JP7630789B2 - Beam window - Google Patents

Description

Application of Article 30, Paragraph 2 of the Patent Act 18th Annual Meeting of the Particle Accelerator Society of Japan (July 30, 2021) Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Selection Results Announced (July 9 and 13, 2021)

The present invention relates to a beam window that is attached to a vacuum vessel or pressure vessel, and more specifically, to a beam window that is inexpensive, reduces beam loss, and can withstand higher pressure differences.

Vacuum vessels and pressure vessels are isolated from the surrounding atmosphere, but sometimes a beam window with a thin, low-density section is required. Examples include X-ray transparent windows in medical X-ray tubes and particle transparent windows in accelerator science. These are used to isolate the pressure difference between vacuum and atmosphere, or between an atmosphere above atmospheric pressure and atmospheric pressure.

When a particle beam passes through a beam window, problems occur due to heat and radiation generated by beam loss, and the efficiency of beam transport decreases. For this reason, it is hoped that the product of the thickness and density of the beam window can be made as small as possible. This is because if the number of particles lost through the beam window can be halved, the same effect can be achieved as by increasing the intensity of the accelerator.

On the other hand, the beam window is required to withstand the pressure difference between vacuum and atmosphere, and in some cases, the pressure difference can be greater than the atmospheric pressure of the ambient gas.

Therefore, it is desirable to realize beam windows made of a material that is thin and has low density, yet has high strength and great elongation.

Conventional beam windows include:
(1) Plate method using high density SUS thin plate or thick titanium alloy plate or beryllium plate (Fig. 10)
(2) There is a method in which the thickness is determined by the workability of the material, by machining from an integral structure.

First, in the plate method, stainless steel plates have a high density but can be made thin, and titanium alloys (Non-Patent Document 1) are available in thicknesses of around 0.6 mm, but the thickness and shape are limited by restrictions on deformation from the plate, and pressure differences are limited due to stress concentration.

Specifically, as shown in FIG. 10, a conventional plate beam window 11 is manufactured by joining a flat plate to a flange portion 15 and attaching it to a receiving flange 16 of a vacuum vessel via a seal member 16a. When the spherical shell portion 12 is formed, the stress generated in the spherical shell portion 12 by the pressure at the center, which is the beam passage portion 12a, is reduced as the recess 12c becomes larger.

In addition, even if the plate thickness becomes thinner, if the plate stretches and the recess 12c becomes larger, the stress is reduced. On the other hand, if the recess 12c becomes larger, the edge of the plate is fixed to the flat flange portion 15 (joint portion 13) and deformation is restricted, so the angle at the end 12b of the spherical shell portion 12 becomes steeper, causing stress concentration and causing the spherical shell portion 12 to break.

Therefore, by enlarging the recess 12c and reducing the stress at the end 12b of the spherical shell portion 12, a thin beam window can be realized. In addition, when manufacturing a conventional plate beam window 11, the edge of the plate is joined to the flange portion 15 (joint portion 13) by brazing or welding, but joining without bending is difficult and expensive to manufacture.

In other words, the performance of the conventional plate beam window 11 is limited by the original plate shape, material, and workability of the window material that is joined to the flange portion 15.

On the other hand, to seal the edge of the plate and the flange, gaskets such as metal O-rings or rubber O-rings can be used, depending on the type of flange, and these can be fastened together with bolts and nuts. However, metal O-rings are technically difficult to use, and rubber O-rings have issues with outgassing, where gas is released when heated, and the temperature range in which they can be used is narrow.

On the other hand, the cutting method has limitations on materials and thickness due to the processability of cutting a one-piece structure from bulk material, and manufacturing costs are high.

Japanese Patent Application Publication No. 10-82900 JP 2001-305281 A

Shunsuke Makimura and Taku Ishida, "Current status and trends of secondary particle generation targets and beam windows for megawatt high-intensity proton beam operation", High Energy News, Volume 36 Number 3 October/November/December 2017

Therefore, the present invention relates to a beam window that is attached to a vacuum vessel or pressure vessel, and more specifically, aims to provide a beam window that is inexpensive, reduces beam loss, and can withstand a higher pressure difference.

