JP2996242B1 - Extraction electrode - Google Patents

Abstract

An object of the present invention is to prevent deformation of an extraction electrode due to heat input. SOLUTION: This extraction electrode 20 has two support members 26a, 26 arranged in parallel at a fixed interval from each other.
b. Then, one end 36a is fixed to the one support 26a, and the other end 36a is fixed to the other support 26b.
b, a metal round rod-shaped first electrode rod 3 that freely supports b
6 are arranged side by side at a constant interval from each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an extraction electrode for extracting charged particles used for, for example, extracting electrons emitted from a filament in an electron beam accelerator or extracting an ion beam from plasma in an ion source. More specifically, the present invention relates to means for preventing deformation of the extraction electrode due to heat input.

[0002]

2. Description of the Related Art FIG. 6 shows an example of an electron beam accelerator used in an electron beam irradiation apparatus.

The electron beam accelerator 2 is of a non-scanning type (or area type) which does not scan the electron beam 12, and has a semi-cylindrical shield electrode 6 in a cylindrical vacuum vessel 4.
And a plurality of (for example, about 30) linear (rod-like) filaments 8 are formed in the shield electrode 6 by Y.
The electrons emitted from each filament 8 are accelerated and extracted as an electron beam 12 through an extraction electrode 10, and the irradiation window 1
4 is transmitted through and emitted to the outside. The direction parallel to each filament 8 is referred to herein as the X direction (ie, short direction; the same applies hereinafter). In the case of an electron beam irradiation device, the emitted electron beam 12 is applied to an object to be irradiated (not shown), and is used for modifying the object to be irradiated.

[0004] The irradiation window 14 has a window foil 14 a through which the electron beam 12 is transmitted in order to separate a vacuum atmosphere inside the vacuum vessel 4 from an external irradiation atmosphere (for example, in the air).

An electric field (for example, a high voltage of about 30 kV to 300 kV) for extracting and accelerating the electron beam 12 includes a shield electrode 6 and an extraction electrode 10 having the same potential as the shield electrode 6, a vacuum vessel 4 having a ground potential, and irradiation with the same potential. Applied between the window 14.

As shown in FIG. 7, the conventional extraction electrode 10 has a structure in which the periphery of a flat mesh electrode 18 is fixed to a frame-shaped support plate 16. The support plate 16 is fixed to the opening of the shield electrode 6 described above.

[0007]

When the electron beam accelerator 2 is operated, the mesh electrode 18 of the extraction electrode 10 is
Since heat input is applied by radiant heat from the filament 8 and incidence of electrons, the mesh electrode 18 thermally expands.

However, since the periphery of the mesh electrode 18 is fixed to the support plate 16 as described above, when the mesh electrode 18 expands, the mesh electrode 18 expands or dents accordingly. This causes distortion (deformation) and impairs planarity.

As a result, as shown in FIG. 8, in a normal state, an acceleration electric field distribution (E in the figure indicates an equipotential surface) between the extraction electrode 10 and the irradiation window 14 is uniform. Due to the distortion of the extraction electrode 10, the acceleration electric field distribution is also distorted as shown in FIG.

As a result, the trajectory of the electron beam 12 extracted through the extraction electrode 10 becomes abnormal, and the irradiation window 14
A part of the electron beam 12 which should pass through the inner wall of the vacuum vessel 4 and the crosspiece for supporting the window foil 14a of the irradiation window 14 (not shown).
For example, see JP-A-62-187300).

As a result, the loss of the electron beam 12 increases, and the extraction efficiency of the electron beam 12 decreases. In addition, the distribution of the extracted electron dose is disturbed, and the uniformity (flatness) of the electron dose distribution is deteriorated. This deterioration in uniformity is greater in the Y direction (longitudinal direction) than in the X direction (short direction). This is because the mesh electrode 18 is longer in the Y direction than in the X direction, so that the distortion in the Y direction is usually larger.

Also in the ion source, the extraction electrode for extracting the ion beam receives heat input from the filament or the plasma, and thus extracts the ion beam using the extraction electrode 10 having the mesh electrode 18 fixed around as described above. In such a case, the same problem as described above exists.

Accordingly, it is a primary object of the present invention to prevent deformation of an extraction electrode due to heat input.

[0014]

According to the present invention, there is provided an extraction electrode comprising a plurality of metal round rod-shaped first electrode rods, one end of which is fixed to a support and the other end of which is supported so as to be freely extendable. It is characterized by being juxtaposed.

