JP7397622B2 - cavity and stem - Google Patents

Description

The present invention relates to a cavity and a stem.

Conventionally, as a technology in this field, a cavity described in Patent Document 1 below is known. An electric field is generated within the cavity that accelerates the charged particles. The cavity includes a Dee electrode, a ground plate, and a stem.

JP 2019-110040 Publication

Here, in the cavity as described above, it is necessary to design the size, shape, etc. of the ground plate, D electrode, or stem, which are the components of the cavity, so that the electromagnetic waves introduced into the cavity resonate. However, the shape of the ground plate and the shape of the D electrode depend on, for example, the shape of the magnetic pole of the cyclotron, and therefore have a smaller degree of freedom than the shape of the stem. Therefore, the shape of the stem is mainly optimized to optimize the resonant frequency of the cavity. On the other hand, as cyclotrons continue to become smaller, the degree of freedom in the shape of the stem is decreasing. Therefore, there has been a need for a stem that can be installed inside the cavity of a miniaturized cyclotron and that can optimize the resonant frequency so that the electromagnetic waves introduced into the cavity resonate.

An object of the present invention is to provide a cavity and a stem that can be installed to match the size or shape of a cyclotron and that can be set to an appropriate resonance frequency for electromagnetic waves.

A cavity according to one aspect of the present invention is a cavity that generates an electric field that accelerates charged particles, and includes a Dee electrode, a ground plate, and a stem extending so as to connect the Dee electrode and the ground plate. , the stem has a first joint part joined to the D electrode, a second joint part joined to the ground plate, and a main body part extending between the first joint part and the second joint part, The main body portion includes a changing portion in which at least one of the cross-sectional area and cross-sectional shape with respect to the extending direction of the stem changes.

In this cavity, the stem joins the Dee electrode at a first joint and the ground plate at a second joint. The main body of the stem extends between the first joint and the second joint. The main body portion has a changing portion that changes at least one of a cross-sectional area and a cross-sectional shape. Here, the stem mainly functions as an inductance component inside the cavity. By changing the cross-sectional area and cross-sectional shape of the changing portion in the main body of the stem, the inductance of the stem can be changed, and the resonant frequency of the stem can be changed. As described above, this cavity can be installed according to the size or shape of the cyclotron, and can be set to an appropriate resonance frequency for electromagnetic waves.

In one embodiment, the changing portion may increase the cross-sectional area in the extending direction.

In one embodiment, the changing portion may be provided at a position where the distance from the first joint portion and the distance from the second joint portion are different in the extending direction. According to such a configuration, even if there is another component between the Dee electrode and the ground plate within the cavity, the main body can be maintained by appropriately changing the position where the changing portion is provided. By connecting the D electrode and the ground plate, an appropriate resonant frequency can be set. Therefore, it is possible to install a stem that matches the shape inside the cavity.

In one embodiment, at least one of the first joint part and the second joint part may be constituted by a flange part that extends toward the outer circumferential side from the end surface of the main body part. According to such a configuration, at least one of the first bonding portion and the second bonding portion that extend toward the outer circumferential side from the end surface of the main body portion is stably bonded to at least one of the D electrode and the ground plate. Therefore, the Dee electrode and the stem can be stably joined by the first joint, and the ground plate and the stem can be stably joined by the second joint.

In one embodiment, at least one of the first joint and the second joint may be formed by an end surface of the main body. According to such a configuration, the stem can be joined to at least one of the Dee electrode and the ground plate with a simple configuration.

A stem according to another aspect of the present invention is a stem extending so as to connect a D-electrode in a cavity that generates an electric field for accelerating charged particles and a ground plate, the stem having a first joint connected to the D-electrode. a second joint part joined to the ground plate; and a main body part extending between the first joint part and the second joint part, the main body part having a cross-sectional area and a cross-sectional area in the extending direction of the stem. It has a changed part in which at least one of the shapes is changed.

