge, and the circular protrusion at the edge is a two-segment broken circular arc with a gap for the connection of the inner and outer superconducting tapes. Six circular holes are uniformly distributed between the center and edge circular protrusions to reduce the weight.

[0033] The covers (upper cover 10, lower cover 6) of the permalloy magnetic shield, the covers (upper cover 9, lower cover 5) of the ferrite magnetic shield, and the holes on the disc of the superconducting coil magnetic shield support 7 are reserved for SERF magnetic field and inertial measurement device pumping light; the four holes at the same position on the side wall 1 of the permalloy magnetic shield, the side wall 2 of the ferrite magnetic shield, and the cylindrical side wall of the superconducting coil magnetic shield support 7, of which two holes in the same direction are reserved for SERF magnetic field and inertial measurement device detection light, one is a liquid nitrogen supplement port, and the remaining one is an exhaust port.

[0034] The magnetic noise of the super-low magnetic noise magnetic shielding device based on a superconducting coil is composed of the environmental magnetic noise remaining after the permalloy, ferrite, and superconducting coil magnetic shielding, the magnetic noise of the permalloy itself remaining after the ferrite and superconducting coil magnetic shielding, and the magnetic noise of the ferrite itself remaining after the superconducting coil magnetic shielding. The total noise calculation formula of the super-low magnetic noise magnetic shielding device based on a superconducting coil is as follows:

[0035] δB tot = δB0S tot + δB p S tc + δB t S c

[0036] Where δB tot is the total magnetic noise, δB0 is the environmental magnetic noise, δBp is the magnetic noise generated by the permalloy magnetic shield, δB t is the magnetic noise generated by the ferrite magnetic shield; S tot is the total shielding coefficient, including the shielding coefficient S of the permalloy and ferrite passive magnetic shield pt and the shielding coefficient S of the superconducting coil active magnetic shield c , S tot =S pt S c ; S tc is the shielding coefficient of the ferrite and superconducting coil except for the outer layer of permalloy, including the shielding coefficient S of the ferrite passive magnetic shield t and the shielding coefficient S of the superconducting coil active magnetic shield c , S tc =S t S c . When calculating, because the permalloy and ferrite magnetic shield are passive magnetic shields, the coupling effect between layers needs to be considered when used together. The superconducting coil magnetic shield is an active magnetic shield, and there is no coupling between the permalloy and the ferrite, so it is considered separately. The present application innovatively analyzes and decomposes the specific source of the magnetic noise of the magnetic shielding device based on the low magnetic noise and high shielding performance of the permalloy-ferrite-superconducting coil, which is of great significance for the analysis of the magnetic noise of the combined magnetic shielding device.

[0037] The contents not described in detail in the specification of the present application belong to the prior art known to those skilled in the art. It is pointed out here that the above description is helpful for those skilled in the art to understand the present application, but does not limit the protection scope of the present application. Any implementation of equivalent replacement, modification, improvement and / or deletion of the above description without departing from the essential content of the present application falls within the protection scope of the present application.

Claims

1. A magnetic shielding device based on permalloy-ferrite-superconducting coils, characterized in that, The device includes a first central cavity formed by a ferrite barrel body, a ferrite lower cover, and a ferrite upper cover, which forms a ferrite magnetic shield. The ferrite magnetic shield is located inside a permalloy magnetic shield, which is formed by a permalloy barrel body, a permalloy lower cover, and a permalloy upper cover. A superconducting coil magnetic shield support is provided in the first central cavity. The superconducting coil magnetic shield support includes a lower disk, a supporting cylinder, and an upper disk. The lower disk is located at the bottom of the first central cavity, and the upper disk extends upward with a cylindrical wall to form a second central cavity. A non-metallic Dewar is provided around the outer periphery of the cylindrical wall of the upper disk. The non-metallic Dewar includes two identical annular discs connected vertically by an adjustable stud. The upper annular disc contains a superconducting coil winding disk, and the lower annular disc contains a superconducting coil winding disk. The second central cavity has left and right through holes, front and back through holes, and upper and lower through holes that connect to the outside of the magnetic shielding device. The permalloy magnetic shield is a multi-layer structure with pads between each layer to control the gap between the layers. There is a pad between the innermost layer of the ferrite magnetic shield and the permalloy magnetic shield to ensure that the ferrite is located at the center of the innermost layer of the permalloy magnetic shield. The non-metallic Dewar is made of ethylene-vinyl acetate copolymer, and each annular disc has an exhaust port on its annular cap to allow for the timely discharge of vaporized liquid nitrogen.

2. The magnetic shielding device with low magnetic noise and high shielding performance based on permalloy-ferrite-superconducting coils according to claim 1, characterized in that, There are four evenly distributed adjustable studs between the two annular discs.

3. The magnetic shielding device with low magnetic noise and high shielding performance based on permalloy-ferrite-superconducting coils according to claim 1, characterized in that, The superconducting coil winding disk is made of polytetrafluoroethylene. There are arc-shaped protrusions at the center and edge of the annular disk for winding superconducting tape. The arc-shaped protrusion at the center is a complete circle, while the circular protrusion at the edge is two broken arcs at a certain distance. The gap is used for the connection section of the inner and outer superconducting tape for routing. There are six circular holes evenly distributed between the arc-shaped protrusions at the center and edge of the superconducting coil winding disk to reduce weight.

4. The magnetic shielding device with low magnetic noise and high shielding performance based on permalloy-ferrite-superconducting coils according to claim 1, characterized in that, The superconducting tape used in superconducting coils is a superconducting tape without copper cladding.

5. The magnetic shielding device with low magnetic noise and high shielding performance based on permalloy-ferrite-superconducting coils according to claim 1, characterized in that, The total magnetic noise of the magnetic shielding device consists of the ambient magnetic noise remaining after magnetic shielding by permalloy, ferrite and superconducting coil, the magnetic noise of the remaining permalloy itself after magnetic shielding by ferrite and superconducting coil, and the magnetic noise of the remaining ferrite itself after magnetic shielding by superconducting coil.

6. The magnetic shielding device with low magnetic noise and high shielding performance based on permalloy-ferrite-superconducting coils according to claim 1, characterized in that, The formula for calculating the total magnetic noise of a magnetic shielding device is as follows: δB tot =δB0S tot +δB p S tc +δB t S c Where δB tot δB represents the total magnetic noise, δB0 represents the ambient magnetic noise, and δB p It is the magnetic noise generated by the permalloy magnetic shielding, δB t It is the magnetic noise generated by ferrite magnetic shielding, S tot The total shielding factor, including the passive magnetic shielding factor S of permalloy and ferrite. pt And the active magnetic shielding coefficient S of the superconducting coil c S tot =S pt S c S tc It is the shielding factor of ferrite and superconducting coils excluding the outer permalloy layer, including the passive magnetic shielding factor S of ferrite. t And the active magnetic shielding coefficient S of the superconducting coil c S tc =S t S c When calculating, since the permalloy and ferrite magnetic shielding are passive magnetic shielding, the coupling effect between layers needs to be considered when they are used together; while the superconducting coil magnetic shielding is active magnetic shielding and there is no coupling between it and the permalloy and ferrite, so it is considered separately.

Images