In order to solve the above problems, the present invention provides:
(1)
A beam window attached to a receiving flange of the apparatus,
A beam window characterized in that it is an integral metal body consisting of a spherical shell portion having a beam passing portion and a flange portion connected to an end of the spherical shell portion and attached to the receiving flange.
(2)
The beam window according to (1), characterized in that the flange portion is provided with a notch.
(3)
A beam window attached to a receiving flange of the apparatus,
a spherical shell portion having a beam passing portion, the spherical shell portion being connected to an end of the spherical shell portion;
A beam window comprising a flange portion attached to the receiving flange by an outer flange body that circumscribes the flange portion, the spherical shell portion and the flange portion being an integral laminated metal object.
(4)
A beam window described in any one of (1) to (3), characterized in that the spherical shell portion connected to the flange portion is provided in two with a space therebetween, and the space serves as a flow path for a cooling medium.
(5)
The beam window according to any one of (1) to (4), wherein a cooling medium flows within the flange portion.
(6)
The beam window according to any one of (1) to (5), wherein a connecting portion connecting the end of the spherical shell portion and the flange portion is thicker than the beam passing portion.
(7)
The beam window according to any one of (1) to (7), characterized in that the metal integral body is an integrally laminated metal object.
It was decided.

The term "flange portion" used here is a broad concept that includes not only the so-called flange that is directly connected and fixed to the receiving flange of the device with bolts and nuts, but also the cylindrical or protruding portion that protrudes from a component and is sandwiched between two components.

Direct connection between flanges and clamping of flanges can be achieved by screwing a screw into a screw hole, tightening together with a bolt and nut, or screwing flanges together. O-rings, metal gaskets, and other necessary sealing materials are used between the components. The "sealing surface" can be provided on either the flange side or the receiving flange side. If it is provided on the flange side, an additional process such as polishing may be required, but this is preferable in terms of shortening the process, as it can be formed at the same time as the molding of the spherical shell through which the beam passes.

The spherical shell and flange parts can be "integrated" by cutting, but additive manufacturing is preferred, such as the additive manufacturing method for titanium disclosed in Patent Document 2. Additive manufacturing melts metal powder using a laser or the like, making it possible to manufacture any shape that cannot be achieved by conventional processing methods. By making the spherical shell and flange parts "integrated," the spherical shell part does not crack, as occurs when the spherical shell and flange parts are prepared separately and welded.

Examples of additive manufacturing for metal materials include powder beds, where powder is laid down, additive manufacturing where powder is melted while being applied or where wire is melted, and plasma additive manufacturing, all of which can be used in the present invention. After additive manufacturing, polishing can be performed if necessary.

Metal materials that can be used for additive manufacturing include titanium alloys such as 64 titanium alloy (Ti-6Al-4V), aluminum alloys such as Al-10Si-Mg, SUS316L, and Inconel 718. Although 64 titanium is generally used for additive manufacturing, β-titanium alloys with a small Young's modulus can also be additively manufactured and are suitable for use as beam windows.

The advantages and characteristics of additive manufacturing are:
(1) Since additive manufacturing is a method for forming any shape without cutting, when forming complex shapes, the process can be shortened compared to cutting methods, and production yields can be improved.
(2) Additive manufacturing can save material by eliminating parts that do not affect mechanical strength.

The present invention takes advantage of the advantages of the additive manufacturing method described above to provide a beam window that "has an optimized spherical shell shape in advance," "has optimized end thickness and angle," and is "integral with the flange portion."

By integrating the spherical shell portion and the flange portion, the present invention can prevent the spherical shell portion from cracking due to distortion when welding to the vacuum flange portion, as occurs with conventional plate beam windows. In addition, by making the beam passing portion thin and making the connecting portion connecting the end of the spherical shell portion to the flange portion thicker than the beam passing portion, it is possible to reduce stress at the end where stress is concentrated, and increase mechanical strength.

Furthermore, by adopting metal additive manufacturing, it is possible to use metal materials that are difficult to process, and to manufacture thin, arbitrary shapes at low cost. This reduces beam loss and provides a beam window that can withstand a higher pressure difference. In other words, the present invention provides a beam window that can withstand a pressure difference that is about 10 times higher when the inner diameter of the beam window is 200 mm, for example, than the conventional plate method or the method of cutting out from a one-piece structure.

The technology disclosed in Patent Document 1 is a plate-shaped beam window made of beryllium, while the technology disclosed in Patent Document 2 is a flat window made of titanium. Patent Documents 1 and 2 do not disclose or suggest a beam window that reduces beam loss and can withstand a higher pressure difference, such as a beam window in which the flange and spherical shell portion are integrally formed by additive manufacturing using titanium, etc., and further in which stress is reduced by keeping the beam passing portion thin and thickening the ends where stress is concentrated. Furthermore, a thin spherical shell portion such as that of the present application cannot be connected to the flange portion like a conventional plate beam window.

