JP2000114028A - Refrigerator-cooled superconducting magnet device for single-crystal pulling equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refrigerator-cooled superconducting magnet device which does not use such a related component that becomes a hindrance when a single- crystal pulling equipment is installed above the magnet device. SOLUTION: A refrigerator-cooled superconducting magnet device is provided with a vacuum vessel 10 which is arranged around a single-crystal growing device and houses superconducting coils 11a and 11b for impressing a magnetic field upon molten silicon, and cryogenic refrigerators 12a and 12b for cooling the coils 11a and 11b. The refrigerators 12a and 12b, current introducing terminals, and evacuating valves are arranged under the vacuum vessel 10. Since the superconducting magnet device is constituted in the above-mentioned way, the device has a simple structure and can generate cusp type magnetic fields that can tolerate thermal stresses.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerator cooled superconducting magnet apparatus, and more particularly to a refrigeration apparatus suitable for a magnetic field generator for applying a magnetic field to molten silicon in a single crystal growth apparatus for producing a single crystal semiconductor from molten silicon. The present invention relates to a machine-cooled superconducting magnet device.

[0002]

2. Description of the Related Art In the production of silicon single crystals, there is known a Czochralski method (CZ method) in which polycrystalline silicon is melted and grown into a single crystal seed crystal. In this method, since the molten silicon is melted in the crucible, thermal convection is generated and the quality of the generated single crystal may be deteriorated.
Therefore, a method of applying a magnetic field to molten silicon and suppressing convection by electromagnetic braking has been known for the purpose of improving the quality of the generated single crystal. This method is called a magnetic field application type Czochralski method (MCZ method).

[0003] As a method of applying a magnetic field, three types of a vertical magnetic field method, a horizontal magnetic field method, and a cusp magnetic field are known, and one example thereof is disclosed in JP-A-8-188493. As a means for applying a magnetic field, a normal conducting magnet and a superconducting magnet are used. However, the normal conducting magnet is heavy in weight because the use of an iron core is indispensable, and requires enormous power and cooling water. On the other hand, a superconducting magnet usually requires liquid helium cooling, so that the device becomes complicated and large. In addition, the handling of liquid helium is complicated and requires the skill of an operator. In addition, liquid helium must be replenished, and liquid helium costs are high.

[0004]

By the way, a superconducting magnet (helium-free superconducting magnet) apparatus using an oxide superconducting current lead and conducting and cooling a superconducting coil only with a refrigerator is provided. This type of superconducting magnet device is called a refrigerator-cooled superconducting magnet device, and its operation is simple.
It is considered suitable for a silicon single crystal pulling apparatus.

[0005] However, there are restrictions on the location of the refrigerator for cooling. This is because the superconducting magnet device is combined with a lifting device, so if a refrigerator or a current introduction terminal is mounted on the upper surface side of the superconducting magnet device, these members will be easier for the worker to perform when lifting. -This is because safety is impaired, or the lifting device also imposes restrictions on the configuration.

Therefore, a refrigerator-cooled superconducting magnet device is
It is preferable that the upper surface side be completely flat and no related members be present, in order to improve workability and safety and to improve the degree of freedom in designing the lifting device.

[0007] Apart from the above points, when a refrigerator is mounted on the upper surface side of the superconducting magnet device, there are the following problems in terms of maintenance.

[0008] The refrigerator is mounted in the following order. 1. Install the refrigerator in the installation space and fix it tightly by bolting. 2. The mounting space is pulled by a vacuum pump and stopped as a vacuum. 3. Start operation and cool the superconducting magnet.

The replacement of the refrigerator during maintenance is performed in the following order while the superconducting magnet is kept cooled. 1. Helium is introduced into the mounting space, and the inside of the mounting space is made a helium atmosphere. 2. Quickly remove the refrigerator, close the lid, or flow a large amount of helium gas so that the helium in the mounting space does not escape. 3. Quickly install another new refrigerator.

[0010] If the above operation is not performed quickly and swiftly, air containing moisture will enter. This is because helium is lighter than air and thus easily escapes from the mounting space, and instead air easily enters. In this case, it is considered that dew condensation occurs in a cooled portion in the mounting space, ice is interposed at the interface of the heat transfer portion, the cooling efficiency is remarkably reduced, and the replacement may be repeated.