According to the above configuration, since a plurality of metal round rod-shaped electrode rods are arranged side by side with an interval therebetween, charged particles can be extracted from between the respective electrode rods.

In addition, since one end of each electrode rod is fixed to the support, positioning of each electrode rod and prevention of falling off can be performed.

Further, since the other end of each of the electrode rods is supported on the support so as to be able to expand and contract freely, even if a thermal input is applied to each of the electrode rods and each of the electrode rods thermally expands, it absorbs (releases) it. be able to. Therefore, deformation of each electrode rod due to heat input, that is, deformation of the extraction electrode due to heat input, can be prevented.

[0018]

FIG. 1 is a plan view showing an example of an extraction electrode according to the present invention. FIG. 2 is a sectional view taken along line AA of FIG.
FIG. Since the extraction electrode 20 is used in place of the conventional extraction electrode 10 in the electron beam accelerator 2 as shown in FIG. 6 as an example, the configuration as the electron beam accelerator is the same as that of FIG. The description is referred to, and the duplicate description is omitted here.

In this example, the extraction electrode 20 is provided with two support members 26a, 2a which are arranged at a fixed distance from each other in the X direction and parallel to each other along the Y direction.
6b. One end 3 is attached to this one support 26a.
6a is fixed, and a first electrode rod 36 in the form of a metal round bar having the other end 36b supported on the other support body 26b so as to be freely expandable and contractible,
A plurality of them are arranged side by side in the Y direction at a fixed interval from each other. The two supports 26a and 26b are fixed to a rectangular frame-shaped support plate 22 in this example. That is, the extraction electrode 20 is fixed to the opening of the shield electrode 6 via the support plate 22 in this example.

More specifically, referring mainly to FIG. 2, the electrode rods 36 are attached to both the supports 26a and 26b.
The holes 28 for inserting the one end 36a and the other end 36b of each of the electrode rods 36 are provided laterally at the portions supporting the electrodes. Each hole 2 of this one support 26a
One end 36a of each electrode rod 36 is inserted into 8a, and is fixed with a fixing screw 32, respectively. For this purpose, a female screw portion 30 to be screwed with the fixing screw 32 is provided above each of the holes 28. The support plate 22 has a hole 24 through which each fixing screw 32 passes.

The other end 36b of each electrode rod 36 is simply loosely inserted into each hole 28 of the other support 26b, and is not fixed by screws or the like. This other end 3
Between the tip of 6b and the back of the hole 28, there is a clearance allowance 34 that can absorb the elongation of the electrode rod 36 due to thermal expansion. In this way, the other end 36b of each electrode rod 36 is supported so as to be able to expand and contract freely.

Each of the electrode rods 36 is preferably formed of, for example, stainless steel or a high melting point metal such as molybdenum, tungsten, tantalum or the like. This is because these have high heat resistance. In addition, it is preferable to increase the thickness of each electrode rod 36 to a certain extent (for example, to a diameter of about 0.5 mm to 1.5 mm), so that the heat capacity and heat resistance of each electrode rod 36 can be improved. it can. The same applies to a second electrode rod 38 described later.

The interval (pitch) between the electrode rods 36 is, for example, 6 mm, but is not limited to this. The number of the electrode rods 36 arranged in parallel may be determined according to the required width of the electron beam 12 (see FIG. 6) in the Y direction.

Instead of using this example, the supports 26a and 26b may be formed as a single rectangular frame-shaped support, and the support plate 22 may be omitted.

According to the extraction electrode 20, since the plurality of metal rod-shaped electrode rods 36 are arranged side by side at intervals, the electron beam 12 can be extracted from between the electrode rods 36.

In addition, since one end 36a of each electrode rod 36 is fixed to the support 26a, positioning of each electrode rod 36 and prevention of falling off can be performed.

Further, since the other end 36b of each electrode rod 36 is supported by the support 26b so as to be freely expandable and contractible, each electrode rod 36
The heat input from the filament 8 etc. is applied to each of the electrode rods 36.
Can be absorbed (released) even if it expands thermally. Specifically, as described above, the extension of each electrode rod 36 is absorbed by the clearance allowance 34 of each hole 28. Therefore, it is possible to prevent deformation of each electrode bar 36 due to heat input, that is, deformation of the extraction electrode 20 due to heat input. In particular,
The flatness of the extraction electrode 20 and the interval between the respective electrode rods 36 can be maintained at the beginning (that is, before the operation of the electron beam accelerator 2).

