Acceleration cavity

Abstract

To provide an acceleration cavity capable of switching energy of charged particles without using a complex mechanism.SOLUTION: An acceleration cavity comprises: a body that is in an electrically conductive cylindrical shape and includes a plurality of division members obtained by division using a plane along the central axis so that division surfaces along the plane are provided in a state of facing each other with a gap; a plurality of cell parts that are disposed inside the body in a state of being arranged in the axial direction of the central axis of the body and are communicated with each other using a communication part through which charged particles can pass; and a switch member that is disposed in the gap of the body, is movable in the gap along the plane, and performs movement to switch the magnitude of an electric field for accelerating the charged particles.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to accelerating cavities. [Background technology]

[0002] When a high frequency wave is input to an acceleration cavity, an acceleration electric field is generated inside the cavity, and the acceleration electric field accelerates charged particles such as electrons. As such an acceleration cavity, for example, a configuration in which a plurality of cells are arranged in the axial direction of a central axis and the cells are connected to each other by communication parts is known (for example, see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 1-107499 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned accelerating cavity, a configuration has been proposed in which the energy of the charged particles can be switched by changing the magnitude of the accelerating electric field. In such an accelerating cavity, a configuration capable of switching the energy of the charged particles without using a complicated mechanism has been required.

[0005] The present disclosure has been made in consideration of the above, and has an object to provide an acceleration cavity capable of switching the energy of charged particles without using a complicated mechanism. [Means for solving the problem]

[0006] The acceleration cavity of the present disclosure comprises a conductive cylindrical housing in which a divided member is divided into multiple pieces on a plane along a central axis, with the divided surfaces along the plane facing each other with a gap between them, a plurality of cell sections arranged inside the housing in a line along the central axis of the housing and connected to each other by connecting sections that allow charged particles to pass through, and a switch member arranged in the gap in the housing and movable through the gap along the plane, the switch member switching the magnitude of the electric field that accelerates the charged particles as it moves. Effect of the Invention

[0007] According to the present disclosure, it is possible to provide an acceleration cavity capable of switching the energy of charged particles without using a complicated mechanism. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a plan view illustrating an example of an acceleration cavity according to an embodiment. [Diagram 2] FIG. 2 is a diagram showing a configuration along the cross section AA in FIG. [Diagram 3] FIG. 3 is a diagram showing a configuration along the cross section BB in FIG. [Figure 4] FIG. 4 is a diagram showing an example of a configuration for moving the switch member. [Diagram 5] FIG. 5 is a diagram showing an example of a configuration for moving a switch member. [Figure 6] FIG. 6 is a diagram showing an example of a configuration for moving a switch member. [Figure 7] FIG. 7 is a diagram showing an example of a configuration for moving a switch member. [Figure 8] FIG. 8 is a diagram showing an example of a configuration for moving a switch member. [Figure 9] FIG. 9 is a diagram showing an example of a configuration for moving a switch member. [Figure 10] FIG. 10 is a diagram showing another example of an accelerating cavity. [Figure 11]FIG. 11 is a diagram showing an example of a usage mode of the accelerating cavity. [Figure 12] FIG. 12 is a diagram showing an example of a usage mode of the accelerating cavity. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, embodiments of an acceleration cavity according to the present disclosure will be described with reference to the drawings. Note that the present invention is not limited to these embodiments. In addition, the components in the following embodiments include those that are replaceable and easy for a person skilled in the art, or those that are substantially the same.

[0010] Fig. 1 is a plan view showing an example of an acceleration cavity 100 according to this embodiment. Fig. 2 is a diagram showing a configuration along the AA cross section in Fig. 1. Note that Fig. 2 shows a state in which the dividing surface 12 is hatched, although it is not a cross section. Fig. 3 is a diagram showing a configuration along the BB cross section in Fig. 2.

[0011] The accelerating cavity 100 shown in FIG. 1 to FIG. 3 generates an accelerating electric field therein by receiving a high frequency wave from a high 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. The accelerator AC is used in various fields, such as academic fields such as high energy physics experiments and synchrotron radiation facilities, medical fields such as radiation therapy or inspection, and industrial fields such as non-destructive inspection. In the following description, when describing the axial direction of the central axis AX among the directions in the accelerating cavity 100, the radiation source BS side (the side where the charged particles M are incident) is referred to as the incident side or rear, and the opposite side to the incident side (the side where the charged particles are emitted) is referred to as the exit side or front. In addition, when the accelerating cavity 100 is placed in a facility or the like, the vertical direction is referred to as the up-down direction, and the direction perpendicular to the up-down direction when looking forward from the rear of the central axis AX is referred to as the left-right direction.

