Quadrupole accelerator and method of manufacturing quadrupole accelerator

Abstract

To provide a quadrupole accelerator that can adjust the resonant frequency in a high frequency accelerator to a desired frequency without using a tuner, and to provide related technology. [Solution] The quadrupole accelerator comprises a central member 11, a first side member 12, and a second side member 13. A cutting surface CS1 is provided on an inner surface of a first wall portion 12b that forms a part of a first hollow cylinder HC1. A cutting surface CS2 is provided on an inner surface of a first wall portion 12b that forms a part of a second hollow cylinder HC2. A cutting surface CS3 is provided on an inner surface of a second wall portion 13b that forms a part of a third hollow cylinder HC3. A cutting surface CS4 is provided on an inner surface of a second wall portion 13b that forms a part of a fourth hollow cylinder HC4. The cross-sectional areas of the first cross section SC1, the second cross section SC2, the third cross section SC3, and the fourth cross section SC4 are each smaller than the cross-sectional area of ​​a cross section corresponding to a target value of the resonant frequency.

Description

[Technical field]

[0001] The present invention relates to a quadrupole accelerator and a method for manufacturing the same. [Background technology]

[0002] Conventionally, a quadrupole accelerator having four electrodes is known as a radio frequency accelerator. In a quadrupole accelerator, the four electrodes form two pairs facing each other. At the tip of each electrode, a waveform suitable for accelerating charged particles in the acceleration axis direction is formed. In the space surrounded by the tips of each electrode, an electric field for accelerating and focusing the charged particles is formed. The charged particles are accelerated by injecting them into the space.

[0003] For example, Patent Document 1 discloses a quadrupole accelerator including a first electrode (21), a second electrode (22), a third electrode (23), and a fourth electrode (24). The four electrodes (21-24) are integrally formed with the member that constitutes the cylindrical portion (2). The four electrodes (21-24) are formed so that the apexes of the triangle in cross section face the acceleration axis of the charged particles. The tip portion of each of the electrodes (21-24) facing the acceleration axis has a corrugated end formed thereon in order to form an electric field that accelerates and focuses the charged particles in the acceleration axis direction.

[0004] Incidentally, in order to accelerate charged particles to a desired energy in a radio frequency accelerator, it is necessary to make the resonant frequency within the radio frequency accelerator close to the frequency of the radio frequency power supplied to the radio frequency accelerator (hereinafter also referred to simply as the "supply frequency").

[0005] For this reason, in conventional radio frequency accelerators including those disclosed in Patent Document 1, a dedicated tuner is used to adjust (tune) the resonant frequency to approach the supply frequency. Specifically, in conventional radio frequency accelerators, the resonant frequency within the radio frequency accelerator is intentionally set low in the initial state after assembly. For this reason, in conventional types, a tuner is attached to the assembled radio frequency accelerator, and the resonant frequency is gradually increased by operating the tuner, thereby bringing the resonant frequency within the radio frequency accelerator closer to the supply frequency.

[0006] Specifically, as shown in FIG. 13, the tuner TN is attached via a tuner port (not shown) formed on the side of a conventional radio frequency accelerator.

[0007] As shown in Fig. 14, the tuner TN has a copper cylindrical part CR that can be inserted into and removed from the internal space of the radio frequency accelerator. When the cylindrical part CR protrudes into the internal space of the radio frequency accelerator, the volume of the internal space decreases. When the volume of the internal space of the radio frequency accelerator decreases, the resonant frequency in the radio frequency accelerator increases, so that the resonant frequency in the radio frequency accelerator can be brought closer to the supply frequency. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 5317062 Summary of the Invention [Problem to be solved by the invention]

[0009] However, the adjustment of the resonant frequency in the radio frequency accelerator using the tuner TN shown in FIGS. 13 and 14 (the conventional tuning method) has the following problems.

[0010] First, a part of the cylindrical section CR of the tuner TN protrudes into the internal space of the high frequency accelerator, and this cylindrical section becomes electrically resistant. The greater the electrical resistance, the greater the power consumption, which causes a problem of a decrease in the Q value (the value obtained by dividing the energy stored in the internal space during operation of the accelerator by the energy consumed). The larger the Q value, the longer the operating time per unit energy, and the more efficient the operation. Therefore, a decrease in the Q value is undesirable. In addition, as power consumption increases, the temperature inside the high frequency accelerator also rises, which causes a problem of a change in volume due to metal expansion.

[0011] In addition, when the cylindrical part CR of the tuner TN is inserted into or removed from the internal space of the RF accelerator while the RF accelerator is in operation, there is a problem that multipacting occurs frequently. The occurrence of multipacting adversely affects the vacuum state and causes abrupt changes in the conditions inside the RF accelerator, which adversely affects the acceleration of charged particles.

[0012] Furthermore, because the cylindrical part CR of the tuner TN is made of metal, frequent insertion and removal of the cylindrical part CR causes friction between the RF contact and the cylindrical part CR, resulting in the problem of metal powder accumulating in the internal space of the RF accelerator. If metal powder accumulates in the internal space of the RF accelerator, it can cause discharges and other problems that interfere with the operation of the RF accelerator.

[0013] Therefore, an object of the present invention is to provide a quadrupole accelerator capable of adjusting the resonant frequency in a radio frequency accelerator to a desired frequency without using a tuner, and a technique related thereto. [Means for solving the problem]

[0014] In order to achieve the above object, the present invention provides a quadrupole accelerator comprising a central member, a first side member fixed to one side of the central member, and a second side member fixed to the other side of the central member, wherein the central member has a central outer frame portion, a first electrode protruding inward from the central outer frame portion, and a second electrode protruding inward from the central outer frame portion, and the first side member has a first side outer frame portion, a first wall portion extending outward from the first side outer frame portion, and a third electrode protruding inward from the first wall portion. the second side member has a second side outer frame portion, a second wall portion extending outward from the second side outer frame portion, and a fourth electrode protruding inward from the second wall portion, the central member is integrally formed from a single member, the first side member is integrally formed from a single member, the second side member is integrally formed from a single member, the first side outer frame portion is fixed to one side of the central outer frame portion by a fixing member, and the second side outer frame portion is fixed to the other side of the central outer frame portion by a fixing member, and the first wall portion and the first electrode and the third electrode, a first hollow cylinder having a long cylindrical shape in the acceleration axis direction of the charged particles is formed, a second hollow cylinder having a long cylindrical shape in the acceleration axis direction is formed in a space surrounded by the first wall portion, the third electrode, and the second electrode, a third hollow cylinder having a long cylindrical shape in the acceleration axis direction is formed in a space surrounded by the second wall portion, the second electrode, and the fourth electrode, a fourth hollow cylinder having a long cylindrical shape in the acceleration axis direction is formed in a space surrounded by the second wall portion, the fourth electrode, and the first electrode, and the first hollow cylinder of the first wall portion is formed in the acceleration axis direction. The present invention provides a quadrupole accelerator, characterized in that a first cutting surface is provided on an inner surface forming a part of a hollow cylinder, a second cutting surface is provided on an inner surface of the first wall portion forming a part of the second hollow cylinder, a third cutting surface is provided on an inner surface of the second wall portion forming a part of the third hollow cylinder, and a fourth cutting surface is provided on an inner surface of the second wall portion forming a part of the fourth hollow cylinder, and the resonant frequency before cutting the first cutting surface, the second cutting surface, the third cutting surface and the fourth cutting surface is higher than the frequency of high frequency power supplied from a power source.

