JP2000012325A - Superconducting magnetic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a superconducting magnetic device capable of suppressing a variation of magnetic field distribution, an increase of magnetic field leakage and weight, by removing at least a part of magnetic material composing a magnetic shield near to a plane of zero electromagnetic field. SOLUTION: A pair of superconducting coils 1a and 1b is coaxially juxtaposed at predetermined gaps in an axial direction A in a vacuum chamber 5. A pair of ring magnetic shields 13a and 13b comprising ferromagnetism material such as pure iron and the like is coaxially provided in an axial direction A at the predetermined gaps and in a symmetrical position against a plane right angled to an axial direction A passing the through an intermediate point of a pair of superconducting coils 1a and 1b, covering an upper, lower, and circumference surface of the vacuum chamber 5. The zero magnetic field face 4 exists in a gap 14a formed between the pair of magnetic shield 13a and 13b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a superconducting magnet device applied to, for example, a crystal pulling apparatus.

[0002]

2. Description of the Related Art FIG. 8 is a structural view showing a superconducting magnet apparatus applied to a conventional crystal pulling apparatus. In FIG. 8, a pair of cylindrical superconducting coils 1a and 1b are placed in a cylindrical vacuum vessel 5 whose inside is kept in a vacuum, in the axial direction A.
Are arranged coaxially with a predetermined gap. A magnetic shield 2 formed of a ferromagnetic material such as pure iron and having a U-shaped cross section is provided so as to cover the upper and lower end surfaces and the outer peripheral surface of the vacuum vessel 5.

In this conventional superconducting magnet apparatus, the superconducting coils 1a and 1b are cooled by a refrigerant such as liquid helium or a cryogenic refrigerator (not shown), and are maintained in a superconducting state with zero resistance. Then, currents in opposite directions are applied to each of the pair of superconducting coils 1a and 1b, as indicated by × in FIG. At this time, the magnetic flux 3 is distributed as shown in FIG. 8, and the pair of superconducting coils 1a, 1
A zero magnetic field surface 4 occurs between b. Such a magnetic field is called a cusp magnetic field.

[0004] The conventional superconducting magnet device configured as described above is applied to, for example, a crystal pulling device. In this case, the chamber of the crystal pulling apparatus is disposed on the inner peripheral side of the vacuum vessel 5 of the superconducting magnet apparatus, and when a transverse magnetic field is applied to the single crystal raw material melt in the chamber, impurities contained in the single crystal are contained. In addition, thermal convection in the melt, which causes the occurrence of transition loops and the occurrence of defects and growth stripes, is suppressed.

[0005]

As described above, in the conventional superconducting magnet device, the magnetic shield 2 is disposed so as to cover the entire outer periphery of the superconducting coils 1a and 1b in order to suppress the leakage of the magnetic field. Therefore, there is a problem that the magnetic shield 2 is also present near the zero-magnetic-field surface 4 and the weight of the device cannot be reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and at least a part of a magnetic material constituting a magnetic shield near a zero-magnetic-field surface is removed to change a magnetic field distribution or to reduce a leakage magnetic field. It is an object of the present invention to obtain a superconducting magnet device capable of suppressing an increase and reducing the weight.

[0007]

According to a superconducting magnet apparatus according to the present invention, at least a pair of substantially cylindrical superconducting coils are placed in a substantially cylindrical vacuum vessel in a symmetrical positional relationship with respect to a plane orthogonal to the axial direction. An annular magnetic shield made of a magnetic material is arranged coaxially and is arranged so as to surround the outer peripheral side of the superconducting coil. In the superconducting magnet device for generating the magnetic field, the magnetic shield has a gap formed by removing at least a part of the magnetic material in a ring shape over a predetermined range in the axial direction including the zero magnetic field plane.

Further, the magnetic shield is provided in the vacuum vessel.

Further, the magnetic shield forms a part of the vacuum vessel.

In addition, a device whose characteristics change under the influence of a magnetic field is disposed in the gap.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. Embodiment 1 FIG. FIG. 1 is a configuration diagram showing a superconducting magnet device according to Embodiment 1 of the present invention. In FIG. 1, a pair of cylindrical superconducting coils 1a and 1b are placed in a cylindrical vacuum vessel 5 made of a non-magnetic material such as stainless steel and the like, which is kept in a vacuum, with respect to a plane orthogonal to the axial direction A. They are arranged coaxially in a symmetrical positional relationship. In addition, a pair of annular magnetic shields 13a and 13b formed of a ferromagnetic material such as pure iron and formed in an L-shaped cross section form a pair of superconducting coils 1a and 1a.
b, coaxially with a predetermined gap in the axial direction A so as to cover the upper and lower end surfaces and the outer peripheral surface of the vacuum vessel 5 in a symmetrical positional relationship with respect to a plane orthogonal to the axial direction A passing through the intermediate point between b. It is arranged.