[0012] As shown in FIGS. 1 to 3, an acceleration cavity 100 according to this embodiment includes a housing 10, a cell unit 20, a coupling cavity 30, a vacuum manifold 40, and a switch member 50.

[0013] The housing 10 has a cylindrical shape having electrical conductivity. The housing 10 is formed by joining a plurality of divided members 11. The divided members 11 have planar divided surfaces 12 along the central axis AX. The divided members 11 are joined in a state where the divided surfaces 12 face each other. The divided members 11 are provided in a state where a gap 13 is provided between the opposing divided surfaces 12. In this embodiment, a configuration in which the housing 10 is divided in the left-right direction of the central axis AX along a plane perpendicular to the horizontal plane and passing through the central axis AX will be described as an example. The number of divisions of the housing 10 is not limited to two, and may be three or more. The divided members 11 have a shape in which the parts facing each other are generally rounded. This suppresses local application of voltage.

[0014] 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.

[0015] The coupling cavity 30 connects the adjacent cell parts 20. The coupling cavity 30 propagates high frequency waves between the adjacent cell parts 20. The coupling cavity 30 is arranged at a location that does not contribute to the acceleration of charged particles. The coupling cavity 30 is arranged on the outside of the cell part 20 in the same direction among directions perpendicular to the central axis AX. In this embodiment, all the coupling cavities 30 are arranged above the cell part 20 with the central axis AX as a reference. The coupling cavity 30 has a first space part 31 connected to the cell part 20, a second space part 32 arranged at a position radially outwardly away from the first space part 31 with respect to the central axis AX, and a connection part 33 that connects the first space part 31 and the second space part 32 in the radial direction. The first space part 31, the second space part 32, and the connection part 33 are cylindrical with the center being on an axis extending along the vertical direction, for example. The first space 31, the second space 32, and the connection portion 33 may be in a rectangular prism shape, etc. The connection portion 33 has a smaller diameter centered in the vertical direction than the first space 31 and the second space 32.

[0016] The vacuum manifold 40 is a part that forms a negative pressure when evacuating the multiple cell parts 20. The vacuum manifold 40 is connected to a vacuum forming part 42 such as a vacuum pump via a pipe 43. In this embodiment, the vacuum manifold 40 is provided, for example, inside the housing 10. The vacuum manifold 40 is formed as one space and is arranged above each of the coupling cavities 30. The vacuum manifold 40 is connected to the multiple cell parts 20 via the gaps 13 between the divided members 11. Each cell part 20 is connected to one vacuum manifold 40. In this embodiment, the vacuum manifold 40 is connected to the coupling cavity 30 via a communication part 45. Therefore, the vacuum manifold 40 is connected to the second space part 32 of each coupling cavity 30, and is connected to the multiple cell parts 20 from the second space part 32 via the coupling cavity 30. This configuration ensures a connection between the vacuum manifold 40 and the multiple cell parts 20.

[0017] As shown in Figure 2, in the housing 10, the dividing surface 12 of each divided member 11 is formed with a unit cell portion 21 and a unit communicating portion 23 which constitute part of the cell portion 20 and the communicating portion 22, a unit connecting cavity 35 which constitutes part of the connecting cavity 30, and a unit manifold 41 which constitutes part of the vacuum manifold 40.

[0018] 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 24 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.

[0019] The switch member 50 is disposed in the gap 13 of the housing 10. The switch member 50 is movable in the gap 13 along a plane passing through the central axis AX. In this embodiment, the switch member 50 is movable in the gap 13 along a plane passing through the central axis AX and perpendicular to the left-right direction. The switch member 50 switches the magnitude of the electric field that accelerates the charged particles as it moves. By switching the magnitude of the electric field with the switch member 50, the magnitude of the energy of the charged particles can be switched.

