JPH04370983A - Superconducting magnet device - Google Patents

Abstract

PURPOSE:To reduce evaporation of a very low temp. cooling medium at the time of servicing and break down of a small refrigerating machine by shortening the time of an initial pre-cooling of a superconducting magnet device. CONSTITUTION:As for a superconducting magnet device provided with a cooling medium container 13 where a superconducting coil 2 is housed in a vacuum container 4 and a heat shields 5a and 5b which cover the container 13 and are cooled by a small refrigerating machine 7, a heat exchanging parts 1a and 11b provided to the heat shields 5a and 5b are connected to pipings 10a and 10b for supplying and restoring a low temperature cooling medium from an outside of the vacuum container, and gas pipings 14 is connected to the low temperature cooling medium supplying pipings 10a and 10b by way of a valve 13 from the upper part of a cooling medium container 3, thus constituting the device. The valve 13 is an automatically controlled valve which performs a releasing operation when it receives a stop signal for the small refrigerator 7.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is applicable to single crystal pulling equipment, MR
This invention relates to a low heat intrusion type superconducting magnet device used in I devices and the like.

0002

2. Description of the Related Art Conventionally, a superconducting magnet device used in a single crystal pulling device, an MRI device, etc. has a configuration as shown in FIG. 3 in order to minimize evaporation of cryogenic refrigerant. That is, the cryogenic refrigerant 1 and the superconducting coil (2
), a vacuum container (4) that covers the refrigerant container (3) and forms a vacuum insulation layer between the refrigerant container (3), and a vacuum container (4) that is provided within the insulation layer. One end of the heat shield (5a, 5b) communicates with the refrigerant container (3), and the other end penetrates the walls of the vacuum insulation layer, the heat shield (5), and the vacuum container (4) and is located in the normal temperature part. It consists of a port (6) provided as shown in FIG.

[0003] The heat shield (5a, 5b) is a vacuum container (
The cooling stage (8) of the small refrigerator (7) installed in
a, 8b) to about 80K and 20K, and the heat entering the refrigerant container (3) is suppressed to about several tens of mW. Further, the heat shields (5a, 5b) are provided with multilayer insulation (super insulation) to suppress the amount of input heat as much as possible. For this reason, a small refrigerator (7) with a cooling capacity of several watts for the second stage (8a) and several tens of watts for the first stage (8b) is sufficient.

[0004] In a superconducting magnet device having such a configuration, each component is assembled at room temperature, the heat shield is cooled with a small refrigerator (7), and the superconducting coil (
2) and the refrigerant container (3) that houses it, and after performing initial precooling to a steady state, it is ready for use.

[0005]

[Problems to be Solved by the Invention] In the superconducting magnet device that is used while being cooled with the cryogenic refrigerant described above, the small refrigerator that cools the heat shield has a cooling capacity that is equivalent to the intrusion heat during steady state. A heat shield weighing several hundred kg is often used at room temperature (300K).
It takes 2 to 3 hours for initial precooling to cool from 80K to 20K. In addition, compressors (not shown) are often manufactured in such a way that maximum capacity is produced when the small refrigerator becomes steady, and at high temperatures (e.g. around 200K), sufficient capacity is not achieved. Does not appear. Furthermore, small refrigerators require maintenance such as replacing parts after being used for a certain period of time, and during the maintenance period, cooling of the heat shield becomes impossible, and an increase in heat entering the refrigerant container due to the rise in the temperature of the heat shield. Maneku. A similar problem occurs when a small refrigerator breaks down.

SUMMARY OF THE INVENTION An object of the present invention is to provide a superconducting magnet device that can shorten the initial precooling time and suppress evaporation of expensive cryogenic refrigerant even during maintenance or failure of a small refrigerator.

[0007]

[Means for Solving the Problems] The superconducting magnet device of the present invention includes piping for supplying low-temperature refrigerant to the heat shield from outside the vacuum container, and a valve from the top of the refrigerant container.
The structure includes a gas pipe connected to the pipe.

[0008]

[Operation] With such a configuration, it becomes possible to perform initial precooling using the refrigerant supplied to the heat shield and a small refrigerator, and the time required for initial precooling can be significantly shortened. Furthermore, during the maintenance period when the small refrigerator is stopped when a superconducting magnet device is used in a steady state, it is possible to cool the heat shield by opening the valve of the gas piping from the top of the refrigerant container. It is possible to prevent an increase in heat entering the container.

