Acceleration cavity

Abstract

This acceleration cavity comprises: a housing which is cylindrical and has electrical conductivity and in which a plurality of split members split at a plane along a central axis are provided, with parts of split surfaces along the plane facing each other with a gap therebetween and other parts of the split surfaces being joined so as to seal the gap; and a plurality of cell parts that are arranged inside the portion of the housing where the split surfaces face each other with the gap therebetween, in a state of being aligned in the central axis direction of the housing, the cell parts communicating with each other via communication parts through which charged particles can pass. The housing has a guide groove formed in the split surfaces so as to extend along the inner surface of a cell part from an end side of the split surfaces, and further comprises: an electromagnetic field adjustment member which is provided so as to be movable along the inner surface of the cell part, and which can be moved to change the state of an electromagnetic field applied inside the cell part; and a movement mechanism having a linear member which is coupled with the electromagnetic field adjustment member via the gap and is moved along the guide groove to move the electromagnetic field adjustment member along the inner surface of the cell part.

Description

acceleration cavity

[0001] The present disclosure relates to acceleration cavities.

[0002] When a high frequency wave is input to an accelerating cavity, the accelerating cavity generates an accelerating electric field therein, accelerating charged particles such as electrons. By matching the resonant frequency of the accelerating cavity with the RF frequency, the acceleration of the charged particles can be maximized. For example, a known configuration of such an accelerating cavity includes a plurality of cells arranged along a central axis of the accelerating cavity that coincides with the beam axis of the charged particles, and the cells are connected to each other via communication sections (see, for example, Patent Document 1).

[0003] Japanese Patent Application Publication No. 5-029097

[0004] In the above-described accelerating cavity, the resonant frequency is typically adjusted after assembly by joining the components. The resonant frequency can be adjusted by, for example, modifying the inner shape of the accelerating cavity or by inserting an object into the accelerating cavity, thereby affecting the electromagnetic field inside the accelerating cavity. However, while these methods can easily increase the resonant frequency, they have difficulty lowering the resonant frequency.

[0005] The present disclosure has been made in view of the above, and aims to provide an acceleration cavity capable of appropriately adjusting the resonant frequency.

[0006] The acceleration cavity according to the present disclosure is a cylindrical, electrically conductive cavity having a central axis that coincides with the central axis of the acceleration cavity, the central axis of the acceleration cavity being a plane along which the acceleration cavity central axis coincides with the beam axis of the charged particles, and the divided members are arranged with a gap between the divided surfaces along the plane facing each other, the divided members being arranged with a gap between the divided surfaces along the plane, the central axis of the acceleration cavity being a plane along which the charged particles are arranged, the central axis of the acceleration cavity being a plane along which the charged particles are arranged, the central axis of the acceleration cavity being a plane along which the divided members are arranged with a gap between the divided surfaces along the plane, the central axis of the acceleration cavity being a plane

[0007] The acceleration cavity according to the present disclosure further comprises: a cylindrical, electrically conductive housing having a divided member divided into a plurality of sections along a plane extending along a central axis, the divided member being arranged with some of the divided surfaces along the plane facing each other with a gap therebetween, and other portions of the divided surfaces being joined together to seal the gap; and a plurality of cell sections arranged side by side along the central axis of the housing within the portions of the housing where the divided surfaces face each other with a gap therebetween, the cell sections being connected to each other by communicating portions through which charged particles can pass. The housing further comprises: an electromagnetic field adjustment member having a guide groove formed in the divided surface from an edge of the divided surface to an inner surface of the cell section, the electromagnetic field adjustment member being movably arranged along the inner surface of the cell section and capable of changing the state of the electromagnetic field applied inside the cell section as it moves; and a moving mechanism having a linear member connected to the electromagnetic field adjustment member via the gap and moving along the guide groove to move the electromagnetic field adjustment member along the inner surface of the cell section.

[0008] According to the present disclosure, an acceleration cavity capable of appropriately adjusting the resonant frequency can be provided.

[0009] FIG. 1 is a plan view showing an example of an acceleration cavity according to an embodiment. FIG. 2 is a diagram showing a configuration along the A-A cross section in FIG. 1. FIG. 3 is a diagram showing a configuration along the B-B cross section in FIG. 2. FIG. 4 is an enlarged view showing a part of the configuration inside the housing. FIG. 5 is an enlarged view showing a part of the configuration inside the housing. FIG. 6 is an enlarged view showing a part of the configuration inside the housing. FIG. 7 is a diagram showing an example of the relationship between the position of an electromagnetic field adjustment member in a cell unit and the resonant frequency of the acceleration cavity.