The stem is connected to the D electrode at a first joint, and to the ground plate at a second joint. The main body of the stem extends between the first joint and the second joint. The main body portion has a changing portion that changes at least one of a cross-sectional area and a cross-sectional shape. Here, the stem mainly functions as an inductance component inside the cavity. By changing the cross-sectional area and cross-sectional shape of the changing portion in the main body of the stem, the inductance of the stem can be changed, and the resonant frequency of the stem can be changed. As described above, this stem can be installed according to the size or shape of the cyclotron and cavity, and can be set to an appropriate resonance frequency for electromagnetic waves.

According to the present invention, it is possible to provide a cavity and a stem that can be installed to match the size or shape of a cyclotron and can be set to an appropriate resonance frequency for electromagnetic waves.

FIG. 1 is a perspective view showing the inside of a cyclotron including a cavity according to an embodiment. FIG. 2 is a cross-sectional view schematically showing the cavity of FIG. 1. FIG. FIG. 3 is a partially enlarged cross-sectional view of the cavity in FIG. 2; It is a schematic sectional view showing a part of cavity and a stem concerning an embodiment. It is a schematic sectional view showing a part of cavity and a stem concerning an embodiment. It is a schematic sectional view showing a part of cavity and a stem concerning an embodiment. It is a schematic sectional view showing a part of cavity and a stem concerning an embodiment.

Embodiments of the present invention will be described below with reference to the drawings. In the description of the drawings, the same or equivalent elements are given the same reference numerals and redundant description will be omitted. Further, the positional relationships such as top, bottom, left and right are based on the positional relationships in the drawings.

First, a cyclotron 1 including a cavity 6 according to the present embodiment will be described. FIG. 1 is a perspective view showing the inside of the cyclotron 1. FIG. In FIG. 1, the upper part of the cyclotron 1 is removed and the built-in components are visible.

The cyclotron 1 generates a proton beam, and accelerates hydrogen cations (charged particles) supplied from an ion source (not shown) inside a vacuum vessel 3 to generate a proton beam and emit it. do. The vacuum container 3 is made of, for example, stainless steel. Further, a vacuum pump (not shown) is connected to the vacuum container 3. The vacuum container 3 forms a vacuum environment in which ions are accelerated.

The cyclotron 1 includes a yoke 4 arranged vertically to face each other, and an excitation coil 5 that forms a magnetic field within the vacuum vessel 3. The cyclotron 1 also includes a cavity 6 that generates a high-frequency electric field and an RF tuner 11 that adjusts the resonance frequency of the cavity 6 in order to impart energy to the proton beam.

A magnetic field is formed in the vacuum vessel 3 by the yoke 4 and the excitation coil 5, and a high-frequency electric field is formed by the cavity 6, so that the proton beam moves in a spiral orbit, and as the radius of the orbit increases, the protons Beam speed increases. Note that in FIG. 1, the lower yoke 4 is illustrated, and the upper yoke 4 is not illustrated.

The cyclotron 1 also includes a deflector 7 installed on the inner surface of the side wall of the vacuum vessel 3 for extracting the accelerated proton beam, and a gradient collector 8 for correcting the magnetic field gradient. A collimator 9 that emits a proton beam in a predetermined direction (horizontal direction), and a permanent quadrupole magnet (quadrupole) 10 that adjusts the focus of the emitted proton beam are provided. The proton beam accelerated within the vacuum chamber 3 is extracted by a deflector 7, the magnetic field gradient is corrected by a gradient collector 8, and the emission direction is adjusted by a collimator 9. The focus of the emitted proton beam is adjusted by a permanent quadrupole magnet 10.

FIG. 2 is a cross-sectional view schematically showing the cavity 6 of FIG. 1. As shown in FIG. In the cyclotron 1, a pair of cavities 6 are provided above and below with a proton beam B passage interposed therebetween. As shown in FIG. 2, the pair of cavities 6 are substantially vertically symmetrical and have the same or equivalent structure. Therefore, in the following, only the structure of the cavity 6 located below will be described in order to avoid redundant explanation.

The cavity 6 has a dee electrode 21, a ground plate 23, and a stem 27. The ground plate 23 is spaced apart from the Dee electrode 21 and has a bottomed cup shape that accommodates the Dee electrode 21 therein, and is fitted into the recess of the yoke 4. The ground plate 23 is made of oxygen-free copper, for example. A stem 27 extends upward from the bottom surface of the ground plate 23, and the D electrode 21 is fixed to the upper end of the stem 27. In addition, in the cross-sectional views and schematic cross-sectional views after FIG. 2, the stem 27 shows a side surface rather than a cross section.