[0015] Here, it is preferable that each of the first cutting surface, the second cutting surface, the third cutting surface and the fourth cutting surface is divided into a plurality of sections with respect to the acceleration axis direction.

[0016] The present invention also provides a quadrupole accelerator comprising a central member, a first side member fixed to one side of the central member, and a second side member fixed to the other side of the central member, wherein the central member has a central outer frame portion, a first electrode protruding inward from the central outer frame portion, and a second electrode protruding inward from the central outer frame portion, the first side member has a first side outer frame portion, a first wall portion extending outward from the first side outer frame portion, and a third electrode protruding inward from the first wall portion, and the second side member has a second side outer frame portion. the central member is integrally formed from a single member, the first side member is integrally formed from a single member, the second side member is integrally formed from a single member, the first side frame member is fixed to one side of the central frame member by a fixing member, and the second side frame member is fixed to the other side of the central frame member by a fixing member, and a space surrounded by the first wall portion, the first electrode, and the third electrode is filled with charged particles. a first hollow cylinder having a long cylindrical shape in the acceleration axis direction is formed, a second hollow cylinder having a long cylindrical shape in the acceleration axis direction is formed in a space surrounded by the first wall portion, the third electrode, and the second electrode, a third hollow cylinder having a long cylindrical shape in the acceleration axis direction is formed in a space surrounded by the second wall portion, the second electrode, and the fourth electrode, and a fourth hollow cylinder having a long cylindrical shape in the acceleration axis direction is formed in a space surrounded by the second wall portion, the fourth electrode, and the first electrode, and a first cutting surface is provided on an inner surface of the first wall portion that forms a part of the first hollow cylinder, a second cutting surface is provided on an inner surface of the second wall portion that forms a part of the third hollow cylinder, a third cutting surface is provided on an inner surface of the second wall portion that forms a part of the fourth hollow cylinder, and a fourth cutting surface is provided on an inner surface of the second wall portion that forms a part of the fourth hollow cylinder, and a resonant frequency before cutting the first cutting surface, the second cutting surface, the third cutting surface and the fourth cutting surface is higher than a frequency of high frequency power supplied from a power source, comprising: a) assembling the quadrupole accelerator by fixing the first side member and the second side member to the central member;The present invention provides a method for manufacturing a quadrupole accelerator, comprising the steps of: measuring a resonant frequency and an electric field strength; b) determining the cutting amount of the first cutting surface, the cutting amount of the second cutting surface, the cutting amount of the third cutting surface, and the cutting amount of the fourth cutting surface based on the measured resonant frequency and the electric field strength; c) disassembling the quadrupole accelerator and cutting the first cutting surface, the second cutting surface, the third cutting surface, and the fourth cutting surface according to the cutting amount determined in step b); d) reassembling the quadrupole accelerator and measuring the resonant frequency and the electric field strength again; e) determining whether the electric field distribution based on the measured resonant frequency and the electric field strength satisfies a completion condition; f) repeating the processing from step b) to step e) if it is determined in step e) that the completion condition is not satisfied; and g) terminating the processing if it is determined in step e) that the completion condition is satisfied. Effect of the Invention

[0017] According to the present invention, since the first cutting surface, the second cutting surface, the third cutting surface, and the fourth cutting surface are provided, the resonance frequency is higher than the frequency of the radio frequency power supplied to the quadrupole accelerator in the initial state. Therefore, the resonance frequency that has been intentionally set higher than the target value can be gradually brought closer to the target value. Therefore, it is possible to adjust the resonance frequency in the radio frequency accelerator to a desired frequency without using a tuner. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic diagram of a quadrupole accelerator according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a schematic perspective view of a quadrupole accelerator. [Diagram 3] FIG. 2 is a schematic perspective view of a quadrupole accelerator cut perpendicular to the direction of the acceleration axis of charged particles. [Figure 4] FIG. 2 is a schematic perspective view of a central member that constitutes a part of a quadrupole accelerator. [Diagram 5] FIG. 2 is a schematic perspective view of a first side member that constitutes a part of the quadrupole accelerator. [Figure 6] FIG. 4 is a diagram showing six cutting surfaces provided on the inside of a first wall portion constituting a first side member. [Figure 7] An enlarged cross-section of a quadrupole accelerator cut perpendicular to the direction of the acceleration axis of charged particles. [Figure 8] 4 is a flowchart showing a process for tuning the resonant frequency in a quadrupole accelerator. [Figure 9] FIG. 13 is a graph plotting the electric field distribution before tuning. [Figure 10] FIG. 13 is a graph plotting the electric field distribution after the first tuning. [Figure 11] FIG. 13 is a graph plotting the electric field distribution after the second tuning. [Figure 12] FIG. 13 is a graph plotting the electric field distribution after the third tuning. [Figure 13] FIG. 1 is a schematic perspective view of a conventional quadrupole accelerator equipped with a tuner. [Figure 14] FIG. 1 is a cross-sectional view of a conventional quadrupole accelerator cut vertically at the tuner mounting position. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] <1. Embodiment> A quadrupole accelerator and a method for manufacturing a quadrupole accelerator according to an embodiment of the present invention will be described with reference to FIGS.

[0020] As shown in Fig. 1, the quadrupole accelerator includes an accelerating cavity 1. The accelerating cavity 1 includes a cylindrical portion 2 formed in a cylindrical shape. The accelerating cavity 1 includes electrodes 21-24 that protrude inward from the cylindrical portion 2 and are called vanes. Each of the electrodes 21-24 is electrically connected to the cylindrical portion 2.

[0021] The quadrupole accelerator includes a first electrode 21, a second electrode 22, a third electrode 23, and a fourth electrode 24. The four electrodes 21 to 24 are formed integrally with the member that constitutes the cylindrical portion 2. Each of the electrodes 21 to 24 is formed so as to extend along the acceleration axis of the charged particles.