[0011] Therefore, the object of the present invention is to provide,
It is an object of the present invention to provide a refrigerator-cooled superconducting magnet device having no device-related components that hinder the installation of the lifting device.

Another object of the present invention is to provide a refrigerator-cooled superconducting magnet device that can safely and reliably mount and remove the refrigerator body to and from the device while keeping the inside of the vacuum vessel at an extremely low temperature.

[0013]

SUMMARY OF THE INVENTION The present invention relates to a refrigerator cooled superconducting magnet apparatus for applying a magnetic field to molten silicon in a single crystal growth apparatus for producing a single crystal semiconductor from molten silicon. A vacuum vessel containing a superconducting coil for generating the magnetic field, and a cryogenic refrigerator for cooling the superconducting coil, wherein the cryogenic refrigerator, a current introduction terminal, and vacuum exhaust are provided. The valve is arranged at a lower portion of the vacuum vessel.

The cryogenic refrigerator is a two-stage cooling type having a first stage and a second stage refrigeration stage, and the superconducting coil is supported by a coil-cooling heat conductor as a winding frame in the vacuum vessel. The lower surface of the vacuum vessel is provided with an insertion port for inserting the cryogenic refrigerator, and extends from the insertion port into the vacuum vessel to house the cryogenic refrigerator in a sealed state. A sleeve for fixing the cryogenic refrigerator is provided at the distal end with a heat transfer member that is in contact with the cold head of the second refrigeration stage of the cryogenic refrigerator. An intermediate heat transfer member that is in contact with the cold head of the first refrigeration stage is provided, and the cryogenic refrigerator main body is configured to be removable while the inside of the vacuum vessel is in a cryogenic state.

The vacuum vessel has a double cylindrical structure capable of surrounding the periphery of the single crystal growth apparatus, the coil cooling heat conductor has a cylindrical shape, and the superconducting coil and the coil cooling The heat conductor is housed in a double-cylindrical heat radiation shield disposed in the vacuum vessel together with the upper portion of the sleeve, and a stress caused by heat shrinkage between the heat radiation shield and the sleeve. In order to prevent the generation, the intermediate heat transfer member of the sleeve and the heat radiation shield are connected by a flexible heat transfer body made of a mesh wire or a multilayer plate.

In order to prevent stress from being generated due to thermal contraction between the coil cooling heat conductor and the sleeve, a connecting portion provided between the tip heat transfer member of the sleeve and the coil cooling heat conductor. Are connected by a multilayer plate-like flexible heat transfer body.

[0017] The coil cooling heat conductor is provided with a bracket having a supported plate at intervals in a circumferential direction thereof, and the heat radiation shield body penetrates the bottom portion of the vacuum vessel inside the vacuum vessel. A vertical load support for supporting the superconducting coil and the coil cooling heat conductor while being in surface contact with the supported plate of the bracket is provided, and the supported plate of the bracket is attached to the vertical load support. The bending load generated in the vertical load supporting body due to the heat shrinkage of the superconducting coil and the heat conductor for cooling the coil is reduced.

A plurality of horizontal load supports are provided on the side wall of the vacuum vessel, penetrating the side wall in a sealed state, and penetrating the heat radiation shield and connected to the heat conductor for cooling the coil. Thereby, the center of the superconducting coil and the center of the vacuum container can be aligned from the outside of the vacuum container, and the horizontal load support can be rotated at a connection portion with the coil cooling heat conductor. To absorb the dimensional difference due to heat absorption between the coil and the vacuum vessel.

The superconducting coil comprises two coils for applying a cusp-shaped magnetic field to the molten silicon, and each coil is concentric with the center of the vacuum vessel above and below the coil cooling heat conductor. It is wound around.

A current lead made of an oxide superconductor for supplying a current to the superconducting coil; one end of the current lead having a thermal anchor on the coil cooling heat conductor;
The other end of the current lead has a thermal anchor on the heat radiation shield, and at least one end of the current lead is a free end.

[0021] A magnetic shield may be provided on the outer periphery of the vacuum vessel to reduce the leakage magnetic field at the outer periphery.

It is preferable that at least two cryogenic refrigerators are arranged adjacent to each other or at positions diametrically opposed to each other in the vacuum vessel.

