JPS6239804B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a superconducting coil and a method for manufacturing the same, and is used, for example, in a superconducting magnet for a nuclear fusion experimental device, in which a superconducting conductor wound a predetermined number of times is maintained at an extremely low temperature. The present invention relates to the superconducting coil used and its manufacturing method.

In recent years, the various coils used in nuclear fusion experimental equipment have been actively developed to be superconducting, as the equipment has become larger and higher voltage and larger current are desired. This is an attempt to take advantage of the so-called superconductivity phenomenon, in which electrical resistance becomes zero when an electrical conductor is cooled to an extremely low temperature.

As an example of a superconducting coil that utilizes this superconducting phenomenon, a superconducting toroidal magnetic field coil used in a tokamak-type nuclear fusion experimental device will be described below.

Generally, the superconducting conductor constituting the superconducting coil, such as the superconducting toroidal magnetic field coil of a tokamak-type nuclear fusion experimental device, is made by cutting a groove into a stabilizing conductor, such as copper, and embedding a bundle of ultrafine superconducting wires along the groove.
A rectangular superconducting conductor is used in which a stabilizing conductor and a bundle of ultrafine superconducting wires are integrated by soldering or the like.

When manufacturing a superconducting toroidal magnetic field coil using this rectangular superconducting conductor, first, the rectangular superconducting conductor is sequentially wound around the core with an interlayer insulator interposed therebetween, using the winding core as a guide. A coil formed by winding is heated and compressed by a predetermined method, and a rectangular superconducting conductor and an interlayer insulator are bonded together to form one pancake coil.

A plurality of such pancake coils are stacked in a cryogenic container for storing liquid helium as a cooling medium for cooling the pancake coils, and are supported by a winding frame support 2 as shown in FIG. A superconducting coil 1 is thus formed.

The winding frame support 2 consists of a lower plate support 2a, an upper plate support 2b, an inner peripheral support 2c, and an outer peripheral support 2d, and it is convenient that these can be disassembled into their respective parts. When stacking individual pancake coils in the winding frame support 2, it goes without saying that spacers are interposed between the pancake coils to form liquid helium cooling channels, and electrical connections are made between the pancakes. Nor.

After storing the superconducting coil 1 in the winding frame support 2, the gap between the winding frame support 2 and the superconducting coil 1, that is, the gap between the inner circumferential support 2c, the outer circumferential support 2d, and the inner and outer circumferences of the superconducting coil 1, The superconducting coil 1 is mechanically attached to the winding frame support 2 in the gap between the superconducting coil 1 and the upper and lower side supports 2a and 2b.
It is common to insert fixing insulating spacers 3a, 3b, 3c, 4a, and 4b for firmly fixing the parts. In particular, the insulating spacers 4a and 4b inserted into the gap between the outer peripheral support 2d and the superconducting coil 1 are tapered wedges and are firmly driven.

On the other hand, superconducting coil 1 and upper and lower side plate supports 2
Insulating plates 3a and 3c installed between a and 2b are an inner support 2c and an outer support 2, respectively.
d is tightened by the upper and lower side plate supports 2a and 2b.
Fixed.

However, conventional superconducting coils that are fixed in this manner are almost effective for small to medium capacity superconducting coils.

This is because the size of the superconducting coil 1 with a small to medium capacity scale is small, and even when cooled to an extremely low temperature, the absolute value of the thermal shrinkage dimension difference between the superconducting coil and the winding frame support 2 is small, and the difference is so large that it directly leads to quenching. Since there are no large gaps, the size of the superconducting conductor is small, and the excitation current is also small, the electromagnetic force is small, so even if movement occurs in the coil due to electromagnetic force, the amount of movement is small and the amount of heat generated is small. Since it is small, it rarely causes quenching.
The quench here refers to the phenomenon in which the superconducting conductor generates heat due to the movement of the superconducting conductor due to electromagnetic force, etc., and the superconducting state of the heating part is broken and becomes normal conductive, and this propagates and the entire superconducting coil becomes normal conductive. This quenching may lead to deterioration of the characteristics and insulation of the superconducting coil 1, or may cause insulation burnout, and is one of the most feared accidents in superconducting coils.

By the way, the size of the superconducting coil 1 has increased contrary to the above, and as the dimensions of the superconducting toroidal magnetic field coil have increased in scale, unique problems have started to occur. This is due to the process of cooling the superconducting coil 1 and the winding frame support 2 to an extremely low temperature state, and due to the difference in thermal expansion coefficient between the superconducting coil conductor and the winding frame support 2 in the extremely low temperature state. Corresponding gaps will occur between these materials. Since the superconducting coil 1 must be excited in this cooled state and in a state where a gap is generated, a strong electromagnetic force is used to
Even the slightest movement of the superconducting coil conductor generates heat and triggers quenching. In other words, even if the superconducting coil 1 is firmly fixed via a spacer at room temperature (approximately 300 °C), the materials constituting the superconducting coil, such as the superconducting coil, may be damaged when cooled to an extremely low temperature by liquid helium or the like. Due to the difference in thermal expansion coefficient between the copper material and the stainless steel material for the winding frame support, a difference in thermal contraction occurs, and the superconducting coil 1
This causes a gap between the reel support 2 and the reel support 2. That is, if the coefficient of thermal expansion of copper material is α ₁ , the coefficient of thermal expansion of stainless steel material is α ₂ , and the temperature difference is 300〓,
The heat shrinkage dimension difference Δl per 1 m is 3×10 ⁵ (α ₁ − α
₂ ). It goes without saying that this heat shrinkage dimensional difference Δl increases in proportion to the increase in the dimensions of the superconducting coil 1 and the winding frame support 2, and is a special problem that occurs only at extremely low temperatures.