[0020] The switch member 50 is formed using a conductor such as a metal. The switch member 50 is, for example, in the form of a plate having a thickness thinner than the dimension of the gap 13. The switch member 50 is arranged so as to appear and disappear from the coupling cavity 30. When the switch member 50 is arranged in a state in which it is inserted inside the coupling cavity 30, it is possible to block the electromagnetic field of the coupling cavity 30. The switch member 50 is movable between a retracted position P1 where the switch member 50 is retracted from the coupling cavity 30 and a blocking position P2 where the switch member 50 is inserted inside the coupling cavity 30. In this embodiment, the blocking position P2 can be set to a position where the switch member is inserted into the connection portion 33 of the coupling cavity 30.

[0021] The switch member 50 is coupled to a transmission mechanism 51. The transmission mechanism 51 is connected to the outside of the housing 10. The transmission mechanism 51 transmits a driving force generated outside the housing 10 to the switch member 50. The driving force to be transmitted to the switch member 50 may be generated manually by an operator, for example, or may be generated by a driving source such as a motor.

[0022] Figures 4 to 9 are diagrams showing examples of a configuration for moving the switch member 50. Figures 4, 6 and 8 are plan views. Figures 5, 7 and 9 are diagrams showing a configuration along the AA cross section of Figure 1.

[0023] In the example shown in FIG. 4 and FIG. 5, the switch member 50 is rotated around a rotation axis BX perpendicular to the central axis AX. The rotation axis BX is set in a direction along the left-right direction. In this example, the transmission mechanism 51A is formed in a rod shape and extends from the switch member 50 along the rotation axis BX through the housing 10 to the outside of the housing 10. In this way, the transmission mechanism 51A extends in a direction perpendicular to a plane along the central axis AX. In addition, a bearing having a seal mechanism may be provided at a portion where the transmission mechanism 51A penetrates the housing 10 so as to maintain a vacuum state inside the housing 10. In addition, the switch member 50 may be rotated from the outside of the housing 10 in a non-contact manner by a magnetic coupling or the like. A rotating unit 52A that rotates the transmission mechanism 51A is provided outside the housing 10. The rotating unit 52A is, for example, a motor device. In addition, the rotating unit 52A may be configured so that an operator manually rotates the transmission mechanism 51A.

[0024] By rotating the transmission mechanism 51A by the rotating part 52A, the switch member 50 rotates about a rotation axis BX. The switch member 50 rotates along a plane including the central axis AX between a retracted position P1A where the switch member 50 is retracted from the coupling cavity 30 and a blocking position P2B where the switch member 50 enters the coupling cavity 30. The rotation range of the switch member 50 may be adjusted by providing an encoder or the like to adjust the amount of rotation by the rotating part 52A, or may be adjusted by a physical mechanism such as a stopper.

[0025] In the example shown in FIG. 6 and FIG. 7, the switch member 50 is configured to slide along the central axis AX. In this example, the transmission mechanism 51B has a rotating member 53B, a rod-shaped member 54B, and a support member 55B. The rotating member 53B is formed in an L-shape extending in two directions (here, for example, the left-right direction and the front-rear direction) from the base end. The rotating member 53B rotates about a rotation axis CX that passes through the base end and runs in the up-down direction. The tip of the part of the rotating member 53B that extends in the left-right direction is connected to the switch member 50. The tip of the part of the rotating member 53B that extends in the front-rear direction is connected to the rod-shaped member 54B. The rod-shaped member 54B extends to the outside of the housing 10 along the left-right direction. In this way, the transmission mechanism 51B extends in a direction perpendicular to a plane along the central axis AX.

[0026] A driving unit 52B for moving the rod-shaped member 54B in the left-right direction is provided outside the housing 10. The driving unit 52B is, for example, a bellows mechanism. The rod-shaped member 54B can be moved in the left-right direction by expanding and contracting the bellows. Note that, instead of the bellows mechanism, other driving mechanisms such as a ball screw mechanism and an air cylinder mechanism may be used as the driving unit 52B.

[0027] By stretching the bellows in the driving unit 52B, the rod-shaped member 54B moves to the right. When the rod-shaped member 54B moves to the right, the rotating member 53B rotates clockwise around the rotation axis CX when viewed from above. In this case, the tip of the part extending in the left-right direction from the base end moves forward. As a result, the switch member 50 moves forward.