[0023]

In the present invention, in order to make the upper surface of the superconducting magnet device completely flat, a structure is adopted in which the refrigerator is mounted from below, and a current introduction terminal, a vacuum exhaust valve, etc. are also mounted in the lower portion of the superconducting magnet device. .

In order to realize such a structure, the load of the superconducting coil is supported from below and from the side, and a mechanism is provided to prevent the stress from being generated on the load support due to the heat shrinkage of the heat radiation shield. . Further, in the cooling stage of each stage of the refrigerator and the heat transfer member of the heat conductor for cooling the coil and the heat radiation shield, a structure for preventing the generation of stress due to the heat shrinkage of the heat conductor for cooling the coil and the heat radiation shield. And On the other hand, the installation of the refrigerator has a structure that enables replacement without returning the superconducting magnet device to room temperature when performing replacement work for maintenance.

As described above, the upper portion of the refrigerator-cooled superconducting magnet device is completely flat, and the workability and safety can be improved. In addition, measures are taken against thermal stress in the internal structure of the refrigerator-cooled superconducting magnet device, and a refrigerator-cooled superconducting magnet device with high reliability is obtained. In addition, since the refrigerator can be taken out in the cryogenic state of the superconducting magnet device, the superconducting magnet device main body does not need to be heated and cooled again with the replacement and maintenance of the refrigerator, thereby improving the operation rate of the device. Further, since a magnetic shield mechanism for reducing the leakage magnetic field can be installed, the influence of the surrounding magnetic field is reduced, and the safety against the magnetic field is improved.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. A refrigerator-cooled superconducting magnet device according to this embodiment is arranged around a single crystal growth device (not shown), and has a sealed vacuum vessel 10 containing superconducting coils 11a and 11b for generating a magnetic field.
And two cryogenic refrigerators (hereinafter referred to as refrigerators) 12a and 12b arranged inside the vacuum vessel 10 from the lower surface side for cooling the superconducting coils 11a and 11b. On the lower surface side of the vacuum vessel 10, a current introduction terminal 2 is further provided.
1 and a vacuum exhaust valve 22 are provided. Vacuum exhaust valve 2
2 is used when the inside of the vacuum container 10 is evacuated.
A compressor for compressing and supplying and circulating helium gas as a refrigerant is connected to the refrigerators 12a and 12b. Briefly, the illustrated refrigerators 12a, 12a
b includes a motor for switching a rotary valve for switching the introduction and discharge of helium gas, and a motion conversion mechanism connected to a displacer to change the reciprocating motion to a rotary motion and to set upper and lower limits of the reciprocating motion. ing.
The details are disclosed in JP-B-63-53469, so that illustration and description are omitted here. Superconducting coil 11
The coils 11a and 11b are supported in the vacuum vessel 10 by a coil cooling heat conductor 13 as a winding frame. Refrigerator 12a, 1
Since 2b has exactly the same structure, only the refrigerator 12a will be described below.

The refrigerator 12a has a first-stage refrigeration stage 12- having a 50K first-stage cold head 12-11.
This is a two-stage refrigerator having a second stage refrigeration stage 12-2 having 1 and 4K second stage cold heads 12-21. The freezing stages 12-1 and 12-2 are housed in the sleeve 23 in a sealed state.

The sleeve 23 is fixed to the edge of the insertion port 10-1 provided on the bottom of the vacuum vessel 10 by welding or the like. A flange 10-2 is provided around the insertion port 10-1, and the head of the refrigerator 12a is attached to the flange 10-2 with bolts in a sealed state. As a result, the internal space of the sleeve 23 is completely partitioned from the internal space of the vacuum vessel 10, and is completely sealed from the outside. A sleeve 23 has a second-stage cold head 12- of a second-stage refrigeration stage 12-2 at its tip.
A first heat transfer member 23-1 is provided for surface contact with the first refrigeration stage 21, and a first refrigeration stage 12-1 is provided at an intermediate portion thereof.
The intermediate heat transfer member 23-2 for contacting the second stage cold head 12-21 is provided.