FIG. 1 shows a first embodiment of a beam window of the present invention, in which FIG. 1(A) is a schematic front view, FIG. 1(B) is a schematic cross-sectional view taken along the line A-A' of FIG. 1(A), and FIG. 1(C) is an enlarged schematic view of the dashed-dotted circle portion of FIG. FIG. 2 is a schematic cross-sectional view at the same position as FIG. 1B when the beam window in FIG. 1 is attached to a mounting destination (receiving flange) such as a vacuum vessel with bolts and nuts (not shown). FIG. 3 is a schematic front view of a beam window according to a second embodiment of the present invention. Fig. 4(A) is a schematic cross-sectional view taken along line A-A' of Fig. 3, and Fig. 4(B) is a schematic cross-sectional view taken along line B-B' of Fig. 3. The lattice portion has a notch 3d, which realizes a reduction in weight and cost of the flange portion 3b. FIG. 5 is a rear view of FIG. FIG. 6 shows a third embodiment of the beam window of the present invention, in which FIG. 3(A) is a schematic front view, and FIG. 6(B) is a schematic cross-sectional view taken along the line A-A' of FIG. Fig. 7(A) is a schematic cross-sectional view at the same position as Fig. 6(B) when the beam window in Fig. 6 is attached to a mounting destination (receiving flange) such as a vacuum vessel with bolts and nuts (not shown). Fig. 7(B) is an exploded schematic cross-sectional view of (A), and (C) is an enlarged schematic view of the dashed-dotted circle portion of (B). FIG. 8 shows a fourth embodiment of the beam window of the present invention, in which FIG. 8(A) is a partially transparent front schematic view, and FIG. 8(B) is a cross-sectional schematic view taken along the line A-A' of FIG. 8(A). FIG. 9 is a schematic cross-sectional view at the same position as FIG. 8B when the beam window in FIG. 8 is attached to a mounting destination (receiving flange) such as a vacuum vessel with bolts and nuts (not shown). FIG. 10 is an explanatory diagram of a conventional plate beam window, in which a beam window is formed by joining a plate to a flange portion.

The following describes in detail the embodiments of the present invention with reference to the attached drawings. Note that the present invention is not limited to the following embodiments.

As shown in Figures 1 and 2, the beam window 1, which is the first embodiment of the present invention, is a one-piece metal object consisting of a spherical shell portion 2 having a beam passage portion 2aa, and a flange portion 3 that is connected to the end of the spherical shell portion 2 and is attached to a receiving flange 4 of the device.

Examples of the device include a vacuum vessel through which the beam passes, a pressure vessel, an X-ray tube, and a beam accelerator. The receiving flange 4 is a flange provided on the device, but the device part is not shown in the figure (same below).

As a metal one-piece, additive manufacturing is preferable, especially for large diameters exceeding 200 mm, but for smaller diameters, cutting can also be used. In either case, the spherical shell portion 2 can be molded with a varying thickness, i.e., the connecting portion 2b where the end of the spherical shell portion 2 and the flange portion 3 are connected can be made thicker than the beam passing portion 2a.

The spherical shell portion 2 is bowl-shaped. Since the stress generated in the window is inversely proportional to the bulge of the window, the bowl-shaped spherical shell portion 2 reduces the stress generated more than a plate-shaped window. Furthermore, as shown in FIG. 1(C), the connecting portion 2b connecting the flange portion 3 and the end of the spherical shell portion 2 is thicker than the beam passing portion 2a, which further improves the mechanical strength and allows it to withstand high pressure differences between the windows. Therefore, even a large-diameter beam window exceeding 200 mm has sufficient strength, and if it is an integrally laminated metal object, it can be manufactured easily and inexpensively.

In addition, in FIG. 2, the spherical shell portion 2 is concave toward the receiving flange 4 side of the device, but the beam window 1 in FIG. 2 may be attached to the receiving flange 4 with the left and right reversed, so that the spherical shell portion 2 is convex toward the device having the receiving flange 4.

The flange portion 3 is flat on both sides, has holes 3a at equal intervals through which bolts pass, and is connected to the receiving flange 4 with bolts and nuts. The receiving flange 4 side of the flange portion 3 is the sealing surface, and an annular seal groove 4a is drilled in the sealing surface of the receiving flange 4, into which a sealing member 4b such as an O-ring is fitted, and the connection provides a seal and ensures the required degree of vacuum. The holes 3a may be screw holes, and the flange portion 3 and receiving flange 4 may be connected with screws.

