JPH0519100A - Electron beam irradiation device - Google Patents

Abstract

PURPOSE:To obtain the device with a wide variable range of electron energy by upward and downward movably providing an absorber of the electron energy in a vacuum duct and setting an electromagnet for converging the direction of an election absorbing the energy with the use of the absorber on the circumference of a duct. CONSTITUTION:An energy absorber 7 is upward and downward movably provided in a vacuum duct 31. A covergent electromagnet 8 is provided on the circumference of the duct 31. An electron passing the absorber 7 is converged with the electromagnet 8 to eliminate the dispersion of the direction, taken out from an electron beam taking-out window 4, scattered by the use of a flattening filter 5, an electron speed is made constant and electron beam energy on an electron beam irradiation face 12 is uniformed. As the result of the structure, even if the variable range of the electron energy caused by the increase and reduction of microwave energy input in an accelerating tube 2 is made wide, an irradiation face 12 can be irradiated by uniform energy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam irradiation device using an electron accelerator.

[0002]

2. Description of the Related Art FIG. 3 is a sectional view of a conventional electron beam irradiation apparatus, in which 1 is an electron gun, 2 is an accelerating tube for accelerating electrons attached to the tip of the electron gun 1, and 2a is an accelerating tube. A plurality of cavities that are provided in 2 to generate an electric field by inputting a microwave, 3 are vacuum ducts attached to the exit of the accelerating tube 2, 4 are electron beam extraction windows made of thin metal foil, and 5 are A flattening filter for flattening the electron beam dose distribution, 6 is an electron beam trajectory, and 12 is an electron beam irradiation surface.

Next, the operation will be described. The electrons emitted from the electron gun 1 enter the accelerating tube 2. On the other hand, microwaves are input to the cavities 2a provided in a large number of stages in the acceleration tube 2, and the microwaves generate an electric field in the acceleration tube 2 to accelerate electrons. At this time, the microwaves input to the cavities 2a of each stage are sequentially considered as they proceed to the subsequent stages in consideration of the velocity of the electrons accelerated in the accelerating tube 2 and the amount of energy given to the electrons by the generated electric field. A standing wave with a delayed phase is input to generate the maximum electric field. In this way, the electrons accelerated by receiving energy in good timing by the electric field from the cavities 2a of each stage are 60 Me at the exit of the acceleration tube 2.
It becomes a high energy of V to 20 MeV.

Electrons accelerated by the accelerating tube 2 and having high energy form an electron beam 6, which passes through the vacuum duct 3 and jumps out into the air through an electron beam extraction window 4 made of a thin metal foil and flattened. The velocity of the electrons is made constant by being scattered by the filter 5, and reaches the electron beam irradiation surface 12.

[0005]

Since the conventional electron beam irradiation apparatus is constructed as described above, it is necessary to change only the energy of the microwave input to the cavity 2a of the accelerating tube 2 to change the energy of the electron. I was going there. However, in this case, in order to protect the timing of the energy received by the electrons in the acceleration tube 2 from the electric field generated by the cavities 2a at each stage, the variable range of the microwave energy must be limited,
Further, since the length of the accelerating tube 2 is fixed, there is a problem that the variable range of electron energy must be narrowed.

As an approximate technical literature, the current state of use of electronic linac (accelerator science, Vol. 1, No. 1, 198)
Published April 4, pp. 29-37, by Bita Fujita).

The present invention has been made to solve the above problems, and an object thereof is to obtain an electron beam irradiation apparatus having a wide electron energy variable range.

[0008]

In the electron beam irradiation apparatus according to the invention described in claim 1, an energy absorber for absorbing electron energy is provided in a vacuum duct so as to be vertically movable, and the energy absorption is performed. A focusing electromagnet that converges the direction of electrons whose energy is absorbed by the body by a magnetic field is provided around the vacuum duct.

In the electron beam irradiation apparatus according to the invention described in claim 2, the vacuum duct of the invention described in claim 1 has a deflection magnet for deflecting electrons by a magnetic field, and a maximum of the electrons dispersed by the deflection. A vacuum duct for a deflection system provided with a slit for cutting high-energy electrons and a slit for cutting low-energy electrons for blocking at the dispersion position is attached.

[0010]

The energy absorber according to the first aspect of the invention absorbs the energy of the electron, reduces the energy of the electron after passing through it, and moves up and down to expand the variable range of the energy of the electron.

In the deflection system vacuum duct according to the second aspect of the invention, electrons are deflected by the magnetic field of the deflection magnet, and the high energy electron cutting slits and the low energy electron cutting slits block the electrons dispersed by the deflection. Then, select only the electrons with a certain energy.

[0012]

【Example】

Example 1. An embodiment of the present invention will be described below with reference to the drawings. In the figure, the same components as those shown in FIG. 3, which is a conventional technique, are designated by the same reference numerals, and the duplicate description thereof will be omitted. FIG. 1 is a cross-sectional view showing an electron beam irradiation apparatus according to an embodiment of the invention described in claim 1. In the figure, 7 is an energy absorber provided in a vacuum duct 31 and movable up and down, and 8 is an energy absorber. A focusing electromagnet that is provided around the vacuum duct 31 to converge the direction of the electron beam, and 31 is a vacuum duct that houses an energy absorber.

