KR20050007498A - Superconducting magnet for generating horizontal magnetic field using bended circle or ellipse-shaped coils - Google Patents

Abstract

PURPOSE: A superconductive magnet device for generating longitudinal magnetic field using crooked shaped circular or oval superconductive coils is provided to distribute a magnetic field effectively and to facilitate a manufacturing operation of the magnet device. CONSTITUTION: A superconductive magnet device for generating longitudinal magnetic field includes a pair of or more than a pair of superconductive coils and a cryostat(21). The superconductive coils are implemented in the cryostat to face one another to generate the longitudinal magnetic field. The longitudinal magnetic field is generated in a magnetic field use space(S) in the cryostat. The superconductive coils are made to have a crooked and circular or oval shape(E,E1,E1',E2,E2') to improve a longitudinal magnetic field characteristic in the magnetic field use space.

Description

SUPERCONDUCTING MAGNET FOR GENERATING HORIZONTAL MAGNETIC FIELD USING BENDED CIRCLE OR ELLIPSE-SHAPED COILS}

The present invention relates to a coil shape suitable for systems requiring a horizontal magnetic field, such as a single crystal growth apparatus, and more particularly to an improvement in a superconducting coil that generates a horizontal magnetic field. Superconducting coils that generate horizontal magnetic fields include saddle coils and solenoid coils, and the most effective coil that reduces magnetic field loss is a saddle coil. However, the saddle coil has a weak point in terms of magnetic force, and has a lot of difficulties in manufacturing. On the other hand, the solenoid coil has the advantage of easy manufacturing, while the loss of the magnetic field has a big disadvantage. In addition, the superconducting coil has to be located in the low temperature container due to the characteristics of the superconducting coil. In the case of the solenoid type coil, the low temperature container has a disadvantage. The present invention is to compensate for the shortcomings of both types of coils.

There are many technical fields that require horizontal magnetic fields. The most representative of them is a single crystal growth apparatus. The magnetic field was not required for the 8-inch single crystal growth device, but the 12-inch single crystal growth device essentially required the magnetic field. That is, a superconducting electromagnet is essential in the 12-inch wafer single crystal growth apparatus to suppress the migration of the dissolved oxygen from the surface of the crucible to the single crystal. The most effective magnetic field for the single crystal growth apparatus is known as the horizontal magnetic field.

First, a conventional technique for generating a horizontal magnetic field such as a single crystal growth apparatus will now be described with reference to FIGS. 1 to 5.

1 is a partial cross-sectional view of a single crystal growth apparatus according to the first conventional technology for generating a horizontal magnetic field, FIG. 2 is a superconducting magnet device for generating a horizontal magnetic field according to the second prior art using a solenoid coil, and FIG. 3 is a saddle type A superconducting magnetic device for generating a horizontal magnetic field according to a third prior art using a coil, and FIG. 4 is a superconducting magnetic device for generating a horizontal magnetic field according to a fourth prior art using two or more pairs of solenoid coils. FIG. 5 is a view of four solenoid type superconducting coils positioned in a low temperature container in the fourth conventional superconducting magnet device.

First, the single crystal growth apparatus according to the first conventional technology for horizontal magnetic field generation in Japanese Patent Application Laid-open No. Hei 10-139599, as shown in Fig. 1, is a device capable of easily converting bore dimensions, magnetic field centers, and transverse and seed fields. For example, a single crystal material 4 for semiconductors such as silicon is dissolved in a crucible 2 by a heater 3, and a superconducting magnet is disposed outside the growth furnace 1 in which the crucible is embedded. In a superconducting magnet for a single crystal growth apparatus in which a single crystal (9) is grown from the molten semiconductor single crystal material by applying a magnetic field, the superconducting magnet each includes two superconducting coils (6a, 6b) deposited in liquid refrigerant facing each other. Built in separate cryostats (5a, 5b), the direction of the magnetic field where each superconducting coil is generated is transverse to the growth direction (8) of the growth path, and is installed between each cryogenic vessel It is characterized in that the space is freely adjustable by the support 7.

On the other hand, the second conventional technology is configured in one doughnut form without separately installing the above cryogenic container is shown in FIG. This penetrates the hollow park barrel 22 in the vertical direction at the center of the upper plate 21a and the lower plate 21b of the donut-type cryogenic container 21 in a vertical direction, and seals both edges of the hollow park cylinder to the upper and lower plates of the vacuum container. Two solenoid type superconducting coils C, which are welded and formed into a hollow field using space (S) at room temperature with an O-ring, and sandwiching a space for using magnetic field (S) in a cryogenic container formed in a donut shape. C ') is installed.