[0022] Each of the electrodes 21-24 is formed in a triangular prism shape. Each of the electrodes 21-24 is formed so that the apex of the triangle in the cross section faces the acceleration axis of the charged particles. The tip portion of each of the electrodes 21-24 facing the acceleration axis has a corrugated end portion formed in order to form an electric field that accelerates and focuses the charged particles in the direction of the acceleration axis. The shape of the electrodes is not limited to this form, and any shape can be adopted in which the electrodes protrude from the cylindrical portion and the tip of the electrode is close to the acceleration axis. For example, the electrodes may be formed in a plate shape.

[0023] The quadrupole accelerator includes a power supply device for supplying radio frequency power. The power supply device includes a radio frequency generator 72. The radio frequency generator 72 is connected to a preamplifier 73 and a main amplifier 74. The radio frequency power generated by the radio frequency generator 72 is amplified by the preamplifier 73 and the main amplifier 74. The radio frequency power output from the main amplifier 74 is supplied to the accelerating cavity 1 via a coupler 75. The power supply device is not limited to this form, and any device capable of supplying radio frequency power to the accelerating cavity 1 can be used.

[0024] The acceleration cavity 1 has a floating capacitance and a floating inductance depending on the shape of the cylindrical part 2 and each of the electrodes 21 to 24. These floating capacitances and floating inductances constitute a part of an electric circuit. An acceleration electric field is formed by supplying high-frequency power to the acceleration cavity. When an electromagnetic field of a TE210 mode or a TE211 mode suitable for a quadrupole accelerator is excited, the voltages (absolute values) of the first electrode 21, the second electrode 22, the third electrode 23, and the fourth electrode 24 become the same, and the electrode pair of the first electrode 21 and the second electrode 22 facing each other and the electrode pair of the third electrode 23 and the fourth electrode 24 facing each other have opposite polarities (positive or negative). The acceleration axis is disposed in the space between the four electrodes 21 to 24. Charged particles move while being accelerated along the acceleration axis.

[0025] Fig. 2 shows a schematic perspective view of the acceleration cavity 1. Fig. 3 shows a schematic perspective view of the acceleration cavity in this embodiment when cut. Fig. 3 is a perspective view of the acceleration cavity when cut along line AA in Fig. 2. Arrow 100 shown in Figs. 2 and 3 indicates the extension direction of the acceleration axis of charged particles. Acceleration cavity 1 is formed to extend parallel to the direction of the acceleration axis.

[0026] As shown in Figures 1 to 3, the accelerating cavity 1 includes three components. The accelerating cavity 1 includes a central member 11 including a first electrode 21 and a second electrode 22. The accelerating cavity 1 includes a first side member 12 including a third electrode 23. The accelerating cavity 1 includes a second side member 13 including a fourth electrode 24. The first side member 12 is disposed on one side of the central member 11. The second side member 13 is disposed on the other side of the central member 11.

[0027] The central member 11 is integrally formed from one member. That is, the central member 11 is formed from one material without having a joining line or a welding line between multiple parts. The first side member 12 is integrally formed from one member. That is, the central member 11 is formed from one material without having a joining line or a welding line between multiple parts. The second side member 13 is integrally formed from one member. That is, the second side member 13 is formed from one material without having a joining line or a welding line between multiple parts. An additional member such as a vacuum port may be disposed in advance in the central member 11, the first side member 12, or the second side member 13.

[0028] The central member 11, the first side member 12 and the second side member 13 are fixed to each other by fixing members. In this embodiment, a bolt 51 and a nut 52 are used as the fixing members.

[0029] O-rings 55 serving as vacuum sealing members are disposed on the contact surfaces between central member 11 and first side member 12 and on the contact surfaces between central member 11 and second side member 13. The vacuum sealing members disposed between the respective components hermetically seal acceleration cavity 1.

[0030] As shown in FIG. 4, the central member 11 has a central outer frame portion 11a that constitutes the central portion of the outer frame portion of the accelerating cavity 1. The central outer frame portion 11a is formed in an annular shape when viewed in a plan view. The central member 11 has a first electrode 21 that protrudes inward from the central outer frame portion 11a. The central member 11 has a second electrode 22 that protrudes inward from the central outer frame portion 11a. The first electrode 21 and the second electrode 22 are both arranged such that their tips point toward the acceleration axis.

[0031] An entrance port 61 through which charged particles enter is formed on the end face in the direction of the acceleration axis among the outer surfaces of the central member 11. An exit port 62 through which charged particles exit is formed on the end face opposite to the end face on which the entrance port 61 is formed. The entrance port 61 and the exit port 62 are formed on an extension of the acceleration axis.

[0032] The central outer frame portion 11a is formed with through holes 14 for passing bolts through. A plurality of through holes 14 are formed along the shape of the central outer frame portion 11a. A recess 16 for arranging an O-ring 55 is formed on the contact surface of the surface of the central outer frame portion 11a that contacts the first side member 12 or the second side member 13. The recess 16 is formed in a closed shape in a plan view. The recess for arranging a vacuum sealing member such as an O-ring may be arranged on the first side member 12 and the second side member 13.

[0033] The central member 11 is formed with a reference mark 31 for determining the relative positions of the members in the assembly process in which the respective members are assembled. The reference mark 31 is formed linearly on the end face on which the entrance port 61 is formed. The reference mark 31 is also formed linearly on the end face on which the exit port 62 is formed.

[0034] As shown in FIG. 5, the first side member 12 has a first outer side frame portion 12a that constitutes a side portion of the outer frame portion of the acceleration cavity 1. The first outer side frame portion 12a is formed in an annular shape in a plan view. The first side member 12 has a first wall portion 12b that has a shape of a part of the acceleration cavity. The first wall portion 12b constitutes the cylindrical portion 2 of the acceleration cavity 1. The first wall portion 12b is formed so as to extend outward from the first outer side frame portion 12a. The first wall portion 12b is formed in a plate shape and is connected to the first outer side frame portion 12a. The first side member 12 includes a third electrode 23 that protrudes inward from the first wall portion 12b.

[0035] The first side outer frame portion 12a is formed with through holes 15 for passing bolts through. The first side outer frame portion 12a is formed with alignment marks 32 for determining the assembly position in the assembly process. The alignment marks 32 are formed on both end faces of the first side outer frame portion 12a in the direction of the acceleration axis.

[0036] 5, the first side member 12 of the two side members is taken as an example for explanation, but the second side member 13 has a similar configuration to the first side member 12. The second side member 13 includes an annular second outer side frame portion 13a. The second side member 13 includes a second wall portion 13b that extends outward from the second outer side frame portion 13a and has a shape of a part of the acceleration cavity. The second side member 13 includes a fourth electrode 24 that protrudes inward from the second wall portion 13b.

[0037] As shown in FIG. 1, a first hollow cylinder HC1 (an example of a first hollow cylinder according to the present invention) having a long cylindrical shape in the acceleration axis direction of the charged particles is formed in the space surrounded by the first wall portion 12b, the first electrode 21, and the third electrode 23.

