JP3896809B2 - Electron beam irradiation device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electron beam irradiation apparatus for irradiating an irradiated object with an electron beam and used for crosslinking, modification, curing, sterilization, and other surface treatment of the irradiated object, and more specifically, the electron emission. The present invention relates to the improvement of the support structure for filaments.
[0002]
[Prior art]
An example of this type of electron beam irradiation apparatus is shown in FIG. This electron beam irradiation apparatus generates an electron beam 10 having a planar shape (for example, a rectangular shape) that is relatively short in the X direction and relatively long in the Y direction orthogonal to the X direction without scanning the electron beam 10. This device is called a non-scanning type or an area type. The Y direction is also called the irradiation width direction.
[0003]
This electron beam irradiation apparatus has a cylindrical vacuum vessel 2 that is long in the Y direction, and a cylindrical shield electrode 4 that is housed therein and is long in the Y direction.
[0004]
In this shield electrode 4, as shown in FIG. 6, a filament array 9, in which a plurality of linear filaments 8 that emit electrons and extend in the X direction, are arranged in the Y direction, is 2 in the X direction. They are arranged side by side.
[0005]
The filaments 8 of each filament row 9 are electrically connected to each other in parallel, and both filament rows 9 are electrically connected to each other in series. This Each filament 8 via the conductive layers 12, 13, filament power P _F for heating the filament transformer 44 is supplied.
[0006]
As shown in FIG. 8, each filament 8 is supported by two leaf springs 60 bent inward. Specifically, both ends of each filament 8 are hooked and supported by the leaf spring 60. Each leaf spring 60 is fixed to the power supply conductors 12 and 13, respectively. A structure similar to this is also described in Japanese Patent Laid-Open No. 11-133197. Since each leaf spring 60 is constantly returning to its initial state (that is, a state where the amount of deflection is 0) due to its elasticity, the filament 8 is energized. When stretched by heating, the amount of bending of the leaf spring 60 can be reduced to absorb the stretch, whereby the required tension for each filament 8 can be maintained even during heating.
[0007]
The power supply conductors 12 and 13 are supported from the support plate 6 via insulators 64 and 65. The support plate 6 is fixed at the same potential as the central feeding conductor 13 and also functions to push back the electrons emitted from the filament 8 to the filament 8 side.
[0008]
Two upper and lower extraction electrodes 14 and 15 for extracting electrons emitted from each filament 8 as an electron beam 10 are provided in the opening of the shield electrode 4. 66 is an insulator.
[0009]
Referring to FIG. 5, both the extraction electrodes 14 and 15 and the shield electrode 4 are at the same potential, and between them and the filament 8, a filament transformer 44 and a controller are used to extract the electron beam 10. A DC extraction voltage V _E is applied from the extraction power supply 54 via 56. The controller 56 controls the amount of the electron beam 10 to be extracted.
[0010]
An irradiation window 22 is provided at the opening of the vacuum vessel 2 facing the extraction electrodes 14 and 15. The irradiation window 22 and the vacuum vessel 2 are at the same potential, and an acceleration power source 58 is provided between the irradiation window 22 and the extraction electrode 14 to accelerate the electron beam 10 extracted from the extraction electrodes 14 and 15. _A high acceleration voltage V _A is applied in direct current. The accelerated electron beam 10 is taken out into an irradiation atmosphere (for example, air) outside the vacuum vessel 2 through the irradiation window 22.
[0011]
The irradiation window 22 has a rectangular planar shape that is long in the Y direction with reference to FIG. 7. The window foil 24 that separates the atmosphere inside and outside the vacuum vessel 2 and transmits the electron beam 10, and the window foil The frame body 28 and the plurality of cooling bars 32 that support the frame 24, and the pressing frame 34 that fixes the peripheral edge of the window foil 24 are provided.
