JPH0779200B2 - Superconducting magnetic shield - Google Patents

Description

TECHNICAL FIELD The present invention relates to a superconducting magnetic shield for shielding a magnetic field by a superconductor.

(Prior Art) Conventionally, as a magnetic shield using superconductivity, a type 1 superconductor and a type 2 superconductor have been used depending on the strength of a magnetic field. The magnetic shield using the type 1 superconductor utilizes perfect diamagnetism (minus-effect), which is a property of superconductivity, but its critical magnetic field is low, so that it cannot shield a strong magnetic field. is there. However, the magnetic shield using the type 2 superconductor utilizes a mixed state of a superconducting state and a normal conducting state, and its critical magnetic field is divided into an upper critical magnetic field and a lower critical magnetic field. Since it is extremely high, it can be used to shield a strong magnetic field. Therefore, recently, this type 2 superconducting magnetic shield has been earnestly studied and partially put to practical use.

As an application example of the magnetic shielding using the second type superconductor, a superconducting sheet or tape wound around a cylindrical core material, for example, one disclosed in JP-A-56-40289 is cited. This magnetic shield body is placed in a strong magnetic field to shield the inner space of the core material from an external magnetic field, or to place a magnet inside the core material to prevent leakage of the magnetic field to the outside. .

(Problems to be Solved by the Invention) By the way, since the magnetic shield body is for electromagnetically blocking the inside and outside of the core material through mutual joining of the superconducting shield or tape, the state of the joined portion Greatly affects the magnetic shielding effect. By the way, in the prior application, the superconducting tape is wrapped around a core material and then impregnated with a low-melting metal to integrally bond the superconducting tapes together. Since the thickness of the impregnated metal layer is not uniform, the shielding effect against the magnetic field parallel to the axis of the core material is weak, and there is a problem that it deteriorates with time. That is, when viewed in a plane area orthogonal to the magnetic field, there is no missing portion of the low melting point metal, so an electrically closed state is not formed by the superconducting tape, and therefore the principle of invariant flux linkage does not work easily. This is because a difference in electric resistance occurs due to a difference in thickness, Joule heat is generated in a thick portion, and this causes the electrical closed state to easily collapse with time.

In addition, there is also one in which mesh tape made of superconducting wire is wrapped around a tubular core material and joined to each other by wood metal or solder, but in this case there are many joints and the magnetic resistance shielding effect due to the electrical resistance generated at the joints over time. In the above magnetic shield, the present inventors have earnestly studied to optimize the joining means of the superconducting thin films corresponding to the part parallel to the magnetic field and the part orthogonal to the magnetic field. We have completed several types of superconducting magnetic shields that are extremely effective and stable, and we propose them here.

(Means for Solving the Problem) A superconducting magnetic shield of the present invention according to claim 1 is composed of a tubular core material with both ends open, and a superconducting thin film wound around the periphery of the core material. The thin film has a ring-closing joint portion that is in an electrically ring-closed state around the axis of the core material, and at least this ring-closing joint portion is thermocompression bonded to the superconducting low-melting-point metal layers adhered to the thin film by vapor deposition. The main point is that they are joined and integrated.

The superconducting magnetic shield according to claim 2 is composed of a tubular core material whose both ends are open, and a superconducting thin film wound around the circumference of the core material. The superconducting low melting point is formed by vapor deposition. The superconducting thin film tape loops closed by thermocompression bonding of metal layers are fitted to both ends of the core material, and the superconducting magnetic shield according to claim 3 is the superconducting thin film. Instead of a tape loop, a closed coil-shaped ring of superconducting wire is fitted over both ends of a core.

In the magnetic shield body according to any one of claims 1 to 3, in order to effectively shield the magnetic field along the axial center of the tubular core member, the surface area orthogonal to the magnetic field is electrically determined by the principle of flux linkage invariance. Since it is essential that the junction be closed, and the electrical resistance of the joint is as small as possible, the superconducting low melting point metal layer formed in a thin layer with the largest possible area at the joint of the superconducting thin film or tape. Is intervened.