[0038] In addition, in the space surrounded by the first wall portion 12b, the third electrode 23, and the second electrode 22, a long cylindrical second hollow cylinder HC2 (an example of a second hollow cylinder according to the present invention) is formed in the acceleration axis direction of the charged particles.

[0039] In addition, in the space surrounded by the second wall portion 13b, the second electrode 22, and the fourth electrode 24, a third hollow cylinder HC3 (an example of a third hollow cylinder according to the present invention) having a long cylindrical shape in the acceleration axis direction of the charged particles is formed.

[0040] Furthermore, in the space surrounded by the second wall portion 13b, the fourth electrode 24, and the first electrode 21, a fourth hollow cylinder HC4 (an example of a fourth hollow cylinder according to the present invention) having a long cylindrical shape in the acceleration axis direction of the charged particles is formed.

[0041] 6 and 7, a cutting surface CS1 (an example of a first cutting surface according to the present invention) is provided on an inner surface of the first wall portion 12b that forms a part of the first hollow cylinder HC1. The cutting surface CS1 is divided into six sections (cutting surfaces CS11, CS12, CS13, CS14, CS15, and CS16) in the direction of the acceleration axis of the charged particles.

[0042] 7, a cutting surface CS2 (an example of a second cutting surface according to the present invention) is provided on the inner surface of the first wall portion 12b that forms a part of the second hollow cylinder HC2. The cutting surface CS2 is divided into six sections (cutting surfaces CS21, CS22, CS23, CS24, CS25, and CS26, not shown) in the acceleration axis direction of the charged particles.

[0043] Similarly, a cutting surface CS3 (an example of a third cutting surface according to the present invention) is provided on the inner surface of the second wall portion 13b that forms a part of the third hollow cylinder HC3. The cutting surface CS3 is divided into six sections (cutting surfaces CS31, CS32, CS33, CS34, CS35, and CS36, not shown) in the acceleration axis direction of the charged particles.

[0044] Similarly, a cutting surface CS4 (an example of a fourth cutting surface according to the present invention) is provided on the inner surface of the second wall portion 13b that forms a part of the fourth hollow cylinder HC4. The cutting surface CS4 is divided into six sections (cutting surfaces CS41, CS42, CS43, CS44, CS45, and CS46, not shown) in the direction of the acceleration axis of the charged particles.

[0045] That is, a total of 24 cutting surfaces are provided on the inner surfaces of the first wall portion 21b and the second wall portion 13b.

[0046] As shown in FIG. 7, due to the presence of the cutting surface CS1, the cross-sectional area of ​​the first cross section SC1 of the first hollow cylinder HC1 taken perpendicular to the acceleration axis direction of the charged particles is smaller than the cross-sectional area when the cutting surface CS1 is not provided.

[0047] Furthermore, due to the presence of the cut surface CS2, the cross-sectional area of ​​a second cross section SC2 taken in the second hollow cylinder HC2 perpendicular to the acceleration axis direction of the charged particles is smaller than the cross-sectional area when the cut surface CS2 is not provided.

[0048] Furthermore, due to the presence of the cut surface CS3, the cross-sectional area of ​​a third cross section SC3 taken in the third hollow cylinder HC3 perpendicular to the acceleration axis direction of the charged particles is smaller than the cross-sectional area when the cut surface CS3 is not provided.

[0049] Furthermore, due to the presence of the cut surface CS4, the cross-sectional area of ​​a fourth cross section SC4 taken in the fourth hollow cylinder HC4 perpendicular to the acceleration axis direction of the charged particles is smaller than the cross-sectional area when the cut surface CS4 is not provided.

[0050] Here, the cross-sectional area of ​​each of the first hollow cylinder HC1, the second hollow cylinder HC2, the third hollow cylinder HC3, and the fourth hollow cylinder HC4 is inversely proportional to the resonance frequency, i.e., as each cross-sectional area becomes smaller, the resonance frequency becomes larger, and conversely, as each cross-sectional area becomes larger, the resonance frequency becomes smaller.

[0051] In this embodiment, by providing the cutting surfaces CS1 to CS4, the quadrupole accelerator has a resonance frequency that is intentionally set higher than the frequency of the high frequency power supplied to the quadrupole accelerator (the target value of the resonance frequency) in the initial state. In other words, in the initial state, the total cross-sectional area of ​​the four cross sections SC1, SC2, SC3, and SC4 is smaller than the total cross-sectional area corresponding to the target value of the resonance frequency.

[0052] 1 to 3, in the acceleration cavity 1, a central outer frame portion 11a and a first side outer frame portion 12a are in close contact with each other. In addition, the central outer frame portion 11a and a second side outer frame portion 13a are in close contact with each other. The central outer frame portion 11a and the side outer frame portions 12a and 13a are fixed to each other by bolts 51 and nuts 52. The outer frame portion of the acceleration cavity 1 is formed by the central outer frame portion 11a and the side outer frame portions 12a and 13a.

[0053] Next, a method for assembling the quadrupole accelerator in this embodiment will be described. First, the central member 11, the first side member 12, and the second side member 13 are formed. A preparation process is performed to prepare these components. The preparation process includes a process of integrally forming each of the central member 11, the first side member 12, and the second side member 13 from a single member.

[0054] In this embodiment, the components are formed by mechanically cutting solid aluminum. In the process of forming each component, it is preferable to perform cutting processing with high precision. In the manufacturing process, it is preferable to check the dimensions of the central member and each of the side members using a three-dimensional measuring device or the like. It is also preferable to reduce the surface roughness of the contact surfaces of the central outer frame portion and the side outer frame portions in order to ensure electrical contact. Furthermore, it is preferable to reduce the surface roughness of the inner surface of the cylindrical portion and the surfaces of the electrodes by performing high-precision processing, polishing, or the like.

[0055] In the preparation step, a reference mark 31 is formed on the central outer frame portion 11a of the central member 11. Furthermore, an alignment mark 32 is formed on the first lateral outer frame portion 12a of the first lateral member 12. An alignment mark 32 is formed on the second lateral outer frame portion 13a of the second lateral member 13. An O-ring 55 serving as a vacuum sealing member is disposed in the recess 16 formed in the central member 11.

[0056] Next, an assembly process is performed in which the central member 11, the first side member 12, and the second side member 13 are fixed to one another with bolts and nuts. The first side member 12 and the second side member 13 are arranged on either side of the central member 11. In this embodiment, alignment is performed so that the reference mark 31 formed on the central outer frame portion 11a matches the alignment marks 32 formed on each of the side outer frame portions 12a, 13a.

