JPS6332900A - Vacuum chamber for synchrotron accelerator - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a vacuum vessel for a high energy synchrotron accelerator.

(Conventional technology) As a general technology trend for vacuum vessels of conventional high-energy synchrotron accelerators, "Vacuum" 9 published by the Japan Vacuum Association,
Vol. 27, No. 3, 1984, page 111, 6th line from the bottom of the right column. It is conceivable to make the walls of the vacuum vessel thinner so that the effect of the change can be sufficiently transmitted and the orbit radius can be prevented from expanding due to acceleration.

As a general technical trend of conventional vacuum containers for accelerators, especially vacuum containers for high-energy synchrotron accelerators, as described in FIG. Consideration has been given to reinforcing the strength by thermally spraying ceramic such as alumina around a thin cylinder with a thickness of about 0.1+m to increase the rigidity of the vacuum vessel and provide it with an external pressure.

In synchrotron accelerators, in order to prevent the orbital radius from expanding, the magnetic field applied perpendicularly to the orbital radius plane increases as the particles accelerate. The rate of change in this magnetic field is quite large, especially in heavy ion synchrotron accelerators such as PS+, which accelerate heavy ion particles to high energy. Since eddy currents are induced in the particles and cannot have a sufficient effect on the particles, it becomes difficult to keep the radius of the orbit constant.

■ Strong electromagnetic force acts on the vacuum container, and there is a high risk of damaging the vacuum container.

It had serious drawbacks such as undesirable effects.

By the way, a thin-walled cylinder of 5US304 ( Inner diameter 100 mm length 2
Figure 3 shows the maximum allowable external pressure at a temperature of 370°C. From FIG. 3, it can be seen that a wall thickness of at least about 1.11 is required to withstand buckling due to atmospheric external pressure. But 5
When constructing a vacuum container for a heavy ion accelerator using US304, a thin wall thickness of about 0.11 is required.

According to FIG. 3, it is clear that the vacuum container cannot withstand atmospheric pressure if the wall is made this thin.

Currently, if ceramic spraying to a thickness of about 3 mm is applied to the vacuum vessel wall (1) made of 5US304 with a wall thickness of about 0.1 nm, the strength against atmospheric external pressure is sufficient due to the ceramic layer 2, and the rigidity of the vacuum vessel itself is also a problem. It turns out that there isn't. By the way, the cross-sectional shape of the vacuum container is generally made into a substantially rectangular flat shape in order to effectively utilize the magnetic flux of the electromagnet that forms the magnetic field and to downsize the electromagnet.

FIG. 5 shows a sectional view of a vacuum container incorporated into an electromagnet for applying a magnetic field.

Figure 5 shows that when ceramic is sprayed onto a thin-walled cylinder with a flat cross-section, the ceramic layer ■ and the thin metal vacuum vessel wall ■ are elongated in cross-section. It has a serious drawback that it peels off at the edges.

As shown in FIGS. 6 and 7, by providing a honeycomb-shaped reinforcing member, the thickness of the vacuum container wall (2) can be reduced to 0.
It can withstand atmospheric external pressure even at a distance of about 1 m. However, this method has the serious drawback that, as shown in Figure 8, one turn is formed in a plane perpendicular to the magnetic field by the small element (2) of the honeycomb-shaped reinforcing member, and eddy currents are likely to be induced in this part. It had

(Problems to be Solved by the Invention) In the conventional device described above, when the cross section is circular as shown in FIG. 4, the magnetic flux of the electromagnet cannot be effectively utilized, and the cross section is flattened as shown in FIG. However, if a honeycomb-shaped reinforcing member is provided as shown in Figs. 6, 7, and 8, the small elements of the reinforcing member are As a result, one turn is formed in a plane perpendicular to the magnetic field and an eddy current is induced, making it unusable.

An object of the present invention is to provide a vacuum vessel for a synchrotron accelerator that has a structure with a flat cross section, has high strength, and does not generate eddy currents.

[Structure of the invention]

(Means for solving the problem) In a vacuum container with a flat cross section, which is placed in a magnetic field for accelerating particles and whose magnetic flux changes over time as the particles accelerate, it is fixed in a direction approximately perpendicular to the axial direction. The vacuum container is reinforced by arranging a plurality of rib-shaped reinforcing members along the axial direction.