However, since the diamagnetic field of the superconducting thin film is used to shield the magnetic field applied to the side portions of the tubular core member in an orthogonal state, it is not necessary to electrically close the ring, and thus the closed ring is used. In addition to the joining portion, for example, joining of overlapping portions of the superconducting thin films on the core material side portion is performed by pressure bonding of the low melting point metal, as well as commercially available low-temperature adhesive (e.g., epoxy adhesive), pressure-sensitive adhesive. Also, either adhesive or adhesive tape (double-sided tape, etc.) can be adopted. However, even when such a bonding method is adopted, the gap between the superconducting thin films is
It should be less than 500 μm. This is because if the thickness exceeds 500 μm, the magnetic field may leak through the adhesive layer.

Further, in the superconducting magnetic shield according to claim 5, the superconducting thin film is adhered to the inner surface and / or the outer surface of the bottom of the cylindrical core material whose one end is closed by the bottom by the insulating adhesive material. It becomes one. As the insulating adhesive material, the above-mentioned low-temperature adhesive, pressure-sensitive adhesive, adhesive tape, or pressure-sensitive adhesive tape can be adopted. This is because one end of the tubular core material is closed, so that the magnetic field parallel to the axis of the core material is shielded by the diamagnetism of the superconducting thin film that substantially covers the closed bottom portion against the vertical magnetic field. This is because it is not necessary to intentionally construct an electrically closed state.

As the superconducting material of the superconducting thin film and wire, niobium metal, niobium-based compound, niobium-based alloy, vanadium-based compound and vanadium-based alloy, etc. are adopted, specifically Nb,
Nb-Ti alloy, Nb-Zr alloy, NbN, NbC, NbN / TiN (mixed crystal), Nb ₃ Sn, Nb ₃ Al, Nb ₃ Ga, Nb ₃ Ge, Nb ₃ (AlGe) and V
₃ Ga etc. are mentioned. Other ceramics-based superconducting materials (eg, Ba-Y-Cu-O-based compounds, La-Sr-Cu-O-based compounds, B
i-Sr-Ca-Cu- O -based compound, Tl-Ba-Ca-Cu -O compounds) or Chevrel superconductor material (e.g., PbMo ₆ S ₆₎ or the like may also be employed. As the superconducting thin film, rolled sheets or films of these alloys may be used alone or laminated with a sheet or film of a normal conducting metal, and the above superconducting compound or ceramic material may be used as a base sheet. It may be vapor-deposited or attached to the surface of the film. Furthermore,
The superconducting magnetic shield disclosed in Japanese Patent Application No. 60-024254, Japanese Patent Application No. 62-068499 and Japanese Patent Application No. 63-028184 can also be used.

Further, as the superconducting low-melting-point metal, if a metal such as bismuth lead, indium tin, or an alloy of lead that exhibits superconductivity at liquid He temperature is used, the electrical resistance of the joint between the superconducting thin films is zero (single layer). It becomes a film) or becomes very small (when it is a laminated film), and an extremely good electrically closed state can be obtained. The low melting point metal is deposited and formed on at least a portion of the superconducting thin film corresponding to the ring-closing joint by vacuum deposition, and is fused and integrated with each other when heated and pressed in a combined state. In this case, in consideration of wettability with the superconducting thin film, it is possible to previously form a copper coating film on the superconducting thin film by vacuum vapor deposition or sputtering, and deposit a low melting point metal layer thereon.

(Operation) The operation of the superconducting magnetic shield of the present invention will be described. When the shield body according to claim 1 is placed in a magnetic field, a shield current flows through a closed loop formed by mutual pressure bonding of superconducting low melting point metal layers under the action of a magnetic field parallel to the axis of the core material. The transmission of the magnetic field is blocked based on this shielding current (the principle of invariant flux linkage). Since the low-melting-point metal layer is formed by deposition by vacuum evaporation, its thickness and the like are uniform, so that the shielding effect is maintained stably and for a long period of time. Further, the demagnetizing force of the superconducting thin film wound around the circumference of the core material acts on the magnetic field loaded in the direction orthogonal to the circumference of the core material, thereby blocking the magnetic field.

In the case of the magnetic shield body according to claim 2, when placed in a magnetic field similar to the above, a shielding current flows through the superconducting thin film annulus fitted on both ends of the core material, and parallel to the axis of the core material as above. Magnetic fields are blocked. Further, the magnetic field applied in the direction orthogonal to the core body is also blocked by the demagnetizing action of the superconducting thin film wound around the body in the same manner as described above.

