JP4162216B2 - How to attach and store the irradiation window unit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
In this invention, an electron beam is irradiated on an object to be irradiated, and the electron beam extraction unit of the electron beam accelerator constituting the electron beam irradiation apparatus used for crosslinking, modification, curing, sterilization, and other surface treatment of the object is used. The present invention relates to a method for mounting (mounting) an irradiation window unit that separates the vacuum side and the atmosphere side, and a method for storing the irradiation window unit before the mounting.
[0002]
[Prior art]
An example of an electron beam irradiation apparatus is shown in FIG. An electron beam irradiation apparatus similar to this is described in Patent Document 1, for example.
[0003]
[Patent Document 1]
JP 2002-243899 A (paragraph numbers 0002 to 0011, FIGS. 6 and 9)
[0004]
This electron beam irradiation apparatus generates an electron beam 16 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 16. It has an electron beam accelerator 2 to be called and is called a non-scanning type or an area type. However, the technique described in this application can also be applied to a scanning type that scans an electron beam.
[0005]
The electron beam accelerator 2 has a cylindrical vacuum vessel 4 that is long in the Y direction. The inside of the vacuum vessel 4 is evacuated.
[0006]
An electron beam source 8 that generates the electron beam 16 that is long in the Y direction and has the planar shape is accommodated inside the vacuum vessel 4. In this example, the electron beam source 8 has a plurality of filaments 10 arranged in parallel in the Y direction, an extraction electrode 12 from which the electron beam 16 is drawn, and a cylindrical shield electrode 14 for housing them. is doing.
[0007]
More specifically, the electron beam take-out portion of the vacuum vessel 4 of the electron beam accelerator 2 has a vacuum side 30 inside the vacuum vessel 4 and an atmosphere outside the vacuum vessel 4 on the flange 6 of the electron beam take-out portion. An irradiation window 20 that separates the side 32 is attached. The atmosphere side 32 may literally be the atmosphere or an inert gas atmosphere close to atmospheric pressure, but in this specification, both are referred to as the atmosphere side. The atmosphere side 32 can also be called the irradiation atmosphere side.
[0008]
The irradiation window 20 separates the atmosphere inside and outside the vacuum vessel 4 and transmits the electron beam 16, the window frame 22 that supports the window foil 26, and the periphery of the window foil 26 with respect to the window frame 22. And a holding frame 28 for holding the part. With the window foil 26 as a boundary, the inside of the vacuum vessel 4 is the vacuum side 30 and the outside of the vacuum vessel 4 is the atmosphere side 32. The window frame 22 and the window foil 26 are vacuum-sealed by packing (see packing 36 in FIG. 5).
[0009]
In this example, the irradiation window 20 has a planar shape that is long in the Y direction, and the window frame 22 is arranged in parallel in the Y direction with reference to FIG. 5 to support and cool the window foil 26. A plurality of crosspieces 24 are provided. However, when the area of the window foil 26 is small or when the window foil 26 is the scanning type, the crosspiece 24 may not be provided.
[0010]
The irradiation window 20 and the vacuum vessel 4 are at the same potential (usually ground potential), and a DC acceleration for accelerating the electron beam 16 drawn from the electron beam source 8 is present between them. A voltage is applied. The accelerated electron beam 16 is taken out to the atmosphere side 32 through the irradiation window 20 and irradiated to the irradiation object 34. As a result, the irradiated object 34 can be subjected to treatments such as crosslinking, modification, curing, and sterilization. The irradiated object 34 is conveyed, for example, in a direction along the X direction (the direction of arrow A in FIG. 4).
[0011]
By the way, the window foil 26 is a very thin (for example, about 10 to 50 μm) metal (for example, titanium or aluminum) foil, and is consumed due to heat generated by transmission loss of the electron beam 16. It needs to be replaced (eg regularly).
[0012]
In the conventional window foil mounting method, the window foil 26 is pasted on the presser frame 28, and the presser frame 28 with the window foil 26 pasted thereon is used by using a large number of bolts (see bolts 38 in FIG. 5). It was the method of attaching to the window frame 22. The window frame 22 remained attached to the vacuum vessel 4 (more specifically, its flange 6) in advance.
