JPH07183116A - Superconducting magnet device - Google Patents

Abstract

(57) [Summary] [Purpose] To suppress the vaporization of liquid helium and reduce the amount of consumption to improve economic efficiency and operating efficiency. A liquid helium 15 is housed in a cryostat 11, and a superconducting coil 13 and a protective resistor 17 for releasing the energy accumulated in the superconducting coil 13 as Joule heat at the time of quenching the superconducting coil 13 to protect the superconducting coil are provided. In the equipped superconducting magnet device,
A gas retention space portion 14 is formed in the upper portion of the cryostat 11, and a protective resistance 17 is provided in the gas retention space portion 14 so that the gas retention space portion 14 is cooled by helium gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting magnet device which contains liquid helium in a cryostat and which is provided with a permanent magnet switch and a protective resistor.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 2, a superconducting magnet device which operates in a permanent current mode has a superconducting coil 2 in a cryostat 1, a permanent current switch 3 and a protective resistor 4 connected in parallel to the superconducting coil 2. Is provided, and the liquid helium 5 is housed therein, and the superconducting coil 2 is cooled to an extremely low temperature and held. The input terminal derived from the cryostat 1 to the outside is connected to the power supply 7 via the external switch 6.

In the superconducting magnet having such a structure,
In order to operate the superconducting coil 2 in the persistent current mode, first, the external switch 6 is turned on, the current is supplied from the power source 7 to fully excite the superconducting coil 2, and then the permanent current switch 3 is turned on. A closed circuit is formed in the coil 2, and current continues to flow in this closed circuit.

On the other hand, when the superconducting coil 2 is operated in such a state, when the superconducting coil 2 is quenched, a normal conducting portion is generated in the coil and resistance appears, so that Joule heat is generated from that portion. And superconducting coil 2
You may burn yourself.

Therefore, a current is shunted to the protective resistor 4 connected in parallel to the superconducting coil 2 so that the energy accumulated in the coil 2 is directly conducted as Joule heat to the liquid helium 5 to be released. This prevents the superconducting coil 2 from burning.

[0006]

As described above, in the conventional superconducting magnet device, the protective resistance 4 is provided in the liquid helium so that a part of the current flowing in the closed circuit at the time of quenching the superconducting coil 2 is shunted to the Joule heat. As a result, heat is directly conducted to the liquid helium 5. A large amount of liquid helium 5 vaporized by the heat is released to the outside of the cryostat 1.

However, since liquid helium is very expensive, the larger the amount of vaporized liquid helium released to the outside, the more economically problematic. Also, the more the liquid helium is replenished, the more the operating efficiency is reduced. But there is a problem.

The present invention has been made in view of the above problems, and an object thereof is to suppress the vaporization of liquid helium and reduce the consumption amount, thereby improving the economical efficiency and the operating efficiency. It is to provide a superconducting magnet device.

[0009]

In order to achieve the above object, the present invention accommodates liquid helium in a cryostat and uses the energy stored in the superconducting coil and the coil when the superconducting coil is quenched as Joule heat. In a superconducting magnet device provided with a protective resistance for releasing and protecting the superconducting coil, a gas retention space is formed in an upper part of the cryostat, and the protection resistance is provided in the gas retention space to cool with a helium gas. It was done like this.

In the above structure, a service port communicating with the gas retention space is provided above the cryostat, and gas is released from the service port when the gas pressure in the gas retention space exceeds a predetermined value. is there.

[0011]

In the superconducting magnet device having such a structure, the protective resistance does not come into direct contact with liquid helium.
Joule heat during normal operation and quenching of the superconducting coil is not conducted to liquid helium, and vaporization of liquid helium can be suppressed.