[0010] Hereinafter, embodiments of an acceleration cavity according to the present disclosure will be described with reference to the accompanying drawings. However, the present invention is not limited to these embodiments. Furthermore, the components in the following embodiments include those that are easily replaceable by those skilled in the art, or those that are substantially identical.

[0011] Fig. 1 is a plan view showing an example of an acceleration cavity 100 according to this embodiment. Fig. 2 is a diagram showing the configuration along the cross section A-A in Fig. 1. Note that in Fig. 2, the dividing surface 12 is shown hatched. Fig. 3 is a diagram showing the configuration along the cross section B-B in Fig. 2.

[0012] The accelerating cavity 100 shown in FIGS. 1 to 3 generates an accelerating electric field therein when a radio frequency is input from a radio frequency input unit WI, and accelerates charged particles M, such as electrons, emitted from a radiation source BS. The accelerating cavity 100 and the radiation source BS constitute an accelerator AC. Accelerators AC are used in various fields, such as academic fields such as high-energy physics experiments and synchrotron radiation facilities, medical fields such as radiation therapy and testing, and industrial fields such as non-destructive testing. In the following description, when describing the axial direction of the central axis AX of the accelerating cavity 100, the radiation source BS side (the side where charged particles M are incident) is referred to as the entrance side or rear, and the side opposite the entrance side (the side where charged particles are exited) is referred to as the exit side or front. Furthermore, when the accelerating cavity 100 is installed in a facility, the vertical direction is referred to as the up-down direction, and the direction perpendicular to the up-down direction when viewed from the rear of the central axis AX to the front is referred to as the left-right direction. The central axis AX of the acceleration cavity 100 coincides with the beam axis of the charged particles M. In this embodiment, the central axis AX is an imaginary straight line that indicates the trajectory along which the charged particles M from the radiation source BS pass.

[0013] As shown in FIGS. 1 to 3 , the acceleration cavity 100 according to this embodiment includes a housing 10, a cell unit 20, a coupling cavity 30, a vacuum manifold 40, an electromagnetic field adjusting member 50, and a movement mechanism 60.

[0014] The housing 10 has a conductive cylindrical shape. The housing 10 is formed using, for example, high-purity copper. Each divided member 11 has a planar dividing surface 12 aligned along the central axis AX. The housing 10 is formed by joining the outer peripheries of the dividing surfaces 12 of the divided members 11 together, for example, by brazing. In FIG. 2 , the outline of the joining region 12J on the dividing surface 12 is indicated by dotted hatching. Note that the housing 10 may also be formed by joining the outer peripheries of the dividing surfaces 12 together by welding. The divided members 11 are joined together such that the regions inside the joining region 12J of the dividing surface 12 face each other. The divided members 11 are provided with a gap 13 between the opposing regions of the dividing surface 12. Such a gap 13 can be formed, for example, by slightly digging down the inside of the joining region 12J of the dividing surface 12 from the joining region 12J using step processing. In this embodiment, a configuration will be described in which the housing 10 is divided in the left-right direction of the central axis AX along a plane that is perpendicular to the horizontal plane and passes through the central axis AX. The number of divisions of the housing 10 is not limited to two, and may be three or more. The division members 11 have a generally rounded shape in the portions that face each other. This prevents voltage from being applied locally.

[0015] The cell units 20 are formed inside the housing 10. The cell units 20 are arranged side by side in the axial direction of the central axis AX of the housing 10. The cell units 20 are connected to each other by communication units 22 that allow charged particles to pass through. The communication units 22 are formed along the central axis AX. The cell units 20 accelerate the charged particles by high frequency waves.

[0016] The coupling cavities 30 connect adjacent cell units 20. The coupling cavities 30 propagate high frequency waves between adjacent cell units 20. The coupling cavities 30 are arranged in locations that do not contribute to the acceleration of charged particles. The coupling cavities 30 are arranged outside the cell units 20 in the same direction perpendicular to the central axis AX. In this embodiment, all of the coupling cavities 30 are arranged above the cell units 20 with respect to the central axis AX. The coupling cavities 30 include a first space 31 connected to the cell units 20, a second space 32 arranged at a position radially outwardly of the first space 31 with respect to the central axis AX, and a connecting portion 33 connecting the first space 31 and the second space 32 in the radial direction. The first space 31, the second space 32, and the connecting portion 33 are, for example, cylindrical in shape with an axis extending in the up-down direction as their center. The first space 31, the second space 32, and the connecting portion 33 may be in the shape of a rectangular prism, etc. The connecting portion 33 has a smaller diameter centered in the vertical direction than the first space 31 and the second space 32.