The upper edge of the ground plate 23 constitutes a counter dee 29. Further, a gap is provided between the upper edge of the ground plate 23 and the Dee electrode 21, and this gap constitutes an acceleration gap G between the Dee electrode 21 and the counter Dee 29. By introducing electromagnetic waves between the Dee electrode 21 and the counter Dee 29, a high frequency electric field is generated according to the rotational phase of the proton beam B, so that the proton beam B is accelerated every time it passes through the acceleration gap G. Ru.

FIG. 3 is a partially enlarged cross-sectional view of the cavity 6 of FIG. 2. As shown in FIG. As shown in FIG. 3, the ground plate 23 includes a bottom plate 31, a side plate 33 vertically rising from the bottom plate 31, and a counter dee 29 projecting outward from the upper end of the side plate 33 in a brim shape.

The bottom plate 31 extends in a plane parallel to the D electrode 21 . A through hole (not shown) is provided in the center of the bottom plate 31. The through hole is provided with a hole for inserting a coupler (not shown). Further, the bottom plate 31 is provided with two mounting seats (not shown) for mounting the stem 27. The stem 27 extends in the vertical direction (extending direction) so as to connect the D electrode 21 and the bottom plate 31 of the ground plate 23. Hereinafter, the vertical direction will be referred to as the extending direction, and the direction of the horizontal plane perpendicular to the extending direction will be referred to as the cross-sectional direction. The bottom plate 31 is manufactured by sheet metal processing of a flat plate material of oxygen-free copper. The thickness of the bottom plate 31 is set to 5 mm or more to ensure mechanical strength. Note that sheet metal processing includes cutting, drilling, punching, bending, or a combination of these processes on a flat metal material.

The side plate 33 is formed into a cylindrical shape by combining a plurality of side plate parts. Each side plate component has a curved or bent thin plate shape and is manufactured by sheet metal processing of a flat plate material of oxygen-free copper. The thickness of each side plate component is set to 5 mm or more in order to ensure the mechanical strength of the side plate 33. Further, the counter dee 29 is also in the form of a thin plate, and is manufactured by sheet metal processing of a flat plate of oxygen-free copper.

Here, the function and design conditions of the cavity 6 will be explained. The frequency of the electromagnetic waves introduced into the cavity 6 needs to be approximately the same as the cyclotron frequency due to the magnetic field generated from the excitation coil 5 of the cyclotron 1. The frequency of the electromagnetic waves is, for example, about several tens of MHz to several hundred MHz. The cavity 6 is designed so that electromagnetic waves introduced into the cavity resonate.

The resonance frequency of the electromagnetic waves within the cavity 6 is affected by the shape of the Dee electrode 21, the shape of the ground plate 23, the size and shape of the stem 27, etc. The shape of the ground plate 23 depends on the shape of the excitation coil 5 on which the ground plate 23 is installed, and the shape of the D electrode 21 depends on the shape of the ground plate 23. Therefore, among the above three factors, the size and shape of the stem 27 have the greatest degree of freedom in design. Since the stem 27 mainly functions as an inductance component within the cavity 6, by changing the size and shape of the stem 27, it is possible to change the inductance and change the resonance frequency of electromagnetic waves within the cavity 6. can. For example, when the stem 27 is formed in a cylindrical shape, the larger the outer diameter (diameter in the cross-sectional direction) of the stem 27 in the extending direction is, the larger the resonant frequency of the electromagnetic waves becomes.

