JP5937025B2 - Superconducting magnetic shield device - Google Patents

Description

  The present invention relates to a superconducting magnetic shield apparatus that performs magnetic shielding using a high-temperature superconductor.

  For example, a weak magnetic field measurement device that measures a weak magnetic field, such as a magnetoencephalograph or a magnetocardiograph, measures an external magnetic field such as geomagnetism as a disturbance. For this reason, the weak magnetic field measurement device is shielded by a magnetic shield device that shields the external magnetic field that becomes a disturbance so that the disturbance does not adversely affect the weak magnetic field measurement device, thereby measuring the weak magnetic field.

  Conventionally, as this magnetic shield device, there is one in which the entire inner wall of a room in which a weak magnetic field measuring device is installed is made of a magnetic shield material, and this magnetic shield room prevents the influence of an external magnetic field (see Patent Document 1). .

JP 2002-291713 A

  However, since the magnetic shield room is configured to magnetically shield the entire room, there is a problem that it becomes a large-scale facility.

  On the other hand, in recent years, tape-like superconducting wires have begun to be provided. It is desired to reduce the size and simplify the structure of the magnetic shield device by configuring the magnetic shield device using this tape-shaped superconducting wire.

  However, when shielding an external magnetic field with a tape-shaped superconducting wire, it is necessary to arrange the superconducting wire over the entire shield and connect the superconducting wires so as to form an electrical closed circuit. Solder is generally used for joining superconducting wires, but the soldered portion has significant resistance.

  On the other hand, when a magnetic field is applied from the outside, the superconducting magnetic shield performs its function by generating a current in the superconductor so as to shield the magnetic field. There arises a problem that the current generated in the superconductor is attenuated and the magnetic shielding effect is lowered.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a superconducting magnetic shield device capable of realizing high magnetic shielding properties even when a tape-shaped superconducting wire is used.

From a certain viewpoint, the above-described problem is a first axial magnetic shield having a first superconducting material for an axial direction in which a tape-shaped superconducting material is formed in a ring shape,
Forming a tape-shaped superconducting material into a ring shape, and a second axial magnetic shield having a second axial superconducting material disposed so as to wrap around the outer periphery of the first axial superconducting material;
The first axial magnetic shield and the second axial magnetic shield are arranged perpendicularly or inclined to the axial direction of the first axial magnetic shield and the second axial magnetic shield, and are electrically connected to the first axial magnetic shield and the second axial magnetic shield. A transverse magnetic shield having a transverse superconductor connected thereto;
A support for supporting the first axial magnetic shield, the second axial magnetic shield, and the lateral magnetic shield;
The first axial superconducting material has a first end portion in which both end portions of the tape-shaped superconducting material are opposed to each other.
The second axial superconducting material has a second end portion in which both end portions of the tape-shaped superconducting material are opposed to each other.
The position of the first end of the first superconducting material for the axial direction is different from the position of the second end of the superconducting material for the second axial direction, and the superconducting material for the first axial direction This can be solved by a superconducting magnetic shield device characterized in that the outer peripheral surface of the second conductive member and the inner peripheral surface of the second axial superconducting material are joined together by a conductive joining material.

  According to the disclosed invention, the end position of the first axial superconducting material is different from the end position of the second axial superconducting material, and each axial superconducting material is joined by the conductive bonding material. As a result, the connection resistance at the end position can be reduced, so that a high magnetic shielding effect can be obtained even when a tape-shaped superconducting material is used.

FIG. 1 is a perspective view of a superconducting magnetic shield device according to an embodiment of the present invention. FIG. 2 is a plan view of a superconducting magnetic shield device according to an embodiment of the present invention. FIG. 3 is an exploded perspective view of the superconducting magnetic shield device according to an embodiment of the present invention. FIG. 4 is an enlarged perspective view showing the first and second axial tape-like superconductors. FIG. 5 is an enlarged cross-sectional view showing a joining position between the first and second axial tape-like superconducting materials and the lateral tape-like superconducting material. FIG. 6 is a diagram showing a superconducting current generated in an axial tape-shaped superconducting material when an axial magnetic field is applied. FIG. 7 is a diagram showing a superconducting current generated between an axial tape-shaped superconducting material and a lateral tape-shaped superconducting material when a transverse magnetic field is applied. FIG. 8 is a diagram for explaining the connection resistance at the connection position of the tape-shaped superconducting material for axial direction (No. 1). FIG. 9 is a diagram for explaining the connection resistance at the connection position of the tape-shaped superconducting material for axial direction (No. 2). FIG. 10 is a diagram showing the relationship between the connection distance of the axial tape-shaped superconducting material and the magnetic shield rate.