[0009]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a superconducting magnet device according to an embodiment of the present invention. Moreover, FIG. 2 shows the flow of the cooling system.

In FIG. 1, the superconducting magnet device is
Liquid nitrogen is supplied from outside the vacuum container (4) to the heat shields (5a, 5b) provided between the superconducting coil (2), the refrigerant container (3) containing liquid helium, and the direct air container (4). A piping (10) is provided. Furthermore, a heat exchanger (1) with a pipe attached to the heat shield (5a, 5b)
1a, 11b) and are connected to a supply pipe (10a) and a recovery pipe (10b) provided with a valve (12) for supplying and recovering cryogenic refrigerant. On the other hand, a gas pipe (14) equipped with a heater that supplies evaporated gas from the refrigerant container (3) via the valve (13) is connected to the cryogenic refrigerant supply pipe 10a.

The flow of the cooling system of this embodiment constructed in this manner is shown in FIG. During initial precooling, the refrigerant flows as shown by the solid arrow 15, and the valve (13) is kept closed. When the small refrigerator (7) is stopped for maintenance or the like, the switching valve (13) is opened and the evaporated gas flows as shown by the broken arrow (16).

[0012] When initially precooling the superconducting magnet device in this manner, the precooling time can be significantly shortened by supplying cryogenic refrigerant from the outside to the heat shield in addition to the small refrigerator. This reduces the number of days required for performance testing and shortens the testing process. In particular, if it is mass-produced, it will be possible to significantly reduce the testing process and the number of testers.

Furthermore, by closing the valve (13), even when the small refrigerator is stopped for maintenance or the like, the heat shield is cooled by the evaporated gas of the cryogenic refrigerant, thereby preventing an increase in heat entering the refrigerant container. To prevent, reduce the consumption of expensive cryogenic refrigerants.

There is a possibility that the valve (13) may become clogged due to solidification of nitrogen gas, but by energizing the heater attached to the gas pipe (14), the solidified gas is turned into a gas, thereby preventing clogging. do.

[0015] Also, as another embodiment, a valve (13)
There is a method in which the valve is configured as an automatic valve, and it is automatically opened by a signal when the small refrigerator stops. in this case,
This is effective even if the small refrigerator stops when maintenance personnel are not available, such as at night or on holidays.

[0016]

As described above, according to the superconducting magnet device of the present invention, the initial precooling time is significantly shortened, making it possible to reduce the number of testing steps in performance testing. This effect becomes larger as mass production increases and the number of manufactured units increases. Furthermore, it is possible to provide a superconducting magnet device with low operating costs that can prevent an increase in consumption of expensive cryogenic refrigerant even when the small refrigerator cooling the heat shield is stopped.

[Brief explanation of the drawing]

FIG. 1 is a diagram of a superconducting magnet device according to an embodiment of the present invention.

FIG. 2 is a flow diagram showing the cooling system of the above embodiment.

FIG. 3 is a diagram showing a conventional superconducting magnet device.

[Explanation of symbols]

1, Cryogenic refrigerant
2, Superconducting coil 3, Refrigerant container
4, Vacuum containers 5a, 5b, heat shield 6, Port 7, Small refrigerator
8a, 8b, cooling stages 10a, 10b, refrigerant piping 11a, 1
1b, heat exchange parts 12, 13, valve 14
, gas piping 15, 16, direction of refrigerant flow

Claims (2)

[Claims] Claim 1: In a superconducting magnet device having a refrigerant container housing a superconducting coil in a vacuum container and a heat shield covering the refrigerant container and cooling the refrigerant coil with a small refrigerator, a heat exchange section provided in the heat shield has a 1. A superconducting magnet device characterized by having a gas pipe connected to a pipe for supplying and recovering a low-temperature refrigerant from the refrigerant container and connected to the low-temperature refrigerant supply pipe from the upper part of the refrigerant container via a valve. 2. The superconducting magnet device according to claim 1, wherein the valve is an automatic control valve that opens in response to a signal to stop the small refrigerator.