JPS63169463A - Cooling device for pulse superconducting magnet - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a cooling device for a pulsed superconducting magnet that generates an intermittently fluctuating magnetic field, and is particularly aimed at reducing heat loss in the magnet. , relates to a cooling device for a pulsed superconducting magnet suitable for use in nuclear fusion, energy storage, etc.

[Conventional technology]

Conventionally, pulsed superconducting magnets have been cooled using very common methods, such as intermittent replenishment of liquid helium or the attachment of a dedicated refrigerator. In addition, as a refrigeration technology using pulsed magnetic fields, JP-A-59-41
A magnetic refrigerator disclosed in Japanese Patent No. 760 is known.

[Problem that the invention sought to solve]

The conventional magnetic refrigerator described above has a problem in that a separate gas refrigerator must be used to cool the magnetic working material, which increases the size of the equipment.

An object of the present invention is to provide a cooling device for a pulsed superconducting magnet that performs magnetic cooling using the fluctuating magnetic field of the magnet itself and the sensible heat of evaporated helium gas.

[Means for solving problems]

To achieve the above object, the pulsed superconducting magnet cooling device of the present invention includes: (1) a magnetic working material is placed near a pulsed superconducting magnet that generates intermittently large magnetic field fluctuations, and liquid helium is evaporated to cool the magnet. A switching valve that guides all or part of the gas to the magnetic working substance is provided in the middle of the gas return pipe, and the switching valve cools the magnetic working substance by the evaporated gas during magnet excitation, and during magnet demagnetization, It is configured such that all or part of the evaporated gas can be led out to the gas return pipe.

[Effect]

According to the above configuration, heat generated in the magnetic working material during excitation of the superconducting magnet is cooled by introducing part or all of the evaporated helium gas into the magnetic working material. On the other hand, during superconducting magnet demagnetization, the magnetic working material becomes lower than the liquid helium temperature and reliquefies some of the helium gas.

In this way, the loss of the coolant can be partially compensated for by effectively utilizing the magnetic field change caused by the pulse operation of the superconducting magnet and the sensible heat of the evaporated gas.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2.

The superconducting magnet 1 is housed in a container 3 together with liquid helium 2, which is a coolant, and is further surrounded by a heat insulating material 4 and placed in a vacuum container 5. Since the containers 3 and 5 are designed so that the superconducting magnet 1 is repeatedly excited and demagnetized in a pulsed manner, that is, intermittently, the containers 3 and 5 are made of a high electrical resistance material that does not generate eddy currents. Liquid helium 2 is supplied from an injection pipe 6 connected to a refrigerator or tank, and evaporated gas helium 10 is supplied from an exhaust pipe 7 forming a gas return pipe.
It is derived from Inside the container 3 is a superconducting magnet 1.
The magnetic working material 8 is placed in the vicinity of where a relatively high magnetic field can be obtained. This magnetic working material is a single crystal of gadolinium, gallium, or garnet, which has a large magnetocaloric effect (a large change in entropy or temperature in response to a change in the magnetic field) near the liquid helium temperature (4.2K). It is best to use something that has been processed into a columnar shape.

Further, the bottom surface 9 of the magnetic working material 8 may be formed into an uneven surface to increase the contact area with the gas helium 10 or the liquid helium 2. Furthermore, the magnetic working material 8 has one opening connected to the container 3 and is vacuum insulated. A cooling channel 12 is housed in the wall 11 so that its side surface is in contact with the wall 11 and is thermally isolated from the outside, and gas flows uniformly in the space formed between the upper surface of the material and the heat insulating wall. is formed. This cooling channel 12 is connected to one outlet of the three-way switching valve 13 and a pipe 15 to the outside of the vacuum vessel 5 via a plumber 4 . The other outlet of the three-way switching valve 13 is connected to a gas return pipe 16.
connected to.

Next, the operation will be explained. For example, the superconducting magnet 1 is
When excited for a short time of ~10 seconds, magnetization loss and eddy current loss occur in the superconducting wire, causing liquid helium 2 to evaporate. At this time, the magnetic field also increases in the magnetic working substance 8, and the temperature rises due to the magnetocaloric effect. Thereupon, the three-way switching valve 13 is opened, and about 50 ml of gaseous helium 1o is guided from the discharge pipe 7 to the pipe 14, and the magnetic working material 8 is cooled through the cooling channel 12.

As a result, the magnetic working material 8 is cooled down to 15 degrees.

Here, gas helium 1o or liquid helium 2 in contact with the bottom surface 9 is also heated, but its thermal conductivity is 2 x 10-
'W/ ((11-K), which is low, has a heat insulating effect, and heat loss from the bottom surface 9 is not large.

After that, when the superconducting magnet 1 is demagnetized, the magnetic field of the magnetic working substance 8 also drops, and its temperature decreases to liquid helium temperature (4
, 2K) and the gas helium 10 in contact with the bottom surface 9 of 5
is condensed and re-liquefied, or the temperature of the liquid helium 2 in contact with the bottom surface 9 decreases to cause natural convection to transfer heat. At this time, the three-way switching valve 13 connects the discharge pipe 7 to the gas return pipe 16 and stops supplying gas to the cooling channel 12. By continuing such a cycle, part of the evaporation loss of liquid helium accompanying the pulse operation of the superconducting magnet 1 can be compensated for.