In the case of the magnetic shield body according to claim 3, since the closed coil-shaped wheel made of a superconducting wire is fitted over both ends of the core material, a shielding current flows in the wheel body by a magnetic field parallel to the axis of the core material, The magnetic field, which is blocked and applied to the circumference of the core, is also blocked in the same manner as above.

In the case of the magnetic shield according to any one of claims 1 to 3, if the joining portion of the superconducting thin film other than the ring-closing joining portion, that is, the overlapping portion of the thin films is tightly joined with an adhesive or an adhesive tape, The wound state of the superconducting thin film is maintained and the shielding of the magnetic field orthogonal to the surrounding body of the core material is not reduced. Therefore, the winding and assembling of the superconducting thin film is simple and inexpensive.

In the magnetic shield body according to claim 5, the peripheral body and the bottom portion of the core material are covered with a superconducting thin film without any gaps and are covered with an insulating adhesive material, and each adjacent superconducting thin film is electrically connected with an adhesive. Since it is in an insulating state, the magnetic field is shielded only by the diamagnetism of the superconducting thin film. Therefore, the magnetic field parallel to the axis of the core directly acts on the closed portion of the bottom. Therefore, the magnetic field is blocked by the demagnetizing force of the superconducting thin film which is integrally bonded to the closed portion without a gap.
Also, the magnetic field acting in a state orthogonal to the side peripheral portion of the core material is also blocked by the diamagnetic effect of the superconducting thin film integrally bonded to the side peripheral portion, and the entire magnetic shielding effect is provided only by the diamagnetism of the superconducting thin film. Will own. Therefore, it is not necessary to electrically bond the thin films to each other, and an inexpensive bonding means such as an adhesive or a double-sided tape can be adopted.

(Example) Next, an example of the present invention will be described in more detail with reference to the accompanying drawings. Here, FIG. 1 is a perspective view showing an example of a magnetic shield according to claim 1 of the present invention, FIG. 2 is a sectional view taken along the line II-II of FIG. 1, and FIG. Similar to FIG. 2, FIG. 4 (a) is another modified example (b) is a developed view of the superconducting thin film, and FIG. 5 is a perspective view showing an example of the magnetic shield according to claim 2. 6 and 6 are perspective views showing an example of the magnetic shield body according to claim 3, FIG. 7 is a perspective view showing an example of the magnetic shield body according to claim 5, and FIG. It is a schematic explanatory drawing which shows the aspect.

[I] FIG. 1 shows that a band-shaped superconducting thin film 2 is wound around a circumference of a cylindrical core material 1 made of aluminum, copper or stainless steel, the both ends of which are open.
2 shows superconducting magnetic shields that are continuously arranged so as to overlap each other in the axial direction of. A low melting point metal layer having a thickness of 3 to 5 μm formed by vacuum deposition on a bonding portion 3 in the circumferential direction of the thin film 2.
The superconducting thin films 2 are formed by attaching the low melting point metal layers 31 and 31 to each other by thermocompression bonding (see FIG. 2). The surroundings are electrically closed. Further, the overlapping portions 4 of the thin films 2 along the axis of the core material 1 are integrally joined by a low temperature adhesive, whereby the outer peripheral surface of the core material 1 is completely covered with the superconducting thin film 2. It The ring-closed joint portions 3 ...
When the core material 1 is wound in multiple layers in the centrifugal direction, it is desirable to arrange the overlapping portions 4 so that they are displaced from each other in the axial direction of the core material 1 in order to perform more effective magnetic shielding.

Thus, when the magnetic shield body having the above-mentioned configuration is arranged in the magnetic field, a shielding current is induced in the closed superconducting thin films 2 by the magnetic field parallel to the axis of the core material 1, and the principle of invariance of the interlinkage magnetic flux is obtained. The magnetic field is shielded. At this time, the ring-closing joint part 3
The low-melting-point metal layers 31, 31 intervening in are good conductors of electricity and are formed to have a uniform thickness, so that the circulation of current is surely induced and is not attenuated over time. The shielding of the magnetic field is effectively performed. Also, the core material 1
The magnetic field orthogonal to the surrounding body is also shielded by the demagnetizing action of the superconducting thin films 2, which are tightly wound and integrated with the surrounding body of the core material 1.