  Next, embodiments of the present invention will be described with reference to the drawings.

  1 to 3 show a superconducting magnetic shield device 10 according to a first embodiment of the present invention. 1 is a perspective view of a superconducting magnetic shield device 10, FIG. 2 is a plan view, and FIG. 3 is an exploded perspective view. The superconducting magnetic shield device 10 is applied to a weak magnetic field measuring device that measures a weak magnetic field such as a magnetoencephalograph or a magnetocardiograph.

  The superconducting magnetic shield device 10 includes a support 11, a first axial magnetic shield 12A, a second axial magnetic shield 12B, a lateral magnetic shield 13, and the like. In the present embodiment, the support 11, the first axial magnetic shield 12A, the second axial magnetic shield 12B, and the lateral magnetic shield 13 are arranged in order from the innermost periphery. Therefore, the superconducting magnetic shield device 10 has a structure in which the support 11, the magnetic shields 12A and 12B in the axial direction, and the magnetic shield 13 in the lateral direction are overlapped in quadruplicate.

  The superconducting magnetic shield device 10 has a cylindrical shape as a whole. Therefore, the space part 14 is formed in the center part, and when the superconducting magnetic shield device 10 is applied to the magnetoencephalograph, the magnetoencephalometer is disposed inside the space part 14 and the object to be measured is The person's head is inserted.

  Hereinafter, each component which comprises the superconducting magnetic shield apparatus 10 is demonstrated.

  First, the support 11 will be described. The support 11 has a cylindrical shape and supports the axial magnetic shields 12 </ b> A and 12 </ b> B and the lateral magnetic shield 13. The material of the support 11 is not particularly limited, but in the present embodiment, a resin or metal that is nonmagnetic and has good moldability is used. In addition, a cooling pipe (not shown) through which a coolant for cooling magnetic shields 12A, 12B, and 13 to be described later flows is disposed on the inner periphery of the support 11.

  The first axial magnetic shield 12A and the second axial magnetic shield 12B shield against an axial magnetic field.

  In this specification, the magnetic field in the axial direction of the cylinder (directions indicated by arrows Z1 and Z2 in the figure) is called the axial magnetic field, and the magnetic field in the direction orthogonal to the axial direction of the cylinder is called the transverse magnetic field. . A magnetic shield against an axial magnetic field is called an axial magnetic shield, and a magnetic shield against a transverse magnetic field is called a transverse magnetic shield. Moreover, the magnetic field applied from directions other than an axial direction or a horizontal direction can be decomposed | disassembled into an axial direction magnetic field and a horizontal direction magnetic field. For this reason, in the following description, only an axial magnetic field and a transverse magnetic field will be described.

  The first axial magnetic shield 12A is composed of a plurality of first axial tape-shaped superconducting materials 15A, and the second axial magnetic shield 12B is composed of a plurality of second axial tape-shaped superconducting materials 15B. (The first and second axial tape-like superconducting materials 15A and 15B correspond to the axial superconducting materials described in the claims). FIG. 4 shows the corresponding pair of first and second axial tape-like superconducting materials 15A and 15B in an enlarged manner.

  The first and second axial tape-like superconducting materials 15A and 15B are both configured by bending the tape-like superconducting material 21 into a ring shape (annular shape). Therefore, the tape-shaped superconducting materials 15A and 15B for the axial direction constituting the axial magnetic shields 12A and 12B constitute a one-turn coil.