[0017] The vacuum manifold 40 is a part that creates negative pressure when evacuating the multiple cell units 20. The vacuum manifold 40 is connected to a vacuum creating unit 43, such as a vacuum pump, via piping 42. In this embodiment, the vacuum manifold 40 is provided, for example, inside the housing 10. The vacuum manifold 40 is formed as a single space and is disposed above each of the coupling cavities 30. Each cell unit 20 is connected to one vacuum manifold 40. In this embodiment, the vacuum manifold 40 is connected to the coupling cavities 30 via a communication unit 45. Therefore, the vacuum manifold 40 is connected to the second space 32 of each coupling cavity 30, and the second space 32 is connected to the multiple cell units 20 via the coupling cavities 30. This configuration ensures a reliable connection between the vacuum manifold 40 and the multiple cell units 20.

[0018] As shown in Figure 2, in the housing 10, the dividing surface 12 of each dividing member 11 is formed with a unit cell portion 21 and a unit communicating portion 23 that form part of the cell portion 20 and the communicating portion 22, a unit connecting cavity 35 that forms part of the connecting cavity 30, and a unit manifold 41 that forms part of the vacuum manifold 40.

[0019] The cell section 20 is formed by combining unit cell sections 21 provided in each divided member 11. The communication section 22 is formed by combining unit communication sections 23 provided in each divided member 11. The coupling cavity 30 is formed by combining unit coupling cavities 35 provided in each divided member 11. The vacuum manifold 40 is formed by combining unit manifolds 41 formed in each divided member 11.

[0020] 4 to 6 are enlarged views showing a part of the internal configuration of the housing 10. In Fig. 4 to Fig. 6, one cell unit 20 is shown enlarged.

[0021] As shown in Figures 4 to 6, the electromagnetic field adjustment member 50 is disposed inside the cell unit 20. The electromagnetic field adjustment member 50 can be disposed inside one or more of the multiple cell units 20. In this embodiment, an example in which the electromagnetic field adjustment member 50 is disposed inside one cell unit 20 will be described. The electromagnetic field adjustment member 50 may also be disposed inside two or more cell units 20.

[0022] The electromagnetic field adjustment member 50 is provided inside the cell unit 20. The electromagnetic field adjustment member 50 is movable inside the cell unit 20. Specifically, the position of the electromagnetic field adjustment member 50 inside the cell unit 20 can be adjusted by moving the electromagnetic field adjustment member 50 inside the cell unit 20. Changing the position of the electromagnetic field adjustment member 50 can change the state of the electromagnetic field applied inside the cell unit 20. That is, the electromagnetic field adjustment member 50 is disposed on the inner surface 20a of the cell unit 20 and is movable along the inner surface 20a. Changing the position of the electromagnetic field adjustment member 50 along the inner surface 20a of the cell unit 20 changes the shape of the inner surface 20a of the cell unit 20. Changing the shape of the inner surface 20a of the cell unit 20 changes the state of the electromagnetic field applied inside the cell unit 20. Note that the accelerating cavity 100 is used with the position of the electromagnetic field adjustment member 50 adjusted in advance. That is, the position of the electromagnetic field adjustment member 50 is not changed when the accelerating cavity 100 is in use.

[0023] The electromagnetic field adjustment member 50 is, for example, spherical. The electromagnetic field adjustment member 50 may be formed using a metal such as gold, copper (e.g., oxide-free copper), or aluminum, or may be formed using ceramic. The electromagnetic field adjustment member 50 may be formed using the same material as the constituent material of the housing 10. Because the acceleration cavity 100 is used under reduced pressure, the electromagnetic field adjustment member 50 is preferably formed using a material that emits little gas. Furthermore, the electromagnetic field adjustment member 50 is preferably formed using a material with low electrical resistance. Furthermore, the electromagnetic field adjustment member 50 preferably has a configuration with a low secondary electron emission coefficient at its surface. For example, the secondary electron emission coefficient can be reduced by coating the surface. Examples of materials with a low secondary electron emission coefficient include copper (oxygen-free copper), gold, silver, titanium, and aluminum. Furthermore, ceramic has a higher secondary electron emission coefficient than the above-mentioned materials. Therefore, when using ceramic, the secondary electron emission coefficient can be reduced by applying, for example, a TiN (titanium nitride) coating or a DLC (diamond-like carbon) coating.

