JPH05129099A - Drift tube containing permanent magnet - Google Patents

Abstract

PURPOSE:To perform alignment of normal position and attitude without impairing each other by preventing a stem from bending with mutually adjacent drift tubes attracting each other due to magnetic force. CONSTITUTION:In a drift tube 1 supported within an acceleration cavity 2 by a stem 3 by containing a permanent magnet 4 of the magnetized type, a magnetic shield 5 made of ferromagnetic substance is made adhere to the outer surface thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drift tube of a drift tube type linear accelerator with a built-in permanent magnet.

[0002]

2. Description of the Related Art A drift tube type linear accelerator is shown in FIG.
As shown in the vertical cross-sectional view, when the microwave 6 is supplied into the vacuum of the acceleration cavity 2, the acceleration electric field generated by the resonance of the microwave 6 is synchronized with the velocity of the ion beam 7 implanted in the center axis of the cavity. A plurality of drift tubes 1 are accurately arranged by the stem 3 so that they can be accelerated.
In order to prevent the accelerated ion beam 7 from scattering in the drift tube 1, a magnet is built in and functions to focus the ion beam 7.

Although an electromagnet or a permanent magnet that is magnetized after attachment is used for the conventional drift tube 1, a small size of the acceleration cavity 2 has recently been required, and the magnetic force is strong. It has become more and more necessary to use electromagnets and permanent magnets that are magnetized after mounting. That is, the electromagnet requires a large current, which makes it difficult to use due to the problem of heat generation.

Therefore, as shown in the longitudinal sectional view of FIG. 3, there has been a demand for a drift tube 1 having a built-in permanent magnet 4 of a previously magnetized type. By the way, conventionally, since the built-in magnet is positioned and attached to the acceleration cavity 2 without a magnetic field, it is not necessary to consider the influence of the magnetic field of the adjacent drift tube 1 at the time of positioning alignment of the drift tube 1, and according to gravity. Although it was possible to perform alignment in a suspended state, the drift tubes 1 containing the permanent magnets 4 attract adjacent ones and bend the stem 3 as shown in the figure, so that the normal alignment of the drift tube 1 is ensured. Becomes difficult.
Moreover, the drift tubes 1 may hit each other and may be damaged.

[0005]

SUMMARY OF THE INVENTION The present invention has been proposed in view of the above circumstances, and prevents the adjacent drift tubes from being attracted to each other by magnetic force so that the stem is not bent, and the stems are not damaged. Also, it is an object of the present invention to provide a drift tube with a built-in permanent magnet that can perform normal position and orientation alignment.

[0006]

To this end, the present invention is directed to a drift tube in which a permanent magnet of a previously magnetized type is built-in and which is supported by a stem in an accelerating cavity. It is characterized in that the shield is attached by magnetic force.

[0007]

In the drift tube with a built-in permanent magnet of the present invention, while the magnetic shield made of a ferromagnetic material is itself attracted to the permanent magnet, the magnetic field is confined in it to prevent it from going out of the drift tube. The drift tube of will not attract due to magnetic force,
Therefore, the bending of the stem can be prevented.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a drift tube with a built-in permanent magnet of the present invention will be described with reference to a vertical sectional view of FIG. 1. The drift tube 1 is suspended and supported by a stem 3 in the vacuum of an accelerating cavity 2. A permanent magnet 4 of a type that is magnetized in advance is stored in the unit 1.
On the outer periphery of the drift tube 1, a thin sheet-like magnetic shield 5 made of, for example, permalloy or pure iron is
The drift tube surface is covered with a protective film of polyethylene, vinyl, etc. to prevent scratches and is attached by magnetic force.

Therefore, in such a drift tube 1, while the magnetic shield 5 itself is attracted to the outer peripheral surface of the drift tube 1 by the magnetic force, at the same time, the magnetic field is confined in the magnetic field to prevent it from going out and the influence of the magnetic force is exerted. I will make it disappear. Therefore, when the drift tube 1 is mounted in the acceleration cavity 2, adjacent ones are not attracted by a magnetic force, the stem 3 is not bent, and a normal position and posture can be aligned, and the drift tube 1 is damaged. Can also be prevented.

[0010]

In summary, according to the present invention, in a drift tube in which a permanent magnet of a type that is magnetized in advance is built-in and supported in an acceleration cavity by a stem, a magnetic shield made of a ferromagnetic material is magnetically attached to the outer peripheral surface. By attaching them by means of the above, the drift tubes adjacent to each other can be prevented from attracting each other due to the magnetic force, and the stem can be prevented from bending, and the drift tubes with a built-in permanent magnet can be aligned without damaging each other and in a normal position and orientation. Therefore, the present invention is extremely useful industrially.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of a drift tube with a built-in permanent magnet of the present invention.

FIG. 2 is a vertical sectional view of a known drift tube type linear accelerator.

FIG. 3 is a vertical cross-sectional view of a conventional drift tube with a built-in permanent magnet.

[Explanation of symbols] 1 drift tube 2 acceleration cavity 3 stem 4 permanent magnet 5 magnetic shield 6 microwave 7 ion beam

Claims (1)

[Claims] 1. A drift tube in which a permanent magnet of a previously magnetized type is built-in and which is supported by a stem in an acceleration cavity, wherein a magnetic shield made of a ferromagnetic material is magnetically attached to an outer peripheral surface of the drift tube. The feature is a drift tube with a built-in permanent magnet.