[0013]
In such a method, since it is necessary to remove and retighten the numerous bolts, there is a problem that it takes a long time to replace the window foil 26.
[0014]
As means for solving such a problem, Patent Document 2 describes a technique in which the irradiation window 20 is unitized.
[0015]
[Patent Document 2]
Japanese Patent Laid-Open No. 11-38196 (paragraph numbers 0008 to 0015, FIG. 2)
[0016]
Referring to FIG. 5 as well, the irradiation window 20 is unitized by attaching a window foil 26 and a holding frame 28 to the window frame 22 as described above, separately from the vacuum container 4 of the electron beam accelerator 2. The irradiation window unit 20a is formed and replaced for each irradiation window unit 20a instead of the window foil 26 alone. That is, the irradiation window unit 20a is attached to or detached from the vacuum vessel 4 (more specifically, the flange 6) of the electron beam accelerator 2. According to this, the number of bolts (see bolt 60 in FIG. 3) for mounting the irradiation window unit 20a is much smaller than the number of bolts 38 (for example, several tens) for mounting the holding frame 28 (for example, several tens). Therefore, the replacement work time can be greatly shortened.
[0017]
[Problems to be solved by the invention]
However, even if the irradiation window unit 20a as described above is employed, the following problems still exist.
[0018]
(1) Before the irradiation window unit 20a is attached to the vacuum vessel 4, both the vacuum side 30 and the atmosphere side 32 of the irradiation window unit 20a are in the atmospheric pressure state and there is no pressure difference. As indicated by the dotted line, the tension is not applied and the state is relaxed. At this time, dust may be caught in the gap 62 between the peripheral edge of the window foil 26 and the window frame 22 or the gap 64 between the window foil 26 and the crosspiece 24 (this is called dust biting). .
[0019]
On the other hand, when the irradiation window unit 20a is attached to the vacuum vessel 4 of the electron beam accelerator 2 and the inside thereof is evacuated, the window foil 26 is located between the vacuum side 30 and the atmosphere side 32 as shown by the solid line in FIG. Is pressed against the vacuum side 30 (in other words, pulled, the same applies hereinafter) to the expanded state. At this time, if the dust is bitten, the window foil 26 is very thin as described above, so there is a possibility that the window foil 26 has a hole and a vacuum leak is caused there. Although the possibility of dust biting is higher when the crosspiece 24 is provided, the possibility of dust biting in the gap 62 still exists even when the crosspiece 24 is not provided.
[0020]
Conventionally, the necessity and method for checking such a leak due to dust biting before attaching the irradiation window unit 20a have not been studied. Neither Patent Document 2 describes nor suggests it.
[0021]
(2) Since the window foil 26 is a metal foil as described above, after the irradiation window unit 20a is formed, if the irradiation window unit 20a is stored in the atmosphere, oxygen, moisture, etc. in the atmosphere The window foil 26 may corrode. Conventionally, in order to prevent this corrosion, the irradiation window unit 20a is put in a dedicated container and stored in an inert atmosphere. However, for that purpose, a dedicated container is necessary, and the cost increases accordingly. There's a problem.
[0022]
Therefore, the present invention can perform a leak test in the same state as when the irradiation window unit is mounted on the vacuum container of the electron beam accelerator, and does not cause new dust biting after the leak test. An object of the present invention is to provide a method for attaching the irradiated window unit.
[0023]
In addition, before mounting the irradiation window unit in the electron beam accelerator vacuum container, a leak test can be performed in the same state as when mounted, and the window foil is placed in an inert atmosphere without using a dedicated container after the leak test. Another object of the present invention is to provide a storage method for an irradiation window unit that can be stored in a storage.