[0028] By contracting the bellows in the driving unit 52B, the rod-shaped member 54B moves to the left. When the rod-shaped member 54B moves to the left, the rotating member 53B rotates counterclockwise around the rotation axis CX when viewed from above. In this case, the tip of the portion extending in the left-right direction from the base end moves rearward. As a result, the switch member 50 moves rearward.

[0029] In this way, the switch member 50 can be slid in the front-rear direction by the transmission mechanism 51B and the drive unit 52B. In the example shown in Fig. 6 and Fig. 7, the position to which the switch member 50 has moved forward is the retracted position P1B, and the position to which the switch member 50 has moved rearward is the blocking position P2B. Note that the position to which the switch member 50 has moved forward may be the blocking position P2B, and the position to which the switch member 50 has moved rearward may be the retracted position P1B.

[0030] In the example shown in FIG. 8 and FIG. 9, the switch member 50 is configured to slide along the central axis AX. In this example, the transmission mechanism 51C has a linear member 53C and a guide member 54C. One end (switch side end) of the linear member 53C is connected to the switch member 50. The linear member 53C may be a member having rigidity in the longitudinal direction and deformable in a direction perpendicular to the longitudinal direction, such as a wire. The linear member 53C is drawn forward from the switch member 50, curved leftward by the guide member 54C, and disposed with its tip extending outside the housing 10. The guide member 54C may be a tubular member such as a tube. The linear member 53C is provided in a state of being passed through the inside of the guide member 54C. In this way, the transmission mechanism 51C extends in a direction perpendicular to a plane along the central axis AX.

[0031] A driving unit 52C for moving the linear member 53C in the left-right direction is provided outside the housing 10. The driving unit 52C is connected to the other end (driving side end) of the linear member 53C. The driving unit 52C is, for example, a bellows mechanism, similar to the driving unit 52B described above. The linear member 53C can be moved in the left-right direction by expanding and contracting the bellows. Note that, instead of the bellows mechanism, other driving mechanisms such as a ball screw mechanism and an air cylinder mechanism may be used as the driving unit 52C.

[0032] By stretching the bellows in the driving section 52C, the driving side end of the linear member 53C is pulled to the right. The linear member 53C is curved by the guide member 54C and the switch side end is arranged along the front-rear direction. Therefore, when the driving side end of the linear member 53C is pulled to the right, the switch side end moves forward. As a result, the switch member 50 moves forward.

[0033] By contracting the bellows in the driving section 52C, the driving side end of the linear member 53C is pushed leftward. The linear member 53C is curved by the guide member 54C so that the switch side end is arranged along the front-rear direction. Therefore, when the driving side end of the linear member 53C is pushed leftward, the switch side end moves rearward. This causes the switch member 50 to move rearward.

[0034] In this way, the switch member 50 can be slid in the front-rear direction by the transmission mechanism 51C and the drive unit 52C. In the example shown in Figures 8 and 9, similar to the example shown in Figures 6 and 7, the position to which the switch member 50 has moved forward is the retracted position P1C, and the position to which the switch member 50 has moved rearward is the blocking position P2C. Note that the position to which the switch member 50 has moved forward may be the blocking position P2C, and the position to which the switch member 50 has moved rearward may be the retracted position P1C.

[0035] Fig. 10 is a diagram showing another example of the acceleration cavity 100. As shown in Fig. 10, a movement gap 14 may be provided in at least a part of the movable range of the switch member 50 in the portion of the gap 13 where the switch member 50 is arranged. The movement gap 14 is a portion where the distance between the dividing surfaces 12 is greater than the gap 13. By providing the movement gap 14, it is possible to prevent the switch member 50 from interfering with the dividing surface 12 of the housing 10.

[0036] 11 and 12 are diagrams showing an example of a usage mode of the acceleration cavity 100. When the switch member 50 is placed in the retracted position P1 as shown in Fig. 11, the radio frequency input from the radio frequency input unit WI is propagated to all the cell units 20. Therefore, the charged particle M emitted from the radiation source BS and entering the inside of the acceleration cavity 100 is accelerated by and emitted from all the cell units 20 through which it passes.

