JP2000315599A - Accelerator with electron gun - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the risk of a collision of an electron beam against an accelerating cavity wall so as to improve acceleration efficiency by arranging an ACS type accelerating cavity serving as an annular type joint cavity between the outlet of an electron gun and an SCS type accelerating tube receiving an electron beam for accelerating it. SOLUTION: A high frequency wave introduced from a wave guiding tube 5 excites an electromagnetic field inside an accelerating cavity 3, and furthermore, excites a similar electromagnetic field in the adjacent accelerating cavity 3 via a joint hole 3b and a joint cavity 7. In addition, an electromagnetic field is excited also inside an accelerating cavity 25 via an annular joint cavity 23 and joint holes 3c, 25a. As the joint hole 25a is positioned symmetrically with respect to an axial passage through which an electron beam 21 passes, the electromagnetic field inside the accelerating cavity 25 is also formed symmetrically. Therefore, when an electron gun 1 emits an electron beam 21, the electron beam 21 passes through a beam hole 9 so as to be accelerated inside the accelerating cavity 25 without deflecting, and then, enters an SCS accelerating cavity 3 via a beam hole 25b so as to be linearly accelerated efficiently.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for electromagnetically accelerating particles, and more particularly to an accelerating tube for electromagnetically accelerating an electron beam emitted from an electron gun.

[0002]

2. Description of the Related Art FIG. 2 shows an example of a conventional .pi. / 2 mode SCS type accelerator. This SCS
An outline of the structure and operation of the accelerator is as follows.
Is accelerated by the accelerating cavities 3 juxtaposed so as to form the trajectory of the electron beam. That is, the high frequency wave introduced into the waveguide 5 excites an electromagnetic field in the acceleration cavity 3. Further, the high frequency excites a similar electromagnetic field in the adjacent acceleration cavity 3 through the coupling hole and the coupling cavity 7 on the side surface of the acceleration cavity 3. On the other hand, the electron beam emitted from the electron gun 1 enters the acceleration cavity 3 through the beam hole 9 and is accelerated by the electromagnetic field excited therein. Such an arrangement structure of the accelerating cavities 3 is SCS (Side-Coupled).
It is called a “structure” type acceleration tube and has good acceleration efficiency. However, since there is a coupling cavity 7 outside the accelerating cavity 3,
The region is not axially symmetric but is distorted due to the electromagnetic field being pulled by the coupling hole and having a low energy of the electron beam, in other words, the electron gun 1
However, there is a problem that the electron beam is easily bent in a region close to.

To solve the above-mentioned problem of the SCS type accelerating tube, as shown in FIG. 3, an APS (Alternating Periodic Structure) type cavity 11 is provided between the electron gun 1 and the upstream accelerating cavity 3. To obtain a stable electron beam. This structure is an axially symmetric structure capable of transmitting a high frequency wave from the on-axis beam hole 13 to the adjacent cavity, so that bending of the electron beam is prevented.

[0004]

However, in the case where the APS type cavity is provided upstream of the SCS type accelerating tube as described above, the APS type cavity has a cavity which does not contribute to acceleration on the axis. Therefore, acceleration efficiency is poor. The high frequency is a cavity 3
Therefore, there is a fundamental problem that the beam hole 13 cannot be reduced because the light propagates through the beam hole 13 to the adjacent cavity. For this reason, as shown in FIG. 3, a portion where the velocity of the electrons is low has a large radial electric field component, so that there is a problem that the diameter of the electron beam increases and there is a risk of colliding with the cavity wall surface. Accordingly, an object of the present invention is to provide an accelerator with an electron gun that has high acceleration efficiency and has no danger of the electron beam colliding with the wall of the acceleration cavity.

[0005]

According to the present invention, there is provided an electron accelerator with an electron gun, comprising: an electron gun for emitting an electron beam; and an SCS type receiving and accelerating the electron beam. An accelerating tube, an exit of the electron gun and the S
It is characterized by having an ACS (Annular-Coupled Structure) -type accelerating cavity which is disposed between the CS-type accelerating tube and which is an annular coupling cavity.

[0006]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Note that the same portions are denoted by the same reference numerals throughout the drawings including the drawings related to the prior art. Referring to FIG. 1, SCS-type accelerating cavities 3 are arranged along a traveling path of an electron beam 21 emitted from the electron gun 1. That is, each of the accelerating cavities 3 is connected by a beam hole 3a.
Used to advance 1. Furthermore, the acceleration cavity 3 has a coupling hole 3b at a position shown in the radial direction outside of the beam hole 3a, which communicates with a coupling cavity 7 provided on the outside of the SCS type acceleration tube. ing. The waveguide 5 communicates with one of the SCS-type accelerating cavities 3, and the waveguide 5 communicates with a high-frequency source (not shown).

On the electron gun 1 side of the SCS-type accelerating cavity 3 closest to the electron gun 1, a coupling hole 3 c is provided symmetrically at a similar position, which connects to the annular coupling cavity 23. I have. The annular coupling cavity 23 communicates with the acceleration cavity 25 via the coupling hole 25a. The accelerating cavity 25 is formed by dividing the accelerating cavity 3 into two parts in the axial direction as shown in the figure. The annular coupling cavity 23 is
An ACS (Annular-Coupled Structure) type acceleration cavity is formed.

In the electron beam accelerator having the above configuration, the interiors of the acceleration cavities 3 and 25, the coupling cavity 7 and the annular coupling cavity 23 are maintained at a high degree of vacuum, and are introduced from the waveguide 5. The generated high frequency excites an electromagnetic field in the acceleration cavity 3. Further, the high frequency wave is supplied to the coupling hole 3b on the side surface of the acceleration cavity 3.
And a similar electromagnetic field is excited in the adjacent acceleration cavity 3 via the coupling cavity 7. Further, the electromagnetic field is also excited in the accelerating cavity 25 through the annular coupling cavity 23 and the coupling holes 3c and 25a. Since the coupling hole 25a is located symmetrically with respect to the axial path through which the electron beam 21 passes, the electromagnetic field in the acceleration cavity 25 is also symmetric. Therefore,
If the electron gun 1 emits the electron beam 21 in such a state, the electron beam 21 is accelerated without being deflected in the acceleration cavity 25 after passing through the beam hole 9. Furthermore,
The beam enters the SCS type acceleration cavity 3 through the beam hole 25b, and is efficiently linearly accelerated.

[0009]

As described above, according to the present invention,
Since the ACS-type accelerating cavity is located between the electron gun and the SCS-type accelerating cavity, the electron beam is linearly accelerated without being deflected by the symmetric electromagnetic field, and is effective without damaging the periphery of the beam hole. The electron beam can be accelerated. Moreover, even between the SCS type acceleration cavity and the electron gun,
Since the electron beam is accelerated by the ACS accelerating cavity without interruption, the acceleration efficiency can be improved as compared with the conventional case.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an electron beam accelerator for explaining an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a conventional device.

FIG. 3 is a partial longitudinal sectional view for explaining a problem of the conventional device.

[Explanation of symbols]

 Reference Signs List 1 electron gun 3 acceleration cavity 3a beam hole 3b, 3c coupling hole 5 waveguide 7 coupling cavity 9 beam hole 21 electron beam 23 annular coupling cavity 25 acceleration cavity 25a coupling hole

Claims (1)

[Claims] 1. An electron gun for emitting an electron beam, an SCS-type accelerating tube for receiving and accelerating the electron beam, and an A-tube disposed between an exit of the electron gun and the SCS-type accelerating tube.
An accelerating device with an electron gun, comprising a CS-type accelerating cavity.