[0024]
[Means for Solving the Problems]
In the method of attaching the irradiation window unit according to the present invention, an irradiation window unit for separating the vacuum side inside the vacuum container and the atmosphere side outside the vacuum container is provided in the electron beam extraction portion of the vacuum container of the electron beam accelerator. In the attaching method, (a) attaching a window foil that transmits an electron beam and a pressing frame that holds the window foil to the window frame to form the irradiation window unit; and (b) then, the vacuum side of the irradiation window unit. Attaching a first flange with a first valve to a surface located at the surface, and attaching a second flange with a second valve to a surface located on the atmosphere side of the irradiation window unit; c) Next, in a state where the first and second valves are opened, the vacuum side of the irradiation window unit is evacuated through the first valve to check the degree of vacuum; and d) Next, a step of introducing a detection gas to the atmosphere side of the irradiation window unit via the second valve to perform a leak test of the irradiation window unit; and (e) Next, the second window Closing the valve after introducing pressurized inert gas to the atmosphere side of the irradiation window unit via a valve, and maintaining the atmosphere side of the irradiation window unit at a positive pressure; (f) Removing the first flange with the first valve from the irradiation window unit; (g) then attaching the irradiation window unit to the vacuum vessel of the electron beam accelerator; and (h) then A step of evacuating the inside of the vacuum vessel of the electron beam accelerator; and (i) a step of removing the second flange with the second valve from the irradiation window unit. Correspondence).
[0025]
According to this attachment method, since the vacuum side of the irradiation window unit is evacuated in the step (c), the window foil is pressed against the vacuum side due to the pressure difference between the vacuum side and the atmosphere side. This is the same state as when mounted. In this state, since the leak test is performed in the step (d), the leak test can be performed in the same state as when the irradiation window unit is mounted in the vacuum container of the electron beam accelerator. Therefore, it is possible to check for leaks due to the bite of dust before mounting the irradiation window unit.
[0026]
In addition, after the leak test, the atmospheric side of the irradiation window unit is maintained at a positive pressure by the step (e), so that the irradiation window is removed by removing the first flange with the first valve in the step (f). Even if the vacuum side of the unit is opened to the atmosphere, the window foil remains pressed against the vacuum side by the positive pressure. That is, since it is almost the same state as when the leak test was performed in the step (d), the tension of the window foil does not loosen, and therefore no new dust biting occurs.
[0027]
In addition, after the irradiation window unit is attached to the vacuum vessel of the electron beam accelerator in the step (g), the inside of the vacuum vessel is evacuated in the step (h). It will be in the state pressed against the vacuum side by the pressure difference. Therefore, after that, even if the second flange with the second valve is removed in the step (i) above, the tension of the window foil will not be loosened. Absent.
[0028]
The storage method according to the present invention is an irradiation window unit that is attached to an electron beam extraction portion of a vacuum container of an electron beam accelerator and separates a vacuum side inside the vacuum container and an atmosphere side outside the vacuum container, In the method of storing before the attachment, (a) a step of forming the irradiation window unit by attaching a window foil that transmits an electron beam and a pressing frame that holds the window foil to the window frame; and (b) the irradiation window. A first flange with a first valve is attached to a surface located on the vacuum side of the unit, and a second flange with a second valve is attached to a surface located on the atmosphere side of the irradiation window unit. (C) Next, with the first and second valves opened, the vacuum side of the irradiation window unit is evacuated through the first valve to check the degree of vacuum. And (d) a step of introducing a detection gas to the atmosphere side of the irradiation window unit via the second valve and performing a leak test of the irradiation window unit; and (e) then, Closing the first valve and maintaining the vacuum side of the irradiation window unit in a vacuum state; and (f) Next, an inert gas is supplied to the atmosphere side of the irradiation window unit via the second valve. A step of closing the valve after introduction and maintaining the atmosphere side of the irradiation window unit in an inert gas atmosphere (corresponding to claim 2).
[0029]
According to this storage method, the steps (a) to (d) are the same as the steps (a) to (d) of the attachment method. Before mounting in the accelerator vacuum vessel, a leak test can be performed in the same state as during mounting. Therefore, before the irradiation window unit is mounted or stored, it is possible to check for leakage due to the dust biting.