[0057] After alignment, the central outer frame portion 11a, the first side outer frame portion 12a, and the second side outer frame portion 13a are fixed to one another by tightening the bolts. The central member 11, the first side member 12, and the second side member 13 are fixed to one another. When bolts or the like are used as fixing members, it is preferable to tighten them while controlling the torque. This method allows the contact surfaces of the components to be in contact with each other with uniform pressure. In this way, an acceleration cavity can be formed. The accelerator can be assembled by connecting a power supply, a vacuum device, etc. to this acceleration cavity.

[0058] The reference mark and alignment mark for alignment are not limited to being linear, and may be of any shape. In the present embodiment, the reference mark and alignment mark are formed on an end face of the outer surface of the accelerating cavity in the direction of the acceleration axis, but the present invention is not limited to this, and the reference mark and alignment mark may be formed at any position on the outer surface of the accelerating cavity. For example, the reference mark and alignment mark may be formed on an end face of the outer surface of the outer frame of the accelerating cavity in the direction perpendicular to the acceleration axis.

[0059] As shown in FIG. 1, in a radio frequency accelerator, when an electromagnetic field of TE210 mode or TE211 mode suitable for a quadrupole accelerator is excited, the magnitude of the potential of each electrode at any time is equal, and the sign is the same for electrodes facing each other. The sign of the potential of electrodes facing each other in one direction is opposite to the sign of the potential of electrodes facing each other in a direction perpendicular to the one direction. By supplying radio frequency power from a power supply device, the potential of each electrode changes over time to correspond to a sine wave. For example, at one time, when the potential of the first electrode 21 and the second electrode 22 is maximum (positive value and maximum magnitude), the potential of the third electrode 23 and the fourth electrode 24 is minimum (negative value and maximum magnitude). After the time of half a period of the resonant frequency has elapsed, the potentials of the electrodes have an inverse relationship.

[0060] As described above, the quadrupole accelerator assembled by the above assembly method (quadrupole accelerator in the initial state) has a resonant frequency that is intentionally set higher than the target value of the resonant frequency (the frequency of the high frequency power supplied to the quadrupole accelerator). As a result, in the initial state after the quadrupole accelerator is assembled, it is not possible to accelerate charged particles to a desired energy.

[0061] Therefore, in this embodiment, a tuning process for bringing the resonance frequency closer to the target value is carried out at the end of the manufacturing process of the quadrupole accelerator. Hereinafter, with reference to the flowchart of FIG. 8, the tuning process of the resonance frequency (the final manufacturing process of the quadrupole accelerator) will be described in detail.

[0062] First, assemble the quadrupole accelerator according to the above-described assembly method, and measure the resonance frequency and the electric field strength of the quadrupole accelerator in the initial state (step S1 in FIG. 8). Here, the resonance frequency and the electric field strength are measured by known instruments such as a detector (antenna) and a vacuum gauge. Note that the instruments are attached to the side surface of the quadrupole accelerator via pickup ports (not shown).

[0063] Specifically, as the resonance frequency (Measured Frequency) of the quadrupole accelerator, the resonance frequency MF (MHz) is measured.

[0064] Also, as the electric field strength, the electric field strengths ME1, ME2, …, ME24 (Measured Electric Field Strength) at 24 locations of the cut surfaces CS11 to CS16, cut surfaces CS21 to CS26, cut surfaces CS31 to CS36, and cut surfaces CS41 to CS46 are measured. The electric field strengths ME1, ME2, …, ME24 are values indicating the relative strength of the electric field.

[0065] Next, based on the measured resonance frequency MF and the 24 electric field strengths ME1, ME2, …, ME24, the cutting amounts at 24 locations of the cut surfaces CS11 to CS16, cut surfaces CS21 to CS26, cut surfaces CS31 to CS36, and cut surfaces CS41 to CS46 are determined respectively (step S2).

[0066] Specifically, with the following formula 1 and the following formula 2 as constraint conditions, the 24 cutting amounts CL1, CL2, …, CL24 (Cut Length) that minimize Φ in the following formula 3 and the final electric field strength FE (Final Electric Field Strength) are calculated.

[0067] More specifically, the NMinimize function provided by Wolfram Mathematica (registered trademark) is used to calculate the cutting lengths CL1, CL2, ..., CL24 (cut lengths) at 24 locations and the final electric field strength FE (Final Electric Field Strength).

[0068] The NMinimize function is defined by NMinimize[{f,cons},{x,y,…}], which means to numerically minimize f subject to the constraints cons.

number

[0069] In the formula 1, TF (target frequency MHz) is a target resonance frequency (set to 200.3 MHz in this embodiment) and is a preset value. i (Delta Frequency) is the predicted change in frequency (amount of change) calculated in advance by simulation. CL i (cut length) is a value calculated by the above-mentioned NMinimize function. Formula 1 is a constraint condition for preventing the resonance frequency after cutting from falling below the target resonance frequency. Note that MF is the actual value of the resonance frequency measured in step S1.

number

[0070] In the formula 2, CL1 to CL24 (cut length) are values ​​calculated by the above-mentioned NMinimize function. MC1 to MC24 (maximum cut mm) are maximum allowable cutting amounts for each cutting surface, and are preset values. The formula 2 functions as a constraint condition for preventing the cutting amount for each cutting surface from exceeding the allowable cutting amount for each cutting surface.

number

[0071] In formula 3, C i_j is a 24×24 coefficient calculated in advance in a simulation. This coefficient is a value used to calculate the change in electric field strength of each cutting surface according to the cutting amount of each cutting surface. The change in electric field strength is C i_j ×CL j Therefore, in the preliminary simulation, C i_j is calculated by dividing the change in electric field strength by the amount of cutting.

[0072] As described above, in this embodiment, there are 24 cutting surfaces, namely, cutting surfaces CS11 to CS16, cutting surfaces CS21 to CS26, cutting surfaces CS31 to CS36, and cutting surfaces CS41 to CS46.

[0073] For example, when cutting the cutting surface CS11, it is necessary to calculate the change in the electric field intensity at all 24 cutting surfaces including the cutting surface CS11. 1_1 From C 1_24 Similarly, when cutting surface CS12, it is necessary to calculate the change in electric field intensity at all 24 cutting surfaces, including cutting surface CS12. Therefore, the coefficient when cutting surface CS12 is C 2_1 From C 2_24 There are 24 of them. The same is true for the remaining cutting surfaces.

[0074] From the above, the coefficient is C 1_1 From C 1_24 , C 2_1 From C 2_24 , … , C 24_1 From C 24_24 There are about 24 x 24 of them.

[0075] When the cutting amounts CL1, CL2, ..., CL24 of the 24 locations and the final electric field strength FE are calculated by the NMinimize function, the quadrupole accelerator is once disassembled. Then, according to the calculated cutting amounts CL1, CL2, ..., CL24 of the 24 locations, cutting surfaces CS11 to CS16, cutting surfaces CS21 to CS26, cutting surfaces CS31 to CS36, and cutting surfaces CS41 to CS46 are cut (step S3 in FIG. 8).