(Function) Since the rib-shaped reinforcing member is provided on the outside of the vacuum container, it is possible to have sufficient bending rigidity against external pressure and to sufficiently reduce eddy currents.

(Embodiments of the Invention) Example 1 A first example of the present invention will be described with reference to FIG. 1st
In the figure, a magnetic field is applied in the direction of arrow 0. In FIG. 1, ■ is a tube-shaped vacuum vessel wall made of thin metal and has a roughly rectangular cross section, and (12) is a rib-shaped first reinforcing member (10) perpendicular to the longitudinal direction of the vacuum vessel wall ■.
and a rib-shaped second reinforcing member (1) provided parallel to the longitudinal direction.
1), which is an element of a reinforcing member fixed to the outside of the wall of the vacuum container. Each element (12) does not touch each other and does not form one turn. Vacuum container wall■
There is a reinforcing member (13) on the side of the magnetic field only in the direction 0 of the magnetic field.
to fix.

Next, the operation of this first embodiment will be explained.

In FIG. 1, the direction of the magnetic field applied to keep the radius of orbit constant as the particles in the vacuum container according to Example 1 are accelerated is perpendicular to the plane of the paper. In Fig. 1, even if the magnetic field changes, the reinforcing member element (12) does not form one turn, so no eddy current flows through the reinforcing member element.Also, since the vacuum vessel wall ■ is thin, this also causes an eddy current. Almost no current flows, so the reinforcing member (10).

In (11) and (13), the vacuum container has enough rigidity to withstand atmospheric external pressure, and since eddy currents hardly flow, almost no electromagnetic force acts on it, so there is no risk of the vacuum container being deformed or damaged. Furthermore, since there is little eddy current in the vacuum container due to changes in the magnetic field, a sufficient effect can be exerted on particles accelerated by changes in the magnetic field to maintain the orbital radius.

Therefore, according to the first embodiment, by reinforcing the thin vacuum vessel wall with a reinforcing member, the thickness of the vacuum vessel wall itself can be made so thin that no eddy current is induced. Further, since the elements (12) of the reinforcing member are arranged so as not to form one turn, no eddy current flows in the reinforcing member either. For this reason, the vacuum container has sufficient rigidity and can withstand atmospheric external pressure. Furthermore, since electromagnetic force does not work, the vacuum container will not be deformed or damaged by electromagnetic force. Furthermore, since no eddy current is induced in the vacuum container by changes in the magnetic field, it is possible to exert a sufficient orbit radius holding force on the accelerated particles.

Embodiment 2 A second embodiment is shown in FIG. 2, which is the same as the first embodiment except that the second reinforcing member of the first embodiment is not provided.

Even in this case, substantially the same effects as in the first embodiment can be obtained.

〔Effect of the invention〕

According to the present invention, it is possible to construct a vacuum container with sufficient rigidity that prevents eddy currents from flowing even in the presence of a changing magnetic field, and is therefore suitable for use in high-energy synchrotron accelerators that can accelerate heavy particles to sufficiently high energies. It became possible to provide a vacuum container.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing the first embodiment of the present invention, Fig. 2 is a perspective view showing the second embodiment, and Fig. 3 is a curve showing the relationship between the wall thickness of a cylindrical vacuum container and the maximum allowable external pressure. 4 to 6 are cross-sectional views showing different conventional examples, and FIG. 7 is a top view of the main part of FIG. 6. FIG. 8 is an explanatory diagram of eddy currents induced in the small elements of FIG. 7. 1... Vacuum container wall, 10... First reinforcing member. 11... Second reinforcing member, 12... Element of reinforcing member.

Claims (2)

[Claims] (1) A vacuum vessel for a synchrotron accelerator, characterized in that a plurality of rib-shaped reinforcing members are arranged and fixed on the outside of a tube-shaped vacuum vessel wall having a generally rectangular cross section. (2) The reinforcing member forms an element with a first reinforcing member provided in a direction substantially perpendicular to the axial direction of the tube and a plurality of second reinforcing members provided at right angles to this first reinforcing member. 2. The vacuum vessel for a synchrotron accelerator according to claim 1, wherein the elements do not contact each other to form one turn.