[0024] The moving mechanism 60 moves the electromagnetic field adjustment member 50 inside the cell unit 20. The moving mechanism 60 moves the electromagnetic field adjustment member 50 along the gap 13. The moving mechanism 60 moves the electromagnetic field adjustment member 50 along the inner surface 20a of the cell unit 20. The moving mechanism 60 has a linear member 61 and a driving unit 62.

[0025] The linear member 61 is inserted into the housing 10 from outside the housing 10. Examples of the linear member 61 include a wire made of metal, resin, etc. The linear member 61 is deformable in response to a force in a direction intersecting the direction in which the linear member 61 extends (hereinafter referred to as the extension direction).

[0026] The linear member 61 is inserted into a space including the gap 13 in the housing 10, for example. In this embodiment, the housing 10 has guide grooves 14 in portions of the divided members 11 that face each other across the gap 13. The guide grooves 14 guide the linear member 61. The guide grooves 14 have openings 14a formed in the outer surface of the housing 10, and are formed so as to extend from the openings 14a to the rear side of the housing 10. The guide grooves 14 have abutment portions 14b at their rear end portions.

[0027] The guide groove 14 is formed in a curved state along the inner surface 20a of the cell portion 20 from the edge 12S, which is the outer surface of the housing 10, at the dividing surface 12. The guide groove 14 is formed on each dividing surface 12 so as to form a passage that can guide the linear member 61 when the divided members 11 are assembled together. When the divided members 11 are joined together to form the housing 10, the portion of the guide groove 14 that is located on the edge 12S of the dividing surface 12 is provided as an opening 14a that opens to the outer surface of the housing 10. The linear member 61 can be deformed into a curved shape along the guide groove 14. The linear member 61 can move inside the housing 10 along the extension direction.

[0028] The linear member 61 is inserted into the guide groove 14 through the opening 14a. One end, or first end 61a, of the linear member 61 is disposed within the housing 10, and the other end, or second end 61b, is disposed outside the opening 14a of the housing 10. The first end 61a is connected to the electromagnetic field adjustment member 50 via a connecting portion 63. The connecting portion 63 is formed in a columnar or plate shape using, for example, metal, resin, or the like. The connecting portion 63 protrudes from the first end 61a through the gap 13 into the interior of the cell unit 20 and is connected to the electromagnetic field adjustment member 50 inside the cell unit 20. The electromagnetic field adjustment member 50 and the linear member 61 are connected together via the connecting portion 63. Therefore, the electromagnetic field adjustment member 50 moves integrally with the linear member 61 via the connecting portion 63.

[0029] The drive unit 62 moves the linear member 61 in the extension direction by inserting and removing the linear member 61 into and from the housing 10. In this embodiment, the drive unit 62 has, for example, a bellows 62a and a bellows support portion 62b. The bellows support portion 62b is movable in the up and down direction. The bellows support portion 62b holds the second end 61b of the linear member 61 on its upper surface. As the bellows support portion 62b moves in the up and down direction, the bellows 62a expands and contracts, and the linear member 61 moves in the extension direction integrally with the bellows support portion 62b. The drive unit 62 may be provided with a stopper mechanism (not shown) for fixing the up and down position of the bellows support portion 62b at a desired position.

[0030] When manufacturing the acceleration cavity 100, the electromagnetic field adjustment member 50 and the linear member 61 are first connected by the connecting portion 63. The linear member 61 of this connected body is arranged, for example, along the guide groove 14 of one of the divided members 11. At this time, the second end 61b of the linear member 61 protrudes outward from the guide groove 14. When arranging the connected body, the linear member 61 can be arranged, for example, so that the electromagnetic field adjustment member 50 is located at the lower end of the cell unit 20. From this state, the divided members 11 are joined together so that the guide groove 14 of one divided member 11 faces the guide groove 14 of the other divided member 11, and the linear member 61 is housed in the space surrounded by the guide grooves 14. Then, a driving unit 62 is attached to the second end 61b of the linear member 61.

