JPH0779039B2 - Beam focusing electromagnet - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electromagnet used for focusing accelerated charged particles (hereinafter referred to as a beam) from an accelerator.

(Prior Art) When an electromagnet is placed in a vacuum chamber, it is difficult to create an ultrahigh vacuum in the chamber because the gas released from the structural material and the insulating material pollutes the vacuum. In order to solve this problem, a beam focusing electromagnet that applies a magnetic field to the beam in a direct current (hereinafter referred to as a DC electromagnet) can be used in a vacuum chamber by sealing the electromagnet in a non-magnetic metal container. Although possible, in the case of a beam focusing electromagnet (hereinafter referred to as a pulse electromagnet) that applies a magnetic field to the beam in a pulsed manner, an eddy current is generated in the wall of the metal container, and the accuracy of the magnetic field on the beam orbit surface deteriorates.

As described above, in the case of a pulse electromagnet in which a metal container cannot be used to shield the electromagnet and the vacuum region, the electromagnet is made using a material with a relatively small amount of released gas, and the whole is housed in a vacuum chamber, and A method of exhausting the vacuum chamber with a pump with a large displacement was used, and it was difficult to maintain an ultrahigh vacuum (Fig. 3). Another method is to run the beam in a non-metallic vacuum chamber and provide a pulse electromagnet in the external atmosphere, but this is a major obstacle to downsizing and high efficiency of the electromagnet (Fig. 4). .

(Problem to be Solved by the Invention) In view of the prior art, it is an object of the present invention to provide a beam focusing electromagnet in an ultrahigh vacuum.

(Means for Solving the Problems According to the Invention) A vacuum chamber in which accelerated charged particles run along a predetermined beam axis, and a pair of excitation units installed in the vacuum chamber and symmetrically arranged with respect to the beam axis. The excitation coil storage container has coils and a storage container for the coils. The excitation coil storage container is formed of a ceramic material on the surface facing the passing beam and a metal material except the surface facing the beam.

(Example) FIG. 1 is a sectional view of an air-core quadrupole pulse electromagnet. 1 in the figure
Is an ultra-high vacuum tank, the inside is the ultra-high vacuum region V, and the outside is the atmosphere A. Reference numeral 2 denotes an air-core coil housing container for housing an exciting air-core coil 3, which is composed of a metal container portion 2a and a ceramic window 2b facing the passing beam B. Metal container part 2a
The ceramic window 2b and the ceramic window 2b are joined together with a silver braze without a gap. Thus, the air-core coil 3 has an external ultra-high vacuum region V
Is quarantined against.

The storage container 2 having the air core coil 3 stored therein has a support 4
Are arranged symmetrically to the beam axis by the ceramic window
2b face each other. The generated pulsed magnetic field is transmitted without being magnetically blocked by the ceramic window 2b and without generating an eddy current.
A predetermined magnetic field as shown in FIG. 2 can be obtained in a region C passing through.

Although the above example is the case of the air-core pulse electromagnet, even in the case of an AC electromagnet or the like, a similar structure can obtain a predetermined magnetic field in a predetermined region without impairing the high vacuum degree. .

(Effects) Due to the above configuration, the ultra-high vacuum region V in the ultra-high vacuum chamber 1
The beam focusing electromagnet can be provided in the ultra-high vacuum without any loss of the direct high vacuum inside, and the magnetic field generated by the electromagnet is the ceramic window 2b (first It is possible to obtain a predetermined magnetic field in a region C through which the beam B passes completely through (FIG. 1). Further, with this configuration, the electromagnet can be installed near the beam axis, so that the electromagnet can be downsized and highly efficient.

Since the surface of the coil housing for excitation that faces the passing beam is made of ceramic material, it is possible to reduce the amount of gas emitted from the ceramic material, and the degree of vacuum is extremely reduced compared to the case of using a full ceramic material. Can be slight.

[Brief description of drawings]

 FIG. 1 shows an electromagnet according to the present invention. FIG. 2 shows the magnetic field generated in the beam passage portion. FIG. 3 shows a conventional example in which an electromagnet is installed in a vacuum chamber. FIG. 4 shows a conventional example in which an electromagnet is installed outside the vacuum chamber. In the figure; 1 ... Ultra-high vacuum chamber 2 ... Air core coil storage container 2a ... Metal container part, 2b ... Ceramic window 3 ... Air core coil, 4 ... Support V ... Ultra high vacuum region, A …… Atmosphere B …… Beam C …… The region where the beam passes

Claims (1)

[Claims] 1. A vacuum chamber in which accelerated charged particles run along a predetermined beam axis, a pair of exciting coils disposed in the vacuum chamber and symmetrically arranged with respect to the beam axis, and A beam focusing container having a coil housing, wherein the exciting coil housing is formed of a ceramic material on a surface facing a passing beam and a metal material other than a surface facing the beam. electromagnet.