JPH07282755A - Electron beam irradiating device - Google Patents

Abstract

PURPOSE:To reduce influence of an electric field fluctuation by insulating a vacuum chamber and a central conductor to supply high voltage to a filament part of an electron beam source part by an insulating mechanism in which insulating rings and ring-shaped electrodes are superposed on each other. CONSTITUTION:A shield electrode 3 to shield a filament part 2 of an electron beam source part 4 is mechanically supported with a wall 1A of a vacuum chamber 1 housing the electron beam source part 4 by an insulating insulator 11 composed of a heat resistant insulating material. The other end of a central conductor 7 whose one end is connected to the filament part 2 is connected to an introducing terminal part 13 in a pressure vessel 5. A part between the introducing terminal part 13 and the vacuum chamber 1 is insulated by an insulating mechanism 14 in which insulating rings 15 and ring-shaped electrodes 16 are superposed on each other in a multistage shape. The final electrode 17 among the electrodes 16 of the insulating mechanism 14 is connected to a flange 18 of the vacuum chamber 1, and voltage divider resistors 19 to equalize sharing voltage of the rings 15 are connected between the respective electrodes 16.

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 apparatus, and more particularly to a non-scanning type electron beam irradiation apparatus.

[0002]

2. Description of the Related Art For example, an area type electron beam irradiation apparatus is constructed by arranging a filament portion for radiating an electron beam inside a cylindrical vacuum chamber. A high voltage for acceleration is introduced into this filament portion. Therefore, in the past, a pressure tank filled with insulating gas was connected to the vacuum chamber via an insulating space cone, the center conductor was pierced through this space cone, and the filament portion was connected via this center conductor. High voltage is introduced.

FIG. 6 shows the structure, and 1 is a vacuum chamber in which an electron beam source section 4 composed of a filament section 2 and a shield electrode 3 for shielding the filament section 2 is arranged. Reference numeral 5 is a pressure tank, the inside of which is filled with insulating gas. A space cone 6 is made of resin or the like, and its bottom portion is attached so as to be sandwiched at a connection portion between the vacuum chamber 1 and the pressure tank 5.

Reference numeral 7 denotes a central conductor which penetrates the space cone 6 and has a filament portion 2 at the tip on the vacuum chamber 1 side.
Are connected. The space cone 6 mechanically supports the electron beam source unit 4 in a cantilever manner, and electrically insulates the vacuum chamber 1 and the pressure tank 5. Reference numeral 8 is an accelerating power source connected to the central conductor 7, 9 is an irradiation window formed on the peripheral wall of the vacuum chamber 1, and 10 is a window foil provided on the irradiation window 9.

As can be understood from this structure, the skirt of the spacer cone 6 is connected to the vacuum chamber 1 or the pressure tank 5 which is at ground potential, and the center is connected to the high-voltage center conductor 7. Therefore, a high voltage is applied between the skirt and the center. Such a structure does not cause any particular problem when the accelerating voltage is low, but when the accelerating voltage exceeds 300 kV, it is necessary to lengthen the insulating distance along the surface of the spacer cone 6.

However, if the insulation distance is increased in this way,
The spacer cone 6 becomes large in size, the handling thereof becomes troublesome, and the manufacturing cost becomes high. In addition, when the insulation distance is increased in this way, the surface area becomes large, so that the area effect affects the discharge easily.
Damage probability is high.

Further, since the heat generated by the filament portion 2 is transferred to the spacer cone 6, the dielectric strength of the spacer cone 6 itself is affected by the bulk property due to the distance effect of the surface thereof, so that the material having good heat resistance property. However, ceramics, which are said to have good heat resistance, have difficulty in manufacturing large space cones. In addition, if the electron beam source unit 4 has a long shape, it becomes difficult to support the space cone made of resin in a cantilever manner due to its mechanical strength.

[0008]

SUMMARY OF THE INVENTION According to the present invention, a mechanism for mechanically supporting an electron beam source section and a mechanism for insulation are separated, and the mechanism for insulation has a small surface area and an electric field. The purpose is to reduce the influence of fluctuations in.