[0031] After assembly of the accelerating cavity 100, such as joining the components including the segments 11 and attaching the drive unit 62, is completed, the resonant frequency of the accelerating cavity 100 is adjusted. The electromagnetic field adjusting member 50 and the moving mechanism 60 are used to adjust the resonant frequency. An example of adjusting the resonant frequency will be described below.

[0032] When adjusting the resonant frequency, the position of the electromagnetic field adjustment member 50 disposed inside the cell unit 20 is adjusted inside the cell unit 20. For example, as shown in FIG. 4 , when the first end 61 a of the linear member 61 is disposed below the lower end of the cell unit 20 by the driving unit 62, the electromagnetic field adjustment member 50 is disposed at a first position P1 at the lower end of the cell unit 20.

[0033] From this state, by moving the bellows support portion 62b upward using the drive portion 62, the linear member 61 moves so as to be unwound toward the rear of the guide groove 14 of the housing 10. This movement of the linear member 61 causes the first end portion 61a to move along the guide groove 14 toward the rear of the guide groove 14. The linear member 61 can move toward the rear of the housing 10 to a position where the first end portion 61a abuts against the abutment portion 14b. The movement of the first end portion 61a causes the connecting portion 63 and the electromagnetic field adjustment member 50 to move along the inner surface 20a of the cell portion 20 together with the first end portion 61a.

[0034] For example, as shown in FIG. 5 , when the linear member 61 is moved until the first end 61 a abuts against the abutment portion 14 b, the electromagnetic field adjustment member 50 is positioned at the third position P3. The third position P3 corresponds to the boundary between the inner surface 20 a of the cell unit 20 and the communication portion 22. In this embodiment, the third position P3 may be, for example, a position where the upper end of the electromagnetic field adjustment member 50 coincides with the lower end of the communication portion 22. Note that the third position P3 is not limited to this position. Furthermore, as shown in FIG. 6 , when the linear member 61 is moved so that the first end 61 a is positioned at a position midway before abutting against the abutment portion 14 b, the electromagnetic field adjustment member 50 is positioned at the second position P2 between the first position P1 and the third position P3. When the electromagnetic field adjustment member 50 is positioned at the second position P2 or the third position P3, the bellows support portion 62 b is moved downward, thereby moving the linear member 61 in a direction to be pulled out of the housing 10. This movement of the linear member 61 allows the electromagnetic field adjustment member 50 to return to the first position P1.

[0035] In this way, by moving the bellows support portion 62b in the up-down direction using the drive portion 62, the linear member 61 moves along the guide groove 14 inside the housing 10. The movement of the linear member 61 causes the connecting portion 63 and the electromagnetic field adjustment member 50 to move integrally with the first end portion 61a of the linear member 61 along the inner surface 20a of the cell portion 20. By adjusting the up-down position of the bellows support portion 62b, the position of the first end portion 61a in the guide groove 14, and therefore the position of the electromagnetic field adjustment member 50, can be adjusted between the first position P1 and the third position P3.

[0036] 7 is a diagram showing an example of the relationship between the position of the electromagnetic field adjustment member 50 in the cell unit 20 and the resonant frequency of the accelerating cavity 100. In FIG. 7, the horizontal axis represents the position of the electromagnetic field adjustment member 50, and the vertical axis represents the resonant frequency. The position of the electromagnetic field adjustment member 50 is shown as the length to the origin in the direction along the gap 13 and the inner surface 20a of the cell unit 20, assuming that the origin is the position of the lower end of the cell unit 20. FIG. 7 shows the resonant frequencies of the accelerating cavity 100 when the electromagnetic field adjustment member 50 is located at a first position P1, a second position P2, and a third position P3.

[0037] The inventors have found that the resonant frequency of the accelerating cavity 100 is smaller when the electromagnetic field adjustment member 50 is at the third position P3 than when it is at the first position P1. They have also found that there is a predetermined position between the first position P1 and the third position P3 where the resonant frequency of the accelerating cavity 100 is maximized. That is, the resonant frequency of the accelerating cavity 100 gradually increases as the position of the electromagnetic field adjustment member 50 approaches the predetermined position from the first position P1, and gradually decreases as the position of the electromagnetic field adjustment member 50 approaches the third position P3 from the predetermined position.