Therefore, if the superconducting coil 1 in the above state is energized and excited, it will be quenched due to the increase in electromagnetic force that accompanies the increase in the excitation current, and not only will it not be possible to obtain the specified current carrying capacity, but it will also cause serious damage. There is a risk of causing an accident.

The present invention has been made in view of the above-mentioned points, and its purpose is to provide a superconducting coil that can prevent the occurrence of quenching by eliminating gaps between the superconducting coil and the support, and a method for manufacturing the same. is to provide.

The present invention relates to a pancake coil formed by winding a superconducting conductor a predetermined number of times with an interlayer insulator interposed, and a cryogenic container in which a plurality of these pancake coils are stacked and stored and cooled to a cryogenic state with a cooling medium. and a superconducting coil that supports these superconducting coils with a support via an insulator, the thermal expansion and contraction difference of which is almost the same as the thermal expansion and contraction difference of the support at room temperature, and a superconducting coil that supports the superconducting coil with At the same time as removing a part of the support, a temporary support having an inlet that can supply a cooling medium is attached to the part, and then a cooling medium is supplied from the temporary support inlet to adjust the difference in thermal expansion and contraction of the superconducting coil.
The method for manufacturing a superconducting coil includes cooling the support until the difference in thermal expansion and contraction becomes almost the same as that at room temperature, and then removing the temporary support and attaching the removed support to the corresponding part. This was done to achieve the objectives of the period.

Hereinafter, the present invention will be explained in detail based on embodiments shown in the drawings. Incidentally, the same reference numerals are used for the same parts as in the past.

An embodiment of the present invention is shown in FIGS. 2 and 3.

In this example, a rectangular superconducting conductor is sequentially wound around it with an interlayer insulating material interposed therebetween, and the rectangular superconducting conductor and interlayer insulating material are bonded together by heating and compressing using a predetermined method. and formed 1
A superconducting coil 1 is formed by stacking a plurality of pancake coils in a cryogenic container for storing a cooling medium for cooling the pancake coils, such as liquid helium, and supporting them with a winding frame support 2. ing. In this embodiment, first, the inner peripheral support 2c is attached on the lower plate support 2a, and the superconducting coil 1 is installed via the insulating plates 3c and 3b. Thereafter, a temporary outer support jig 5 made of a thin steel plate having an inlet piping section 6a for supplying a cooling medium is attached to a portion corresponding to the outer support 2d, and the superconducting coil 1 and temporary outer support jig 5 are then attached. Insulating tapered wedges 4a and 4b are inserted into the gap between them and temporarily fixed. Next, after attaching the upper plate support 2b via the insulating plate 3a, a cooling medium such as cooling nitrogen gas is supplied from the inlet piping section 6a attached to the outer surface of the temporary outer peripheral support jig 5, and the superconducting coil 1 at a predetermined temperature, that is, superconducting coil 1
Cooling is performed until the difference in thermal expansion and contraction of the winding frame support 2 becomes approximately the same as the difference in thermal expansion and contraction of the winding frame support 2. During this cooling period, the outer surface of the winding frame support 2 is covered with a polyester film 7 or the like.
It is more effective to prevent dew condensation on the outer surface of the winding frame support 2 by sealing a dry gas (for example, N ₂ gas) 8 between the winding frame support 2 and the winding frame support 2 .

When the superconducting coil 1 has been cooled to a temperature equivalent to the difference in thermal contraction dimensions due to the difference in coefficient of thermal expansion (the difference in thermal expansion and contraction is about the same), the temporary outer support jig 5, the upper plate support 2b, and the insulating plate 3a are removed. Dismantle.

Next, a peripheral support 2d of about 300 mm is attached, and insulating tapered wedges 4a and 4b are firmly driven into the gap between the superconducting coil 1 and the peripheral support 2d. At this time, the insulating taper keys 4a and 4b may be coated with adhesive and firmly driven into place. Insulated tapered wedge 4
After a and 4b are driven in, the upper plate support 2b is attached to the proper position with the insulating plate 3a interposed as shown in FIG. Furthermore, if the entire assembly is heated to room temperature after the assembly work is completed as described above, an expansion force corresponding to the temperature difference will continue to act between the superconducting coil 1 and the winding frame support 2, and they will be fixed and fixed extremely tightly. The Rukoto.