The superconducting coils of the first and second prior arts described above are solenoid type. However, the above-mentioned solenoid coil is easy to manufacture, but as mentioned above, the solenoid coil has a large magnetic field loss, and therefore, a large solenoid coil must be used to reduce the loss. There is a disadvantage that the low-temperature container to accommodate the coil is large.

In order to overcome this problem, saddle coils D and D 'of the third prior art as shown in FIG. 3 have been proposed. This improves the magnetic field generation efficiency in the required space and reduces the size of the cryogenic vessel. However, it is extremely difficult to manufacture a saddle coil, and a large electromagnetic force acts on the superconducting wire forming the coil accompanying ferromagnetic generation. If the superconducting wire has a small movement due to the action of the electromagnetic force, the coil temperature rises due to frictional heat, the superconducting state is damaged, and the transition to the phase conducting state occurs. This is different and has another problem. This is an important problem for a superconducting magnet that must maintain -269 ° C (4 ° K), and a serious problem occurs even if only 1μ error occurs.

To solve this problem, the invention of Japanese Patent Laid-Open No. 2001-203106 has been proposed. In the fourth conventional technique, as shown in FIG. 4, in the cryogenic container 21 having the magnetic field using space S of the hollow park barrel 22 in the vertical direction, the magnetic field using space S is interposed therebetween. At least two or more pairs of solenoid superconducting coils C1, C1 '; C2, C2'; C3, C3 'are provided to face each other.

The fourth prior art solves the above problem to some extent. However, the fourth conventional superconducting coil also has the same problem as the solenoid coil.

In particular, the solenoid coil has a large space occupied, which causes other problems that the load is increased due to the characteristics of the superconducting coil to solve the shield problem.

The present invention is to solve the above problems, to provide a coil that is easy to manufacture while generating a horizontal magnetic field, effectively distributes the magnetic force, and generates a magnetic field efficiently, the size of the low-temperature container does not increase.

1 is a partial cross-sectional view of a single crystal growth apparatus according to the first prior art for generating a horizontal magnetic field.

Figure 2 is a superconducting magnet device for generating a horizontal magnetic field according to the second prior art using a solenoid coil.

Figure 3 is a superconducting magnet device for generating a horizontal magnetic field according to the third prior art using a saddle coil.

Figure 4 is a superconducting magnet device for generating a horizontal magnetic field according to the fourth prior art using two or more pairs of solenoid coils.

FIG. 5 is a view of four solenoid type superconducting coils positioned in a low temperature container in the fourth conventional superconducting magnet device.

6 is a shape of a round or elliptical superconducting coil of a curved shape according to the present invention.

Figure 7 is a view from above of the shape of four bent round or elliptical superconducting coils located in the low temperature container according to the present invention.

8 is a view showing a state in which four bent round or elliptical superconducting coils are located in a low temperature container according to the present invention.

9 is a view showing a state in which six curved round or elliptical superconducting coils according to the present invention are placed in a low temperature container.

10 is an analytical model for comparing the magnetic field effects of the superconducting coil of the fourth prior art and the superconducting coil according to the present invention under the same conditions.

11 is a magnetic field distribution of a solenoid type superconducting coil of the fourth prior art in the analysis model of FIG.

12 is a magnetic field distribution of the curved superconducting coil of the bent form of the present invention in the analysis model of FIG.

Description of the main parts of the drawing

1: growth furnace 2: crucible

3: heater 4: material for semiconductor

5a, 5b: cryostat 6a, 6b: superconducting coil

7: support 8: growth direction

9: single crystal

21: cryostat 21a: top plate

21b: Bottom 22: Heavy Park

23, 24: vacuum space

C, C ', C1, C2, C3, C1', C2 ', C3': Solenoid Superconducting Coil

D, D ': Saddle-type Superconducting Coil

E, E1, E2, E3, E1 ', E2', E3 ': Solenoid type superconducting coil

S: magnetic field

L: space width of conventional solenoid type superconducting coil

L ': space width occupied by the superconducting coil of the present invention

In order to achieve the object of the present invention, a superconducting magnet device for generating a horizontal magnetic field according to the present invention, in order to generate a horizontal magnetic field, a pair or more superconducting coils are disposed in the cryogenic container 21 so as to face each other, and an internal magnetic field. A horizontal magnetic field is generated in the use space S, but the superconducting coil is a curved or elliptical superconducting coil (E; E1, E1 '; E2, E2'; E3, E3 '). The horizontal magnetic field characteristic in the space S is improved.