In the superconducting magnet device thus constructed, the superconducting coils 1a and 1b are cooled by a refrigerant such as liquid helium or a cryogenic refrigerator (not shown), and are maintained in a superconducting state with zero resistance. ing. Then, currents in opposite directions are applied to each of the pair of superconducting coils 1a and 1b, as indicated by × in FIG.
A cusp magnetic field is generated. That is, the magnetic flux 3 is distributed as shown in FIG. 1, and a zero magnetic field surface 4 is generated between the pair of superconducting coils 1a and 1b. The zero magnetic field surface 4 exists in a gap 14a formed between the pair of magnetic shields 13a and 13b.

This superconducting magnet device is applied to, for example, a crystal pulling device. In this case, the chamber of the crystal pulling apparatus is disposed on the inner peripheral side of the vacuum vessel 5 of the superconducting magnet apparatus, and when a transverse magnetic field is applied to the single crystal raw material melt in the chamber, impurities contained in the single crystal are contained. The occurrence of a transition loop,
Thermal convection in the melt, which causes defects and growth stripes, is suppressed.

As described above, according to the first embodiment,
The pair of magnetic shields 13a and 13b cover the upper and lower end surfaces and the outer peripheral surface of the vacuum vessel 5 in a symmetrical positional relationship with respect to a plane orthogonal to the axial direction A passing through the intermediate point between the pair of superconducting coils 1a and 1b. As described above, since it is coaxially disposed with a predetermined gap in the axial direction A, the magnetic material corresponding to the gap 14a can be omitted, and the weight of the device can be reduced accordingly. At this time, the zero magnetic field surface 4 is
a and 13b, there is almost no magnetic field in the gap 14a.
There is no change in the magnetic field distribution inside the superconducting magnet device and no extreme increase in the leakage magnetic field. Further, since there is almost no magnetic field in the gap 14a, the gap 14a can be used in a place where a device whose characteristics are changed by the magnetic field is disposed.

Embodiment 2 In the second embodiment, as shown in FIG. 2, a magnetic shield 15 formed of a ferromagnetic material such as pure iron and formed in a U-shaped cross section is provided with a vacuum container 5.
Are disposed so as to cover the upper and lower end surfaces and the outer peripheral surface, and the thickness of the magnetic shield 15 is reduced by a pair of superconducting coils 1a,
A gap portion 14b is formed annularly thin over a predetermined range in the axial direction A including an intermediate point between the gap portions 1b. In addition,
The second embodiment has the same configuration as the first embodiment except that a magnetic shield 15 is used instead of the magnetic shields 13a and 13b.

In the second embodiment, the air gap 14b is formed in the magnetic shield 15 in an annular shape over a predetermined range in the axial direction A including the intermediate point between the pair of superconducting coils 1a and 1b. 4 are present in the void portion 14b, and the same effect as in the first embodiment can be obtained. Also,
According to the second embodiment, since the gap 14b is formed by reducing the thickness of the magnetic shield 15, the gap 1b is formed.
The magnetic material constituting the magnetic shield 15 is present on the outer peripheral side of 4b, and the leakage magnetic field can be reduced as compared with the first embodiment in which the magnetic material does not exist in the gap 14a at all.

Embodiment 3 In the third embodiment, as shown in FIG. 3, a pair of annular magnetic shields 13a made of a ferromagnetic material such as pure iron and formed in an L-shaped cross section.
13b is an upper end surface of the superconducting coil 1a in a cryogenic region in the vacuum vessel 5 in a symmetrical positional relationship with respect to a plane orthogonal to an axial direction A passing through an intermediate point between the pair of superconducting coils 1a and 1b. It is arranged coaxially with a predetermined gap in the axial direction A so as to cover the outer peripheral surface and to cover the lower end surface and the outer peripheral surface of the superconducting coil 1b. In the third embodiment, the magnetic shields 13a, 13b
Is configured in the same manner as in the first embodiment, except that is disposed in the vacuum vessel 5.

In the third embodiment, the air gap 14a is formed between the magnetic shields 13a and 13b over a predetermined range in the axial direction A including an intermediate point between the pair of superconducting coils 1a and 1b. The same effect as in the first embodiment can be obtained. Further, according to the third embodiment, since the magnetic shields 13a and 13b are provided in the cryogenic region in the vacuum vessel 5, the magnetic shields are provided outside the vacuum vessel 5 in the above embodiment. Compared with the first embodiment, the shield areas of the magnetic shields 13a and 13b are smaller, and the magnetic shields 13a and 13b can be reduced in size. As a result, the device can be reduced in weight and size.