Next, the operation will be described. By varying the microwave energy input to the accelerating tube 2, the electron energy variable range was 6 MeV to 20 MeV. If, for example, an energy absorber 7 having a thickness of 5 mm of aluminum is used in the vacuum duct 31 at the outlet of the acceleration tube 2, the energy variable range of the electrons after passing through the energy absorber 7 is 4 MeV to 18 MeV, and the energy variable range width is energy. It is the same as when the absorber 7 is not used, but it attenuates as a whole. As a result, the energy absorber 7
By moving up and down, the energy variable range of electrons can be expanded to 4 MeV to 20 MeV.

The electrons transmitted through the energy absorber 7 have a broad scattering angle and a broad absorption energy. In other words, there are variations in direction and speed. In order to correct this, the focusing electromagnet 8 is used to converge the direction of the electrons by the magnetic field. Electrons whose variations in direction are eliminated by the magnetic field of the converging electromagnet 8 are taken out from the electron beam extraction window 4 and scattered by the flattening filter 5 so that the speed of the electrons is constant and the electron beam irradiation surface 1
At 2, the electron beam energy is made uniform.

Example 2. Although the electron beam irradiation device in which the electrons that have passed through the energy absorber 7 are directly scattered by the flattening filter 5 has been shown in the above-described embodiment, after passing through the energy absorber 7, an energy selection system such as a deflection electromagnet is added. Further, the electron beam energy can be made uniform.

FIG. 2 is a sectional view showing an electron beam irradiation apparatus according to an embodiment of the invention described in claim 2. In the figure, 9 is a 270 ° deflection magnet (deflection magnet) and 10 is a high energy electron cut. Is a slit for low energy electron cutting, and 32 is a vacuum duct for a 270 ° deflection system (deflection system vacuum duct).

Next, the operation will be described. The electrons transmitted through the energy absorber 7 have a spread in the scattering angle and a spread in the absorbed energy. In other words, there are variations in direction and speed. This electron is focused by the electromagnet 8
After the direction of the electrons is converged by the magnetic field at 270 °, it is deflected by 270 ° by the 270 ° deflection electromagnet 9 and is incident on the flattening filter 5.

The electrons whose directions are converged by the converging electromagnet 8 have variations in speed, and the maximum position dispersion occurs at the 135 ° deflection position where the high energy electron cutting slit 10 and the low energy electron cutting slit 11 are present. The high energy electron cutting slit 10 blocks the electrons dispersed on the high electron velocity side, and the low energy electron cutting slit 11 blocks the electrons dispersed on the low electron velocity side. By selecting only the electrons having the fixed energy, that is, the high-energy electron cutting slit 10 and the low-energy electron cutting slit 11, the electron beam energy reaching the electron beam irradiation surface 12 can be made more uniform.

[0019]

As described above, according to the invention described in claim 1, an energy absorber for absorbing electron energy is provided in the vacuum duct so as to be vertically movable, and the energy is absorbed by the energy absorber. Since the converging electromagnet for converging the direction of the absorbed electrons by the magnetic field is provided around the vacuum duct, there is an effect that an electron beam irradiation device having a wide variable range of electron energy can be obtained.

According to the invention described in claim 2, in the vacuum duct of the invention described in claim 1, the deflection magnet for deflecting the electrons by the magnetic field and the electrons dispersed by this deflection are blocked at the maximum dispersion position. Since a high-energy electron cutting slit and a low-energy electron cutting slit are installed in the deflection system vacuum duct, only electrons with a certain energy can be selected. There is an effect that an electron beam irradiation device capable of further homogenizing the electron beam can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing an electron beam irradiation apparatus according to an embodiment of the invention described in claim 1.

FIG. 2 is a sectional view showing an electron beam irradiation apparatus according to an embodiment of the invention described in claim 2.

FIG. 3 is a sectional view showing a conventional electron beam irradiation apparatus.

[Explanation of symbols]

1 Electron Gun 2 Accelerator 2a Cavity 5 Flattening Filter 7 Energy Absorber 8 Converging Electromagnet 9 270 ° Deflection Magnet (Deflection Magnet) 10 High Energy Electron Cutting Slit 11 Low Energy Electron Cutting Slit 31 Vacuum Duct 32 270 ° Deflection System vacuum duct (deflection system vacuum duct)

Claims (2)

[Claims] 1. An electron gun for emitting electrons, an accelerator tube for accelerating the electrons emitted from the electron gun by generating an electric field by inputting a microwave into a cavity provided in multiple stages, An energy absorber that is provided movably up and down in a vacuum duct attached to the outlet of the acceleration tube and that absorbs the energy of electrons, and is provided around the vacuum duct, and the energy is absorbed by the energy absorber. An electron beam irradiation apparatus comprising: a converging electromagnet that converges the direction of electrons by a magnetic field; and a flattening filter that scatters the electrons whose directions are converged by the magnetic field of the converging electromagnet to make the energy of the electrons uniform. 2. A deflection magnet, wherein the vacuum duct is provided with a deflection magnet for deflecting electrons by a magnetic field, slits for cutting high-energy electrons and slits for cutting low-energy electrons for blocking electrons dispersed by deflection at a maximum dispersion position. A vacuum duct for a system is attached to the system.
The electron beam irradiation apparatus described.