Preferably, the superconducting coil is a pair of two or more bent round or oval superconducting coils (E1, E1 '; E2, E2' or E1, E1 '; E2, E2'; E3, E3 '). It is characterized by.

Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 5 to 9.

FIG. 5 is a view of the four solenoid type superconducting coils positioned in a low temperature container in the fourth prior art superconducting magnet device, and FIG. 6 is a shape of a curved or elliptical superconducting coil having a curved shape according to the present invention. 7 is a view of the four bent round or oval superconducting coil according to the present invention located in the low temperature container, Figure 8 is a view of the four bent round or oval superconducting coil according to the present invention is located in the low temperature container Figure 9 is a shape showing a state in which six curved circular or oval superconducting coils according to the present invention is located in a low temperature container.

6 and 7, the superconducting coils (E; E1, E2; E1 ', E2') of the present invention have a planar shape of a circular or elliptical shape, but the side shape thereof is curved as shown in FIG. .

That is, the inventor invented a curved or elliptical superconducting coil of a curved shape in order to compensate for the disadvantages of the saddle coil of the third prior art and the solenoid coil of the second and fourth prior art.

At this time, the ratio of the vertical axis (a) and the horizontal axis (b), that is, a / b is considered a number of conditions, it is preferred from 0.6 to 1.4, the most stable is a / b is 1 when the most stable (ie circular) to be. In order to reduce the height of the low temperature container, a / b should be made smaller than 1, and a / b may be made larger than 1 when mounting multiple coils in a certain space.

In addition, the degree of bending of the coil is determined in consideration of the curvature of the inner wall and the outer wall of the cryogenic container, and the smaller the bending, the more stable form, but because the present invention is to make the cryogenic container less, the curvature of the inner diameter of the cryogenic container and the coil It is preferable that the degree of bending of coincide.

As shown in Figure 6, the bent form of the circular or elliptical superconducting coil fabrication is made as follows. First, the central magnetic field and the inner diameter of the low temperature container (for example, about 5000-6000 G and 1600 mm in diameter for a 12-inch wafer single crystal growth device) are determined. Once the diameter of the low temperature vessel is determined, it is possible to determine the degree of bending of the superconducting coil. Once the central magnetic field is determined, the height and inner diameter of the coil are determined through program analysis. The winding frame is made with the height, the inner diameter, and the degree of bending of the superconducting coil thus determined, and the superconducting wire is wound around the winding frame to produce a curved or elliptical superconducting coil.

These are two pairs (E1, E2; E1 ', E2') arranged opposite each other as in FIGS. 7 and 8, or three pairs (E1, E2, E3; E1 ', E2', E3 ') as shown in FIG. Or more than one is preferable, but a pair of superconducting coils also show better performance than conventional solenoid coils.

In particular, the superconducting coil of the present invention is disposed in the form of facing each other at the center, using the magnetic field of the magnetic field use space (S of FIG. 8) of the mesopark cylinder in the cryogenic vessel, the magnetic field in the cryogenic vessel Use the vertical direction of. In addition, the magnet equipment of the present invention uses the space in the curved or elliptical superconducting coil of the bent form, the magnetic field is generated from the opposite side. In other words, the coils are arranged in an opposite shape, and the magnetic field direction is from one coil to the other coil, so the magnetic field is horizontal, and the single crystal growth apparatus moves in a direction perpendicular to the horizontal magnetic field. The vertical direction of the magnetic field is used.

In FIG. 7, a cylindrical magnetic field using space S is formed inside the donut-type cryogenic container 21, and the cryostat is blocked by the vacuum spaces 23 and 24, respectively. The space in which the superconducting coils exist is present between the vacuum spaces 23 and 24.

In the case of the superconducting coil according to the fourth conventional art of FIG. 5, each of the superconducting coils uses, for example, a solenoid coil having a thickness of 80 mm and a diameter of 1000 mm. In this case, the magnetic field use space of the 12-inch wafer single crystal growth apparatus is used. The inner diameter should be about 1600mm. In this case, when comparing the length of the solenoid type coil and the curved circular or elliptical superconducting coil in the low temperature container, the length of the conventional solenoid type coil in the low temperature container ( L) of FIG. 5 is 178.83 mm, and the length (L ′ of FIG. 5) of the curved circular or elliptical superconducting coil of the present invention is 80 mm.