[0037] In contrast, as shown in FIG. 12, when the switch member 50 is placed at the cut-off position P2, the high frequency input from the high frequency input unit WI is cut off at the cut-off position P2. In the acceleration cavity 100, the high frequency is not propagated to the cell unit 20 beyond the cut-off position P2. Therefore, the charged particle M emitted from the radiation source BS and entering the acceleration cavity 100 is accelerated in the cell unit 20 through which the high frequency is propagated among the cell units 20 through which the charged particle M passes, and is emitted without being accelerated from the cell unit 20 through which the high frequency is not propagated. In this case, the energy of the charged particle M is smaller than that when the switch member 50 is placed at the retract position P1. In this way, by switching the energy of the charged particle M, the acceleration cavity 100 can be widely used for an examination device, a treatment device, and the like.

[0038] As described above, according to the first aspect of the present disclosure, an acceleration cavity is provided which includes a conductive cylindrical housing 10 in which a dividing member 11 is divided into a plurality of parts on a plane along a central axis AX, with dividing surfaces 12 along the plane facing each other with a gap 13 therebetween, a plurality of cell sections 20 arranged inside the housing 10 in a line along the axial direction of the central axis AX of the housing 10 and connected to each other by connecting sections 22 that allow charged particles to pass through, and a switch member 50 arranged in the gap 13 in the housing 10 and movable through the gap 13 along a plane passing through the central axis AX, and which switches the magnitude of the electric field that accelerates the charged particles as it moves.

[0039] According to this configuration, in a configuration in which the housing 10 is arranged with the divided surfaces 12 of the divided members 11 divided into multiple parts facing each other with a gap 13 therebetween, by moving the switch member 50 using the gap 13, it is possible to easily switch the energy of the charged particles M without using a complex mechanism.

[0040] In the acceleration cavity according to the second aspect of the present disclosure, in the first aspect, a coupling cavity 30 is provided inside the housing 10 and connects adjacent cell sections 20, and the switch member 50 is arranged so as to appear and disappear in the coupling cavity 30.

[0041] According to this configuration, the switch member 50 is disposed so as to appear and disappear from the coupling cavity, so that it is possible to efficiently switch between transmitting and blocking high frequency waves.

[0042] In the acceleration cavity according to the third embodiment of the present disclosure, in the second embodiment, all of the coupling cavities 30 are disposed on the same side of the cell unit 20 in the direction perpendicular to the central axis AX.

[0043] According to this configuration, by moving the coupling cavities 30 to the same side of the cell unit 20 in the direction perpendicular to the central axis AX, the center of the electric field distribution in the direction perpendicular to the central axis AX can be aligned with the central axis AX. This makes it possible to suppress the bias of the charged particle beam.

[0044] In the acceleration cavity according to the fourth aspect of the present disclosure, in the second aspect, the coupling cavity 30 has a first space portion 31 connected to the cell portion 20, a second space portion 32 arranged at a position radially outwardly spaced from the first space portion 31 with respect to the central axis AX, and a connection portion 33 radially connecting the first space portion 31 and the second space portion 32, and the switch member 50 is arranged so as to appear and disappear from the connection portion 33.

[0045] According to this configuration, the switch member 50 is disposed so as to appear and disappear from the connection portion 33 of the coupling cavity 30, so that it is possible to efficiently switch between transmitting and blocking high frequency waves.

[0046] In the acceleration cavity according to the fifth aspect of the present disclosure, in the first aspect, the second space portion 32 of the coupling cavity 30 is connected to the vacuum manifold 40 .

[0047] According to this configuration, since the vacuum manifold 40 is connected to the cell portion 20 via the coupling cavity 30, the cell portion 20 can be evacuated to a vacuum by the vacuum manifold 40 more reliably.

[0048] In the acceleration cavity according to the sixth aspect of the present disclosure, in any of the first to fifth aspects, the housing 10 has a movement gap 14 in at least a part of the movable range of the switch member 50, in which the distance between the dividing surfaces 12 is greater than the gap 13.

[0049] According to this configuration, by providing the movement gap 14, interference of the switch member 50 with the dividing surface 12 of the housing 10 can be suppressed.

[0050] The acceleration cavity according to the seventh aspect of the present disclosure is in any one of the first to sixth aspects, further including a transmission mechanism 51 that transmits a driving force generated outside the housing 10 to the switch member 50.

[0051] According to this configuration, the transmission mechanism 51 is provided, so that the switch member 50 can be moved from outside the housing 10.