The material of the sleeve 23 is preferably made of stainless steel, and the material of the tip heat transfer member 23-1 and the intermediate heat transfer member 23-2 is preferably made of copper, but is not limited thereto. The distal end heat transfer member 23-1 of the sleeve 23 is located near the connection portion 13-1 provided on the coil cooling heat conductor 13. Then, the tip heat transfer member 23-1 and the connection portion 13-1
Are connected by a multilayer plate-shaped heat transfer member 14 having flexibility. As a result, generation of stress due to thermal contraction between the coil cooling heat conductor 13 and the sleeve 23 is prevented.

The vacuum vessel 10 has a double cylindrical structure capable of surrounding the periphery of the single crystal growing apparatus, and the coil cooling heat conductor 13 is also formed in a cylindrical shape. That is, the single crystal growth apparatus is arranged in a space formed inside vacuum chamber 10. Since this single crystal growth apparatus is the same as the conventional one, its illustration and description are omitted. The superconducting coils 11a and 11b are two coils for applying a cusp-shaped magnetic field to the molten silicon in the crucible of the single crystal growth device. Superconducting coil 1 consisting of these two coils
1 a and 11 b are wound so as to be concentric with the center of the vacuum vessel 10 above and below the coil cooling heat conductor 13.

Further, two superconducting coils 11a, 11b
The heat conductor 13 for cooling the coil is housed in a double-cylindrical heat radiation shield 15 arranged in the vacuum vessel 10 together with the upper part of the sleeve 23. The heat radiation shield body 15 is for preventing radiation heat from entering. The sleeve 23 extends upward through the bottom of the heat radiation shield 15. In order to prevent the generation of stress due to heat shrinkage between the heat radiation shield body 15 and the sleeve 23, the space between the intermediate heat transfer member 23-2 of the sleeve 23 and the heat radiation shield body 15 is formed by a mesh wire or a multilayer plate. They are connected by flexible heat transfer bodies 25a and 25b.

In FIG. 4, two superconducting coils 11
a, 11b, the coil-cooling heat conductor 13, and the heat radiation shield 15 are provided on the bottom of the vacuum vessel 10 at a plurality of vertical load supports 1 provided at circumferential intervals.
6 is supported. More specifically, the coil cooling heat conductor 13 is provided with a bracket 13-2 having a supported plate 13-2a that extends in the horizontal direction at intervals in the circumferential direction. The vertical load support 16 is provided at the bottom of the vacuum vessel 10, penetrates the bottom of the heat radiation shield 15, makes surface contact with the supported plate 13-2 a of the bracket 13-2, and superconducting coils 11 a and 11 b. And the heat conductor 13 for cooling the coil. In particular, the contact portion of the upper end of the vertical load support 16 with the supported plate 13-2a is provided with a metal member having a small coefficient of friction with respect to the supported plate 13-2a, for example, a plate member 16-1 such as Teflon. Is provided. Thereby, the supported plate 13-2a of the bracket 13-2 is configured to be slidable with respect to the vertical load support 16, and the vertical load is generated by the thermal contraction of the superconducting coils 11a and 11b and the coil cooling heat conductor 13. The bending load generated on the support 16 is reduced. Although not shown in detail, the heat radiation shield 15 is supported at its bottom by a support plate 16-2 provided at an intermediate portion of the vertical load support 16. The heat radiation shield 15 is slidable between the support plate 16-2 and the heat radiation shield 15 with a material having a small coefficient of friction in the same manner as described above.

On the side wall of the vacuum vessel 10, a horizontal load support 17 penetrating the side wall in a sealed state and penetrating the heat radiation shield 15 and connected to the coil cooling heat conductor 13 is formed. A plurality are provided at intervals in the direction. The horizontal load support 17 includes a support strap 17-1 formed of a resin endless belt, a screw shaft 17-2 connected to one end of the support strap 17-1,
A nut 1 screwed into a screw portion protruding outside from the side wall of the vacuum vessel 10 at the opposite end of the screw shaft 17-2.
7-3. The other end of the support strap 17-1 is rotatably supported by the coil cooling heat conductor 13 in a rotatable state.
It is rotatably supported by 7-2. This absorbs the dimensional difference due to the thermal contraction of the vacuum vessel 10, the superconducting coils 11a and 11b, and the coil cooling heat conductor 13. The space between the screw shaft 17-2 and the side wall of the vacuum vessel 10 is sealed. A screw portion and a nut 17-3 projecting from the side wall of the vacuum vessel 10 to the outside are provided with an openable / closable lid 10-.
3 is covered. Screw shaft 17-2 and nut 17-
3 denotes superconducting coils 11a, 1
This is for enabling alignment between the center of 1b and the center of the vacuum vessel 10. For this purpose, the superconducting coil 1
The heat shrinkage of the heat conductors 1a, 11b and the coil cooling heat conductor 13 is calculated in advance, and the superconducting coils 11a, 11b are calculated.
The nut 17-3 is loosened so that the b and the coil cooling heat conductor 13 can be displaced by this heat shrinkage.