[0009]

According to the present invention, a shield electrode of an electron beam source section is mechanically supported on a wall of a vacuum chamber by an insulator made of a heat resistant material, and a central conductor connected to a filament section. Is connected to the introduction terminal portion, and an insulating ring is provided between the introduction terminal portion and the vacuum chamber,
It is characterized in that the ring-shaped electrodes are insulated by an insulating mechanism in which they are alternately superposed in multiple stages, and a voltage dividing resistor for equalizing the shared voltage between the ring-shaped electrodes is connected.

[0010]

[Function] Since a voltage dividing resistor is connected to the ring-shaped electrode of the insulation mechanism, a uniform electric field is applied to each insulation ring, which is much higher than the electric field received in a single stage like the conventional space cone. And stable, and the influence of electric field fluctuation during discharge is reduced. Since the surface area of the insulating ring is small, the area effect is reduced. The electron beam source section is supported by the insulator regardless of insulation with respect to the center conductor.

[0011]

Embodiment An embodiment of the present invention will be described with reference to FIG. In addition, the portions denoted by the same reference numerals as those in FIG. 6 indicate the same or corresponding portions. According to the present invention, the electron beam source unit 4 comprises an insulating insulator 11 made of a heat resistant insulating material such as ceramics.
Is supported by the wall 1A of the vacuum chamber 1.
Reference numeral 12 is a hoop for relaxing the electric field between the insulator 11 and the wall 1A. A specific configuration for connecting the insulator 11 and the electron beam source unit 4 will be described later.

As described above, the electron beam source section 4 is mainly composed of the filament section 2 and the shield electrode 3. However, since the filament section 2 is mechanically connected to the shield electrode 3, the shield electrode 3 Is supported on the wall 1A of the vacuum chamber 1, the electron beam source unit 4 is mechanically supported on the wall 1A.

The other end of the center conductor 7 whose one end is connected to the filament part 2 is connected to the introduction terminal part 13 in the pressure vessel 5. An insulating mechanism 14 is provided between the introduction terminal portion 13 and the vacuum chamber 1. The insulating mechanism 14 is configured by stacking insulating rings 15 made of an insulating material such as ceramic and ring-shaped electrodes 16 alternately and in multiple stages.

The center conductor 7 passes through the center of the insulating mechanism 14. The final electrode 17 of the electrodes 16 of the insulation mechanism 14 is connected to the flange 18 of the vacuum chamber 1. A voltage dividing resistor 19 is connected between the electrodes 16.
The insulating mechanism 14 functions as a partition that partitions the vacuum chamber 1 and the pressure vessel 5.

In order to alleviate the electric field between the outer periphery of the insulating mechanism 14 and the pressure vessel 5, a plurality of electric field alleviating rings 20 are provided on the outer periphery of the insulating mechanism 14. The electric field relaxation ring 20 is connected to each electrode 16. The diameter of the insulating ring 15 is selected so that the spatial electric field between the final electrode 17 and the central conductor 7 is minimized within the allowable range.

In the above structure, the electron beam source section 4 is mechanically supported by the insulator 11 with respect to the vacuum chamber 1. Since the insulator 11 is insulative and heat resistant, the insulating property is sufficiently maintained against the heat transfer from the electron beam source section 4.

The insulating mechanism 14 controls the insulation between the central conductor 7, the vacuum chamber 1 and the pressure vessel 5. Insulation mechanism 1
The insulating ring 16 forming the
And the voltage-dividing resistor 19 connected to this, the electric field between the central conductor 7 and the vacuum container 1 is substantially evenly shared.
Therefore, the sharing of the electric field is stable, and even if the electric field fluctuates, its influence is reduced. Moreover, since the surface area of the insulating mechanism 14 is small, the area effect can be reduced and the occurrence of discharge can be avoided as much as possible.

In the structure shown in FIG. 1, the insulator 11 is provided at the center of the shield electrode 3 along the length direction thereof. However, when the shield electrode extends over a long length, two places are provided like the insulator 11A shown by the dotted line. Alternatively, it may be supported at more places. Although the example of FIG. 1 has a structure in which the electron beam is irradiated vertically downward, the present invention is also applicable to a structure in which the electron beam is irradiated in the horizontal direction. In this case, the insulator 11 is preferably provided above the shield electrode, as in FIG.

