JPS6397221A - Vacuum vessel - Google Patents

Abstract

PURPOSE:To prevent buckling caused by external pressure by providing a junction part to the part different from a linear symmetrical part of the cross-section of a vacuum vessel in the vacuum vessel wherein a ceramic layer is coated to the outside of the cylinder of the vacuum vessel having a noncircular cross- section joined with the plate end of an extremely thin-walled nonmagnetic metallic plate. CONSTITUTION:An inner vacuum vessel cylinder 1 is formed by using one sheet or plural sheets of nonmagnetic metallic plates having about 0.2mm thickness and rounding them so that the cross-section is made to a noncircular cylindrical shape and joining the plate ends. A protective layer 4 is provided by laminating and applying ceramics on the outer surface. (In the vacuum vessel having this constitution, stress sigma caused in the interface between the inner vacuum vessel cylinder 1 and the protective layer 4 has peaks in (a), a1, (b) and b1 on linear symmetry and stress sigma becomes zero in A, A1, B and B1 on rectilinear parts. Therefore the peeling of the protective layer 4 from the junction part which is caused by external pressure can be prevented by previously performing numerical analysis and providing the junction part to the part different from the parts on the linear symmetry of the cross-section of the vacuum vessel.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a vacuum vessel used, for example, in a particle accelerator.

(Prior Art) Currently, a high-energy heavy ion device is being developed to accelerate uranium to the speed of light and collide it with other uranium to elucidate various phenomena. Since heavy ion equipment accelerates heavy ions such as uranium to high energy in a vacuum using a strong magnetic field, an ultra-high vacuum container is required.

Moreover, since electromagnets are placed around the vacuum container to create a strong magnetic field, the vacuum container must be made of non-magnetic and ultra-thin metal material, such as O, B+A, to minimize eddy current loss. It is necessary to do so. However, in vacuum containers made of ultra-thin materials, it is necessary to prevent buckling due to external pressure.

Therefore, as shown in Figures 4 and 5, in addition to providing flanges (2) at both ends of the inner vacuum container cylinder (2), a protective layer (A) is formed by coating the outside with ceramics by plasma spraying. A method was devised for mechanically reinforcing the inner vacuum container cylinder ■ by (f). In this case, since the rigidity of sprayed ceramics is lower than that of metal materials, the thickness of the protective layer (4) must be several meters or more, but since this ceramic is non-magnetic and an insulator,
The problem of eddy current losses does not arise.

Ceramic coating by plasma spraying is the 6th
As shown in the figure, ceramic powder is
is supplied to the plasma jet 6, melts and accelerates, flies and collides with the inner vacuum container cylinder (■), where it absorbs heat while getting wet and solidifies into a protective layer (
b). As a result, the interface between the inner vacuum container cylinder ■ and the protective layer has an adhesion force σA shown in Figure 6.
This occurs and the inner vacuum container cylinder is damaged due to buckling due to external pressure.
The effect of mechanically reinforcing the

By the way, as is clear from FIG. 5, which shows the structure of the cross section taken along the line ■-■ in FIG. The inner vacuum container cylinder (2) is formed by rolling the ultra-thin metal plate and joining the ends of the plates by 74G welding or EB welding to form a flat cylindrical shape. Due to the symmetry of the cross-sectional shape of the vacuum vessel, the horizontal line center line (X) shown in Fig. 5,
A line-symmetrical part (a) with respect to the vertical center line (Y), (al
), or (b), (b,).

However, according to the FEM (finite element method) analysis of the vacuum vessel 1, the stress σ generated at the interface between the inner vacuum vessel cylinder (υ and the protective layer (A)) due to external pressure is distributed at line-symmetrical locations as shown in Figure 7. The joints located (a), (al) and (b),
It was found that (b□) shows a peak although the direction is opposite. On the other hand, it is generally unavoidable that some misalignment, undercuts, and undercuts occur in joints made by TIG welding, EB welding, etc.; , it is difficult to make sufficient corrections for misalignment, undercuts, undercuts, etc. As a result, as shown in Figure 8, the outer surface shape of the joint becomes discontinuous compared to other parts, so the adhesion force σ8 at the joint between the inner vacuum container cylinder (■) and the protective layer (A) This will be inferior to the adhesion force at the site. Furthermore, at joints, there are differences in mechanical properties and residual stress between weld metal and base metal due to TIG welding, EB welding, etc.
There is also a possibility that stress σ generated at the interface between the inner vacuum container cylinder (g) and the protective layer @) due to external pressure is locally concentrated.

(Problems to be Solved by the Invention) As mentioned above, the joint of the inner vacuum container cylinder (■) is a weak point in terms of strength due to poor adhesion with the protective layer (protective layer) and local stress concentration. Nevertheless, since the stress σ generated at the interface between the inner vacuum container cylinder (■) and the protective layer (A) by external pressure is located at the peak on the tensile or compressive side, the protective layer may peel or crack from the joint due to external pressure. There is a risk that this may occur.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a highly reliable vacuum container that can withstand external pressure by minimizing eddy current loss and also being mechanically reinforced.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention is made of an ultra-thin non-magnetic metal plate with a thickness of about 0.2 I (0.1 to 0.3 mm is preferable). In a non-circular vacuum vessel, the outer surface of the internal vacuum vessel tube with a non-circular cross section is coated with a layer of ceramic by plasma spraying to form a protective layer. Provided in a different location from the location.

