JPH0713923B2 - Superconducting magnet - Google Patents

Description

The present invention relates to a superconducting magnet in which a cooling structure for a superconducting coil is devised.

[Prior Art] A conventional superconducting magnet is a superconducting coil and a Tc
It is configured by combining with a cryogenic container for cooling to (a critical temperature for the superconducting wire for coil to be in a superconducting state), and the cooling of the coil is a dual cryogenic container via a vacuum heat insulation layer. It was carried out by the method of directly immersing it in the liquid helium inside.

[Problems to be solved by the invention]

The above-mentioned conventional superconducting magnet in which the coil is linearly cooled with liquid helium has the following drawbacks.

(1) It is necessary to provide the cryogenic container with a port for supplying liquid helium and exhausting evaporative gas, and moreover, the port needs to be long in order to reduce the amount of external heat transmitted through the port. Therefore, the magnet lacks compactness.

(2) In order to reduce the evaporation amount of liquid helium during normal operation, it is necessary to increase the heat insulation layer between the inner and outer layers of the cryogenic container to improve the heat insulation performance. This also causes the downsizing of the magnet. Become.

(3) When quenching the magnet, a large amount of liquid helium is evaporated by the heat generated in the coil, so the inner tank is designed to withstand pressure, and the evaporative gas exhaust port has a sufficient diameter and a safety valve is installed. However, the freedom of designing the magnet is lost, and the weight and the size of the magnet become larger, and the cost increases due to the increase in accessories.

(4) Since liquid helium is consumed, running costs are high, and regular replenishment is troublesome.

The present invention aims to eliminate the above-mentioned problems.

[Means for solving problems]

In order to eliminate the above-mentioned problems, the present invention provides a superconducting magnet, a cold container having a vacuum atmosphere inside, a superconducting coil housed therein, and one or a plurality of heat shield layers surrounding the superconducting coil in the cold container. The refrigerator has multiple stages of temperature cooling stages, and the temperature of the lowest temperature cooling stage is set to Tc (critical temperature) of the superconducting wire that constitutes the coil, and the cooling stage of this refrigerator and the heat shield layer The cooling gas circulation path that is wound around each cooling stage, the heat shield layer, and the superconducting coil so that the superconducting coil reaches the superconducting coil from the lowest temperature cooling stage and returns to the start end from the superconducting coil. A power lead for supplying electric power from the outside is provided, and the superconducting coil is cooled to a critical temperature by using only the refrigerant gas in the circulation path. Than it is.

[Action]

Since the superconducting coil is maintained in a vacuum atmosphere and indirectly cooled by the helium gas in the circulation path, all the above-mentioned problems associated with direct cooling can be eliminated. That is, there is no need for an indirect cooling port, a pressure resistant design of the inner tank, or a safety valve. Also, the coil is in a vacuum atmosphere, heat is not penetrated through the port, and the coil inside has a lower temperature. Since it is surrounded by the heat shield layer to be cooled, the heat insulation performance with the outside is improved, so the heat insulation layer may be thin, which allows the magnet to be made smaller and lighter, and also the design flexibility. Will increase and cost will decrease.

Further, since the refrigerant gas for indirect cooling is circulated, the running cost is increased due to the consumption of liquid helium and the trouble of supplying liquid helium is eliminated.

〔Example〕

 The attached drawings show an embodiment of the present invention.

As shown in FIG. 1, in the illustrated superconducting magnet, the cold insulation container is composed only of the outer tank 1, and the heat shield layer 2 and the superconducting coil 3 surrounded by the heat shielding layer 2 are provided inside the outer tank. . 4 is between the outer tank 1 and the heat shield layer 2,
A vacuum space 5 provided between the heat shield layer 2 and the coil 3 and in the center of the coil is a circulation path for a refrigerant gas (helium or the like) wound around the heat shield layer 2 and the coil 3.

The circulation path 5 is also wound around the cooling stage of the refrigerator 6. That is, in the case of the figure, the compressor 7 provided outside the cold insulation container
After being drawn out and drawn into the outer tub 1, it is first wound on the high temperature side cooling stage 6a of the refrigerator facing the outer tub. Next, it is wound around the outer periphery of the heat shield layer 2 and then wound around the low temperature side cooling stage 6b which is drawn into the heat shield layer 2 and faces the layer 2. Then, from here, it is guided to the coil 3 and wound around the outer periphery of the coil, and then, the heat shield layer 2 and the outer tank 1 are sequentially drawn out and returned to the compressor 7.

Heat exchangers 8a and 8b are provided as needed, and function to transfer the residual cold heat of the return gas to the outgoing gas.