FIG. 2 shows a specific structure for mounting the insulator 11. In this example, a metal fitting 21 having a screw hole is embedded in the lower end surface of the insulator 11, and a mounting metal fitting 23 is fixed by tightening a screw 22 in the metal fitting 21.
The mounting bracket 23 is fixed to the shield electrode 3 with screws 24. As a result, the lower end of the insulator 11 is connected to the shield electrode 3. In this case, as the screw 24, a screw for a jack capable of leveling is desirable. Further, the metal fitting 21 is designed to be housed in the shield electrode 3.

A metal fitting 25 having a screw hole is also embedded in the upper end surface of the insulator 11, and an insulator is attached to the metal fitting 27 fixed to the vacuum chamber 1 via the hoop 12 by a screw 26 screwed into the metal fitting 25. 11 is connected. In this way, the shield electrode 3 is attached to the vacuum chamber 1. As the insulator 11, when it is necessary to increase the creepage distance, a fold 28 may be provided as shown by the dotted line in FIG.

As described above, the electrode 16 of the insulating mechanism 14 and the final electrode 17 at the ground potential are exposed to the high electric field of the central conductor 7. Therefore, in order to alleviate this electric field, as shown in FIG. 3, it is preferable to bend the inner end of each electrode 16 and conceal the insulating ring 15 on the ground potential side so as not to be exposed from the central conductor 7. Especially near the final stage, the electrode 16
It is preferable that the insulating ring 15 is covered with a large bend. As a result, the central conductor 7 and the insulation mechanism 1
The electric field between 4 and 4 can be relaxed.

As shown by the dotted lines in FIG. 1, a plurality of insulators 1
When the electron beam source unit 4 is supported by 1A, the shield electrode 3 expands in the lengthwise direction due to heat, so that the insulator 1
There is a possibility that a stress will act between 1A and the 1A. In order to avoid this, as shown in FIG. 4 and FIG.
It is advisable to make the hole through which the long hole 29 passes. According to this, since the escape of the screw 22 due to expansion is formed, it is possible to avoid the stress acting between the shield electrode 3 and the insulator 11A.

[0023]

As described above, according to the present invention, the insulation between the central conductor for supplying a high voltage to the filament of the electron beam source section and the vacuum chamber is not directly involved in the mechanical support of the electron beam source section. This insulation mechanism is constructed by superposing an insulating ring and a ring-shaped electrode and connecting a voltage dividing resistor to the ring-shaped electrode. Since it is more stable than the insulation configuration with a space cone, the influence of electric field fluctuations is reduced and its surface area can be reduced, so that the area effect is reduced and the occurrence of discharge can be prevented as much as possible. Furthermore, since the electron beam source is mechanically supported in the vacuum chamber through the heat-resistant insulator, sufficient insulation characteristics are maintained against heat transfer from the electron beam source. Achieve the kind of effect.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing a supporting portion of the insulator of FIG.

FIG. 3 is a partial cross-sectional view showing a modified example of the insulating mechanism of FIG.

FIG. 4 is a partial cross-sectional view showing a modified example of a connecting portion between an insulator and a shield electrode.

FIG. 5 is a bottom view of FIG.

FIG. 6 is a sectional view of a conventional example.

[Explanation of symbols]

 1 Vacuum Chamber 2 Filament Part 3 Shield Electrode 4 Electron Beam Source 5 Pressure Vessel 7 Center Conductor 8 Accelerating Power Supply 11 Insulator 14 Insulation Mechanism 15 Insulation Ring 16 Ring Electrode 19 Voltage Dividing Resistance 20 Electric Field Relaxation Ring

Claims (2)

[Claims] 1. A shield electrode, which shields a filament portion of an electron beam source portion, is mechanically supported on a wall of a vacuum chamber in which the electron beam source portion is housed by an insulator made of a heat resistant material. , A central conductor connected to the filament portion is connected to an introduction terminal portion, and an insulation mechanism in which insulating rings and ring-shaped electrodes are alternately and multiply stacked between the introduction terminal portion and the vacuum chamber An electron beam irradiation apparatus which is insulated and has a voltage dividing resistor connected between the respective ring-shaped electrodes for equalizing the shared voltage of the insulating ring. 2. The ring-shaped electrode of the insulating mechanism is bent inside the insulating mechanism so that the insulating ring on the ground potential side is hidden from the center conductor.
The electron beam irradiation apparatus according to.