The conventional stem includes a pair of connection parts (corresponding to a first joint part 50 and a second joint part 60 described later) that are connected to the D electrode 21 and the bottom plate 31 of the ground plate 23, respectively, and a pair of connection parts. (corresponding to the main body section 70 described later). Each connection part is connected to a mounting seat (not shown) provided on the D electrode 21 and a mounting seat provided on the bottom plate 31 of the ground plate 23 via connection members (corresponding to the joining member 37 described later). ing. The connecting member is disposed along the outer periphery of the connecting portion in the cross-sectional direction, and is attached in the extending direction. The connecting portion extends without changing the cross-sectional area in the extending direction (the area of the cross section when the connecting portion is cut in the cross-sectional direction). The connecting portion is joined to a portion of each connecting portion where the connecting member is not attached. Therefore, since the cross-sectional area of the connecting portion in the extending direction depends on the size of the portion of each connecting portion to which the connecting member is not attached, there is an upper limit to the cross-sectional area and volume that can be changed. For this reason, there is a possibility that the conventional stem cannot be set to a resonant frequency of electromagnetic waves depending on the size or shape of the cyclotron or cavity.

The stem 27 in the cavity 6 according to this embodiment, which can solve the problems of the conventional stems as described above, will be described in detail. As shown in FIG. 3, the stem 27 extends in the extending direction so as to connect the Dee electrode 21 and the ground plate 23. The stem 27 includes a first joint portion 50 that is joined to the D electrode 21, a second joint portion 60 that is joined to the ground plate 23, and a main body portion that extends between the first joint portion 50 and the second joint portion 60. 70.

The first joint portion 50 is joined to the D electrode 21 . The first joint portion 50 faces and contacts the lower surface of the Dee electrode 21 in the extending direction. The first joint portion 50 has, for example, a fastening hole (not shown). The first joint portion 50 is joined to a mounting seat (not shown) provided on the D electrode 21 via a joining member 37. The joining member 37 is, for example, a bolt. For example, the joining member 37 is inserted into the fastening hole and the mounting seat from the Dee electrode 21 toward the first joint portion 50 and is fitted with the Dee electrode 21 and the first joint portion 50 . The first joint portion 50 has, for example, a disk shape. The fastening hole of the first joint part 50 is, for example, a recess provided along the outer periphery of the upper surface of the first joint part 50. The fastening hole may pass through the first joint portion 50 in the extending direction. For example, the joining member 37 may be inserted into the fastening hole and the mounting seat from the first joining portion 50 toward the D electrode 21.

The second joint portion 60 is joined to the D electrode 21 . The second joint portion 60 faces and contacts the bottom plate 31 of the ground plate 23 in the extending direction. The second joint portion 60 has, for example, a fastening hole (not shown). The second joint portion 60 is joined to a mounting seat provided on the ground plate 23 via a joining member 37. For example, the joining member 37 is inserted into the fastening hole and the mounting seat from the second joint portion 60 toward the ground plate 23 and is fitted into the second joint portion 60 and the earth plate 23 . The second joint portion 60 has, for example, a disk shape. The fastening hole of the second joint part 60 is provided, for example, along the outer periphery of the upper surface of the second joint part 60. The fastening hole passes through the second joint portion 60 in the extending direction. For example, the joining member 37 may be inserted into the fastening hole and the mounting seat from the ground plate 23 toward the second joint portion 60, for example.

The main body part 70 extends between the first joint part 50 and the second joint part 60. The main body portion 70 has a first extending portion 71 , a second extending portion 74 , and a changing portion 77 . In the extending direction, from the Dee electrode 21 to the bottom plate 31 of the ground plate 23 (downward), the stem 27 has the first joint part 50, the first extending part 71, the changing part 77, and the second extending part 74. , the second joint portion 60 are arranged in this order. A cooling conduit may be provided inside each of the first extending portion 71, the second extending portion 74, and the changing portion 77. The lengths of the first extending portion 71, the second extending portion 74, and the changing portion 77 in the extending direction are appropriately set depending on the set resonance frequency. The first extending portion 71, the second extending portion 74, and the changing portion 77 are formed as one piece, for example. For example, the center lines of each of the first joint portion 50, the first extension portion 71, the changing portion 77, the second extension portion 74, and the second joint portion 60 are arranged on the same axis.