[0030]
Moreover, after the leak test, the vacuum side of the window foil can be kept in a vacuum state by closing the first valve in the step (e). The vacuum state is an inert atmosphere for the window foil. In the step (f), the air side of the window foil can be kept in an inert gas atmosphere by closing the second valve after introducing the inert gas. As described above, the irradiation window unit can be stored by placing the window foil in an inert atmosphere without using a dedicated container. That is, corrosion of the window foil can be prevented without using a dedicated container, and dust can be prevented from entering due to dust.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
In the following, the same reference numerals are given to the same or corresponding parts as those in the conventional example shown in FIGS. 4 and 5, and differences from the conventional example will be mainly described.
[0032]
(1) First, an embodiment of the method for attaching the irradiation window unit will be described in the order of the steps constituting the attachment method.
[0033]
(A) First, as shown in FIG. 1, the window window 22 is attached with the window foil 26 that transmits an electron beam and the pressing frame 28 that holds the window foil 26 to form the irradiation window unit 20a. This is performed before the irradiation window unit 20a is attached (mounted) to the vacuum container 4 of the electron beam accelerator 2. The packing 36 and the bolt 38 are as described above. In this example, a packing groove 39 for receiving a packing 44 (described later) (see FIG. 2) is provided on the surface of the window frame 22 on the vacuum side 30.
[0034]
(B) Next, as shown in FIG. 2, a first flange 42 with a first bulb 40 is attached to the surface of the irradiation window unit 20a located on the vacuum side 30, and the irradiation window unit 20a A second flange 52 with a second valve 50 is attached to a surface located on the atmosphere side 32. The both flanges 42 and 52 are attached using bolts 46 and 56 in this example. The gap between the flange 42 and the window frame 22 is vacuum-sealed by a packing 44, and the gap between the flange 52 and the holding frame 28 is sealed by a packing 54. The packings 36, 44, 54 are, for example, O-rings. The bolts 38, 46, 56 and a bolt 60 described later (see FIG. 3) are provided at positions that do not interfere with each other.
[0035]
(C) Next, an appropriate evacuation device and a vacuum gauge are connected to the first valve 40, and the first and second valves 40 and 50 are opened, via the first valve 40, As shown by the arrow B, the vacuum side 30 (more specifically, the window foil 26 to the vacuum side 30) of the irradiation window unit 20a is evacuated to check the degree of vacuum. At this time, the window foil 26 is pressed against the vacuum side 30 due to the pressure difference between the vacuum side 30 and the atmosphere side 32 (see FIG. 5). This is the same state as when mounted.
[0036]
(D) Next, a detection gas (for example, helium gas or the like) is supplied as a gas 58 to the atmospheric side 32 of the irradiation window unit 20a (more specifically, the atmospheric side 32 of the window foil 26) via the second valve 50. ) To perform a leak test of the irradiation window unit 20a. This confirms that there are no leaks. In the leak test, leakage (leak) of the detection gas to the vacuum side 30 is detected. For this detection, for example, a partial pressure gauge is used. By this leak test, before the irradiation window unit 20a is mounted on the vacuum vessel 4 of the electron beam accelerator 2, the leak test can be performed in the same state as that at the time of mounting. Therefore, before the irradiation window unit 20a is mounted, it is possible to check for leakage due to the dust biting.
[0037]
(E) Next, after introducing an inert gas (for example, nitrogen gas, helium gas) as a gas 58 to the atmosphere side 32 of the irradiation window unit 20a via the second valve 50, the valve 50 is closed and the atmospheric side 32 of the irradiation window unit 20a is kept at a positive pressure. The window foil 26 of the irradiation window unit 20a is pressed against the vacuum side 30 by this positive pressure.