  Further, the first and second axial tape-like superconducting materials 15A and 15B are formed by forming the tape-like superconducting material 21 into a ring shape, and thus both end portions thereof are in a state of being close to each other. Hereinafter, a portion where both ends of the first axial tape-shaped superconducting material 15A are opposed to and separated from each other is referred to as a first end portion 17A, and a portion where both ends of the second axial tape-shaped superconducting material 15B are opposed to and separated from each other. The second end portion 17B is assumed (see FIG. 4).

  The tape-shaped superconducting material 21 constituting the first and second axial tape-shaped superconducting materials 15A and 15B is configured such that the outer periphery of the superconducting material is covered with a metal. Further, as the superconducting material, a high temperature superconducting material having a high critical temperature is used. As this tape-shaped superconducting material 21, for example, DI-BSCCO (product name) manufactured by Sumitomo Electric Industries, Ltd. can be used.

  Here, attention is focused on the size of the first axial magnetic shield 12A and the second axial magnetic shield 12B. The diameter of the second axial tape-shaped superconducting material 15B constituting the second axial magnetic shield 12B is the diameter of the first axial tape-shaped superconducting material 15A constituting the first axial magnetic shield 12A. Is set larger.

  Specifically, the first axial tape-shaped superconducting material 15A and the second axial tape-shaped superconducting material 15B are configured to overlap each other in the radial direction. The material 15B is disposed so as to wrap around the outer periphery of the first axial tape-like superconducting material 15A.

  The first axial tape-like superconducting material 15A and the second axial tape-like superconducting material 15B are joined by solder 18 which is a conductive joining material. Specifically, the outer peripheral surface excluding the first end portion 17A of the first axial tape-shaped superconducting material 15A and the inner peripheral surface excluding the second end portion 17B of the second axial tape-shaped superconducting material 15B. Are soldered together using solder 18.

  At this time, the positions of the first axial tape-shaped superconducting material 15A and the second axial tape-shaped superconducting material 15B are different so that the positions of the first end 17A and the second end 17B are different. It is set (the reason for this will be described later).

  By soldering and joining as described above, the first axial tape-like superconducting material 15A and the second axial tape-like superconducting material 15B are electrically and mechanically joined.

  In the first axial magnetic shield 12A and the second axial magnetic shield 12B, a plurality of the first and second axial tape-like superconducting materials 15A and 15B are laminated in the axial direction of the support 11 ( Stacked) configuration.

  In addition, the attachment method to the support body 11 of the 1st and 2nd axial direction magnetic shield 12A, 12B is not specifically limited. For example, first, the first axial tape-shaped superconducting material 15A constituting the first axial magnetic shield 12A is fixed to the support 11 using an adhesive or the like, and then the first axial tape-shaped superconducting material is used. A method of soldering the second axial tape-like superconducting material 15B to the material 15A may be used. Also, the first axial tape-shaped superconducting material 15A and the second axial tape-shaped superconducting material 15B are soldered first, and then the integrated axial tape-shaped superconducting materials 15A and 15B are integrated. A method of fixing the substrate to the support 11 using an adhesive or the like may be used. By using these attachment methods, the first axial magnetic shield 12 </ b> A and the second axial magnetic shield 12 </ b> B are supported by the support 11.

  Next, the transverse magnetic shield 13 will be described.

  The transverse magnetic shield 13 has a structure in which a plurality of transverse tape-like superconducting materials 16 (the transverse superconducting materials described in the claims) are arranged in parallel in the circumferential direction of the support 11 (arranged in parallel). Yes. Similar to the tape-shaped superconducting material 21 described above, the lateral tape-shaped superconducting material 16 has a configuration in which the outer periphery of the high-temperature superconducting material is covered with a metal.

  Unlike the axial magnetic shields 12A and 12B, the lateral magnetic shield 13 is linear. Therefore, the axial magnetic shields 12A and 12B and the horizontal magnetic shield 13 are configured to extend in directions orthogonal to each other, as shown in FIGS.

  Moreover, in this embodiment, it is comprised so that the longitudinal direction of each tape-shaped superconducting material 16 for each horizontal direction may become parallel to an axial direction. Further, the lateral tape-like superconducting material 16 is disposed so as to surround the outer peripheral position of the cylindrical second magnetic shield 12B.