In FIG. 1, a magnetic shield 26 is provided on the outer periphery of the vacuum vessel 10 so that the leakage magnetic field at the outer periphery can be reduced. In addition, legs 10-4 are provided at a plurality of locations on the bottom of the vacuum vessel 10 in order to secure a space for replacement work accompanying maintenance of the refrigerators 12a and 12b.

Although one refrigerator may be used, two
In the case of disposing one vacuum container, as shown in FIG.
It is preferable to arrange them at positions facing each other in the diametrical direction or adjacent to each other.

In FIG. 5, the heat conductor 13 for cooling the coil
Is provided with a current lead 27 made of an oxide superconductor for supplying a current to the superconducting coils 11a and 11b.
One end of the current lead 27 has a thermal anchor on the heat conductor 13 for cooling the coil, and the other end of the current lead 27 has a thermal anchor on the heat radiation shield 15. And the current lead 27
At least one end is a free end. The current lead 27
It is connected to the current introduction terminal 21 shown in FIG.

Next, each of the above components will be described.

The vacuum vessel 10 is a vessel for suppressing a rise in the temperature of the superconducting coil by vacuum insulation, and is made of stainless steel, aluminum or the like. The vacuum container 10
Superconducting coils 11a, 11b, heat radiation shield body 15,
It serves as a fulcrum for supporting loads such as refrigerators. Vacuum container 10
Can be formed by a welding structure or a flange structure. In the case of a flange structure as in this embodiment, it can be easily disassembled. In the case of a welding structure, the current introduction terminal 2
1. It is preferable to provide a partly removable box so that only the part where the vacuum exhaust valve 22 is installed can be maintained.

The superconducting coils 11a, 11b are formed in the metal-based superconducting conductor (NbTi conductor, Nb ₃ Sn conductors, etc.) and oxide superconductor (Bi-based conductor, Y-based conductor, Nd-based conductor, etc.) superconducting wire . Superconducting coil 11a, 1
Reference numeral 1b denotes a split type in which two coils wound in a cylindrical shape are installed at an interval in the vertical direction, and currents in opposite directions are applied to each coil to form a cusp-shaped magnetic field. The winding portion may be impregnated with a resin such as epoxy to improve superconducting stability.

From the current introduction terminal 22 to the superconducting coil 11
a, current lead 2 as a means for supplying current to 11b
For 7, a current lead made of an oxide superconductor was used.
A current is supplied to the superconducting coils 11a and 11b while reducing the heat penetrating into the heat radiation shield body 15. The shape is
The shape may be cylindrical, linear, angular, or the like. As a material,
An oxide-based superconductor such as Bi-based or Y-based is used. At both ends of the current lead 26, a bonding layer of silver or the like is provided by plating, thermal spraying, or the like to facilitate the solder bonding of the electrodes. As a result, a current lead having a small contact resistance and a small Joule heat can be obtained. Electrodes are joined to both ends, one end of which has a thermal anchor in the superconducting coil temperature range, and the other end has a thermal anchor in the heat radiation shield temperature range. In this case, at least one end is a free end to prevent stress from being applied to the superconductor due to thermal stress or the like. Further, the strength of the current lead 27 can be improved by using an epoxy resin, a GFRP member or the like in combination.

As the refrigerators 12a and 12b, use is made of a highly reliable small refrigerator such as a regenerative two-stage Gifford McMahon refrigerator. When a two-stage refrigerator is applied as in this embodiment, the first-stage cold head 12-11 is connected to the heat radiation shield body 15 via a heat transfer member, and the first-stage refrigeration stage 12-11 is connected. Heat radiation shield body 15 at -1
And the second stage cold head 12-21 is coupled to the connection portion 13-1 via the heat transfer member, and the superconducting coils 11a and 11b can be cooled by the second stage freezing stage 12-2.