On the other hand, in the saddle coil of the third prior art, the magnetic force acts to the outside of the coil, and in the case of the horse saddle coil, the magnetic force is largely received at a portion (part B of FIG. 3). In the vulnerable part, the phenomenon of Quench, which is changed from superconductor to phase conduction, is likely to occur, and it is impossible to produce the desired magnetic field value. In addition, since the curve is changed from a straight line (part A of FIG. 3), the winding has a very difficult disadvantage. In contrast, in the case of the curved circular or elliptical superconducting coil of the present invention, the magnetic force is distributed as a whole, and since both are curved, winding is also very easy.

On the other hand, as described above, in the case of the solenoid coils of the second and fourth prior arts, the magnetic field leaking outwards is large, so that it is not effective in terms of the magnetic field. In addition, in the case of a general low temperature container, it is a cylinder type. On the basis of the arrangement for generating a horizontal magnetic field, the low temperature container of the solenoid type coil has a large space width (L) occupied by the superconducting coils (C1, C2; C1 ', C2'), and thus is extremely low. The container becomes very large (see FIG. 5). On the contrary, in the case of the curved or elliptical superconducting coil of the present invention of FIG. 7, the leaking magnetic field can be reduced, and the size of the low temperature container can be greatly reduced. In the case of manufacturing a coil for making the same central magnetic field, the thickness of the solenoid coil in the low temperature container (L in FIG. 5) is greater than that of the curved circular or elliptical superconducting coil in the low temperature container (L ′ in FIG. 5). It is about twice as thick.

On the other hand, the magnetic field generating efficiency can be determined based on the amount of windings on the premise of first generating the same central magnetic field. In other words, it is necessary to calculate the total amount of wire used to manufacture the coil, and then determine how much contributes to the central magnetic field per 1m. When the operating current is 200A, the core magnetic field is 3691 Gauss to determine the specifications of the coil to manufacture the coil, respectively, in the case of the conventional solenoid coil, the total wire amount is 13.87km. In the end, when the magnetic field generating efficiency is a magnetic field per meter, the magnetic field generating efficiency is 0.266 (Gauss / m). In contrast, in the case of the curved circular or elliptical superconducting coil of the present invention, the total wire amount is 12.23 km. After all, if the magnetic field generating efficiency is a magnetic field per 1m, the magnetic field generating efficiency is 0.301 (Gauss / m).

On the other hand, the magnetic field uniformity will be described with reference to Figs. 10 to 12, where the magnetic field uniformity indicates how large the magnetic field changes in a certain space. In a single crystal growth device, this magnetic field uniformity becomes an important variable.

FIG. 10 shows an analytical model for comparing the magnetic field effects of the superconducting coil of the fourth prior art and the superconducting coil according to the present invention under the same conditions, and FIG. 11 is the solenoid type of the fourth prior art in the analytical model of FIG. It is a graph which shows the magnetic field distribution of a superconducting coil, and FIG. 12 is a graph which shows the magnetic field distribution of the curved superconducting coil of the curved shape of this invention in the analysis model of FIG.

As shown in FIG. 10, when two phase superconducting coils are used, the difference in the horizontal magnetic flux density between the X and Y axes is measured. When comparing the graphs of FIGS. 11 and 12, the magnetic field in the z-axis (vertical) direction does not show a significant difference between the two coils.

For reference, in FIGS. 11 and 12, only the uniformity is compared, and the absolute intensity of the magnetic field between the x-axis and the y-axis is not compared under the same conditions. Although shown as being larger, if the implementation in the same conditions as described below, in the case of the present invention even in the strength of the magnetic field is more advantageous than in the prior art. That is, the reason why the magnetic flux density in the x direction is large in FIG. 11 is that the central magnetic field at the distance of 0 mm is set as in FIG. 12. In other words, the center magnetic field is set to 0.45 (Tesla) for the two types of comparisons. In reality, the magnet size and the number of turns are different in both cases. If the coils are of the same specification, the bent circular coil of the present invention has a much higher central magnetic field and a larger magnetic field in the x direction.

