JPS62239504A - Cryostat - Google Patents

Abstract

PURPOSE:To simplify the assembling work the title cryostat by a method wherein a vacuum heat-insulated chamber is divided into the upper cover, the lower chamber and an inside cylindrical body, a liquid helium chamber and an outside radiant shield are supported and fixed to the upper cover, and after each part has been inspected and adjusted, they are assembled by inserting into the lower chamber. CONSTITUTION:The upper cover 9 of a vacuum heat-insulated chamber is attached using a coil-housed liquid helium chamber 1 and the outside radiant shield 2a, which is arranged surrounding the liquid helium chamber, and a heat-insulated supporting device 3. A chimney part 7 is also attached to the liquid helium chamber 1, and an outside multiplier heat-insulated material 8a is also attached to ontside the external radiant shield 2a. A refrigerator 11, a liquid helium chamber 1, and the heat-insulated supporting device, to be used for prevention of the lateral deflection of the external radiant shield 2a, are attached to the upper cover. After the above-mentioned materials to be contained have been suspended in the upper cover, they are placed in the lower chamber 5c of the vacuum heat-insulated chamber 5c, a vacuum sealing is performed by a vacuum sealing part 10, and they are assembled.

Description

[Detailed Description of the Invention] [Purpose] (Field of application on N beams) The present invention relates to a cryostat incorporating a superconducting coil.

(Conventional technology) A conventional cryostat will be explained using FIG. 2.

Conventional cryostats such as nuclear magnetic resonance imaging diagnostic equipment have a liquid helium tank ■ containing a superconducting coil, a radiation shield placed around this, and an adiabatic liquid helium tank ■ and radiation shield placed in a vacuum space. (2) A heat insulating device (■) that supports and a liquid helium tank (■) that forms a vacuum space (A).

It consists of a vacuum insulation tank ■ that supports the radiation shield ■ and forms the outer shell of the device. The vacuum insulation tank (c) is kept at room temperature,
The radiation shield (2) is a combination of an 80K (absolute temperature) shield cooled with liquid nitrogen and another 20K (absolute temperature) shield cooled with gas helium. The liquid helium tank (2) is filled with liquid helium and maintained at a temperature of approximately 4.2°C at 1 atmosphere to keep the built-in coil in a superconducting state.

In the center of the device, a room temperature space 0 is formed in a cylindrical shape.
The magnetic field generated by the superconducting coils in this space will be used for various purposes. ■ is the chimney connected to the liquid helium tank, which leads the liquid helium inlet, helium gas outlet, current supply lead, measurement wire, etc. to the outside. This chimney part (2) serves as a heat inflow path between the room temperature part and 4.2, so it is configured to have a small heat conduction cross section and a long insulation distance. The heat insulating support device ① also serves as a heat infiltration path, so use a strong metal or resin rod with low thermal conductivity. With this configuration, maintenance is facilitated by reducing the consumption of expensive cryogens such as liquid helium.

On the other hand, in order to further reduce the consumption of liquid helium and liquid nitrogen, there is a means to cool the radiation shield and the helium tank using a small refrigerator (not shown). In this case, the refrigerator is installed by penetrating the wall of the vacuum insulation tank (1) and making thermal contact with a radiation shield, etc.

On the other hand, in the chimney part (2), the vacuum insulation tank (2) was cylindrical, so it could not be attached to the liquid helium tank in advance, but was attached after assembly.

(Problems to be Solved by the Invention) In the above-mentioned conventional device, the installation of the small refrigerator is limited to an accessible part of the end of the vacuum insulation tank, and the radiation shield ■ etc. are cooled by thermal conduction. This makes it disadvantageous to cool parts that are far away, and it is difficult to secure a sufficient effective area for thermal contact.

On the other hand, because the vacuum insulation tank in the chimney part (■) is cylindrical, it cannot be attached to the liquid helium tank (■) from the beginning and must be welded after assembly, which requires work to be done in a narrow space and prevents leaks. There were drawbacks, such as difficult tests.

In addition, when assembling the contents of the multi-cylindrical structure in the vacuum insulation tank ■, it is difficult to fix the contents suspended in the air using the insulation support device ■ because the device is placed horizontally on the floor. Extremely bad. In addition, between the radiation shield and the vacuum insulation tank, there is a multilayer insulation material (c) to reduce the inflow of radiation heat.
It is called. Since the aluminum-deposited polyester film and nylon net are attached alternately, when installing the liquid helium tank ■ and the radiation shield ■ into the vacuum insulation tank ■, the multilayer insulation material (8) may peel off. Even if it was deformed, it was impossible to modify it. This multilayer insulation material (8) is used in a vacuum, but its performance is greatly affected by the lamination density and the construction method of the joint, and if it peels off, the high temperature part will be directly exposed to the cryogenic surface, resulting in a large amount of heat intrusion. There were some drawbacks as well.

The present invention aims to solve the above problems and provide a cryostat that is easy to assemble, highly reliable, and stable in terms of performance.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides a vacuum insulation tank consisting of an upper lid, a lower tank, and an inner cylindrical body.
A cryostat is provided in which the liquid helium tank (2) and the outer radiation shield (2a) are supported and fixed on the upper lid by a heat insulating support device (2), and after each part is inspected and adjusted, the cryostat is assembled by inserting it into the lower tank.