The first joint portion 50 and the second joint portion 60 are constituted by a flange portion that extends outward from the end surface of the main body portion 70 . The end surfaces refer to an end surface (upper surface) of the first extending portion 71 and an end surface (lower surface) of the second extending portion 74, which will be described later. It should be noted that the size relationship is not limited in the size of the cross-sectional area or the diameter in the cross-sectional direction of the flange portion, and the size of the cross-sectional area or the diameter in the cross-sectional direction of the changing portion 77. That is, the size of the cross-sectional area or the diameter in the cross-sectional direction of the flange portion and the size of the cross-sectional area or the diameter in the cross-sectional direction of the changing portion 77 may be larger. Further, both the first joint portion 50 and the second joint portion 60 may not be flange portions, and one may be configured as a flange portion and the other may be configured as an end surface of the main body portion 70.

The first extending portion 71 is located between the changing portion 77 and the first joint portion 50 . The first extending portion 71 has a cylindrical shape, for example. The first extending portion 71 joins to a portion of the lower surface of the first joint portion 50 where the fastening hole and the joint member 37 fitted into the first joint portion 50 are not provided. That is, when the first joint part 50 is constituted by a flange part, the fastening hole of the first joint part 50 and the joint member 37 fitted into the first joint part 50 are connected to the first joint part 50 in the cross-sectional direction. and the outer periphery of the first extension portion 71 . The cross-sectional area of the first extending portion 71 in the extending direction is less than or equal to the cross-sectional area of the first joint portion 50 . The first extending portion 71 extends, for example, between the first joint portion 50 and the changing portion 77 in parallel to an axis extending in the extending direction. The first extending portion 71 is joined to the first joint portion 50 by, for example, welding. The first joint portion 50 and the main body portion 70 may be formed as a single piece.

The second extending portion 74 is located between the changing portion 77 and the second joint portion 60 . The second extending portion 74 has a cylindrical shape, for example. The second extending portion 74 joins to a portion of the upper surface of the second joint portion 60 where the fastening hole and the joining member 37 fitted into the second joint portion 60 are not provided. That is, when the second joint part 60 is constituted by a flange part, the fastening hole of the second joint part 60 and the joint member 37 fitted into the second joint part 60 are connected to the second joint part 60 in the cross-sectional direction. and the outer periphery of the second extension portion 74. The cross-sectional area of the second extending portion 74 in the extending direction is less than or equal to the cross-sectional area of the second joint portion 60 . The second extending portion 74 extends, for example, between the second joint portion 60 and the changing portion 77 in parallel to an axis extending in the extending direction. The second extending portion 74 is joined to the second joint portion 60 by, for example, welding. The second joint portion 60 and the main body portion 70 may be formed as a single piece.

The changing portion 77 is a portion of the main body portion in which at least one of the cross-sectional area (area in the cross-sectional direction) and the cross-sectional shape with respect to the extending direction has changed. For example, the changing portion 77 has at least one of a cross-sectional area and a cross-sectional shape in the extending direction changing from at least one of the first extending portion 71 and the second extending portion 74 . The changing portion 77 may be formed, for example, in a cylindrical shape. At this time, the changing portion 77 is solid except for the cooling pipe.

First, a case where the changing portion 77 changes the cross-sectional area in the extending direction will be described. The changing portion 77 has, for example, an enlarged cross-sectional area in the extending direction. The changing part 77 has an enlarged cross-sectional area by increasing the outer diameter in the cross-sectional direction (hereinafter simply referred to as "outer diameter") of at least one of the first extending part 71 and the second extending part 74. You may let them. For example, the changing portion 77 has an outer surface of at least one of the first extending portion 71 and the second extending portion 74 at each boundary surface between the first extending portion 71 and the second extending portion 74 and the changing portion 77. The diameter is expanded to a preset outer diameter. In the changing portion 77, for example, the outer diameter of the changing portion 77 between the interface between the first extending portion 71 and the changing portion 77 and the interface between the second extending portion 74 and the changing portion 77 is the same. be. The changing portion 77 may have a smaller outer diameter than at least one of the first joint portion 50 and the second joint portion 60.

FIG. 4 is a schematic cross-sectional view showing a part of the cavity 6 and the stem 27 according to the embodiment. FIG. 4A is a schematic cross-sectional view showing a state where the outer diameter of the stem 27 is larger than the outer diameter of the first joint portion 50 and the outer diameter of the second joint portion 60. As shown in FIG. 4A, the changing portion 77 may have a larger outer diameter than at least one of the first joint portion 50 and the second joint portion 60.