Reference numeral 9 is a power lead for supplying electric power to the coil 3 from the outside, and it is desirable to have a structure which can be separately cooled by liquid nitrogen or the like when the magnet is excited. If a cooling liquid storage part is provided inside or outside the lead and liquid nitrogen is poured into it, or a liquid nitrogen circulation path is wound around the lead, etc. Heat does not flow to the coil.

In the exemplary superconducting magnet configured as described above, the refrigerant gas discharged from the compressor 7 flows from the supply end 5a to the circulation path 5,
Next, after the cold heat is absorbed from the returned low temperature gas in the first heat exchanger 8a portion, it is further cooled in the winding portion around the cooling stage 6a of the refrigerator, and the winding portion around the heat shield layer 2 from here. Cool layer 2 to 5a.

After this, the heat exchanger 8b again exchanges heat with the returned gas, and further, it is cooled to the final temperature in the winding portion around the low temperature side cooling stage 6b of the refrigerator, and then the winding portion around the coil 3.
The coil 3 is cooled to Tc while flowing through 5c. Then, the cooled gas passes through the heat exchangers 8b and 8a and the end portion 5 of the circulation path 5
It returns to the compressor 7 from d, is recompressed, and follows the same path as above.

In addition, in order to further improve the heat insulating performance, the heat shield layer 2 may increase the number of installed layers in a range that does not become excessive.
When the layer 2 is made up of a plurality of layers, the number of cooling stages of the refrigerator 6 is also increased in accordance with the increased number of the layers 2, and each of the heat shield layers is gradually cooled toward the inner side to be cooled to an appropriate temperature. Be prepared to do so.

In order to improve the heat insulation performance, it is also possible to use a double container having an inner tank as the cold insulation container, arrange the inner tank having a vacuum atmosphere inside the heat shield layer, and house the coil 3 therein. Can be said to be effective.

In addition, for indirect cooling with circulating gas, for example, if the gas is helium, the coil can be cooled to the liquid helium temperature (4.2
Since there is a surface that is difficult to cool down to ° k), the coil 3 can be sufficiently cooled to Tc by helium gas, that is, Tc.
It is preferable to use a superconducting wire having a temperature of 10 ° to 30 ° k.

[Effect] As described above, the superconducting magnet of the present invention does not require direct cooling with liquid helium, so that the port of the container, the pressure resistant design of the inner tank, the safety valve, etc. are not required, and the heat insulation is improved. As a result, the heat insulating layer can be made thin, which leads to reduction in size and weight, reduction in manufacturing and cost, and increase in design freedom.Also, liquid helium is regularly supplied and liquid nitrogen is precooled. Since such troublesome work is not required, and further, such work is not required, it is possible to obtain an excellent effect that the automatic operation is easily performed.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of the superconducting magnet of the present invention, and FIG. 2 is a diagram showing a circulation path of a refrigerant gas in the magnet. 1 ... Outer tank, 2 ... Heat shield layer, 3 ... Superconducting coil, 4 ...
Vacuum space, 5 ... Refrigerant gas circulation path, 5b ... Winding part around heat shield layer, 5c ... Winding part around coil, 6 ... Refrigerator,
6a, 6b ... cooling stage, 7 ... compressor, 8a, 8b ... heat exchanger,
9 ... Power lead

Claims (5)

[Claims] 1. A cold insulating container having a vacuum atmosphere inside, a superconducting coil housed in the cold insulating container, one or a plurality of heat shield layers surrounding the superconducting coil in the cold insulating container, and a cooling stage having a plurality of stages of temperature. The temperature of the lowest temperature cooling stage is set to Tc (critical temperature) of the superconducting wire that makes up the coil, and the cooling stage of this refrigerator and the heat shield layer reciprocate to finally cool the lowest temperature. A cooling gas circulation path wound around each cooling stage, the heat shield layer and the superconducting coil so as to reach the starting point from the stage to the superconducting coil, and a power lead for supplying electric power to the superconducting coil from the outside. And a superconducting magnet configured to cool the superconducting coil to a critical temperature using only the refrigerant gas in the circulation path. 2. The superconducting magnet according to claim 1, wherein the power lead is additionally provided with a cooling means such as liquid nitrogen. 3. A circulation container is provided in the cool container with a heat exchanger for transferring the cold heat of the return gas to the outgoing gas between the forward and return paths of the helium gas. A superconducting magnet according to the range (1) or (2). 4. The cold container according to claim 1, further comprising an inner tank of a vacuum atmosphere surrounding the superconducting coil inside the heat shield layer. Superconducting magnet described in crab. 5. The superconducting magnet according to any one of claims (1) to (4), wherein Tc of the superconducting coil is 10 ° k to 30 ° k.