Returning to the uniformity problem again, in more detail, the uniformity literally means how uniform the magnetic field is, and the difference from the magnetic field at the first zero is important for determining the uniformity in the graph. In addition, since the diameter of the 12-inch single crystal growth crucible is approximately 880 mm, the strength of the magnetic field is compared with each other at about 400 mm (0.4 m). In the graph, the y- and z-directions look almost the same in terms of uniformity, so if we talk only about the x-direction graphs separately, that is, if we compare only the x-directions in the graphs, the two magnetic fields will be equal to 0.45 (Tesla). However, looking at the magnetic field when the distance of about 400mm from the center, 0.55 (Tesla) for the conventional solenoid type, but 0.49 (Tesla) for the curved form of the present invention. That is, when the uniformity is expressed as the ratio of the central magnetic field (a) and the magnetic field (b) 400 mm away from the center, a / b = 0.818 for the conventional solenoid type, but a / b = for the curved circle of the present invention. It was 0.918. For reference, the uniformity is preferably closer to 1.

Intuitively comparing magnetic field graphs in the x and y directions, it can be seen that the magnetic field of the conventional solenoid coil changes more significantly. As a result, in view of the magnetic field uniformity, it can be seen that a curved circular or elliptical superconducting coil has a better magnetic field uniformity than a solenoid coil. For example, the magnetic flux density at a position 440 mm (0.44 m) from the center, as in a single crystal growth device for a 12 inch wafer, is indicated by arrows in Figs. 11 and 12, respectively, in the case of the present invention the X axis and The difference between the Y axes (see the arrow in FIG. 12) is smaller than that in the fourth prior art (see the arrow in FIG. 11), and consequently, it can be seen that the magnetic field uniformity of the present invention is much more uniform than that of the prior art. have.

Finally, even when comparing the weight of the magnetic shield, it can be seen that the present invention is advantageous. That is, referring to the comparison of the length of the coil in the low temperature container, the solenoid coil of the prior art is significantly increased compared to the circular or elliptical superconducting coil of the low temperature container. As a result, the weight of the vacuum chamber and the weight of the magnetic shield are larger than those of the curved circular or elliptical superconducting coil. Due to the material characteristics, the weight of the vacuum chamber is very small compared to the weight of the magnetic shield. When comparing the weight of the magnetic shield, the magnetic shield of the solenoid coil and the round shape of the magnetic shield of the solenoid coil is made when the magnetic shield is made of the steel with the upper 50t and the circumference 120t. Alternatively, when comparing the magnetic shield weight of the elliptical superconducting coil, for example, the magnetic shield of the solenoid type coil outputs 13.21 tons, but the magnetic shield of the curved circular or elliptical superconducting coil of the present invention under the same conditions. It weighs only 11.69 tons.

The present invention has been described above with reference to the embodiments shown in the accompanying drawings, but the present invention is not limited thereto, and various modifications are possible within a range that can be easily conceived by those skilled in the art. Therefore, the limitation of the present invention should be limited only by the following claims.

Therefore, according to the present invention, as described above, the curved or elliptical superconducting coil of the curved shape can effectively disperse the magnetic force as compared to the saddle coil, is easy to manufacture, and can generate an efficient magnetic field compared to the solenoid coil have. In the case of curved or elliptical superconducting coils, the manufacturing time can be cut in half compared to saddle-type coils, and compared with solenoid coils, a 15% higher magnetic field increase can be achieved when winding with the same amount of superconducting wire. have.

Claims (5)

In order to generate a horizontal magnetic field, a pair or more superconducting coils are disposed to face each other in the cryogenic vessel 21, so that a horizontal magnetic field is generated in the inner magnetic field using space S, wherein the superconducting coil is of a curved shape or An elliptical superconducting coil (E; E1, E1 '; E2, E2'; E3, E3 '), wherein the superconducting magnetic device for horizontal magnetic field generation to improve the horizontal magnetic properties in the magnetic field using space (S). The method of claim 1, The superconducting coil may be a pair of two or more curved circular or oval superconducting coils (E1, E1 '; E2, E2' or E1, E1 '; E2, E2'; E3, E3 '). Superconducting magnetic device. The method according to claim 1 or 2, The ratio of the radius of the vertical axis (a) to the horizontal axis (b) of the superconducting coil is a superconducting magnet device, characterized in that the range of 0.6 ~ 1.4. The method of claim 3, wherein And a ratio (a / b) between the vertical axis (a) and the horizontal axis (b) of the superconducting coil is one. The method according to claim 1 or 2, The bending degree of the coil is a superconducting magnet device, characterized in that the curvature of the inner diameter of the cryogenic vessel.