The coil cooling heat conductor 13 is formed of a material having a high heat conductivity such as copper or aluminum. In the case of using a material having poor thermal conductivity, for example, stainless steel or FRP, a foil-like high heat conductive material such as copper or aluminum is attached to the surface thereof.

The multilayer plate-like heat transfer member 14 is made of a material having a large thermal conductivity, for example, a laminate of a copper plate and a high-purity aluminum plate. As an example, it is assumed that a laminate of two copper plates each having a thickness of 1 mm and a high-purity aluminum plate is bent into a substantially U shape as illustrated. One end of the multilayer plate-shaped heat transfer member 14 is bolted to the tip end heat transfer member 23-1 of the sleeve 23, and the other end is a connection portion 13-1 of the coil cooling heat conductor 13.
Bolted. When the multilayer plate-shaped heat transfer member 14 having such a laminated structure is used, the time required for cooling is the same as that of the copper-only plate, and the cooling characteristic is lower than that of the copper-only plate when kept at a low temperature (about 4K). Get better. The number of layers of the copper plate and the high-purity aluminum plate is not limited to two, but it is preferable that the total thickness be small. Furthermore,
The multilayer plate-shaped heat transfer member 14 can also be composed of a flat net conductor, a single-layer plate, a wire, or the like.

The heat radiation shield body 15 is configured such that heat radiation from the inner surface of the vacuum vessel 10 is directly transmitted to the superconducting coils 11a and 11b.
The superconducting coil is provided so as to surround the superconducting coil so that the temperature does not rise. Heat radiation shield 15
Is connected to a first stage call head 12-11 of a first stage refrigeration stage 12-1 of the refrigerator via a heat transfer member. Also in this case, the thermally favorable joining is realized by the flexible heat transfer members 25a and 25b so that excessive heat stress is not generated in the cylinder of the refrigerator due to the heat shrinkage. The heat radiation shield 15 is made of a material having excellent heat transfer characteristics, such as copper and aluminum. In order to reduce the emissivity of the surface, mirror polishing or plating may be provided. In order to enhance the effect of reducing heat radiation,
Multi-layer insulation (super insulation) can be used together. When mechanical strength is required, stainless steel can be used as the strength member and copper or aluminum can be used as the heat member. Further, the superconducting coils 11a, 11
In order to prevent quench of b or eddy current due to rapid magnetic field fluctuation, a slit may be partially formed in the length direction.
In this case, the width of the slit is set to several mm in consideration of the influence of heat radiation.

The vertical load support 16 is a member that supports the superconducting coils 11a and 11b, the coil cooling heat conductor 13, and the heat radiation shield 15, and has excellent heat insulation performance while maintaining mechanical strength. Need to be. As the material, for example, GFRP, CFRP, stainless steel, etc. can be applied. As an example of the support structure, a configuration is known in which a superconducting coil is supported from a vacuum vessel by a plurality of pipe-shaped GFRP materials. This pipe-shaped GFR
The P material takes a heat radiation shield body and an anchor at an intermediate portion to reduce heat penetration by conduction. In the present embodiment, a plurality of pipe-shaped vertical load supports 16 are provided at the bottom of the vacuum vessel 10 at intervals in the circumferential direction to support the superconducting coils 11a and 11b insulated. At the interface between the bracket 13-2 and the supported plate 13-2a, the bracket 13-2 is vertically constrained, but is free to move in the horizontal direction (radial direction), so that the superconducting coils 11a and 11b, The deformation of the vertical load support 16 due to the thermal contraction of the heat conductor 13 can be prevented.

The horizontal load support 17 is made of a material such as a cylindrical or belt-shaped material which is difficult to conduct heat by GFRP, CFRP or the like. The support strap 17-1 is rotatably supported at both ends, but may be configured so that at least only the connection with the coil cooling heat conductor 13 is rotatable.

The sleeve 23 is a member fixed to the vacuum vessel 10 and for mounting a refrigerator. An end heat transfer member 23-1 and an intermediate heat transfer member 23-2 to which each stage of the two-stage cooling refrigerator can be thermally bonded are provided. The sleeve 23 is formed of a vacuum-tight member, and can maintain the vacuum of the vacuum container 10 even when the refrigerator is removed.