[0038] 7 illustrates an example in which the predetermined position of the electromagnetic field adjustment member 50 at which the resonant frequency of the accelerating cavity 100 is maximized is the second position P2. As shown in FIG. 7 , the resonant frequency of the accelerating cavity 100 is higher when the electromagnetic field adjustment member 50 is positioned at the second position P2 than when it is positioned at the first position P1 (f1<f2). In this case, the closer the electromagnetic field adjustment member 50 is positioned between the first position P1 and the second position P2, the lower the resonant frequency of the accelerating cavity 100. In other words, the closer the electromagnetic field adjustment member 50 is positioned to the second position P2, the higher the resonant frequency of the accelerating cavity 100. Therefore, by adjusting the position of the electromagnetic field adjustment member 50 between the first position P1 and the second position P2, the resonant frequency of the accelerating cavity 100 can be adjusted between f1 and f2.

[0039] Furthermore, when the electromagnetic field adjustment member 50 is positioned at the third position P3, the resonant frequency of the accelerating cavity 100 is smaller than when it is positioned at the second position P2 (f2 > f3). In this case, the closer the electromagnetic field adjustment member 50 is positioned between the second position P2 and the third position P3, the higher the resonant frequency of the accelerating cavity 100. In other words, the closer the electromagnetic field adjustment member 50 is positioned to the third position P3, the lower the resonant frequency of the accelerating cavity 100. Furthermore, when the electromagnetic field adjustment member 50 is positioned at the third position P3, the resonant frequency of the accelerating cavity 100 is smaller than when it is positioned at the first position P1 (f1 > f3). Therefore, by adjusting the position of the electromagnetic field adjustment member 50 between the second position P2 and the third position P3, the resonant frequency of the accelerating cavity 100 can be adjusted over a wider range than when it is adjusted between the first position P1 and the second position P2.

[0040] Furthermore, for example, if the resonant frequency f1 when the electromagnetic field adjustment member 50 is disposed at the first position P1 is taken as a reference value, the resonant frequency of the acceleration cavity 100 can be set higher or lower than the reference value f1. Therefore, for example, by assembling the components so that the electromagnetic field adjustment member 50 is disposed at the first position P1, the resonant frequency can be adjusted to be higher or lower than the resonant frequency at the time of assembly.

[0041] As described above, according to the first aspect of the present disclosure, there is provided an acceleration cavity comprising: a cylindrical, electrically conductive accelerating cavity housing having a central axis coincident with the central axis AX, the dividing members being divided into a plurality of parts on a plane along the central axis AX of the acceleration cavity which coincides with the beam axis of the charged particles, the dividing surfaces being arranged opposite each other with a gap 13 between them; a plurality of cell units being arranged inside the housing in a line along the axial direction of the central axis AX and connected to each other by connecting parts which allow the charged particles to pass through; an electromagnetic field adjustment member being movably arranged inside the cell unit and capable of changing the state of the electromagnetic field applied inside the cell unit by movement; and a moving mechanism being configured to move the electromagnetic field adjustment member inside the cell unit along the gap 13. For example, the acceleration cavity includes a cylindrical housing 10 having conductive shape, in which divided members 11 are divided into a plurality of parts on a plane along a central axis AX, with parts of divided surfaces 12 along the plane facing each other with gaps 13 therebetween, and joint regions 12J, which are other parts of the divided surfaces 12, are joined together; and a plurality of cell units 20 arranged in the axial direction of the central axis AX inside the parts of the housing 10 where the divided surfaces 12 face each other with gaps 13 therebetween, and communicated with each other by communication parts through which charged particles can pass. The configuration may include an electromagnetic field adjustment member 50 having a guide groove 14 formed on the surface 12 from the edge 12S which is the outer surface of the housing 11 to the inner surface 20a of the cell unit 20, and which is movable along the inner surface 20a of the cell unit 20 and can change the state of the electromagnetic field applied inside the cell unit 20 by moving it, and a moving mechanism 60 having a linear member 61 which is connected to the electromagnetic field adjustment member 50 via a gap 13 and moves along the guide groove 14 to move the electromagnetic field adjustment member 50 along the inner surface 20a of the cell unit 20.