  As shown in an enlarged view in FIG. 5, each lateral tape-shaped superconducting material 16 is soldered to the second axial tape-shaped superconducting material 15 </ b> B constituting the second axial magnetic shield 12 </ b> B located outside. Are joined together. Accordingly, the second axial tape-shaped superconducting material 15B and the lateral tape-shaped superconducting material 16 are configured such that the second axial magnetic shield 12B and the lateral magnetic shield 13 are electrically connected. It becomes.

  Next, the operation when a magnetic field is applied from the outside in the superconducting magnetic shield device 10 having the above configuration will be described with reference to FIGS.

  The first axial magnetic shield 12A and the second axial magnetic shield 12B perform the same operation when a magnetic field is applied from the outside. Therefore, for convenience of explanation and illustration, only the second axial magnetic shield 12B (second axial tape-like superconducting material 15B) is shown and described in FIGS.

As shown in FIG. 6, when an axial magnetic field (B _A ) is applied to the superconducting magnetic shield device 10, the axial magnetic shield 12B (12A) functions. That is, when an axial magnetic field (B _A ) is applied, a superconducting current A is generated in the circumferential direction in each axial tape-shaped superconducting material 15B (15A) constituting the axial magnetic shield 12B (12A), Thereby, it is possible to prevent the axial magnetic field (B _A ) from affecting the space portion 14.

On the other hand, as shown in FIG. 7, when a transverse magnetic field (B _S ) is applied to the superconducting magnetic shield device 10, the transverse magnetic shield 13 functions. That is, when the horizontal direction magnetic field (B _S) is applied, axially tape-like superconducting material 15B (15A) and lateral tape-like superconducting material 16, the applied position of the transverse field (B _S) A superconducting current A flowing in the circular direction as a center is generated.

As described above, the tape-like superconducting material 15B for the axial direction and the tape-like superconducting material 16 for the lateral direction are electrically connected by joining with the solder 19 (see FIG. 5). Therefore, the superconducting current A generated by the transverse magnetic field (B _S ) flows inside each tape-shaped superconducting material 15B (15A), 16 or across each tape-shaped superconducting material 15B (15A), 16, thereby laterally It is possible to prevent the magnetic field (B _S ) from affecting the space portion 14.

  Here, the first axial tape-shaped superconducting material 15A constituting the first axial magnetic shield 12A and the second axial tape-shaped superconducting material 15B constituting the second axial magnetic shield 12B are used. Focusing on the formed first end 17A and second end 17B will be described below.

  Since the first and second axial tape-like superconducting materials 15A and 15B are formed in a ring shape of the tape-like superconducting material 21, the first and second end portions inevitably facing the tape end portions. 17A and 17B are formed.

On the other hand, as described with reference to FIG. 6, when an axial magnetic field (B _A ) is applied to the superconducting magnetic shield device 10, the superconductivity generated in each axial tape-shaped superconductor 15 B (15 A). Current needs to flow in the circumferential direction. For this reason, it is necessary to electrically connect the first end 17A and the second end 17B.

  As a method of electrically connecting the first and second end portions 17A and 17B, for example, a method of electrically connecting the first and second end portions 17A and 17B by arranging solder can be considered. However, when the superconducting magnetic shield device 10 is in use, the tape-like superconducting material 21 constituting the first and second axial tape-like superconducting materials 15A and 15B is in a superconducting state, and the tape-like superconducting state in the superconducting state. The electrical resistance of the solder is greater than the electrical resistance of the material 21.

  For this reason, it is conceivable that the flow of the superconducting current is hindered at the first and second end portions 17A and 17B where the solder is disposed, and thus the magnetic shield of the superconducting magnetic shield device 10 is lowered.

  Therefore, in the present embodiment, as shown in FIGS. 2 and 4, the first end 17A and the second end 17B have different positions. In the present embodiment, the arrangement position of the first end portion 17A and the arrangement position of the second end portion 17B are set to be separated by about 180 degrees.