[0076] Thereafter, the quadrupole accelerator is reassembled, and the resonant frequency and the electric field strength of the quadrupole accelerator after cutting are measured (step S4).

[0077] Then, it is determined whether the measured resonant frequency and the electric field distribution based on the measured electric field intensity satisfy the respective completion conditions (step S5).

[0078] Specifically, if the measured resonant frequency falls within ±0.3 MHz of a reference value, it is determined that the measured resonant frequency satisfies the frequency completion condition. Here, the reference value is the frequency of the high frequency power supplied to the quadrupole accelerator, which is 200 MHz in this embodiment.

[0079] In addition, when the electric field distribution based on the electric field strength is plotted on a graph (see Figures 9 to 12), if the electric field distributions of the first hollow cylinder HC1, the second hollow cylinder HC2, the third hollow cylinder HC3, and the fourth hollow cylinder HC4 are all flat and do not intersect, it is determined that the electric field distribution satisfies the completion condition of the electric field strength. Note that a flat electric field distribution means that the beam of charged particles does not bend and accelerates in a straight line.

[0080] FIG. 9 is a graph plotting the electric field distribution before tuning, FIG. 10 is a graph plotting the electric field distribution after the first tuning, FIG. 11 is a graph plotting the electric field distribution after the second tuning, and FIG. 12 is a graph plotting the electric field distribution after the third tuning.

[0081] The horizontal axis of each graph indicates the distance from the entrance port 61 in the direction of the acceleration axis of the charged particles. Also, the vertical axis of each graph indicates the predicted value of the electric field strength when the correct value of the electric field strength is set to 100%.

[0082] 9 to 12 show that by repeating tuning, the graphs of the electric field distribution gradually become flatter in all of the first hollow cylinder HC1, the second hollow cylinder HC2, the third hollow cylinder HC3 and the fourth hollow cylinder HC4.

[0083] 9 to 12, when the third tuning is completed, the measured resonant frequency falls within ±0.3MHz of the reference value, and the electric field distributions of the first hollow cylinder HC1, the second hollow cylinder HC2, the third hollow cylinder HC3, and the fourth hollow cylinder HC4 are generally flat (within ±5% of 100%). However, since some graphs are not within ±5% and some graphs intersect, the completion condition has not yet been met.

[0084] If it is determined in step S5 above that both the frequency completion condition and the field strength completion condition are satisfied (YES in step S5), the tuning process ends.

[0085] On the other hand, if it is determined that both or either one of the frequency completion condition and the field strength completion condition is not satisfied (NO in step S5), the processes in steps S2 to S5 are repeated until it is determined that both completion conditions are satisfied.

[0086] According to the above-described embodiment, the radio frequency current flows on the inner surface of the cylindrical part of the accelerating cavity 1 due to the skin effect. Therefore, the current flows along the surfaces of the electrodes 21-24 and the inner surface of the cylindrical part 2, as shown by arrow 104. Since the surfaces of the electrodes 21-24 and the inner surface of the cylindrical part 2 in this embodiment are free of irregularities such as welding marks, it is possible to reduce power loss. As a result, it is possible to increase the Q value of the accelerator.

[0087] In the present embodiment, the central member and the two side members are formed in advance, and these components are fixed to each other by the fixing members, so that the components can be assembled while avoiding a rise in temperature during the assembly process.

[0088] For example, in the assembly process, it is possible to avoid heating the components as a whole, as occurs when joining is performed by brazing, and it is possible to suppress thermal deformation of each component. Thermal deformation includes deformation caused by the release of internal stress when the fixing of the cylindrical part by the fixing device is released. In this embodiment, deformation of the accelerating cavity can be suppressed, and therefore deviation of the resonant frequency caused by deformation can be suppressed. The accelerator can be manufactured with high precision relative to the design values.

[0089] Thus, the quadrupole accelerator of this embodiment has excellent electrical performance, such as a high Q value and a small deviation in the resonant frequency.

[0090] Furthermore, the quadrupole accelerator of this embodiment does not have any joints between components by welding or the like, and therefore does not require mechanical finishing after joining multiple components, and can be easily manufactured. For example, when each component is joined by electron beam welding, the surface roughness is large, and therefore further grinding or polishing is required. The quadrupole accelerator of this embodiment can manufacture an accelerating cavity with small inner surface roughness without such finishing work.

[0091] Moreover, the quadrupole accelerator of this embodiment allows the assembly status to be checked during the assembly process. For example, by using a predetermined measuring device, defects can be found during the assembly process, and the work can be corrected. As a result, the yield can be improved. Furthermore, even after assembly, the accelerator can be easily disassembled by removing the fixing members as necessary. For example, alignment can be readjusted. Also, when a sealing member needs to be replaced, it can be easily replaced.

[0092] In this embodiment, the preparation step includes a step of forming a reference mark 31 on an end face of the central member 11 and alignment marks 32 on end faces of the first side member 12 and the second side member 13. The assembly step includes a step of aligning by matching the reference mark 31 with the alignment mark 32. By employing this method, the central member 11 and each of the side members 12 and 13 can be easily aligned.

[0093] The method of alignment in the assembly process is not limited to this embodiment, and any method can be adopted. For example, alignment can be performed using a laser tracker. In this case, for example, among the outer surfaces of the central outer frame portion 11a and the side outer frame portions 12a and 13a, the outer surface extending in a direction parallel to the acceleration axis is formed with high precision. This outer surface can be used as a reference surface on which a reflector (reflecting body) is disposed.

[0094] Alternatively, the central member and the side members can be formed in advance with mating portions having shapes that fit together, and the mating portions can be mated together to perform alignment. In a preparation step, a first mating portion is formed in the central member, and a second mating portion is formed in each of the first and second side members. In an assembly step, the first mating portion and the second mating portion are mated together to perform alignment between the respective members. This method allows easy alignment.

[0095] For example, in a preparation step, a convex portion as a first fitting portion is formed on the central member and a concave portion as a second fitting portion is formed on the side member so that the central member and the side member can be aligned. In an assembly step, the central member and the side member can be easily aligned by fitting the convex portion and the concave portion together.

[0096] Alternatively, alignment holes that communicate when the central member and the side members are aligned can be formed in advance, and alignment can be performed by inserting pins into the alignment holes. In a preparation step, a first alignment hole is formed in the central member, and second alignment holes are formed in the first and second side members. In an assembly step, alignment can be performed between the respective members by inserting alignment pins into the first and second alignment holes. This method makes it easy to perform alignment.

[0097] For example, in a preparation step, alignment holes are formed in the central member and the side members between the through holes of the bolts serving as the fixing members. The alignment holes are formed so that the alignment holes in the central member communicate with the alignment holes in the side members when assembled into the acceleration cavity. It is preferable to form alignment holes in a plurality of locations. In an assembly step, the central member and the side members can be easily aligned by inserting pins that fit tightly into the alignment holes in the central member and the alignment holes in the side members.