[0012]
When the length of the window foil 24 in the X direction is lengthened, it becomes difficult to cool the vicinity of the center of the window foil 24. In order to prevent this, the irradiation window 22 is arranged at the center of the X direction, that is, the two rows. The cooling water passage portion 30 extending in the Y direction is provided at a position corresponding to the middle of the filament row 9, and two rows of openings 40 through which the electron beam 10 passes are sandwiched therebetween. A cooling water channel 36 through which the cooling water 38 flows is provided in the frame body 28 and the cooling water channel part 30.
[0013]
[Problems to be solved by the invention]
When the filament 8 is heated, each leaf spring 60 has a smaller amount of bending due to the elongation of the filament 8. At this time, the amount of bending of the two leaf springs 60 at both ends of each filament 8 may be reduced evenly. However, due to the individual difference between the two leaf springs 60, a difference in reduction in the amount of bending occurs.
[0014]
At that time, due to the difference in the deflection amount of the two leaf springs 60, the filament 8 (that is, its center 8a) moves (shifts) toward the center or outward from the initial state before the filament 8 extends in the X direction. It will be.
[0015]
FIG. 8 shows an initial state before the filament 8 is stretched. The dose distribution of electrons emitted from each filament 8 has a mountain-shaped distribution in which the vicinity of the center 8a is the largest and the base is widened. Therefore, the electron beam emitted from the two filament arrays 9 and incident on the extraction electrode 14 The dose distribution of 10 has a double mountain shape shown in FIG. 8A.
[0016]
The portion of the bottom of the electron dose distribution that is outside the electron beam extraction region 14 a of the extraction electrode 14 is blocked by the extraction electrode 14 without passing through the extraction electrode 14, and a loss portion in the extraction electrode 14. E. However, since the electron beam 10 corresponding to the loss part E is not extracted from the extraction electrode 14, it does not cause a loss in the irradiation window 22. Since the electron beam extraction region of the lower extraction electrode 15 is usually wider than the electron beam extraction region 14a of the upper extraction electrode 14, the upper extraction electrode 14 is focused here. The loss part E increases the extraction power source current I _E (see FIG. 5) flowing through the extraction power source 54 and increases the load of the extraction power source 54.
[0017]
On the other hand, in the irradiation window 22, since the electron beam 10 collides with the cooling water channel portion 30 at the center and the electron beam 10 is blocked there, a loss portion G is generated in the cooling water channel portion 30 as shown in FIG. 8B. This loss part G increases the acceleration power supply current I _A (see FIG. 5) flowing in the acceleration power supply 58 and increases the load of the acceleration power supply 58.
[0018]
Under such a situation where the loss parts E and G are generated, if the filament 8 is stretched by heating and moves toward the center, the problem becomes much more serious than when the filament 8 moves toward the center.
[0019]
Explaining this, FIGS. 9A and 9B show schematic examples of electron dose distributions in the extraction electrode 14 and the irradiation window 22 when the filament 8 moves toward the center. The above-described two peaks of the electron dose distribution approach each other, resulting in an electron dose distribution in which the vicinity of the center is higher and the width in the entire X direction is narrower. Therefore, although the electron dose of the loss part E in the edge part of the electron beam extraction area | region 14a of the extraction electrode 14 reduces, the electron dose of the loss part G in the cooling water channel part 30 of the irradiation window 22 increases.
[0020]
When the electron dose in the loss portion E decreases, the extraction power source current _IE decreases accordingly, and the load on the extraction power source 54 decreases. However, the acceleration power supply current increases as the electron dose in the loss portion G increases. who amount load increases in I _a acceleration increases power source 58 is much larger. This is because the magnitude of the extraction voltage V _E output from the extraction power supply 54 is, for example, about 400 V to 700 V, whereas the magnitude of the acceleration voltage V _A output from the acceleration power supply 58 is, for example, about 80 kV to 300 kV. Yes, 2 to 3 orders of magnitude higher than the extraction voltage V _E. Therefore, if the decrease amount of the extraction power source current I _{E and} the increase amount of the acceleration power source current I _A are approximately the same, the load increase amount in the acceleration power source 58 is much larger because the voltage is two to three orders of magnitude larger. growing. For example, even if the extraction power supply current _IE increases by 0.1 A, the load of the extraction power supply 54 increases only by about 40 W to 70 W, so this can be easily dealt with. However, if the acceleration power supply current I _A increases by 0.1 _A , The load of the acceleration power source 58 increases by about 8 kW to 30 kW.