FIG. 3 is a partial system diagram showing another embodiment of the present invention.
What is different from the diagram is that the gas return pipe 16 is connected to the regenerator 20, and its outlet pipe 17 is joined to the pipe 15, while the pipe 1
4 is the first flow path 21 out of which the cooling flow path 12 is divided into two parts.
After passing through, it once enters the flow path 22, passes through the regenerator 2o, flows from the flow path 23 through the second flow path 24, and reaches the pipe 15.

FIG. 4 shows an embodiment of the regenerator 20 shown in FIG.
Filled with b. The mesh 26 and the tube 25 are brazed together at the periphery of the mesh.

Further, a thin copper tube 28 is soldered to the outer periphery of the tube 25.
It is connected to channels 22 and 23.

According to the above other embodiment, during magnet demagnetization, the pipe 14
While stopping the supply of gas helium to.

The gas helium, which remains at a low temperature, is guided to the regenerator 20.

The entire system is lowered to around the liquid helium temperature (4.2K), and while the magnet is energized, the flow to the gas return pipe 16 is stopped, while the gas flowing to the pipe 14 is temporarily
Heat exchange is carried out in the flow path 21 of.

As a result, the temperature of the gas helium rises, so it is guided to the regenerator 20 and recooled, and then supplied again to the second flow path 24 from the flow path 23 as a low-temperature gas. Since heat is generated in the superconducting wire even during magnet demagnetization, a large amount of helium evaporates at this time.In this embodiment, the sensible heat of the gas helium released at such times can be stored in the regenerator 20, It's even more effective. The heat capacity body of the regenerator 20 is the mesh 26 and gas helium interposed in the gap therebetween.

FIG. 5 shows a cylindrical case 30, which is an embodiment of the three-way switching valve 13 shown in FIGS. 1 to 3, and a discharge pipe 7. Gas return pipe 16. Piping 14 is open. A piston 34 having flow passages 31, 32, and 33 is inserted inside the case 30 with a narrow distance between the piston 34 and the case 3o. 35 and 36 are gas pressure communication pipes, 37 is a spring, 38 is a stopper, and 39 is the direction of the attractive force of the external magnetic field.

The three-way switching valve 13 is shown in a state when the magnet is not generating a magnetic field, and gas helium is flowing from the discharge pipe 7 to the gas return pipe 16.

If the piston 34 is made of a magnetic material and has good sliding properties with the case 30, the piston 34 will be pulled in the direction of the arrow 39 when a magnetic field is generated. If it is made so that it can be sucked up to the stopper 38, gas helium will flow from the discharge pipe 7 to the pipe 14. This results in a valve that operates automatically without external manipulation.

FIG. 6 shows another embodiment of the present invention.

The gas helium 10 always passes wholly or partly through the discharge pipe 7 through a case 41 containing a magnetic working substance 8 having a number of through holes 40 . The three-way switching valve 42 allows the helium gas 10 to flow toward the piping 15 side and lead out to the outside while the magnet is energized.

At this time, the gas return pipe 16 is closed by the on-off valve 43. On the other hand, while the magnet is being demagnetized, the pipe 15 is closed, and the fluid condensed in the through hole 40 falls under its own weight and returns to the container 3 via the switching valve 42. The gas that cannot be completely condensed is led out to the gas return pipe 16 by opening the on-off valve 43.

According to the other embodiment described above, as shown in FIG. 1, there is no need to use part of the magnetic working material 8 as a cooling surface or a condensing surface, so there is no heat loss, and all surfaces are the same. It is effective because it can be used for targeted heat exchange. In this case as well, efficiency can be further improved by using a regenerator as shown in FIG.

〔Effect of the invention〕

As described above, according to the present invention, since the magnetic field change generated by the superconducting magnet and the accompanying sensible heat of the evaporated gas of liquid helium are utilized, magnetic cooling can be performed with a simple structure.
Can compensate for loss of liquid helium.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention, FIG. 2 is a cross-sectional view showing another embodiment of the present invention, FIG. 3 is a partial system diagram showing another embodiment of the present invention, and FIG. The figure is a sectional view of one embodiment of the regenerator shown in FIG. 3, FIG. 5 is a sectional view of the embodiment of the three-way switching valve shown in FIGS. 1 to 3, and FIG. 6 is a sectional view of another embodiment of the present invention. It is a partial sectional view showing an example. 1...Superconducting magnet, 2...Liquid helium,
3.5... Container, 8... Magnetic working substance,
10... Gas helium, 12... Cooling channel, 1
3...Three-way switching valve, 20...Regenerator. 25...Copper tube, 26...Copper net, 3
4...Piston, 40...Through hole. 41...Case.

Claims (3)

[Claims] (1) A magnetic working material is placed near a pulsed superconducting magnet that generates intermittently large magnetic field fluctuations, and a valve is installed to guide all or part of the evaporated gas of liquid helium that cools the magnet to the magnetic working material. Installed in the return pipe,
A pulsed superconducting magnet characterized in that the magnetic working material is cooled by the evaporated gas while the valve is magnetized, and all or part of the evaporated gas can be led out to a gas return pipe while the magnet is demagnetized. cooling system. (2) A regenerator cooled by the evaporated gas during the magnet demagnetization is disposed in the gas return line, and the evaporated gas after cooling the magnetic working material is recooled in the regenerator and re-magnetized. A cooling device for a pulsed superconducting magnet according to claim 1, characterized in that the cooling device cools a working material. (3) A cooling device for a pulsed superconducting magnet according to claim 1, wherein the valve is operated by the magnetism of the magnet.