[0098] In this embodiment, the central member, the first side member, and the second side member are fixed using a bolt that penetrates these components, but this is not limited to this embodiment, and any fixing member can be used to fix the central member and the side members. For example, a through hole or a blind hole with a thread groove is formed in the central member. The first side member can be fixed to the central member by inserting a bolt from the outside of the through hole of the first side member. Also, the second side member can be fixed to the central member by inserting a bolt from the outside of the through hole of the second side member. In this way, each side member may be fixed to the central member individually. This method makes it easier to align the respective members with each other and to fix the members with each other.

[0099] The assembly method of the present embodiment makes it possible to easily manufacture a quadrupole accelerator having a long axial length along the acceleration axis. For example, when manufacturing a quadrupole accelerator having a long axial length by brazing, the accelerating cavity must be placed inside a high-temperature furnace. This requires a large high-temperature furnace. However, in the present embodiment, the central member and the side members are integrally formed, so that an accelerator having a long length along the acceleration axis can be easily manufactured.

[0100] In this embodiment, the electrodes and the members constituting the cylindrical portion of the accelerating cavity are integrally formed. In assembling the accelerating cavity, it is possible to manufacture the cylindrical portion and each electrode separately, and then fix the electrodes to the cylindrical portion with bolts or the like. However, this method increases the number of parts, making it difficult to align the components. In contrast, by employing components in which each electrode and the members constituting the cylindrical portion are integrally formed, as in this embodiment, it is possible to easily align them. In addition, the positional relationship between the cylindrical portion and the electrodes is maintained with the accuracy during machining, so that the dimensional accuracy is high, and a quadrupole accelerator with excellent electrical performance can be provided.

[0101] According to the above-described embodiment, since the cutting surfaces CS11-CS16, CS21-CS26, CS31-CS36, and CS41-CS46 are provided, the resonance frequency is higher than the frequency of the high frequency power supplied to the quadrupole accelerator in the initial state. Then, by gradually cutting the cutting surfaces CS11-CS16, CS21-CS26, CS31-CS36, and CS41-CS46, the cross-sectional area of ​​the cross section SC1 (FIG. 7), the cross-sectional area of ​​the second cross section SC2 (FIG. 7), the cross-sectional area of ​​the third cross section SC3 (FIG. 7), and the cross-sectional area of ​​the fourth cross section SC4 (FIG. 7) gradually increase.

[0102] If the cross-sectional areas of the cross sections SC1, SC2, SC3, and SC4 are gradually increased, the resonant frequency in the quadrupole accelerator is gradually decreased. That is, the resonant frequency that was set higher than the target value can be gradually brought closer to the target value. Therefore, it is possible to adjust the resonant frequency in the RF accelerator to a desired frequency without using a tuner as shown in FIG. 13 and FIG. 14.

[0103] Furthermore, according to the embodiment described above, the cutting amount for each of the 24 cutting surfaces is calculated in advance (step S2 in FIG. 8), so the cutting amount for one cut can be set to a relatively large value (1 to 4 mm (millimeters)). As a result, the number of cuts in step S3 in FIG. 8 can be reduced, and manufacturing costs can be significantly reduced.

[0104] According to the embodiment described above, each of the cutting surfaces CS1, CS2, CS3, and CS4 is divided into six sections. This makes it possible to calculate the cutting amount for each section, and allows the cutting process in the tuning step to be performed for each section.

[0105] <2. Modifications> The quadrupole accelerator according to the present invention is not limited to the above-described embodiment, and various modifications and improvements are possible within the scope of the claims.

[0106] For example, in the quadrupole accelerator in the above-described embodiment, a conductive member can be interposed in the region where the central member 11 and the first side member 12 contact each other and in the region where the central member 11 and the second side member 13 contact each other. Specifically, instead of a rubber O-ring as a vacuum sealing member, a metal sealing member can be disposed. Alternatively, in addition to the recess in which the vacuum sealing member is disposed, a recess can be additionally formed on the contact surface of at least one of the central member and the side members, and a conductive member such as a metal wire can be disposed in the recess.

[0107] Furthermore, by fixing the central member 11 and the side members 12 and 13 via conductive members, it is possible to improve the electrical conductivity between the central member 11 and each of the side members 12 and 13. Alternatively, it is possible to ensure desired electrical performance.

[0108] Furthermore, the temperature of the quadrupole accelerator rises due to electrical resistance during operation. If the temperature rises significantly, there is a risk of the O-ring being damaged. In such a case, the damage to the sealing member can be avoided by using a metallic sealing member. For example, a metallic vacuum sealing member is suitable for a quadrupole accelerator that operates continuously. Furthermore, the radio frequency accelerator may be equipped with a cooling device for cooling the accelerating cavity. For example, a cooling pipe for flowing cooling water may be arranged inside the electrode or on the surface of the side member.

[0109] In addition, in the quadrupole accelerator in the above-described embodiment, the cross-sectional shape of the cylindrical portion is formed to be approximately a regular octagon, but this is not limited to this form, and any shape that can achieve appropriate electrical performance as a quadrupole accelerator can be adopted. For example, the cross-sectional shape of the cylindrical portion can be formed to be a circle or any polygon.

[0110] In the above embodiment, the central and side members are made of aluminum, but the present invention is not limited to this and the central and side members can be made of any material. For example, in the preparation process, the components can be made of solid copper. Alternatively, the components can be made of any material and have their surfaces plated with copper.

[0111] In addition, in the above-described embodiment, an example was given of calculating cutting amounts CL1, CL2, ..., CL24 at 24 locations using the NMinimize function, and cutting each cutting surface based on the calculated cutting amounts CL1, CL2, ..., CL24, but this is not limited to the above.

[0112] For example, the cutting amount may be set to a minute value (0.3 to 0.5 mm (millimeters)) for one cutting operation without calculating the cutting amount, and the resonance frequency may be tuned by repeating cutting according to the set minute cutting amount.

[0113] According to the above-described modified example, the cutting amount per one cut is smaller than the cutting amount (1 to 4 mm (millimeters)) in the above-described embodiment. Therefore, although the number of cuts increases compared to the above-described embodiment, it is not necessary to calculate the cutting amount in advance.

[0114] In the above-described embodiment, the cutting surface CS1, the cutting surface CS2, the cutting surface CS3, and the cutting surface CS4 are each divided into six sections, and the cutting amount is calculated for each section, but the present invention is not limited to this.

[0115] For example, the cutting surface CS1, the cutting surface CS2, the cutting surface CS3, and the cutting surface CS4 may not be divided into a plurality of sections, and the cutting amount may be calculated as a continuous value according to the distance in the acceleration axis direction of the charged particles.