As a result, even if a heat input is applied to the extraction electrode 20, the acceleration electric field is not distorted as in the conventional example, so that there is no abnormality in the trajectory of the electron beam 12 extracted through the extraction electrode 20. Therefore, it is possible to prevent a decrease in the extraction efficiency of the electron beam 12 during the operation of the electron beam accelerator 2. In addition, it is possible to prevent the uniformity of the electron dose distribution from being deteriorated not only in the X direction but also in the Y direction.

Each of the above-mentioned linear filaments 8 is positioned between the electrode rods 36 (preferably at the center therebetween) in plan view, as in the example shown in FIG. 1, for example. It is preferable to arrange them. By doing so, the rate at which the electron beam 12 extracted from each filament 8 is obstructed by the electrode bar 36 is reduced, and the extraction efficiency of the electron beam 12 is further improved.

In the example of FIG. 1, the interval (pitch) between the filaments 8 is reduced for the sake of illustration. However, in actuality, for example, the interval between the filaments 8 is set to 36 mm, and the filaments are provided for every six electrode rods 36. 8 are arranged. However, it is not limited to this.

FIG. 3 is a plan view showing another example of the extraction electrode according to the present invention. FIG. 4 is a sectional view taken along line BB of FIG. Explaining mainly the differences from the examples shown in FIGS. 1 and 2 above, in the extraction electrode 20, the vicinity of the center in the length direction of the first electrode rod 36 (that is, the X direction) becomes a right angle. In the crossing direction (that is, the Y direction), three metal round rod-shaped second electrode rods 38 are arranged side by side at a predetermined interval.

In this example, each electrode rod 38 is connected to the support plate 2.
2, one end 38a is fixed to the other end 38a.
b is freely stretchable. Fixing screw 5 shown in FIG.
4 is for fixing the one end 38a. The support structure at the end of the electrode rod 38 may be the same as the above-described support structure of the first electrode rod 36, for example, and a detailed description thereof will be omitted. Note that both ends of each of the electrode rods 38 may be supported so as to freely expand and contract. Further, as described above, the support 26a
And 26b may be one rectangular frame-shaped support, and the end of each electrode rod 38 may be fixed and freely supported on the support as described above.

The second electrode rods 38 are separate from and independent of the first electrode rods 36. That is, the electrode rods 38 and the electrode rods 36 are not restricted to each other. Therefore, since each of the electrode rods 36 and each of the electrode rods 38 can freely expand and contract with each other, even if the electrode rods 38 are provided, deformation of the electrode rods 36 and 38 due to heat input, that is, deformation of the extraction electrode 20 is prevented. Thus, the flatness and the like of the extraction electrode 20 can be maintained.

The above-mentioned support structure of each electrode rod 38 will be described more specifically. A plurality of support plates 40 are mounted on the first electrode rod 36 at a fixed interval (pitch). This pitch is, for example, 72 mm, but is not limited to this.

The support plate 40 and the electrode bar 36 thereunder may or may not be fixed to each other. It is preferable not to fix them, since they can freely expand and contract with each other, and to prevent deformation of both.

In order to prevent each support plate 40 from falling down, both ends of each support plate 40 are supported by support fittings 44. Each support fitting 44 has a downwardly curved shape, and has a groove 46 at its tip end for supporting the end of the support plate 40 so as to be able to freely expand and contract. Each support fitting 44 is fixed to the support plate 22 in this example using the fixing screw 32, the nut 48, and the fixing screw 50 which are longer than in the example of FIG. However, as described above, when the support plate 22 is omitted or the like, each support fitting 44 may be fixed to the supports 26a and 26b.

At the center of each support plate 40 and at equal distances on the left and right sides thereof, holes 42 are provided for allowing the respective electrode rods 38 to freely extend and contract. That is, the inner diameter of each hole 42 is larger than the outer diameter of each electrode rod 38. Thereby, each electrode rod 3
The support plate 40 does not restrict (allow) the elongation caused by the heat of No. 8. In addition, between both ends of each support plate 40 and the inner walls of the supports 26a and 26b opposed thereto,
Gap 52 is provided to allow thermal expansion of each support plate 40.