(b) of FIG. 4 shows that the outer diameter of the changing portion 77 is smaller than the outer diameter of the first extending portion 71 and the outer diameter of the second extending portion 74 toward the center in the extending direction of the changing portion 77. FIG. 3 is a schematic cross-sectional view showing a state in which the size is gradually increased. As shown in FIG. 4B, the outer diameter of the changing portion 77 increases from the interface with the first extending portion 71 toward the center of the changing portion 77 in the extending direction. Similarly, the outer diameter of the changing portion 77 increases from the interface with the second extending portion 74 toward the center of the changing portion 77 in the extending direction. As shown in FIG. 4(b), the outer diameter of the changing portion 77 does not have to increase toward the center in the extending direction of the changing portion 77. . The outer diameter of the changing portion 77 may be the same in the vicinity of the center of the stem 27 in the extending direction. As described above, the outer diameter of the changing portion 77 in the extending direction may be increased only at the changing portions with respect to the first extending portion 71 and the second extending portion 74, or The distance between the second extending portion 74 and the second extending portion 74 may be increased in stages.

For example, the changing portion 77 may have a reduced cross-sectional area in the extending direction. The cross-sectional area of the changing portion 77 may be reduced by making the outer diameter smaller than at least one of the first extending portion 71 and the second extending portion 74. The outer diameter of the changing portion 77 in the extending direction may be reduced only at the respective changing portions with respect to the first extending portion 71 and the second extending portion 74, or the outer diameter of the changing portion 77 in the extending direction may be reduced at the respective changing portions with respect to the first extending portion 71 and the second extending portion 74. It may be decreased stepwise between 74 and 74.

The changing portion 77 is not limited to the number of portions whose cross-sectional area in the extending direction changes with respect to the first extending portion 71 and the second extending portion 74. That is, the changing portion 77 may have, for example, three or more portions whose cross-sectional area in the extending direction changes with respect to the first extending portion 71 and the second extending portion 74. The cross-sectional area of the changing portion 77 may be expanded or decreased for each portion in the extending direction. The changing portion 77 may not be vertically symmetrical, and the degree of change in cross-sectional area in the extending direction may vary depending on the portion.

Further, a case will be described in which the changing portion 77 changes its cross-sectional shape in the extending direction. The changing portion 77 may change the cross-sectional shape (hereinafter simply referred to as “cross-sectional shape”) of at least one of the first extending portion 71 and the second extending portion 74 in the extending direction. For example, the changing portion 77 has a cross section of at least one of the first extending portion 71 and the second extending portion 74 at each boundary surface between the first extending portion 71 and the second extending portion 74 and the changing portion 77. The shape is changed to a preset cross-sectional shape.

FIG. 5 is a schematic cross-sectional view showing a part of the cavity 6 and the stem 27 according to the embodiment. FIG. 5A is a schematic cross-sectional view showing a state in which the cross-sectional shape of the stem 27 in the extending direction is a regular octagon. FIG. 5B is a cross-sectional view showing the cross-sectional shape of the first extending portion 71 in the extending direction. FIG. 5C is a cross-sectional view showing the cross-sectional shape of the changing portion 77 in the extending direction. As shown in FIGS. 5(a) to 5(c), the first extending portion 71, the second extending portion 74, and the changing portion 77 do not have to be formed in a columnar shape. The first extending portion 71 and the second extending portion 74 may have the same cross-sectional shape as the changing portion 77. In this case, the changing portion 77 has a different cross-sectional area from the first extending portion 71 and the second extending portion 74. The changing portion 77 has a different cross-sectional shape from at least one of the first extending portion 71 and the second extending portion 74. The cross-sectional shape of the changing portion 77 may be a polygon, a perfect circle, an ellipse, or the like.

The changing portion 77 does not need to change the cross-sectional area in the extending direction. In this case, the cross-sectional area of the changing portion 77 in the extending direction is the same as the cross-sectional area of at least one of the first extending portion 71 and the second extending portion 74 in the extending direction. At this time, the cross-sectional shape of the changing portion 77 in the extending direction is different from the cross-sectional shape of at least one of the first extending portion 71 and the second extending portion 74 in the extending direction. The changing portion 77 may change both the cross-sectional area and the cross-sectional shape in the extending direction.