[0116] In the above embodiment, the electric field distribution is determined to satisfy the electric field intensity completion condition when the electric field distribution is entirely flat and does not intersect, but this is not limiting. Even if a part of the electric field distribution (for example, both ends of the graph) intersects, the electric field distribution may be determined to satisfy the electric field intensity completion condition as long as the electric field distribution is entirely substantially flat (within 5% variation). This is because both ends of the graph (both ends of the electric field distribution) are easily affected by external factors.

[0117] In the above-mentioned embodiment, the cutting surface CS1, the cutting surface CS2, the cutting surface CS3, and the cutting surface CS4 are cut to enlarge (widen) the cross-sectional areas of the cross sections SC1, SC2, SC3, and SC4 shown in FIG. 7, but the present invention is not limited to this. For example, the roots of the electrodes 21, 22, 23, and 24 may be processed to be thicker than usual without providing the cutting surface CS1, the cutting surface CS2, the cutting surface CS3, and the cutting surface CS4, and the cross-sectional areas of the cross sections SC1, SC2, SC3, and SC4 may be enlarged by cutting the thickened roots of the electrodes 21, 22, 23, and 24. Of course, the cross-sectional areas may be enlarged by cutting the cutting surface CS1, the cutting surface CS2, the cutting surface CS3, and the cutting surface CS4 together with the roots of the electrodes 21, 22, 23, and 24.

[0118] In addition, in each of the above-mentioned drawings, the same or corresponding parts are given the same reference numerals. [Industrial Applicability]

[0119] As described above, the quadrupole accelerator according to the present invention is suitable for adjusting the resonant frequency to a desired frequency without using a tuner. [Explanation of symbols]

[0120] 1 acceleration cavity 2 Cylindrical part 11 Central member 11a Central outer frame 12,13 Side members 12a, 13a Side outer frame part 12b,13b Wall part 21~24 electrodes 31 Reference Mark 32 Alignment mark HC1 First hollow cylinder HC2 Second hollow cylinder HC3 Third hollow cylinder HC4 4th hollow cylinder CS1,CS2,CS3,CS4 Cutting surface SC1 First section SC2 Second Section SC3 Third Section SC4 Fourth Section

Claims

1. A quadrupole accelerator, A central member; a first side member secured to one side of the central member; a second side member secured to the other side of the central member; Equipped with The central member is A central outer frame portion; A first electrode protruding inward from the central outer frame portion; A second electrode protruding inward from the central outer frame portion; having The first side member is A first side outer frame portion; a first wall portion extending outward from the first side outer frame portion; a third electrode protruding inwardly from the first wall portion; having The second side member includes: A second side outer frame portion; a second wall portion extending outward from the second side outer frame portion; a fourth electrode protruding inwardly from the second wall portion; having the central member being integrally formed from one piece of material; the first side member is integrally formed from a single member; the second side member is integrally formed from one member; The first side frame portion is fixed to one side of the central frame portion by a fixing member, The second side frame portion is fixed to the other side of the central frame portion by a fixing member, a first hollow cylinder having a long cylindrical shape in an acceleration axis direction of the charged particles is formed in a space surrounded by the first wall portion, the first electrode, and the third electrode; a second hollow cylinder having a long cylindrical shape in the acceleration axis direction is formed in a space surrounded by the first wall portion, the third electrode, and the second electrode, a third hollow cylinder having a long cylindrical shape in the acceleration axis direction is formed in a space surrounded by the second wall portion, the second electrode, and the fourth electrode, a fourth hollow cylinder having a long cylindrical shape in the acceleration axis direction is formed in a space surrounded by the second wall portion, the fourth electrode, and the first electrode, A first cutting surface is provided on an inner surface of the first wall portion that forms a part of the first hollow cylinder, A second cutting surface is provided on an inner surface of the first wall portion that forms a part of the second hollow cylinder, a third cutting surface is provided on an inner surface of the second wall portion that forms a part of the third hollow cylinder; a fourth cut surface is provided on an inner surface of the second wall portion that forms a part of the fourth hollow cylinder.

2. 2. The quadrupole accelerator according to claim 1, wherein the first cutting surface, the second cutting surface, the third cutting surface, and the fourth cutting surface are all divided into a plurality of sections with respect to the acceleration axis direction.

3. A central member; a first side member secured to one side of the central member; a second side member secured to the other side of the central member; Equipped with The central member is A central outer frame portion; A first electrode protruding inward from the central outer frame portion; A second electrode protruding inward from the central outer frame portion; having The first side member is A first side outer frame portion; a first wall portion extending outward from the first side outer frame portion; a third electrode protruding inwardly from the first wall portion; having The second side member includes: A second side outer frame portion; a second wall portion extending outward from the second side outer frame portion; a fourth electrode protruding inwardly from the second wall portion; having the central member being integrally formed from one piece of material; the first side member is integrally formed from a single member; the second side member is integrally formed from one member; The first side frame portion is fixed to one side of the central frame portion by a fixing member, The second side frame portion is fixed to the other side of the central frame portion by a fixing member, a first hollow cylinder having a long cylindrical shape in an acceleration axis direction of the charged particles is formed in a space surrounded by the first wall portion, the first electrode, and the third electrode; a second hollow cylinder having a long cylindrical shape in the acceleration axis direction is formed in a space surrounded by the first wall portion, the third electrode, and the second electrode, a third hollow cylinder having a long cylindrical shape in the acceleration axis direction is formed in a space surrounded by the second wall portion, the second electrode, and the fourth electrode, a fourth hollow cylinder having a long cylindrical shape in the acceleration axis direction is formed in a space surrounded by the second wall portion, the fourth electrode, and the first electrode, A first cutting surface is provided on an inner surface of the first wall portion that forms a part of the first hollow cylinder, A second cutting surface is provided on an inner surface of the first wall portion that forms a part of the second hollow cylinder, a third cutting surface is provided on an inner surface of the second wall portion that forms a part of the third hollow cylinder; a fourth cutting surface is provided on an inner surface of the second wall portion that forms a part of the fourth hollow cylinder, a) assembling the quadrupole accelerator by fixing the first side member and the second side member to the central member, and measuring a resonant frequency and an electric field strength; b) determining a cutting amount based on the measured resonant frequency and the measured electric field strength; c) disassembling the quadrupole accelerator and cutting the quadrupole accelerator according to the cutting amount determined in step b); d) reassembling the quadrupole accelerator and measuring the resonant frequency and the electric field strength again; e) determining whether an electric field distribution based on the measured resonant frequency and the electric field intensity satisfies a completion condition; f) if it is determined in step e) that the completion condition is not satisfied, repeating the processes from step b) to step e); g) terminating the process when it is determined in step e) that the completion condition is satisfied.

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