Also, when the gas pressure in the gas retention space exceeds a predetermined value, gas is released from the service port,
Even if the gas pressure in the gas retention space increases, safety can be ensured.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a structural example of a superconducting magnet device used in a nuclear magnetic resonance imaging apparatus. In FIG. 1, reference numeral 11 designates a cryostat having a double-tube configuration composed of an inner cylinder 11a and an outer cylinder 11b.
A diagnostic space portion is formed at the center of 1 in the axial direction. In addition, a service port 1 connected to a pressure reducing valve for releasing gas helium to the outside of the cryostat 11
Two are provided.

The inner cylinder 11a in the cryostat 11
Side, the superconducting coil 13 is arranged along the axial direction, and the gas retention space portion 1 is provided in the upper portion of the cryostat 11.
Liquid helium 15 is stored except for 4. Also,
A permanent current switch 16 is provided in the lower liquid helium in the cryostat 11, and the gas retention space 1
4 is provided with a protection resistor 17.

The permanent current switch 16 and the protection resistor 17 are connected in parallel to the superconducting coil 13 as in the electric circuit shown in FIG. In the superconducting magnet device having such a configuration, the protective resistor 17 is cooled by the gas helium staying in the upper gas retaining space 14 in the cryostat 11, and the Joule heat from the protective resistor 17 is absorbed. In this case, the helium gas absorbs heat and expands according to the Boyle-Charles law, and the pressure in the retention space portion 14 rises. When the gas pressure exceeds the planned value, the pressure reducing valve operates and the service port 12
More released to the outside.

Also, when the superconducting coil 13 is quenched and the closed circuit current flowing through the permanent current switch 16 is shunted to flow into the protective resistor 17 and Joule heat is generated, the same operation is performed.

Therefore, by providing the protective resistor 17 in the gas retention space 14 formed in the upper portion of the cryostat 11 as in the above embodiment, any deviation between the normal operation and the occurrence of the quench is compared with the conventional apparatus. It is possible to significantly suppress the vaporization of helium. Further, during quenching, the Joule heat generated from the protective resistor 17 is large, but since it is not in direct contact with the liquid helium 15, vaporization of the liquid helium 15 can also be suppressed. As a result, the consumption of expensive liquid helium 15 can be reduced, so that the running cost can be reduced.

Further, since the consumption of the liquid helium 15 is reduced, the number of times of replenishing the liquid helium is reduced, and efficient operation can be performed. Furthermore, the gas retention space 1
When the gas pressure of 4 exceeds the predetermined value, the pressure reducing valve of the service port 12 operates to release the gas, so that safety can be secured even if the gas pressure of the gas retention space portion 14 rises.

In the above embodiment, the superconducting magnet device used in the nuclear magnetic resonance imaging apparatus has been described, but the same can be applied to the superconducting magnet device used in other devices. is there.

[0020]

As described above, according to the present invention, since the vaporization of liquid helium is suppressed and the consumption amount is reduced, the superconducting magnet which can improve the economical efficiency and the operation efficiency can be achieved. A device can be provided.

[Brief description of drawings]

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

FIG. 2 is a connection circuit diagram of a superconducting coil, a persistent current switch and a protection resistor in a cryostat of a superconducting magnet device and an external power source.

[Explanation of symbols]

11 ... Cryostat, 12 ... Service port,
13 ... Superconducting coil, 14 ... Gas retention space, 15 ...
… Liquid helium, 16 …… Permanent current switch, 17 ……
Protection resistance.

Claims (2)

[Claims] 1. A superconducting device which contains liquid helium in a cryostat and which has a superconducting coil and a protective resistance for releasing energy stored in the superconducting coil as Joule heat when the superconducting coil is quenched to protect the superconducting coil. A superconducting magnet device, wherein in the magnet device, a gas retention space is formed in an upper part of the cryostat, and the gas resistance space is provided with the protective resistance to cool with a helium gas. 2. A service port communicating with the gas retention space is provided above the cryostat, and gas is discharged from the service port when the gas pressure in the gas retention space exceeds a predetermined value. The superconducting magnet device described in.