[0021]
Therefore, the acceleration power source 58 must have a capacity that can withstand the large increase in load as described above, and the acceleration power source 58 must have a large capacity accordingly. In addition, since the acceleration power supply 58 outputs a very high voltage as described above, the acceleration power supply 58 increases in size, weight, and cost due to an increase in capacity.
[0022]
Moreover, since the increase in the electron dose in the loss part G causes an increase in the amount of heat generated in the cooling water channel 30 due to the incidence of the electron beam, the cooling capacity for the window foil 24 decreases, and the temperature increase of the window foil 24 increases. In order to prevent this, it is necessary to increase the cooling capacity of the irradiation window 22.
[0023]
Further, in the support structure of the filament 8 by the two leaf springs 60 as described above, both the leaf springs 60 are shaken by mechanical vibration applied from the outside, and the position of the filament 8 is fluctuated, and the loss portions E and G Therefore, there is a problem that the output and dose distribution of the electron beam 10 taken out through the irradiation window 22 becomes unstable.
[0024]
Accordingly, the main object of the present invention is to prevent the movement of each filament toward the center due to the elongation of each filament when heated and the fluctuation of the position of each filament due to vibration or the like.
[0025]
[Means for Solving the Problems]
In the electron beam irradiation apparatus of the present invention, the outer ends of the filaments are supported by metal leaf springs bent inward, and the inner ends of the filaments are supported by the leaf springs. It is characterized by being supported by rigid metal fittings with little deflection.
[0026]
According to the above configuration, when each filament is stretched by energizing and heating each filament, almost all of the elongation of each filament is absorbed by the decrease in the amount of deflection of the leaf spring supporting the outer end. Each filament will always move outward. Therefore, it is possible to prevent the above-described increase in the capacity of the acceleration power source and the decrease in the cooling capacity for the window foil due to the movement toward the center.
[0027]
In addition, since the inner end of each filament is supported by a rigid metal fitting, it is possible to prevent the position of the filament from fluctuating due to mechanical vibration applied from the outside. Therefore, it is possible to prevent the output of the electron beam taken out to the outside and the dose distribution from becoming unstable.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is an enlarged view showing an example around a filament of an electron beam irradiation apparatus according to the present invention, and an electron dose distribution (A) in an extraction electrode and an electron dose distribution (B) in an irradiation window before the filament extends. Are shown together. Portions that are the same as or correspond to those in the conventional example shown in FIG. 8 are denoted by the same reference numerals, and differences from the conventional example will be mainly described below. Moreover, the structure of the whole electron beam irradiation apparatus, the top view of the filament row | line | column 9, and the top view of the irradiation window 22 shall refer to the said FIGS. 5-7 and its description, The duplication description is abbreviate | omitted here.
[0029]
In this example, the end of each filament 8 constituting the two filament rows 9 (the side located outside the two filament rows 9) is bent inward as in the conventional example. Each is supported by a leaf spring 60 made of metal. In addition, the end portions on the inner side of each filament 8 (the side positioned on the inner side of the two filament rows 9) are supported by rigid metal fittings 62 that are less bent than the leaf spring 60, respectively. The amount of bending of each leaf spring 60 may be set to an amount that can absorb the elongation of the filament 8 during heating and maintain a predetermined tension. Each leaf spring 60 is supported by the power supply conductor 12, and each rigid fitting 62 is supported by the power supply conductor 13.
[0030]
An example of each leaf spring 60 is shown in FIG. 3, and an example of each rigid fitting 62 is shown in FIG. Both 60 and 62 have a cut groove 68 and a hole 70 for hooking the filament 8 by passing the end of the filament 8 bent back in a U-shape.