FIG. 3 shows an example in which an intermediate layer 32 made of copper is interposed between the superconducting thin film 2 and the low melting point metal layer 31. The intermediate layer 32 is formed on the superconducting thin film 2 by vacuum vapor deposition or sputtering, and functions so as to more firmly integrate the superconducting thin film 2 and the low melting point metal layer 31 with each other.

[2] FIG. 4 shows a sheet-shaped superconducting thin film 2 having a width equal to the length of the core material 1 wound around the circumference of a metal cylindrical core material 1 similar to the above. As shown in FIG. 4 (b), the thin film 2 is provided with projecting joint pieces 21, 21 at the widthwise end of the winding start portion, and is wound around the core body 1 as shown in FIG. 4 (a). After being turned, the joining pieces 21, 21 are folded back on the surface of the wound thin film 2 to be joined and integrated. In the case of the present embodiment, a low melting point metal layer similar to the above is deposited and formed on the entire surface of the thin film 2, and the folded joint pieces 21, 21 are heated and pressed to heat the low melting point metal layers. The superconducting thin film 2 is substantially pressure-bonded to obtain an electrically closed state of the superconducting thin film 2. The winding end portion of the superconducting thin film 2 is bonded and integrated with the surface of the wound thin film 2 by a low temperature adhesive, a double-sided tape or the like as described above.
When the low melting point metal layers are formed on both surfaces of the thin film 2, the joining of the winding end portions can be performed by thermocompression bonding of the low melting point metal layers. A ring-closed state can be joined. It can be easily understood from the description that the magnetic shield constructed in this way has the same magnetic shielding effect as in the case of the above [1], and therefore the detailed description thereof is omitted here.

[3] FIG. 5 shows that a tape-shaped superconducting thin film 2 is spirally wound around a peripheral body of a core material 1 similar to the above without a gap, and the overlapping portion of the thin films accompanying the spiral winding is applied with a low temperature adhesive or The superconducting thin film tape loop bands 2a, 2a similar to the above, which are joined integrally by a double-sided tape or the like, and which are closed loops by thermocompression bonding of the low melting point metal layers to both ends of the core material 1, are integrally fitted. . In this embodiment, since the electrically closed ring state is formed by the superconducting thin film tape loops 2a, 2a, the magnetic field parallel to the axis of the core 1 is shielded by the same as above, and the core 1 The magnetic field orthogonal to the circumference is shielded by the tape-shaped superconducting thin film 2 spirally wound around the circumference of the core 1.

[4] FIG. 6 shows that, instead of the above-mentioned superconducting thin film tapes 2a and 2a, a closed coil-shaped wheel body 2b and 2b made of a superconducting wire is used as a core material
It is the one that is fitted over both ends of. Both ends of each ring 2b, 2b are joined and integrated by melting and fixing of a low melting point metal so that an electrically closed state is formed, whereby the same principle of invariant flux linkage as described above is developed, and the same magnetic shielding effect as above. Is played. Since the other magnetic shielding effects are the same as the above, detailed description thereof will be omitted.

[5] FIG. 7 shows a magnetic shield body in which the superconducting thin film pieces 2c ... Are adhered to the entire outer surface of the metal-made cylindrical core material 1 ′ with one end closed with a similar low temperature adhesive or the like without any gap. Indicates. In this case, the magnetic field applied parallel to the axis of the core material 1 tries to pass through the bottom closed portion of the core material 1, but the superconducting thin film pieces 2c ... Are adhered to the closed portion without a gap. Therefore, the magnetic field is shielded by this diamagnetic effect. Also,
The magnetic field acting on the side peripheral surface of the core material 1 in a state orthogonal to each other is shielded by the superconducting thin film pieces 2c ...
In the case of the present embodiment, the magnetic field can be shielded only by the demagnetizing effect of the superconducting thin film pieces 2c ... Therefore, it is not necessary to join in the electrically closed state as in the above embodiment. But,
It is of course possible to jointly use the thermocompression bonding of the low melting point metal layers as in the above embodiment.