[0038]
(F) Next, the first flange 42 with the first valve 40 is removed from the irradiation window unit 20a. This is to prepare for attaching the irradiation window unit 20a to the vacuum vessel 4 of the electron beam accelerator 2 (see FIG. 3). At this time, the vacuum side 30 of the irradiation window unit 20a is opened to the atmosphere by removing the first flange 42 and the like, but the atmosphere side 32 of the irradiation window unit 20a is kept at a positive pressure by the step (e). Thus, the window foil 26 remains pressed against the vacuum side 30. That is, since the state is almost the same as when the leak test is performed in the step (d), the tension of the window foil 26 is not loosened, and therefore no new dust biting occurs.
[0039]
(G) Next, as shown in FIG. 3, the irradiation window unit 20 a is attached to the vacuum vessel 4 (more specifically, the flange 6) of the electron beam accelerator 2 using, for example, a bolt 60. The number of the bolts 60 is, for example, four or six.
[0040]
(H) Next, the inside of the vacuum vessel 4 of the electron beam accelerator 2 is evacuated by a vacuum evacuation device (not shown). As a result, the window foil 26 of the irradiation window unit 20a is pressed against the vacuum side 30 due to the pressure difference between the vacuum side 30 and the atmospheric side 32. Therefore, the window foil 26 does not change greatly.
[0041]
(I) Next, the second flange 52 with the second bulb 50 is removed from the irradiation window unit 20a. Even if these are removed, the window foil 26 is pressed against the vacuum side 30 by the pressure difference between the vacuum side 30 and the atmosphere side 32 in the step (h), so that the tension of the window foil 26 does not loosen. Therefore, in this case as well, no new dust biting occurs. By this removal, the attachment (mounting) of the irradiation window unit 20a is completed, and the state is the same as shown in FIG.
[0042]
(2) Next, an embodiment of an irradiation window unit storage method will be described. In short, the storage method is as follows. The first flange 42 with the first valve 40 and the second flange 52 with the second valve 50 used in the leak test are attached without being removed. These are used in place of dedicated storage containers. Hereinafter, it demonstrates in order of a process.
[0043]
First, the same steps as the steps (a) to (d) of the mounting method are performed. The contents and operational effects are as described above. This completes the leak test of the irradiation window unit 20a.
[0044]
(E) Next, referring to FIG. 2, the first valve 40 is closed to keep the vacuum side 30 of the irradiation window unit 20a in a vacuum state. The vacuum state is an inert atmosphere for the window foil 26.
[0045]
(F) Next, after introducing an inert gas (for example, nitrogen gas, helium gas, etc.) as the gas 58 to the atmosphere side 32 of the irradiation window unit 20a via the second valve 50, the valve 50 is closed. The air side 32 of the irradiation window unit 20a is kept in an inert gas atmosphere. At this time, it is not necessary to keep the atmospheric side 32 of the irradiation window unit 20a at a positive pressure with an inert gas, but it may be kept at a positive pressure.
[0046]
As described above, the irradiation window unit 20a can be stored by placing the window foil 26 in an inert atmosphere without using a dedicated container. That is, without using a dedicated container, it is possible to prevent the window foil 26 from being corroded and to prevent the dust from entering due to dust entering.
[0047]
When the irradiation window unit 20a is attached to the vacuum vessel 4 of the electron beam accelerator 2 after this storage, (a) when the atmospheric side 32 of the irradiation window unit 20a is kept at a positive pressure, the attachment method (f ), And (b) when the positive pressure is not maintained, it may be started from the step (e) of the above attachment method.
[0048]
【The invention's effect】
Since this invention is comprised as mentioned above, there exist the following effects.
[0049]
According to the first aspect of the present invention, the leak test is performed with the window foil pressed against the vacuum side. Therefore, before the irradiation window unit is mounted on the vacuum container of the electron beam accelerator, the leakage is performed in the same state as at the time of mounting. Test can be done. Therefore, it is possible to check for leaks due to the bite of dust before mounting the irradiation window unit.
[0050]
In addition, even after the leak test, the window foil can be kept pressed against the vacuum side until the mounting of the irradiation window unit is completed, so that no new dust biting occurs.