The flexible heat transfer bodies 25a and 25b can be composed of a flat net conductor, a single-layer board, a multilayer board, a wire or the like. The material is
A heat conductive good conductor such as copper or aluminum is used.

In addition to the above components, a magnetic shield 26 made of a ferromagnetic material such as iron is provided on the outer side (upper and lower surfaces, outer peripheral surface, or both) of the vacuum vessel 10 so that the peripheral part of the vacuum vessel 10 can be provided. The leakage magnetic field to the power supply can be reduced.

The installation of the refrigerator is performed in the following order. 1. The refrigerator is installed on the sleeve 23 and is airtightly fixed by bolting. 2. The inside of the sleeve 23 is pulled by a vacuum pump and stopped as a vacuum. 3. Start operation and cool the superconducting magnet.

The replacement of the refrigerator due to the maintenance is performed in the following order while the superconducting coils 11a and 11b are cooled. 1. Helium is introduced into the sleeve 23 to make the inside of the sleeve 23 a helium atmosphere. 2. Quickly remove the refrigerator and close the lid to prevent the helium in the sleeve 23 from escaping. 3. Quickly install another new refrigerator.

Since the helium gas has a small specific gravity, it is difficult for the helium gas to escape from the sleeve 23 and accumulates therein.

With the above configuration, it is possible to provide a refrigerator-cooled superconducting magnet device which is simple in structure, resistant to thermal stress, lightweight and compact, easy to operate, and highly suitable for the magnetic field application type Czochralski method. . INDUSTRIAL APPLICABILITY The refrigerator-cooled superconducting magnet apparatus according to the present invention is suitable for generating a cusp-type magnetic field as a magnetic field source in a silicon single crystal pulling apparatus by a Czochralski method using a magnetic field.

[0054]

The refrigerator-cooled superconducting magnet device according to the present invention has a completely flat upper portion, and can improve workability and safety. In addition, thermal stress countermeasures are taken in the internal structure of the device, resulting in a refrigerator-cooled superconducting magnet device with high reliability. In addition, since the refrigerator can be taken out in the cryogenic state of the superconducting magnet device, the superconducting magnet device main body does not need to be heated and cooled again with the replacement and maintenance of the refrigerator, thereby improving the operation rate of the device. Further, since a magnetic shield mechanism for reducing the leakage magnetic field can be installed, the influence of the surrounding magnetic field is reduced, and the safety against the magnetic field is improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a refrigerator-cooled superconducting magnet device according to an embodiment of the present invention.

FIG. 2 is a bottom view of the device of FIG.

FIG. 3 is a cross-sectional view illustrating a mounting structure of the refrigerator in FIG. 1;

FIG. 4 is a cross-sectional view illustrating a vertical load support and a horizontal load support according to the present invention.

FIG. 5 is a cross-sectional view showing a current lead installation structure according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Vacuum container 10-1 Insertion opening 10-2 Flange 10-4 Leg 11a, 11b Superconducting coil 12a, 12b Refrigerator 12-1 First stage freezing stage 12-2 Second stage freezing stage 12-11 First-stage cold head 12-21 Second-stage cold head 13 Heat conductor for coil cooling 13-1 Connection part 14 Multi-layer plate-like heat transfer member 15 Heat radiation shield 16 Vertical load support 17 Horizontal load support 23 Sleeve 23-1 Tip heat transfer member 23-2 Intermediate heat transfer member 26 Magnetic shield 27 Current lead

Claims (10)