When the second electrode rod 38 is provided near the center in the X direction as described above, for example, as shown by a solid line C in FIG. 5, the electron dose distribution in the X direction is flattened (improved uniformity). ) Can be achieved. This is because the electron beam 12 is drawn out while avoiding the electrode rods 38. The distribution shown by the two-dot chain line D in the figure is an example in the case where the electrode rod 38 is not provided. The total amount of electron dose does not differ much between the two.

As described above, by reducing the peak of the electron dose distribution and flattening, it is possible to prevent the above-mentioned local temperature rise of the window foil 14a of the irradiation window 14 for transmitting the electron beam 12. Therefore, the life of the window foil 14a can be extended. In addition, the uniformity of treatment of the irradiation object is improved.

The distribution of the electron dose in the X direction is based on the electrode rod 3
It can be adjusted by the number of the eight, the interval thereof, and the like. The number of the electrode rods 38 is preferably about 2 to 5 and more preferably about 3 because the effect of flattening the electron dose distribution is small when one electrode rod 38 is used, and when the number of electrode rods 38 is too large, the efficiency of extracting the electron beam is reduced.

The extraction electrode 20 having the above structure can be used for extracting an ion beam from plasma in an ion source. Since both the extraction of the electron beam and the extraction of the ion beam are common to the extraction of the charged particles, the above-described effect is also obtained in the case of the extraction of the ion beam.

[0042]

Since the present invention is configured as described above, it has the following effects.

According to the first aspect of the present invention, one end of each electrode rod is fixed to the support, and the other end is supported so as to be freely expandable and contractible. It is possible to escape, so that deformation of each electrode rod due to heat input can be prevented, and deformation of the extraction electrode due to heat input can be prevented. As a result, it is possible to prevent a reduction in the extraction efficiency of the charged particles during operation and a deterioration in the uniformity of the charged particle amount distribution.

[0044] According to the second aspect of the invention, as described above
Since the second electrode rod is provided, the distribution of the amount of charged particles in the length direction of the first electrode rod can be flattened. In addition, the uniformity of treatment of the irradiation object is improved.

According to the third aspect of the present invention, since the filaments are arranged so as to be located between the first electrodes when viewed two-dimensionally, the efficiency of extracting an electron beam can be further improved.

[Brief description of the drawings]

FIG. 1 is a plan view showing an example of an extraction electrode according to the present invention.

FIG. 2 is a cross-sectional view taken along line AA of FIG.

FIG. 3 is a plan view showing another example of the extraction electrode according to the present invention.

FIG. 4 is a sectional view taken along line BB in FIG. 3;

FIG. 5 is a diagram showing an example of an electron dose distribution by the extraction electrode of FIG. 3;

FIG. 6 is a schematic diagram illustrating an example of an electron beam accelerator.

FIG. 7 is a plan view showing an example of a conventional extraction electrode.

FIG. 8 is a diagram illustrating an example of a state of an acceleration electric field when the extraction electrode is normal.

FIG. 9 is a diagram showing an example of a state of an acceleration electric field when the extraction electrode is deformed.

[Explanation of symbols]

 Reference Signs List 8 filament 12 electron beam 14 irradiation window 20 extraction electrode 22 support plate 26a, 26b support 36 first electrode rod 38 second electrode rod

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kenichi Mizusawa 47, Umezu Takaune-cho, Ukyo-ku, Kyoto-shi, Kyoto Nissin High Voltage Co., Ltd. (58) Field surveyed (Int. Cl. ⁶ , DB name) G21K 5 / 04

Claims (3)

(57) [Claims] 1. An extraction electrode for extracting charged particles, in which a plurality of metal round rod-shaped first electrode rods, one end of which is fixed to a support and the other end of which is freely extended and contracted, are arranged at intervals. An extraction electrode characterized by comprising: 2. A be one crossing the first electrode rod
Te, and wherein the first electrode rod be those separated,
A metal round bar-shaped second electrode rod at least one end of which is supported on the support or another support so as to freely expand and contract ,
2. The extraction electrode according to claim 1, wherein a plurality of the extraction electrodes are arranged side by side at an interval in the length direction of the first electrode rod . 3. An electron beam accelerator for extracting electrons emitted from a plurality of linear filaments, wherein each of said filaments is located between said first electrode rods in a plan view. The extraction electrode according to claim 1, wherein the extraction electrode is arranged to be positioned.