[0031]
Each of the rigid fittings 62 has an L-shaped cross section in this example, and the rigidity becomes very high by making such a shape. Compared with the leaf spring 60, the bending can be almost ignored. Further, the effect of preventing the filament 8 from wobbling is great. Of course, the L-shaped cross-section is convenient and preferable for enhancing the rigidity, but of course other shapes may be used.
[0032]
The rigid fittings 62 are preferably made of the same material, the same length and the same cross-sectional area as the leaf spring 60. By doing so, the heat conduction with respect to the heat from the filament 8 can be made the same as that of the leaf spring 60, so the temperature distribution of each filament 8 and thus the symmetry of the emitted electron quantity distribution (the symmetry in the X direction with respect to the center 8a). ) Can be improved.
[0033]
In this electron beam irradiation device, when each filament 8 is heated by energizing each filament 8, almost all of the elongation of each filament 8 is reduced in the amount of deflection of the leaf spring 60 supporting the outer end. Is absorbed by. Since each rigid fitting 62 has high rigidity and little bending, and unlike the leaf spring 60, the rigid fitting 62 is not bent inward from the beginning, so that the rigid fitting 62 does not deform even when the filament 8 extends. Therefore, each filament 8, that is, the center 8 a of each filament 8 always moves outward. In the conventional example, as described above, there are a case of moving toward the center and a case of moving toward the outside, but this apparatus always moves outward.
[0034]
2A and 2B show schematic examples of electron dose distributions in the extraction electrode 14 and the irradiation window 22 when the filament 8 moves outward.
[0035]
Compared to the initial state of FIG. 1, the two peaks of the electron dose distribution are slightly separated from each other, the central portion is slightly lowered, and the entire X-direction width is widened. Therefore, although the electron dose of the loss portion E at the end of the electron beam extraction region 14a of the extraction electrode 14 increases, the electron dose of the loss portion G in the cooling water channel portion 30 of the irradiation window 22 decreases. That is, it is opposite to the case of FIG.
[0036]
When the electron dose in the loss part E increases, the extraction power source current _IE increases correspondingly and the load of the extraction power source 54 increases. The amount by which I _A becomes smaller and the load of acceleration power supply 58 decreases is much larger. The reason is due to the difference in magnitude between the extraction voltage V _E and the acceleration voltage V _A , and the details are as described above.
[0037]
In this way, in this electron beam irradiation apparatus, each filament 8 can be prevented from moving toward the center, so that the acceleration power supply current I _A increases with the extension of each filament 8, that is, the load of the acceleration power supply 58. An increase can be prevented. Therefore, the acceleration power source 58 does not need to consider the load increase accompanying the elongation of the filament 8, and accordingly, the capacity of the acceleration power source 58 can be reduced. As a result, the acceleration power source 58 can be reduced in size, weight, and cost.
[0038]
Further, even if the filament 8 extends, the electron dose of the loss part G in the cooling water channel portion 30 of the irradiation window 22 does not increase, and the amount of heat generated in the cooling water channel portion 30 due to the incidence of the electron beam does not increase. It is possible to prevent the cooling capacity from being lowered and the temperature rise of the window foil 24 associated therewith. Therefore, it is not necessary to increase the cooling capacity for cooling the irradiation window 22.
[0039]
In addition, the inner end of each filament 8 is supported by the rigid fitting 62, and unlike the leaf spring 60, the rigid fitting 62 does not swing even when mechanical vibrations are applied from the outside. It is also possible to prevent the position of the filament 8 from fluctuating due to mechanical vibration applied. Therefore, it is possible to prevent the output and dose distribution of the electron beam 10 taken out from being unstable.
[0040]
The extraction electrode is not limited to the configuration of the two extraction electrodes 14 and 15 as in the above example, and may be one. In that case, for example, it may be considered that there is no extraction electrode 15 and the extraction electrode 14 exists. It is clear from the above description that even with a single extraction electrode, the above-described operational effects can be obtained by adopting the support structure for the filament 8 as described above.