(Function) When assembling the cryostat with this structure, the top lid of the vacuum chamber is installed on the work stand, and the liquid helium tank and outer radiation shield are suspended from the top lid, so it is different from the conventional cryostat. As shown in the figure, there is no possibility that visual inspection cannot be performed after insertion into the vacuum container, and it is possible to visually check according to the assembly order. Can be inserted into the tank. Furthermore, with this configuration, it is possible to attach the chimney of the liquid helium tank to the liquid helium tank in advance and perform a leak test, etc., thereby improving reliability and significantly reducing the number of work procedures. In addition, the location of the refrigerator is no longer restricted to the limited area at the shaft end of the vacuum insulation tank.
This means that it can be manufactured with a sufficient thermal contact area.

(Example) An example of the present invention will be described below with reference to FIG.

The liquid helium tank (2) containing the coil and the outer radiation shield (2a) arranged so as to surround it are attached to the vacuum insulation tank upper lid (9) by the heat insulation support device (2). In this case, the chimney part (■) is also attached in advance to the liquid helium tank (■). An outer multilayer insulation material (8a) is also attached to the outside of the outer radiation shield (2a).

A heat insulating support device (not shown) for preventing lateral vibration of the refrigerator (11), liquid helium tank (2), and outer radiation shield (2a) is also attached to the upper lid (9) in the same way as the other support device (2). After the above contents are suspended on the upper lid (9), they are inserted into the lower tank (5c) of the vacuum insulation tank, and vacuum sealed by welding or a vacuum sealing part (10) such as backing, etc., to assemble.

In addition, the radiation shield (2b) on the side of room temperature space (e) and the inner multilayer insulation material (8b) are connected to the inner cylinder (5a) of the vacuum insulation tank.
) is attached to the flange (5d), and after the above assembly,
Cut-out holes (
13) and is vacuum-sealed by welding or backing after one assembly, which is the same as in the conventional device.

Next, the operation of this embodiment will be explained.

As mentioned above, since the contents are suspended from the top lid of the vacuum insulation tank (■), there are fewer restrictions on the location of the refrigerator, and a design that provides sufficient heat transfer area is possible. Adjustment of the thermal contact area can also be performed with sufficient reliability.

Also, there are fewer restrictions on the position of the chimney part■.

Furthermore, since it can be installed in advance, highly reliable welding can be performed with sufficient space, and leak tests can be performed together with the liquid helium tank, which significantly reduces the amount of work.

In addition, the installation of liquid helium tanks, radiation shields, thermal support devices, multilayer insulation materials, etc. is completely visible.
Adjustment of each part becomes easier and overall reliability in terms of performance is improved. Furthermore, the assembly into the lower tank (5o) requires only insertion and slight adjustment, which greatly reduces the amount of work required compared to conventional assembly structures.

In Figure 1, the shape of the top lid 0 of the vacuum insulation tank is square, and the vacuum seal part (1o) is the top end, but the contents include the liquid helium tank ■, the outer radiation shield (2a), etc. The upper lid (9) can be inserted into the lower tank (5C).
) It is clear from its function and purpose that there are no restrictions on the shape of the seal or the position of the seal.

In addition, the shape of the lower tank (5c) is a square box in Figure 1, but it is also made U-shaped so that the lower side follows the cylindrical shape of the radiation shield ■, and the side plate of the lower tank (5c) is It is also possible to press a single plate and attach the legs. In this case, there are advantages of cost reduction, such as fewer weld lines and fewer plate materials.

〔Effect of the invention〕

As described above, according to the present invention, the installation of the refrigerator and the chimney becomes much easier in terms of design, manufacturing and assembly, and inspection, thereby reducing costs and improving product reliability. .

[Brief explanation of drawings]

FIG. 1 is a sectional elevational view of a main part showing an embodiment of the cryostat of the present invention, and FIG. 2 is a sectional view of a conventional cryostat. 1...Liquid helium tank, 2...Radiation shield. 2a... Outer radiation shield, 2b... Inner radiation shield, 3... Heat insulation support device, 4... Vacuum space, 5...
・Vacuum insulation tank, 5a...inner cylinder, 5c...
Lower tank, 5d... flange. 7...Chimney part, 8...Multilayer insulation material, 9...
...Top lid, 10...Seal part, 11...
・Freezer, 12... End plate, 13... Cutout hole.

Claims (2)

[Claims] (1) In a cryostat, which consists of a liquid helium tank containing a superconducting coil, a radiation shield surrounding it, a vacuum insulation tank that keeps these in vacuum, and a refrigerator, the vacuum insulation tank is located concentrically with the liquid helium tank. an inner cylinder;
A cryostat consisting of an upper lid and a lower tank, and characterized in that a liquid helium tank, an outer radiation shield, a refrigerator, etc. are attached to the upper lid and housed in the lower tank. (2) A patent claim characterized in that the inner radiation shield is attached to the flange of the inner cylindrical body and inserted into the lower tank through a cutout hole in a side plate previously provided in the lower tank, thereby forming an airtight vacuum insulation tank. A cryostat according to item 1 of the scope.