[0042] The inventors have found that the resonant frequency of the accelerating cavity 100 can be appropriately adjusted by disposing the electromagnetic field adjusting member 50 inside the cell unit 20 and adjusting the position of the electromagnetic field adjusting member 50 inside the cell unit 20. Therefore, by moving the electromagnetic field adjusting member 50 along the gap 13 inside the cell unit 20 using the moving mechanism 60, the resonant frequency of the accelerating cavity 100 can be made higher or lower than the reference value. This allows the resonant frequency of the accelerating cavity 100 to be appropriately adjusted.

[0043] In the acceleration cavity according to the second aspect of the present disclosure, in the first aspect, the moving mechanism 60 moves the electromagnetic field adjustment member 50 along the inner surface 20 a of the cell unit 20 .

[0044] The inventors have found that the resonant frequency of the accelerating cavity 100 can be more appropriately adjusted by adjusting the position of the electromagnetic field adjusting member 50 along the inner surface 20 a of the cell unit 20. Therefore, by moving the electromagnetic field adjusting member 50 along the inner surface 20 a of the cell unit 20 using the moving mechanism 60, the resonant frequency of the accelerating cavity 100 can be more appropriately adjusted.

[0045] In the acceleration cavity according to the third aspect of the present disclosure, in the first or second aspect, the electromagnetic field adjustment member 50 is spherical.

[0046] If the electromagnetic field adjustment member 50 has protrusions, corners, or the like, excessive voltage may be applied to the protrusions, corners, or the like when the accelerating cavity 100 is in use. In contrast, in the accelerating cavity according to the fourth aspect, the electromagnetic field adjustment member 50 is spherical, which prevents excessive voltage from being applied to the electromagnetic field adjustment member 50 when the accelerating cavity 100 is in use.

[0047] In the acceleration cavity according to the fourth aspect of the present disclosure, in any of the first to third aspects, the movement mechanism 60 has a linear member 61 that is inserted into the housing 10 from outside the housing 10 and connected to the electromagnetic field adjustment member 50 via the gap 13, and the electromagnetic field adjustment member 50 is moved by inserting and removing the linear member 61 into and from the housing 10. For example, in this acceleration cavity, the guide groove 14 may be provided as an opening 14a that opens into the outer surface of the housing 10 at a portion that is located on the edge 12S of the dividing surface 12 when the divided members 12 are joined to form the housing 10, and the linear member 61 is inserted into the guide groove 14 from the opening 14a and inserted and removed from the outside of the housing 10 to move the electromagnetic field adjustment member 50.

[0048] According to this configuration, the electromagnetic field adjustment member 50 can be moved appropriately by the linear member 61.

[0049] In the acceleration cavity according to the fifth aspect of the present disclosure, in the fourth aspect, the housing 10 has a guide groove 14 for guiding the linear member 61 in the portions of the divided members 11 that face each other across the gap 13 .

[0050] According to this configuration, by moving the linear member 61 along the guide groove 14 , the linear member 61 can be moved appropriately along the gap 13 .

[0051] In the acceleration cavity according to the sixth aspect of the present disclosure, in any of the first to fifth aspects, the multiple cell units 20 are connected by communication units 22 along the central axis AX, and the electromagnetic field adjustment member 50 is movable along the gap 13 on the inner surface 20 a of the cell unit 20 between a first position P1 farthest from the central axis AX and a third position P3 corresponding to the communication units 22. For example, in the acceleration cavity, the third position P3 may be a position corresponding to the boundary between the inner surface 20 a of the cell unit and the communication units 22.

[0052] The inventors have found that the resonant frequency of the accelerating cavity 100 is smaller when the electromagnetic field adjustment member 50 is located at the third position P3 than when it is located at the first position P1. Furthermore, they have found that a second position P2 exists between the first position P1 and the third position P3, at which the resonant frequency of the accelerating cavity 100 is maximized. That is, the resonant frequency of the accelerating cavity 100 gradually increases as the position of the electromagnetic field adjustment member 50 approaches the second position P2 from the first position P1, and gradually decreases as the position of the electromagnetic field adjustment member 50 approaches the third position P3 from the second position P2. Therefore, with this configuration, the resonant frequency of the accelerating cavity 100 can be set higher or lower than the reference value, assuming that the resonant frequency when the electromagnetic field adjustment member 50 is located at the first position P1 is a reference value. Therefore, for example, by assembling the components so that the electromagnetic field adjustment member 50 is positioned at the first position P1, the resonant frequency can be adjusted to be higher or lower than at the time of assembly.