[0051]
According to the second aspect of the present invention, since the leak test is performed with the window foil pressed against the vacuum side, before the irradiation window unit is mounted on the vacuum container of the electron beam accelerator, the leakage is performed in the same state as when mounting. Test can be done. Therefore, before the irradiation window unit is mounted or stored, it is possible to check for leakage due to the dust biting.
[0052]
In addition, after the leak test, the vacuum side of the window foil is kept in a vacuum state by closing the first valve, and the inert side of the window foil is closed by closing the second valve after introducing the inert gas. Since the atmosphere can be maintained, the irradiation window unit can be stored by placing the window foil in an inert atmosphere without using a dedicated container. That is, corrosion of the window foil can be prevented without using a dedicated container, and dust can be prevented from entering due to dust.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of an irradiation window unit.
2 is a cross-sectional view showing a state in which first and second flanges with valves are respectively attached to the irradiation window unit of FIG. 1;
FIG. 3 is a cross-sectional view showing a state in which the irradiation window unit of FIG. 1 is attached to a vacuum container of an electron beam accelerator together with a second flange with a valve.
FIG. 4 is a cross-sectional view showing an example of an electron beam irradiation apparatus.
FIG. 5 is an enlarged partial cross-sectional view of the irradiation window unit in the Y direction.
[Explanation of symbols]
2 Electron beam accelerator 4 Vacuum container 20a Irradiation window unit 22 Window frame 26 Window foil 28 Holding frame 30 Vacuum side 32 Atmosphere side 40 First valve 42 First flange 50 Second valve 52 Second flange 58 Gas

Claims (2)

In the method of attaching an irradiation window unit for separating the vacuum side inside the vacuum container and the atmosphere side outside the vacuum container to the electron beam extraction part of the vacuum container of the electron beam accelerator,
(A) attaching to the window frame a window foil that transmits an electron beam and a holding frame that holds the window foil to form the irradiation window unit;
(B) Next, a first flange with a first valve is attached to a surface located on the vacuum side of the irradiation window unit, and a second surface is located on the atmosphere side of the irradiation window unit. Attaching a second flange with a valve;
(C) Next, in a state where the first and second valves are opened, a step of confirming the degree of vacuum by evacuating the vacuum side of the irradiation window unit through the first valve;
(D) Next, a step of introducing a detection gas to the atmosphere side of the irradiation window unit via the second valve and performing a leak test of the irradiation window unit;
(E) Then, after introducing the pressurized inert gas to the atmosphere side of the irradiation window unit via the second valve, the valve is closed, and the atmosphere side of the irradiation window unit is positively pressurized. The process of keeping
(F) Next, removing the first flange with the first valve from the irradiation window unit;
(G) Next, attaching the irradiation window unit to a vacuum container of the electron beam accelerator;
(H) Next, evacuating the inside of the vacuum vessel of the electron beam accelerator;
(I) Next, a step of removing the second flange with the second valve from the irradiation window unit, and a method of attaching the irradiation window unit. In a method of storing an irradiation window unit attached to an electron beam take-out portion of a vacuum container of an electron beam accelerator and separating a vacuum side inside the vacuum container and an atmosphere side outside the vacuum container before the attachment ,
(A) attaching to the window frame a window foil that transmits an electron beam and a holding frame that holds the window foil to form the irradiation window unit;
(B) Next, a first flange with a first valve is attached to a surface located on the vacuum side of the irradiation window unit, and a second surface is located on the atmosphere side of the irradiation window unit. Attaching a second flange with a valve;
(C) Next, in a state where the first and second valves are opened, a step of confirming the degree of vacuum by evacuating the vacuum side of the irradiation window unit through the first valve;
(D) Next, a step of introducing a detection gas to the atmosphere side of the irradiation window unit via the second valve and performing a leak test of the irradiation window unit;
(E) Next, closing the first valve and maintaining the vacuum side of the irradiation window unit in a vacuum state;
(F) Next, after introducing an inert gas to the atmosphere side of the irradiation window unit via the second valve, the valve is closed to keep the atmosphere side of the irradiation window unit in an inert gas atmosphere. And a storage method for the irradiation window unit.

Images