Although the third embodiment is described as being applied to the superconducting magnet device according to the first embodiment, the same effect can be obtained by applying the same to the superconducting magnet device according to the second embodiment. Is obtained.

Embodiment 4 FIG. 4 is a configuration diagram showing a superconducting magnet device according to Embodiment 4 of the present invention. In FIG. 4, a vacuum vessel 5 has a permanent current switch 6 whose outer peripheral wall is formed to have an outer diameter extending into a gap portion 14a, and switches the superconducting magnet circuit after excitation to a closed loop with zero resistance.
Are disposed in the vacuum vessel 5 so as to be located in the voids 14a. The pair of superconducting coils 1 a and 1 b and the permanent current switch 6 are connected by a superconducting wire 7. The other configuration is the same as that of the first embodiment.

In the fourth embodiment, since the permanent current switch 6, which is a device that is liable to cause superconducting breakdown, is disposed in the void portion 14a where there is almost no magnetic field, superconducting breakdown in the permanent current switch 6 does not occur. It is suppressed, and deterioration of characteristics can be prevented.

Embodiment 5 FIG. 5 is a configuration diagram showing a superconducting magnet device according to Embodiment 5 of the present invention. In FIG. 5, a current lead 8 composed of an oxide superconductor or the like is shown.
Is attached to the vacuum vessel 5 so as to extend into the cavity 14a. And a pair of superconducting coils 1a, 1
b and the current switch 6 are connected by a superconducting wire 7.
The other configuration is the same as that of the first embodiment.

In the fifth embodiment, the current lead 8 which is a device whose superconductivity is deteriorated by the magnetic field and is easily damaged by the electromagnetic force is arranged in the void portion 14a where there is almost no magnetic field. Thus, the deterioration of the superconducting characteristics due to the magnetic field and the damage due to the electromagnetic force are suppressed, and the superconducting coil can be stably energized.

Although the fifth embodiment has been described as being applied to the superconducting magnet device according to the first embodiment, the same effect can be obtained by applying it to the superconducting magnet device according to the second embodiment. Is obtained.

Embodiment 6 FIG. FIG. 6 is a configuration diagram showing a superconducting magnet device according to Embodiment 6 of the present invention. In FIG. 6, a cryogenic refrigerator 9 such as a GM refrigerator whose refrigeration capacity is reduced by application of a magnetic field is attached to the vacuum vessel 5 so as to extend into the gap 14a. The pair of superconducting coils 1a and 1b can be simultaneously cooled via the heat transfer member 10 thermally connected to the heat stage 9a of the cryogenic refrigerator 9. The other configuration is the same as that of the first embodiment.

In the sixth embodiment, since the cryogenic refrigerator 9 is disposed in the space 14a where there is almost no magnetic field, the refrigeration capacity of the cryogenic refrigerator 9 can be maintained.

Embodiment 7 FIG. 7 is a configuration diagram showing a superconducting magnet device according to Embodiment 7 of the present invention. In FIG. 7, a pair of cylindrical superconducting coils 1a and 1b are coaxially arranged with a predetermined gap in an axial direction A. Further, a pair of annular magnetic shields 13a and 13b formed of a ferromagnetic material such as pure iron and formed in an L-shaped cross section are orthogonal to an axial direction A passing an intermediate point between the pair of superconducting coils 1a and 1b. Coaxial with a predetermined gap in the axial direction A so as to cover the upper end surface and the outer peripheral surface of the magnetic shield 1a and to cover the lower end surface and the outer peripheral surface of the magnetic shield 1b, respectively, in a symmetrical positional relationship with respect to the plane. It is arranged in. Further, a pair of magnetic shields 13a, 13a is formed by a vacuum sealing plate 11 made of a non-magnetic material such as stainless steel.
b is hermetically connected on the inner peripheral side and the outer peripheral side to form a vacuum vessel 5b for housing the superconducting coils 1a and 1b therein.

In the superconducting magnet device thus constructed, similarly to the superconducting magnet device according to the first embodiment, the superconducting coils 1a and 1b are cooled by a refrigerant such as liquid helium or a cryogenic refrigerator. The pair of superconducting coils 1a and 1b are maintained in a superconducting state with zero resistance, and currents in opposite directions are applied to each of the pair of superconducting coils 1a and 1b to generate a cusp magnetic field. The zero-magnetic-field surface 4 generated between the pair of superconducting coils 1a and 1b forms a pair of magnetic shields 13a and 1a.
It is present in the gap 14a formed between 3b.