[Claims] 1. A refrigerator cooled superconducting magnet apparatus for applying a magnetic field to said molten silicon in a single crystal growth apparatus for producing a single crystal semiconductor from molten silicon, wherein said magnetic field is disposed around said single crystal growth apparatus. And a cryogenic refrigerator for cooling the superconducting coil, wherein the cryogenic refrigerator, a current introduction terminal, and a vacuum exhaust valve are provided at a lower portion of the vacuum container. A refrigerator cooled superconducting magnet device for a single crystal pulling device, wherein the superconducting magnet device is arranged. 2. The refrigerator according to claim 1, wherein said cryogenic refrigerator is a two-stage cooling type having a first stage and a second stage. The vacuum vessel is supported by a coil-cooling heat conductor as a winding frame.A lower surface of the vacuum vessel is provided with an insertion port for inserting the cryogenic refrigerator, and the vacuum vessel is inserted through the insertion port. A sleeve extending inward to accommodate the cryogenic refrigerator in a sealed state is fixed, and the sleeve has a distal end contacting a cold head of a second refrigeration stage of the cryogenic refrigerator at the distal end. A heat member is provided, and an intermediate heat transfer member that is in contact with a cold head of a first refrigeration stage of the cryogenic refrigerator is provided at an intermediate portion thereof. Detachable as is A refrigerator-cooled superconducting magnet device for a single crystal pulling device, characterized by having a simple structure. 3. The refrigerator according to claim 2, wherein the vacuum vessel has a double cylindrical structure capable of surrounding a periphery of the single crystal growing apparatus, and the heat conduction for cooling the coil. The body has a cylindrical shape, and the superconducting coil and the coil-cooling heat conductor, together with the upper part of the sleeve, are housed in a double-cylindrical heat radiation shield disposed in the vacuum vessel, In order to prevent the occurrence of stress due to thermal contraction between the heat radiation shield and the sleeve, the flexibility between the intermediate heat transfer member of the sleeve and the heat radiation shield by a mesh wire or a multilayer plate is used. A refrigerator-cooled superconducting magnet device for a single crystal pulling device, which is connected by a heat transfer body. 4. The refrigerator-cooled superconducting magnet device according to claim 2, wherein the tip transmission of the sleeve is performed to prevent stress from being generated due to thermal contraction between the coil cooling heat conductor and the sleeve. A refrigerator-cooled superconducting magnet device for a single crystal pulling device, wherein a heat member and a connecting portion provided on the coil cooling heat conductor are connected by a multilayer plate-like flexible heat conductor. 5. The refrigerator-cooled superconducting magnet device according to claim 3, wherein the coil cooling heat conductor is provided with a bracket having a supported plate at intervals in a circumferential direction of the coil cooling heat conductor. A vertical load support for supporting the superconducting coil and the coil cooling heat conductor while penetrating the heat radiation shield body and making surface contact with the supported plate of the bracket is provided at the bottom of the container. A bending load generated in the vertical load support by thermal contraction of the superconducting coil and the coil cooling heat conductor, wherein the supported plate of the bracket is slidable with respect to the vertical load support. A refrigerator cooled type superconducting magnet device for a single crystal pulling device, wherein the superconducting magnet device is adapted to reduce the temperature. 6. The refrigerator-cooled superconducting magnet device according to claim 5, wherein the coil cooling member is penetrated by penetrating the side wall of the vacuum vessel in a sealed state and penetrating the heat radiation shield. By providing a plurality of horizontal load supports connected to a heat conductor, the center of the superconducting coil and the center of the vacuum container can be aligned from the outside of the vacuum vessel, and the horizontal load support is provided. Is
A refrigerator-cooled superconducting magnet device for a single crystal pulling device, which is rotatably supported at a connection portion with the coil cooling heat conductor. 7. The refrigerator-cooled superconducting magnet device according to claim 2, wherein said superconducting coil comprises two coils for applying a cusp-shaped magnetic field to said molten silicon, and each coil is used for cooling said coil. A refrigerator-cooled superconducting magnet device for a single crystal pulling device, which is wound so as to be concentric with the center of the vacuum vessel above and below a heat conductor. 8. The refrigerator-cooled superconducting magnet device according to claim 3, further comprising a current lead made of an oxide superconductor for supplying a current to the superconducting coil, and one end of the current lead for cooling the coil. A refrigeration system for a single crystal pulling apparatus, wherein a heat anchor is provided on a heat conductor, the other end of the current lead is provided with a heat anchor on the heat radiation shield, and at least one end of the current lead is a free end. Machine superconducting magnet device. 9. The refrigerator according to claim 1, wherein a magnetic shield is provided on an outer periphery of the vacuum vessel so that a leakage magnetic field at the outer periphery can be reduced. Refrigerator-cooled superconducting magnet device for pulling device. 10. The refrigerator-cooled superconducting magnet device according to claim 1, wherein at least two cryogenic refrigerators are provided.
A refrigerator-cooled superconducting magnet device for a single crystal pulling device, which is arranged adjacent to each other or at a position facing each other in the diameter direction of the vacuum vessel.