  When the first end portion 17A and the second end portion 17B are spaced apart in this way, the first end portion 17A is in contact with the inner periphery of the second axial tape-like superconducting material 15B, and the second The end portion 17B is in contact with the outer periphery of the first axial tape-like superconducting material 15A.

Suppose that an axial magnetic field (B _A ) is applied to the superconducting magnetic shield device 10, thereby generating a superconducting current indicated by an arrow A 1 in FIG. 4 in the first axial tape-like superconducting material 15 _A. . When the superconducting current A1 reaches the first end portion 17A having a high electric resistance, a flow indicated by an arrow A2 in FIG. 4 is formed.

  That is, the first axial tape-shaped superconducting material 15A and the second axial tape-shaped superconducting material 15B are electrically connected by the solder 18, and the second axial tape-shaped superconducting material 15B Since the electrical resistance is smaller than the electrical resistance of the first end portion 17A, the superconducting current A1 flowing through the first axial tape-shaped superconducting material 15A becomes the second axial tape-shaped superconducting material 15B having a small electrical resistance. Flows in.

  Thereby, the superconducting current forms a flow indicated by an arrow A2 in FIG. Thereafter, the superconducting current A2 flows through the second axial tape-shaped superconducting material 15B as it is, or again forms a flow returning to the first axial tape-shaped superconducting material 15A.

If a superconducting current indicated by an arrow B1 in FIG. 4 is generated in the second axial tape-like superconducting material 15B by applying an axial magnetic field (B _A ), the superconducting current B1 has an electric resistance. When the high second end portion 17B is reached, a flow indicated by an arrow B2 in the figure is formed.

  That is, similar to the superconducting current A1 generated in the first axial tape-shaped superconducting material 15A, the superconducting current B1 flowing through the second axial tape-shaped superconducting material 15B is more electrically than the second end 17B. It flows into the first axial tape-like superconducting material 15A having a low resistance. Thereafter, the superconducting current B2 flows as it is through the first axial tape-shaped superconducting material 15A or returns to the second axial tape-shaped superconducting material 15B again.

  In particular, in the present embodiment, the first and second axial tape-like superconducting materials 15A and 15B are soldered with the solder 18 over the entire surface except the first and second end portions 17A and 17B. The electrical resistance between the axial tape-like superconducting material 15A and the second axial tape-like superconducting material 15B is small. Therefore, the superconducting current is easy to flow between the first axial tape-shaped superconducting material 15A and the second axial tape-shaped superconducting material 15B, and the superconducting current indicated by the arrows A2 and B2 described above. A current flow can be ensured.

As described above, according to the superconducting magnetic shield device 10 according to the present embodiment, the first and second axial tapes are formed by changing the arrangement positions of the first end 17A and the second end 17B. Since the superconducting materials 15A and 15B are solder-bonded in a wide area, the end portions 17A. Even if 17B is formed, a superconducting current that moderates the rate of change of the axial magnetic field (B _A ) applied to the superconducting magnetic shield device 10 can be satisfactorily passed, and thus the shielding effect of the superconducting magnetic shield device 10 It is possible to prevent the decrease.

  Here, attention is paid to the connection resistance between the first axial tape-like superconducting material 15A and the second axial tape-like superconducting material 15B in the vicinity of the end portions 17A and 17B.

In the embodiment described above, the axial tape-shaped superconducting material 15B is configured to cover the first axial tape-shaped superconducting material 15A except for the first end portion 17A. However, in the following description of the connection resistance, as shown in FIGS. 8 and 9, the second axial tape-shaped superconducting material 15B is in the vicinity of the first end portion 17A with respect to the axial tape-shaped superconducting material 15A. It is assumed that they are connected at a length l _sl (hereinafter, this length is referred to as a connection distance).

Now, assuming that the connection resistance value at the first end portion 17A is R _sl , the width of each axial tape-shaped superconductor 15A, 15B is a, and the product of the solder resistivity and the solder thickness is R ct, R _sl = (R _ct / a × l _sl ). It is assumed that the solder resistivity of the solder 18 joining the first axial tape-shaped superconductor 15A and the second axial tape-shaped superconductive material 15B is ρ _sl and the thickness of the solder 18 is δ _sl. , R _ct ≈ρ _sl × δ _sl .