[0041]
【The invention's effect】
Since this invention is comprised as mentioned above, there exist the following effects.
[0042]
According to the first aspect of the present invention, by adopting the above configuration, it is possible to prevent the filaments from moving toward the center, thereby preventing an increase in the load of the acceleration power source accompanying the elongation of each filament. Can do. Therefore, the acceleration power source does not need to consider the load increase accompanying the elongation of the filament, so that the capacity of the acceleration power source can be reduced, and the acceleration power source can be reduced in size, weight, and cost. Can be planned.
[0043]
In addition, even if the filament is stretched, the amount of electron loss lost in the cooling water channel of the irradiation window does not increase, and the amount of heat generated in the cooling water channel due to the incidence of the electron beam does not increase. The temperature rise of the foil can be prevented. Therefore, it is not necessary to increase the cooling capacity for cooling the irradiation window.
[0044]
In addition, since the inner end portion of each filament is supported by the rigid metal fitting, it is possible to prevent the filament position from fluctuating due to mechanical vibration applied from the outside. Therefore, it is possible to prevent the output of the electron beam taken out to the outside and the dose distribution from becoming unstable.
[0045]
According to the second aspect of the present invention, the heat conduction with respect to the heat from each filament can be made the same between the leaf spring and the rigid metal fitting, so that the symmetry of the temperature distribution of each filament and thus the emission electron quantity distribution is improved. can do. In addition, since the rigidity is very high when the rigid fitting has an L-shaped cross section, the position of the filament can be more reliably prevented from fluctuating due to external vibration or the like.
[Brief description of the drawings]
FIG. 1 is an enlarged view showing an example around a filament of an electron beam irradiation apparatus according to the present invention, in which an electron dose distribution (A) in an extraction electrode and an electron dose distribution (B) in an irradiation window before the filament extends. Are shown together.
2 is a diagram showing an outline of an electron dose distribution (A) at an extraction electrode and an electron dose distribution (B) at an irradiation window when the filament extends and the center moves outward in the structure of FIG. 1; .
FIG. 3 is a perspective view showing an example of a leaf spring.
FIG. 4 is a perspective view showing an example of a rigid metal fitting.
FIG. 5 is a diagram showing an example of an electron beam irradiation apparatus.
FIG. 6 is a plan view showing an example of a filament arrangement.
FIG. 7 is a plan view showing an example of an irradiation window.
FIG. 8 is an enlarged view showing an example around a filament of a conventional electron beam irradiation apparatus, and shows an outline of an electron dose distribution (A) at an extraction electrode and an electron dose distribution (B) at an irradiation window before the filament extends. Are shown together.
9 is a diagram showing an outline of an electron dose distribution (A) in an extraction electrode and an electron dose distribution (B) in an irradiation window when a filament extends and its center moves toward the center in the structure of FIG. .
[Explanation of symbols]
8 Filament 9 Filament array 10 Electron beam 14 Extraction electrode 22 Irradiation window 24 Window foil 30 Cooling channel portion 60 Leaf spring 62 Rigid metal fitting

Claims (2)

A filament for emitting electrons, an extraction electrode for extracting the electrons emitted from the filament as an electron beam, and an irradiation window for extracting the electron beam extracted from the extraction electrode into the irradiation atmosphere through the window foil An apparatus for generating an electron beam having a planar shape that is short in the X direction and long in the Y direction perpendicular to the X direction. The filament array is formed by arranging a plurality of linear filaments extending in the X direction in the Y direction. In the electron beam irradiation apparatus that has two rows in the X direction and the irradiation window has a cooling water channel portion extending in the Y direction at a position corresponding to the middle of the two filament rows,
The outer end of each filament is supported by a metal leaf spring bent inward, and the inner end of each filament is supported by a rigid metal fitting that is less bent than the leaf spring. An electron beam irradiation apparatus characterized by comprising: 2. The electron beam irradiation apparatus according to claim 1, wherein the rigid fitting has an L-shaped section, and has the same material, the same length, and the same sectional area as the leaf spring.

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