According to this embodiment, the thermal expansion coefficient α ₁ of the superconducting coil and the thermal expansion coefficient α ₂ of the winding frame support are changed in the process of bringing the superconducting coil from room temperature (approximately 300°C) to the final cryogenic state. Because it can absorb the heat shrinkage dimensional difference Δl caused by the difference,
There is no gap between the superconducting coil and the reel support, and when the superconducting coil is energized or excited,
This eliminates the possibility of quenching due to an increase in electromagnetic force due to an increase in excitation current, which can lead to serious accidents or
There is no reduction in current carrying capacity.

In Fig. 2, temporary piping is temporarily fixed to the outer surface of the reel support 2, and liquid nitrogen or other cooling medium is flowed or sprayed into the piping, or cooling is performed using a solid cooling material such as dry ice. However, similar effects can be obtained, and in the case of a forced cooling type hollow superconducting conductor or a type of superconducting coil with a similar cooling pipe, cooling can be performed directly using a cooling medium in these hollows or cooling pipes. You can also do that. Furthermore, in FIG. 2, instead of the temporary outer support jig 5, the outer support 2d may be directly attached and cooled by the method described above. However, in this case, it is necessary to dismantle only the outer peripheral support 2d that is being cooled, raise the temperature between it and the superconducting coil 1 that is being cooled to a temperature corresponding to the difference in heat shrinkage dimensions, and then reinstall it. Of course.

According to the superconducting coil and the manufacturing method of the present invention described above, the superconducting coil has a thermal expansion/contraction difference that is almost the same as the thermal expansion/contraction difference of the support supporting it at room temperature, and In order to obtain a superconducting coil, a part of the support supporting the superconducting coil is removed, a temporary support having an inlet part that can supply a cooling medium is attached to the part, and then a cooling medium is supplied from the temporary support inlet part. and cooling the superconducting coil until the difference in thermal expansion and contraction of the superconducting coil becomes almost the same as the difference in thermal expansion and contraction of the support at room temperature, and then removing the temporary support and attaching the removed support to the part. Because the manufacturing method was adopted, it is possible to absorb the difference in thermal contraction dimensions caused by the difference in thermal expansion and contraction between the superconducting coil and the support.
There is no gap between the superconducting coil and the support, so quenching does not occur, which is very effective when used in superconducting coils.

[Brief explanation of the drawing]

FIG. 1 is a partially cross-sectional front view of a conventional superconducting coil, and FIGS. 2 and 3 are partially cross-sectional front views showing the manufacturing process of the superconducting coil of the present invention. 1...Superconducting coil, 2...Reeling frame support, 2a...
Lower plate support, 2b...Upper plate support, 2c...
Inner circumference support, 2d...Outer circumference support, 3a, 3
b, 3c... Insulating plate, 4a, 4b... Insulating taper wedge, 5... Temporary outer peripheral support jig, 6a... Inlet piping section.

Claims (1)

[Claims] 1. A pancake coil formed by winding a superconducting conductor a predetermined number of times with an interlayer insulator interposed, and a plurality of pancake coils stacked and stored and cooled to an extremely low temperature with a cooling medium. A superconducting coil consisting of a cryogenic container and a cryogenic container supported by a support via an insulator, wherein the thermal expansion/contraction difference of the superconducting coil is made almost the same as the thermal expansion/contraction difference of the support at room temperature. A superconducting coil characterized by: 2. A patent claim characterized in that, among the insulators surrounding the superconducting coil, the insulator located on the outside of the side surface is a tapered wedge, and the wedge is inserted between the superconducting coil and the support. The superconducting coil according to the range 1 above. 3 A superconducting conductor is wound a predetermined number of times with an interlayer insulator interposed to form a pancake coil, and a plurality of the pancake coils are stacked and stored in a cryogenic container in a cryogenic medium, and the insulator is In a method for manufacturing a superconducting coil formed by supporting the superconducting coil on a support, a part of the support supporting the superconducting coil is removed, and a temporary support having an inlet part that can supply a cooling medium to the part is attached, After that, a cooling medium is supplied from the temporary support inlet, and the difference in thermal expansion and contraction of the superconducting coil is
A method for producing a superconducting coil, characterized in that the support is cooled until the difference in thermal expansion and contraction at room temperature becomes almost the same, and then the temporary support is removed and the removed support is attached to the corresponding part. . 4 Among the insulators surrounding the superconducting coil, the insulator located on the outside of the side surface is a tapered wedge, and the wedge is temporarily fixed between the superconducting coil and the temporary support when the superconducting coil is in a cooled state. 4. The method of manufacturing a superconducting coil according to claim 3, wherein the superconducting coil is firmly and tightly inserted between the superconducting coil and the support after the superconducting coil has been cooled. 5. The method of manufacturing a superconducting coil according to claim 3 or 4, wherein the temperature of the entire superconducting coil is raised to room temperature after the assembly work of the superconducting coil is completed. 6. Claim 3, characterized in that, during the cooling period of the superconducting coil, the outer surface of the support is covered with a polyester film, and dry gas is sealed between the polyester film and the support. , or the method for manufacturing a superconducting coil according to item 4.