Here, based on the above equations, the connection resistance R _sl5 and the connection distance when the connection distance L _sl between the first axial tape-shaped superconducting material 15A and the second axial tape-shaped superconducting material 15B is 5 mm. when determining the respective connection resistance R _SL2000 when L _sl is 2000 mm, the _R sl5 ₌ 0.24μΩ next _R sl2000 = 0.000675μΩ. Therefore, it can be seen that the connection resistance R _sl can be reduced as the connection distance L _sl between the first axial tape-like superconducting material 15A and the second axial tape-like superconducting material 15B increases.

Next, based on the connection distance L _sl and the connection resistance R _{sl of the} tape-shaped superconducting materials 15A and 15B for each axial direction obtained as described above, the relationship between the connection distance L _sl and the magnetic shield rate was obtained by simulation. . The result is shown in FIG. Here, the shield rate refers to the ratio of the strength of the external magnetic field B _{OUT to} the strength of the magnetic field (B _IN ) in the space 14 of the superconducting magnetic shield device 10 (magnetic shield rate = B _OUT). / B _IN ).

As shown in FIG. 10, the magnetic shield ratio when the connection distance L _sl is 5 mm is about 500, whereas the magnetic shield ratio when the connection distance L _sl is 2000 mm is greatly improved to about 10,000. ing. Therefore, from the result of this simulation, the longer the connection distance between the first axial tape-like superconducting material 15A and the second axial tape-like superconducting material 15B, the higher the magnetic shielding rate of the superconducting magnetic shield device 10. I found out that

  As described above, in the present embodiment, the first axial tape-shaped superconducting material 15A and the second axial tape-shaped superconducting material 15B are the solder 18 except for the first end 17A and the second end 17B. The structure is joined. Therefore, according to the superconducting magnetic shield device 10, a high magnetic shield effect can be realized.

  The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific embodiments described above, and various modifications are possible within the scope of the gist of the present invention described in the claims. It can be modified and changed.

10 Superconducting Magnetic Shield Device 11 Support 12A First Axial Magnetic Shield 12B Second Axial Magnetic Shield 13 Lateral Magnetic Shield 14 Space 15A First Axial Tape Superconducting Material 15B For Second Axial Tape-shaped superconducting material 16 Horizontal tape-shaped superconducting material 17A First end 17B Second end 18, 19 Solder 21 Tape-shaped superconducting material

Claims (3)

A first axial magnetic shield having a first axial superconducting material formed into a ring shape from a tape-shaped superconducting material;
Forming a tape-shaped superconducting material into a ring shape, and a second axial magnetic shield having a second axial superconducting material disposed so as to wrap around the outer periphery of the first axial superconducting material;
The first axial magnetic shield and the second axial magnetic shield are arranged perpendicularly or inclined to the axial direction of the first axial magnetic shield and the second axial magnetic shield, and are electrically connected to the first axial magnetic shield and the second axial magnetic shield. A transverse magnetic shield having a transverse superconductor connected thereto;
A support for supporting the first axial magnetic shield, the second axial magnetic shield, and the lateral magnetic shield;
The first axial superconducting material has a first end portion in which both end portions of the tape-shaped superconducting material are opposed to each other.
The second axial superconducting material has a second end portion in which both end portions of the tape-shaped superconducting material are opposed to each other.
The position of the first end of the first superconducting material for the axial direction is different from the position of the second end of the superconducting material for the second axial direction, and the superconducting material for the first axial direction A superconducting magnetic shield device, characterized in that an outer peripheral surface of the second conductive member and an inner peripheral surface of the second axial superconducting material are joined together by a conductive joining material. 2. The first axial superconducting material and the second axial superconducting material are soldered on the entire surface except for the positions of the first end and the second end. The superconducting magnetic shield device described.   3. The superconducting magnetic shield apparatus according to claim 1, wherein the first axial superconducting material and the second axial superconducting material constitute a one-turn coil.

Images