(Function) Figure 7 shows the phenomenon that occurs at the interface between the inner vacuum vessel cylinder (■) and the protective layer (A) due to external pressure in the flat cylindrical inner vacuum vessel cylinder (■) shown in Figure 5, which consists of a straight part and an arcuate part. This shows the distribution of stress σ, and as mentioned above, the line-symmetrical part al
A, b, and b have peaks on the tension side or compression side, but A on the straight section.

At 80, B, and B□, the stress σ becomes zero. The reason for this will be explained below. As shown in Figure 9, in the case of a circular inner vacuum container cylinder (■), the stress σ generated at the interface between the inner vacuum container cylinder (■ and the protective layer) due to external pressure is a uniform compressive stress in all parts. Become. However, in the case of a flat cylindrical vacuum vessel like the one mentioned above, the stress σ is relatively influenced by bending stress, and as shown in Figure 7, the stress σ is Becomes zero. Therefore, the stress on the bonded portion at a portion different from the line-symmetrical portion of the cross section of the vacuum vessel, particularly on the straight portion, becomes almost zero. By providing it at the joint, the stress at the joint, which is a weak point in terms of strength due to poor adhesion with the protective layer (a) and local stress concentration, as mentioned above, can be reduced to the peaks on the tension side and compression side. The stress can be significantly lowered.

(Examples) Example 1 Hereinafter, a vacuum container in a first embodiment of the present invention will be described with reference to FIG. 1.

In this embodiment, two ultra-thin non-magnetic metal plates with a thickness of 0.1 mm are rolled up and their ends are connected to joints C and C.

to form a flat cylindrical inner vacuum container tube (2) consisting of a straight portion and an arcuate portion. The joint part of the inner vacuum container is C,
C, and are provided at two locations on the straight portion, each of which is different from the horizontal center line (X) and the vertical center line (Y). Welding the inner direct air container cylinder (1) to the flange (3) at the welding part (3) and providing the protective layer (A) by thermal spraying are the same as in the conventional case.

Next, the effect will be explained.

The joints C and C1 are determined in advance by numerical analysis such as FEM at locations where the stress generated at the interface with the protective layer due to external pressure is almost zero.

Therefore, it is possible to prevent the protective layer (a) from peeling off or cracking from the joint, which is a weak point in terms of strength, as described above. And the inner vacuum container cylinder ■ is 0.1mm
Because of the thickness, eddy current losses are extremely low.

Embodiment 2 FIG. 2 shows a second embodiment according to the present invention. This is a single ultra-thin metal plate rolled up, with an inner vacuum container cylinder.
There is only one joint, and the vertical and horizontal center lines X on the straight part,
It is provided at a location d that is different from the Y line symmetry. The rest is the same as in Example 1, and the effects are also the same as in Example 1.

FIG. 3 shows a third embodiment according to the invention. In this case, the inner vacuum container cylinder (1) has an elliptical cross section. Here, there are two joints of the inner vacuum container cylinder (2), and they are provided at positions C and C1 that are different from the line symmetry of the vertical and horizontal center lines X and Y, respectively. The rest is the same as in Example 1, and the effect is also the same as in Example 1. The effect is also the same as in Example 1.

〔Effect of the invention〕

As described above, in the present invention, a protective layer is formed by laminating ceramics by plasma spraying on the outside of the inner vacuum container cylinder made of an ultra-thin non-magnetic metal plate.The cross section is non-circular. In this vacuum vessel, the joints of the ultra-thin metal plates are placed in locations that are different from the line-symmetrical areas of the vacuum vessel's cross section. A vacuum container having a protective layer that does not peel or crack between the vacuum container cylinder and the vacuum container cylinder is obtained.

[Brief explanation of the drawing]

1 to 3 are cross-sectional views showing different embodiments of the vacuum container according to the present invention, FIG. 4 is a vertical cross-sectional view of the vacuum container showing parts common to the conventional and each embodiment of the present invention, and FIG. The figure is a cross-sectional view of the conventional example shown in Figure 4, Figure 6 is an explanatory diagram showing a general ceramic coating by plasma spraying, and Figures 7 and 9 show the phenomenon occurring at the interface between the vacuum container and the protective layer. The stress distribution diagram, FIG. 8, is an enlarged sectional view of the vicinity of the joint of the vacuum container. 1...Inner vacuum container cylinder, 2...Flange, 4...
・Protective layer, aT811blb11cIcI
Id"' Junction. Agent Patent Attorney Inoue - Male Figure 3 Figure 41!!!!!

Claims (1)

[Claims] An inner vacuum container cylinder made of one or more ultra-thin non-magnetic metal plates with a thickness of about 0.2 mm, rolled so that the cross section becomes a non-circular cylinder shape, and the ends of the plates joined; 1. A vacuum container having a protective layer formed by laminated ceramic coating on the outer surface of the vacuum container by plasma spraying, characterized in that the joint portion is provided at a location different from a line-symmetrical location in a cross section of the vacuum container.