[6] FIG. 8 shows various forms of the joint portion adopted above. In FIG. 8 (a), the ends of the superconducting thin film 2 are simply overlapped, but the same (b) and (c) show that the ends of the thin film 2 are bent in a so-called folded or folded shape. The state of joining is shown. In the case of FIG. 8 (a), since a force acts to peel off the bonded portion due to the magnetic field, it is necessary to increase the adhesive strength of the bonded portion. However, in the case of FIG. 8B, since the ends of the superconducting thin film 2 are connected so as to mesh with each other, the superconducting thin film 2 can withstand even a strong peeling action by a magnetic field. Fig. 8 (a) and (c)
When the ring-closing bonding is performed by thermocompression bonding of the low-melting point metal layer by the method described above, it is necessary to separately form the low-melting point metal layer on the corresponding surface of the thin film 2 or to form the entire surface of both surfaces of the thin film 2. In the case of the figure (b), it may be formed on only one side.
In the case of FIG. 8 (c), it is desirable to sandwich and fix from both sides of the joint.

[7] Next, a comparative test was conducted on the magnetic shielding effect according to the bonding forms of FIGS. 8A to 8C, and the results will be described.

First, a NbTi thin film sheet with a thickness of 2 μm is processed into a disc shape with a diameter of 45 mm, which is further cut in the diametrical direction to combine the various joining methods described above with the joining forms of FIGS. 8 (a) to 8 (c). The cut pieces were joined together. The overlap margin of the joint is 10 mm in Fig. 8 (a) and (c), and 5 mm in Fig. 8 (b).
Is. The thickness of the adhesive layer and adhesive tape layer is 0.
1 mm and 0.2 mm. A constant magnetic field was applied to the central portion of the joint portion in an orthogonal state, and the magnetic shielding effect was calculated assuming that the thin film sheet having no joint portion was 100.
The results are shown in Table 1.

In addition, Bi-Pb, wood metal, In-Sn-Pb, and In were formed on the corresponding joint part of the superconducting thin film by vacuum vapor deposition with a thickness of 5 μm, and they were thermocompression-bonded to each other by heating and pressing. .

From Table 1, in the joining form of FIG. 8 (a), the matching material is
It is understood that in the case of In, low-temperature adhesive and double-sided tape, the magnetic shielding effect is slightly inferior, but in other cases, it is equivalent to that without bonding.

[8] Next, the shield body shown in FIGS. 1 and 4 (a) to 7 was prepared and the magnetic shielding amount was measured. The test results will be described below.

Four cylindrical aluminum cores having a thickness of 0.049 mm, a diameter of 25.4 mm and a length of 200 mm, both ends open, and one core having the same shape and closed at one end were prepared.

(A) At both ends of a strip-shaped NbTi thin film with a thickness of 2 μm and a width of 30 mm
Bi-Pb is deposited over 30 mm by vacuum evaporation to a thickness of 5 μm, and this is first coated on the circumference of the cylindrical core material with both ends open.
As shown in the drawing, the Bi-Pb layers were wound and thermocompression-bonded to each other, and the overlapping portions (overlapping width 10 mm) of the thin films were joined and integrated with a low-temperature adhesive.

(B) B having a thickness of 2 μm and a width of 200 mm and a thickness of 5 μm on the surface
The NbTi thin film sheet on which the vacuum deposition film of i-Pb is formed
Cut it as shown in Fig. (B), wind it around the circumference of the core material as shown in Fig. 4 (a), and bond the winding end end with low temperature adhesive (200 mm in width). The protruding joining piece (10 × 30 mm) at the winding start portion was folded back, and this was thermocompression bonded to the already wound portion by thermocompression bonding.

(C) NbTi thin film tape with a thickness of 2 μm and a width of 30 mm
As shown in Fig. 6 or Fig. 6, the core material was spirally wound around the surface of both ends open, and the overlapping portion (overlapping width 10 mm) was integrally joined with a low temperature adhesive. A Bi-Pb vacuum deposition film with a thickness of 5 μm covering a width of 30 mm is adhered and formed on both ends of the cut short piece of the NbTi thin film tape, and the Bi-Pb films are wound around both ends of the core material and the Bi-Pb films are heated and pressed to each other. It was thermocompression bonded and fixed by fitting as shown in FIG.

(D) The same NbN / TiN thin film tape as above was spirally wound around the core material, and the overlapping portion was similarly adhesively fixed. In addition, a NbTi wire rod having a wire diameter of 2 mm was wound around the core material for several tens of times (so that the central magnetic field was equal to or higher than the strength of the environmental magnetic field), and the ends were adhesively fixed by Bi-Pb.