Therefore, also in the seventh embodiment, the same effects as in the first embodiment can be obtained. Also,
Since the pair of magnetic shields 13a and 14b constitute a part of the vacuum vessel 5b, the size and weight of the device can be reduced, and the device whose characteristics change due to the influence of the magnetic field, for example, a current lead or a permanent current switch Can be inserted from the part without magnetic material through the vacuum sealing plate 9, and the attachment of the current lead and the permanent current switch can be improved.

In each of the above embodiments, a superconducting magnet device having a pair of superconducting coils 1a and 1b has been described. However, the present invention forms a pair with respect to a plane orthogonal to the axial direction A. The same effect can be obtained by applying the present invention to a superconducting magnet apparatus having a plurality of pairs of superconducting coils arranged geometrically symmetrically. In this case, the air gap may be formed in the magnetic shield so as to correspond to the zero magnetic field surface formed by each pair of superconducting coils. In addition, by adjusting the amount of electricity of each of the plurality of pairs of superconducting coils,
The zero-field planes of each pair of superconducting coils can be matched or changed. Embodiments 3 to 5
It is needless to say that the respective effects can be obtained by combining. Further, in each of the above embodiments, the superconducting coil and the vacuum vessel are described as cylindrical, but the outer diameter of the superconducting coil and the vacuum vessel is not limited to the cylindrical shape, and may be, for example, elliptical. Is also good.

[0031]

Since the present invention is configured as described above, it has the following effects.

According to the present invention, at least a pair of substantially cylindrical superconducting coils are coaxially disposed in a substantially cylindrical vacuum vessel in a symmetrical positional relationship with respect to a plane orthogonal to the axial direction. The superconducting magnet device is arranged such that an annular magnetic shield is disposed so as to surround an outer peripheral side of the superconducting coil, and a current in opposite directions is applied to the pair of superconducting coils to generate a cusp magnetic field. Since the magnetic shield has a gap formed by removing at least a part of the magnetic material in a ring shape over a predetermined range in the axial direction including the zero magnetic field plane, a change in the internal magnetic field distribution and an extreme of the leakage magnetic field are caused. Thus, a superconducting magnet device that achieves weight reduction while minimizing the increase can be obtained.

Further, since the magnetic shield is provided in the vacuum vessel, the size and weight of the device can be reduced.

Further, since the magnetic shield forms a part of the vacuum vessel, the size and weight of the apparatus can be reduced, and the mountability of equipment whose characteristics change due to the influence of a magnetic field can be improved. be able to.

Since the device whose characteristics change due to the influence of the magnetic field is arranged in the gap, the device can be operated stably while suppressing the effect of the magnetic field.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a superconducting magnet device according to Embodiment 1 of the present invention.

FIG. 2 is a configuration diagram showing a superconducting magnet device according to Embodiment 2 of the present invention.

FIG. 3 is a configuration diagram showing a superconducting magnet device according to Embodiment 3 of the present invention.

FIG. 4 is a configuration diagram showing a superconducting magnet device according to Embodiment 4 of the present invention.

FIG. 5 is a configuration diagram showing a superconducting magnet device according to Embodiment 5 of the present invention.

FIG. 6 is a configuration diagram showing a superconducting magnet device according to Embodiment 6 of the present invention.

FIG. 7 is a configuration diagram showing a superconducting magnet device according to Embodiment 7 of the present invention.

FIG. 8 is a configuration diagram showing a conventional superconducting magnet device.

[Explanation of symbols]

1a, 1b superconducting coil, 4 zero magnetic field plane, 5, 5a, 5
b Vacuum container, 6 permanent current switch (equipment), 8 current lead (equipment), 9 cryogenic refrigerator (equipment), 13
a, 13b, 15 Magnetic shield, 14a, 14b Air gap, A axis direction.

Claims (4)

[Claims] At least one pair of substantially cylindrical superconducting coils are coaxially disposed in a substantially cylindrical vacuum vessel in a symmetrical positional relationship with respect to a plane orthogonal to the axial direction, and are formed of an annular magnetic material made of a magnetic material. In a superconducting magnet device in which a shield is disposed so as to surround the outer peripheral side of the superconducting coil and generates a cusp magnetic field by supplying currents in opposite directions to the pair of superconducting coils, the magnetic shield comprises: A superconducting magnet device having a void formed by removing at least a part of the magnetic material in a ring shape over a predetermined range including the zero magnetic field plane in the axial direction. 2. The superconducting magnet device according to claim 1, wherein said magnetic shield is provided in said vacuum vessel. 3. The superconducting magnet device according to claim 1, wherein the magnetic shield forms a part of the vacuum vessel. 4. The device according to claim 1, wherein a device whose characteristics change under the influence of a magnetic field is arranged in said gap.
The superconducting magnet device according to claim 3.