As shown in Figure 3-5, the beam window 1a of the second embodiment of the present invention differs from that of Example 1 in the flange portion 3b. That is, on the front side of Figure 3, the area around the holes 3a is a flat surface 3c, and between the holes 3a is a notch 3d, and an annular seal groove 3e is drilled in the flange portion 3b on the rear side, providing a seal surface on the rear side of the beam window 1a.

When sealing surfaces are provided on both the flange portion 3b and the receiving flange 4 of the device, sealing is performed with a metal gasket. On the other hand, when sealing with an O-ring, only one of the sealing grooves (sealing surfaces) is required, either the seal groove 3e of the flange portion 3b or the seal groove 4a of the receiving flange 4.

By providing the notches 3d by simply cutting, recessing, or by forming a honeycomb structure or a group of slits while maintaining the connection strength with the receiving flange 4, the amount of metal material used can be reduced and manufacturing costs can be kept down. In particular, these notch shapes can be easily formed with additive manufacturing.

As shown in Figures 6 and 7, the beam window 1b, which is a third embodiment of the present invention, is composed of a spherical shell portion 2 having a beam passage portion 2a, and a flange portion 3h that is connected to the end of the spherical shell portion 2 and is attached to the receiving flange 4 of the device by an outer flange body 3f that circumscribes the end of the spherical shell portion 2. The spherical shell portion 2 and the flange portion 3h are integrally laminated metal objects.

That is, the flange portion 3 in Example 1 is divided into an outer flange body 3f and a flange portion 3h, and is different in that a groove 3g for the flange portion 3h is provided on the back surface. This allows the molding time to be short and the amount of metal used to be reduced when it is an additive manufacturing product. The outer flange body 3f may be manufactured by other processing methods such as cutting.

As shown in Figures 8 and 9, the beam window 1c, which is the fourth embodiment of the present invention, has a spherical shell portion connected to a flange portion 3i, which is provided with two spherical shell portions 2 and 2c with a space therebetween, and the space serves as a flow path 2d for the cooling medium. The spherical shell portion 2 and the spherical shell portion 2c and the flange portion 3i are integrally laminated metal objects, and are attached to the receiving flange 4 of the device at the flange portion 3i. As in the previous embodiments, the connection portion 2b between the spherical shell portion 2 and the spherical shell portion 2c and the flange portion 3i is thicker than the beam passing portion 2a.

The flange portion 3i is provided with a flow path 3j that is connected to the flow path 2d, but the flange portion 3i may also be provided with an annular flow path structure (not shown) that allows a cooling medium to flow within the flange portion 3i or only in the flange portion 3i. Examples of the cooling medium include water and helium. Heat generated by the passage of the beam can also be cooled by flowing a cooling medium through the flow path 2d between the spherical shell portions 2 and 2c and the annular flow path structure of the flange portion 3i.

1 Beam window 1a Beam window 1b Beam window 1c Beam window 2 Spherical shell portion 2a Beam passage portion 2b Connection portion 2c Spherical shell portion 2d Flow path 3 Flange portion 3a Hole 3b Flange portion 3c Flat surface 3d Notch 3e Seal groove 3f Outer flange body 3g Groove 3h Flange portion 3i Flange portion 3j Flow path 4 Receiving flange 4a Seal groove 4b Seal member 11 Conventional plate beam window 12 Spherical shell portion 12a Beam passage portion 12b End portion 12c Recess 13 Joint portion 15 Flange portion 16 Receiving flange 16a Seal member

Claims (6)

A beam window attached to a receiving flange of the apparatus,
a spherical shell portion having a beam passing portion, the spherical shell portion being connected to an end of the spherical shell portion;
A beam window comprising a flange portion attached to the receiving flange by an outer flange body that circumscribes the flange portion, the spherical shell portion and the flange portion being an integral laminated metal object. A beam window attached to a receiving flange of the apparatus,
a spherical shell portion having a beam passing portion and a flange portion connected to an end of the spherical shell portion and attached to the receiving flange ;
The beam window is an integral metal laminate molded product . 3. The beam window according to claim 1, wherein the flange portion is provided with a notch. A beam window according to any one of claims 1 to 3, characterized in that the spherical shell portion connected to the flange portion is provided in two with a space therebetween, and the space serves as a flow path for the cooling medium. A beam window as described in any one of claims 1 to 4, characterized in that a cooling medium flows within the flange portion. 6. The beam window according to claim 1, wherein a connecting portion where the end of the spherical shell portion and the flange portion are connected is thicker than the beam passing portion.

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