(E) A rectangular NbTi thin film piece having a thickness of 2 μm and a size of 20 × 20 mm was adhered to the outer surface of the core material having one end closed by an adhesive for low temperature so that the overlapping width was 5 mm or less without gap (7
See figure).

The shield bodies (a) to (e) were arranged in a magnetic field of 400 gauss such that the axis of the shield body was parallel to the magnetic field, and the strength of the magnetic field at the center of the shield body was measured. Incidentally, FIG. 8 (a) was adopted as the joining form. As a result, the strength of the magnetic field at the central portion of the shield bodies of (a) to (e) was zero.

If the magnetic shielding layer made of a superconducting thin film is formed in multiple layers, the magnetic shielding effect will be further enhanced. The magnetic shielding effect did not decrease even after 24 hours, and no deterioration in performance was observed even after repeating such operation 10 times or more.

Then, by using the laminated film having an excellent magnetic shielding effect as described above, a shield body having more excellent performance can be formed. Further, even in shielding of a high magnetic field, the number of layers to be multilayered can be reduced, so that the shield body can be very easily produced.

(Effects of the Invention) As described above, the superconducting magnetic shield body of the present invention employs two kinds of magnetic shielding functions of the superconducting thin film, that is, the proper joining means corresponding to the principle of invariant flux linkage and diamagnetism. However, this makes it possible to use bonding means such as adhesives and double-sided tape that have not been considered in the past, and in the case of electrical ring-closing bonding of low melting point metal layers by vapor deposition, magnetic shielding is sure and uniform. Moreover, it is maintained for a long time. Therefore, when shielding the leakage magnetic field of a superconducting magnet for research or forming a shielded space in a high magnetic field, to MRI, superconducting magnetic levitation train, superconducting magnetic propulsion ship, superconducting energy storage, superconducting generator and MHD generator etc. It is effective for the application of and its value is extremely large.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a magnetic shield body according to claim 1 of the present invention, FIG. 2 is a sectional view taken along the line II-II of FIG. 1, and FIG. 3 is another modification of FIG. The same figure, FIG. 4 (a) shows another modified example (b) showing a developed view of the superconducting thin film, and FIG.
6 is a perspective view showing an example of the magnetic shield body according to claim 2, FIG. 6 is a perspective view showing an example of the magnetic shield body according to claim 3, and FIG. 7 is a magnetic shield body according to claim 5. FIG. 8 is a perspective view showing an example of the body, and FIG. 8 is a schematic explanatory view showing various aspects of the joint portion. (Explanation of symbols) 1 ... Core material, 2 ... Superconducting thin film, 3 ... Ring-closing joint part,
31 ... Low melting point metal layer.

Continuation of front page (56) References JP-A-56-40289 (JP, A)

Claims (7)

[Claims] 1. A ring-closure joint comprising a tubular core material having both ends open, and a superconducting thin film wound around a circumference of the core material, wherein the thin film is in an electrically closed state around the axis of the core material. A superconducting magnetic shield body having a portion, and the ring-closing joint portion is formed by thermocompression bonding the superconducting low-melting-point metal layers adhered to the thin film by vapor deposition to be joined and integrated. 2. A tubular core material having open both ends, and a superconducting thin film wound around a peripheral body of the core material, through thermocompression bonding of superconducting low melting point metal layers formed by vapor deposition. A superconducting magnetic shield body in which the superconducting thin film tape ring body which has been closed is fitted to both ends of the core material. 3. The superconducting magnetic shield according to claim 2, wherein a closed coil-shaped ring of a superconducting wire is fitted over both ends of the core instead of the superconducting thin film tape annulus. 4. The superconducting magnetic shield according to claim 1, 2 or 3, wherein the superconducting thin films other than the ring-closed joint are joined by a low-temperature adhesive, an adhesive and an adhesive tape or an adhesive tape. body. 5. A superconducting magnetic shield which is integrally formed by adhering a superconducting thin film to an inner surface and / or an outer surface of the bottom portion at one end with a bottom portion and an insulating adhesive material on the inner surface and / or the outer surface of the bottom portion. . 6. The superconducting magnetic shield according to claim 5, wherein the insulating adhesive material is any one of a low temperature adhesive, a pressure sensitive adhesive and an adhesive tape or a pressure sensitive adhesive tape. 7. The core material is made of any metal selected from aluminum, copper and stainless steel.
The superconducting magnetic shield according to 2, 3 or 5.