Moreover, the changing portion 77 does not have to be formed solidly. That is, the changing portion 77 may be formed hollow. For example, when the changing portion 77 has a cylindrical shape, the changing portion 77 does not need to change at least one of the outer diameter and the outer shape in the cross-sectional direction. The outer shape in the cross-sectional direction refers to the outer edge facing the side plate 33. At this time, the cross-sectional area may be reduced by decreasing the solid portion and increasing the hollow portion within the changing portion 77 without changing at least one of the outer diameter and the outer shape of the changing portion 77. The cross-sectional shape may be changed by forming a hollow portion within the changing portion 77 and changing the shape of the solid portion and the shape of the hollow portion without changing at least one of the outer diameter and the outer shape of the changing portion 77. . The changing portion 77 may have a shape including a recess in the cross-sectional direction.

FIG. 6 is a schematic cross-sectional view showing a part of the cavity 6 and the stem 27 according to the embodiment. As shown in FIG. 6, the changing portion 77 is provided at a position where the distance from the first joint portion 50 and the distance from the second joint portion 60 are different in the extending direction. In the extending direction, the length of the first extending portion 71 and the length of the second extending portion 74 may be different. That is, the center position of the changing portion 77 in the extending direction may be different from the center position of the entire stem 27 in the extending direction.

FIG. 7 is a schematic cross-sectional view showing a part of the cavity 6 and the stem 27 according to the embodiment. As shown in FIG. 7, at least one of the first joint portion 50 and the second joint portion 60 is configured by an end surface of the main body portion 70. The first joint portion 50 may be an end surface (upper surface) of the first extension portion 71 in the extending direction. The second joint portion 60 may be the end surface (lower surface) of the second extension portion 74 in the extending direction. That is, the first extending portion 71 may extend toward the changing portion 77 with the first joint portion 50 as the end face in the extending direction, and the second extending portion 74 may have the first connecting portion 50 as the end face in the extending direction. The joint portion 60 may be used as an end surface and may extend toward the changing portion 77 . Note that both the first joint portion 50 and the second joint portion 60 do not have to be the end surfaces of the main body portion 70, and one may be formed by the end surface of the main body portion 70, and the other may be formed by the flange portion.

The fastening hole provided in the first joint portion 50 is, for example, a recessed portion provided along the outer periphery of the first joint portion 50 and having a depth in the extending direction in the first extension portion 71 . The width of the first joint portion 50 in the cross-sectional direction is less than or equal to the size of the D electrode 21 . The first extending portion 71 has, for example, a length at least equal to or greater than the depth of the fastening hole in the extending direction. The fastening hole provided in the first joint portion 50 may reach the changing portion 77 in the extending direction.

The fastening hole provided in the second joint portion 60 is, for example, a recess that is provided along the outer periphery of the second joint portion 60 and has a depth in the extending direction in the second extension portion 74 . The width of the second joint portion 60 in the cross-sectional direction is less than or equal to the size of the bottom plate 31 of the ground plate 23 . The second extending portion 74 has, for example, a length at least equal to or greater than the depth of the fastening hole in the extending direction. The fastening hole provided in the second joint portion 60 may reach the changing portion 77 in the extending direction.

As described above, the cavity 6 and stem 27 according to the present embodiment can be installed according to the size or shape of the cyclotron 1, and can be set at an appropriate resonance frequency for electromagnetic waves. By changing the cross-sectional area and cross-sectional shape of the changing portion 77 in the main body portion 70 of the stem 27, the inductance of the stem 27 can be changed, and the resonant frequency of the stem 27 can be changed.

The changing portion 77 may have a larger cross-sectional area in the extending direction. In the conventional stem, the cross-sectional area in the extending direction at the connecting part (corresponding to the main body part 70 of this embodiment) was the same at each part, so the connecting member ( There is an upper limit to the cross-sectional area that can be changed depending on the placement location of the bonding member 37 (corresponding to the bonding member 37 of this embodiment). According to the configuration of this embodiment, the cross-sectional area of the changing portion 77 in the extending direction can be increased compared to a conventional stem within a range where the changing portion 77 does not come into contact with the side plate 33.