[0053] In the acceleration cavity according to the seventh aspect of the present disclosure, in any one of the first to sixth aspects, the electromagnetic field adjustment member 50 is made of metal or ceramic.

[0054] According to this configuration, the electromagnetic field adjusting member 50 is made of metal or ceramic, and therefore can appropriately affect the electromagnetic field inside the cell unit 20 .

[0055] The technical scope of the present invention is not limited to the above-described embodiment, and appropriate modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the electromagnetic field adjustment member 50 and the linear member 61 of the movement mechanism 60 are separate members, but this configuration is not limiting. The electromagnetic field adjustment member 50 and the linear member 61 may be formed as a single member. For example, the first end 61 a of the linear member 61 may be bent so that the bent portion protrudes from the gap 13 into the interior of the cell unit 20, and the linear member 61 including the bent portion may be used as the electromagnetic field adjustment member.

[0056] In the above embodiment, the electromagnetic field adjustment member 50 is described as being spherical, but is not limited to this configuration. The electromagnetic field adjustment member 50 may have any shape other than spherical, such as an ellipsoid, as long as it does not have any protrusions, corners, or the like to which an excessive voltage may be applied when the accelerating cavity 100 is in use.

[0057] In the above embodiment, the driving unit 62 of the movement mechanism 60 has been described as having the bellows 62 a and the bellows support unit 62 b, but is not limited to this configuration. The driving unit 62 may have a different configuration from the above as long as it is capable of moving the linear member 61 along the extension direction.

[0058] In the above embodiment, the linear member 61 has been described as an example of a configuration for moving the electromagnetic field adjustment member 50, but the present invention is not limited to this configuration. As long as the configuration allows the electromagnetic field adjustment member 50 to move along the gap, the configuration is not limited to a linear member (linear member 61), and members of other shapes may also be used.

[0059] DESCRIPTION OF SYMBOLS 10 Housing 11 Divided member 12 Divided surface 12J Bonding region 12S Edge 13 Gap 14 Guide groove 14a Opening 20 Cell portion 21 Unit cell portion 22, 45 Communication portion 23, 24 Unit communication portion 30 Coupled cavity 31 First space portion 32 Second space portion 33 Connection portion 35 Unit coupled cavity 40 Vacuum manifold 41 Unit manifold 42 Vacuum forming portion 43 Piping 50 Electromagnetic field adjusting member 60 Moving mechanism 61 Linear member 61a First end portion 61b Second end portion 62 Driving portion 62a Bellows 62b Bellows support portion 63 Connection portion 100 Acceleration cavity M Charged particle AC Accelerator P1 First position P2 Second position P3 Third position BS Radiation source AX Central axis WI High frequency input section

Claims

1. An acceleration cavity comprising: a cylindrical, electrically conductive housing in which a divided member is divided into a plurality of sections along a plane along a central axis, with some of the divided surfaces along the plane facing each other with a gap therebetween and other portions of the divided surfaces joined together; and a plurality of cell sections arranged side by side along the central axis of the housing within the sections of the housing where the divided surfaces face each other with a gap between them, and connected to each other by communicating sections that allow charged particles to pass through, the housing having a guide groove formed in the divided surface from an edge that forms the outer surface of the housing to the inner surface of the cell section; an electromagnetic field adjustment member that is arranged movably along the inner surface of the cell section and whose movement can change the state of the electromagnetic field applied inside the cell section; and a movement mechanism having a linear member that is connected to the electromagnetic field adjustment member via the gap and that moves along the guide groove to move the electromagnetic field adjustment member along the inner surface of the cell section.

2. The accelerating cavity according to claim 1, wherein the electromagnetic field adjusting member is spherical.

3. The acceleration cavity according to claim 1, wherein the guide groove is provided as an opening that opens into the outer surface of the housing at a portion that is located on the edge of the divided surface when the divided members are joined together to form the housing, and the linear member is inserted into the guide groove from the opening, and is inserted and removed from the housing from the outside to move the electromagnetic field adjustment member.

4. An acceleration cavity as described in claim 1, wherein the multiple cell sections are connected by a connecting section along the central axis, and the electromagnetic field adjustment member is movable along the gap on the inner surface of the cell section between a position farthest from the central axis and a position corresponding to the boundary between the inner surface of the cell section and the connecting section.

5. The accelerating cavity according to claim 1, wherein the electromagnetic field adjusting member is made of metal or ceramic.

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