[0052] In an acceleration cavity according to an eighth aspect of the present disclosure, in the seventh aspect, the transmission mechanism 51 extends in a direction perpendicular to the plane.

[0053] According to this configuration, since the transmission mechanism 51 extends in a direction perpendicular to the plane, the driving force can be appropriately transmitted in either case of rotating or sliding the switch member 50, for example.

[0054] In the acceleration cavity according to the ninth aspect of the present disclosure, in any of the first to seventh aspects, the transmission mechanism 51 transmits a driving force so that the switch member 50 rotates about a rotation axis BX along a direction perpendicular to the central axis AX.

[0055] According to this configuration, the transmission mechanism 51 can move the switch member 50 so as to rotate about the rotation axis BX along the direction perpendicular to the central axis AX.

[0056] In the acceleration cavity according to the tenth aspect of the present disclosure, in any of the first to seventh aspects, the transmission mechanism 51 transmits a driving force such that the switch member 50 slides in a direction along the central axis AX.

[0057] According to this configuration, the transmission mechanism 51 can move the switch member 50 so as to slide in a direction perpendicular to the central axis AX.

[0058] In the above embodiment, a configuration in which one switch member 50 is provided has been described as an example, but the present invention is not limited to this configuration. A plurality of switch members 50 may be provided. In this case, the plurality of switch members 50 can be provided so as to be individually movable and to appear and disappear in different coupling cavities 30. [Explanation of symbols]

[0059] 10. Chassis 11 Partition 12 Split plane 13. Gap 14 Movement gap 20 Cell Section 21 Unit cell section 22,45 Communication part 23,24 Unit communication part 30 Combined Cavity 31 1st space part 32 Second space 33 Connection 35 Unit Coupled Cavities 40 Vacuum Manifold 41 unit manifold 42 Vacuum forming section 43 Piping 50 Switch parts 51, 51A, 51B, 51C Transmission mechanism 52A Rotating part 52B, 52C Drive unit 53B Rotating member 53C Linear members 54B Rod-shaped member 54C Guide member 55B Support member 100 Acceleration Cavity AC accelerator AX center axis BS source BX, CX rotating shaft M charged particles P1,P1A,P1B,P1C Retreat position P2,P2A,P2B,P2C Shutoff position WI High frequency input section

Claims

1. a conductive cylindrical housing, in which divided members are divided into a plurality of sections along a plane extending along a central axis, with parts of the divided surfaces along the plane facing each other with gaps between them, and other parts of the divided surfaces being joined together; a plurality of cell units arranged inside the housing in a lined-up state in the axial direction of the central axis of the housing and connected to each other by communication units through which charged particles can pass; a switch member that is disposed in the gap of the housing, is movable in the gap along the plane, and switches the magnitude of the electric field that accelerates the charged particles by the movement; An accelerating cavity comprising:

2. a coupling cavity provided inside the housing and communicating with adjacent cells at positions offset from the central axis, The switch member is disposed so as to appear and disappear from the coupling cavity. The acceleration cavity of claim 1 .

3. All of the coupling cavities are arranged on the same side of the cell portion in a direction perpendicular to the central axis. The acceleration cavity of claim 2 .

4. the coupling cavity has a first space portion connected to the cell portion, a second space portion disposed at a position spaced apart radially outward with respect to the central axis from the first space portion, and a connecting portion connecting the first space portion and the second space portion in the radial direction, The switch member is disposed so as to appear and disappear from the connection portion. The acceleration cavity of claim 2 .

5. a vacuum manifold connected to the plurality of cell portions via the gap; The coupling cavity has the second space portion connected to the vacuum manifold. The acceleration cavity of claim 4 .

6. The housing has a movement gap in at least a part of the movable range of the switch member, in which the distance between the divided surfaces is larger than the gap. The acceleration cavity of claim 1 .

7. The switch member further includes a transmission mechanism that transmits a driving force generated outside the housing to the switch member. The acceleration cavity of claim 1 .

8. The transmission mechanism extends in a direction perpendicular to the plane. The acceleration cavity of claim 7 .

9. The transmission mechanism transmits the driving force so that the switch member rotates about a rotation axis extending in a direction perpendicular to the central axis. The acceleration cavity of claim 7 .

10. The transmission mechanism transmits the driving force so that the switch member slides in a direction along the central axis. The acceleration cavity of claim 7 .

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