The changing portion 77 may be provided at a position where the distance from the first joint portion 50 and the distance from the second joint portion 60 are different in the extending direction. According to such a configuration, even if there is another component between the Dee electrode 21 and the ground plate 23 in the cavity 6, the position where the changing portion 77 is provided can be appropriately changed. , the main body part 70 connects the D electrode 21 and the ground plate 23, and can set an appropriate resonance frequency. Therefore, the stem 27 can be installed to match the shape inside the cavity 6.

At least one of the first joint portion 50 and the second joint portion 60 may be configured by a flange portion that extends outward from the end surface of the main body portion 70 . According to such a configuration, at least one of the first bonding portion 50 and the second bonding portion 60 that extend toward the outer circumferential side from the end surface of the main body portion 70 is stably connected to at least one of the D electrode 21 and the bottom plate 31 of the ground plate 23. and join. Therefore, the D electrode 21 and the stem 27 can be stably joined by the first joint part 50, and the ground plate 23 and the stem 27 can be stably joined by the second joint part 60, respectively.

At least one of the first joint portion 50 and the second joint portion 60 may be configured by an end surface of the main body portion 70. According to such a configuration, the stem 27 can be joined to at least one of the Dee electrode 21 and the bottom plate 31 of the ground plate 23 with a simple configuration.

The invention is not limited to the embodiments described above. For example, the changing portion 77 may combine changes in cross-sectional area and cross-sectional shape for each of a plurality of parts.

1... Cyclotron, 3... Vacuum vessel, 4... Yoke, 5... Excitation coil, 6... Cavity, 7... Deflector, 8... Gradient collector, 9... Collimator, 10... Permanent quadrupole magnet, 11... RF tuner, 21... Dee electrode, 23... Earth plate, 27... Stem, 29... Counter Dee, 31... Bottom plate, 33... Side plate, 37... Joining member, 50... First joining part, 60... Second joining part, 70... Main body part, 71 ...first extension part, 74...second extension part, 77...change part, B...proton beam, G...acceleration gap.

Claims (4)

a cavity that generates an electric field that accelerates charged particles,
A D electrode, a ground plate, and a stem extending to connect the D electrode and the ground plate,
The stem is
a first joint part joined to the D electrode;
a second joint part joined to the ground plate;
a main body extending between the first joint and the second joint;
has
The main body portion includes a changing portion in which at least one of a cross-sectional area and a cross-sectional shape with respect to the extending direction of the stem is changed,
The first joint part and the second joint part are constituted by a flange part that extends toward the outer circumference from the end surface of the main body part ,
The flange portion, the D electrode, and the ground plate are each connected by a connecting member,
The main body portion is located between the changing portion and each of the flange portions in the extending direction of the main body portion, and is further away from the position where the connecting member is connected in a cross-sectional direction with respect to the extending direction of the stem. also includes an extension located inside;
cavity. The cavity according to claim 1, wherein the changing portion expands a cross-sectional area in the extending direction. The cavity according to claim 1 or 2, wherein the changing portion is provided at a position where a distance from the first joint portion and a distance from the second joint portion are different in the extending direction. A stem extending to connect a ground plate and a D electrode in the cavity that generates an electric field that accelerates charged particles,
a first joint part joined to the D electrode;
a second joint part joined to the ground plate;
a main body extending between the first joint and the second joint;
Equipped with
The main body portion has a changing portion in which at least one of a cross-sectional area and a cross-sectional shape with respect to the extending direction of the stem is changed,
The first joint part and the second joint part are constituted by a flange part that extends toward the outer circumference from the end surface of the main body part ,
The flange portion, the D electrode, and the ground plate are each connected by a connecting member,
The main body portion is located between the changing portion and each of the flange portions in the extending direction of the main body portion, and is further away from the position where the connecting member is connected in a cross-sectional direction with respect to the extending direction of the stem. also has an extension located inside;
stem.

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