Beam Transport System

Abstract

To provide a beam transportation system that can restrain a beam current from falling..SOLUTION: A beam transportation system 1 comprises a suppression unit 7 that suppresses gas generated from a degassing source 6 from flowing toward a beam orbit 3 side, and guides the gas toward a suction means 4 side. The gas generated in the degassing source 6 is suppressed from flowing toward the beam orbit 3 side by the suppression unit 7. These suppressed gas are guided toward the suction means 4 side. Therefor, the gas is suppressed from flowing to a beam orbit 3, sucked by the suction means 4, and discharged from a vacuum space SP. Thereby, a collision of the gas with a beam B is suppressed. Accordingly, a fall of a beam current can be suppressed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a beam transport system. [Background technology]

[0002] A conventional device that generates plasma in a chamber and extracts negative ions as a beam is described in Patent Document 1. In this device, negative ions are generated in an ion source, and then extracted by an extraction electrode, and transported downstream as a beam in a vacuum space. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-161228 Summary of the Invention [Problem to be solved by the invention]

[0004] Here, components such as steering coils that control the beam may be placed near the beam orbit through which the beam passes. Such components may become degassing sources that generate gas in the vacuum space. In this case, if the gas generated from the degassing source collides with the beam, a problem occurs in that the beam current decreases.

[0005] The present invention has been made to solve such problems, and has an object to provide a beam transport system that can suppress a decrease in beam current. [Means for solving the problem]

[0006] The beam transport system of the present invention comprises a beam orbit that passes a beam within a vacuum space, suction means that sucks gas within the vacuum space and discharges the gas from the vacuum space, a degassing source that is at least partially disposed within the vacuum space and generates gas within the vacuum space, and an inhibiting section that inhibits the gas generated from the degassing source from moving toward the beam orbit and directs it toward the suction means.

[0007] The beam transport system is at least partially disposed within the vacuum space and includes a degassing source that generates gas within the vacuum space. Therefore, gas may be generated from the degassing source within the vacuum space. In response to this, the beam transport system includes an inhibiting section that inhibits the gas generated from the degassing source from moving toward the beam orbit and directs the gas toward the suction means. The inhibiting section inhibits the gas generated in the degassing source from moving toward the beam orbit. The inhibited gas is then directed toward the suction means. Therefore, the gas is inhibited from flowing toward the beam orbit and is sucked out of the vacuum space by the suction means. This inhibits collisions between the gas and the beam. As a result, a decrease in beam current can be suppressed.

[0008] The inhibiting section may be configured as a chamber that accommodates the degassing source in a vacuum space. In this case, the degassing source is surrounded by walls of the chamber from all sides. Therefore, the walls of the chamber inhibit gas generated from the degassing source from moving toward the beam orbit.

[0009] The outlet of the chamber may be formed at a position around the beam corresponding to the suction means. In this case, the gas coming out of the outlet of the chamber quickly flows toward the suction means. Therefore, the suction means can suck the gas before it flows toward the beam orbit.

[0010] A first path connecting the outlet and the suction means and a second path connecting the outlet and the beam orbit are formed in the vacuum space, and the conductance of the second path may be smaller than that of the first path. In this case, gas flows more easily through the first path toward the suction means than through the second path toward the beam orbit. This prevents the gas from flowing toward the beam orbit and makes it easier for the gas to be discharged by the suction means.

[0011] The second path has an opening that guides the gas exiting the outlet to the beam trajectory, and the cross-sectional area of ​​the opening may be smaller than that of the outlet. In this way, by making the cross-sectional area of ​​the opening of the second path smaller than that of the outlet, the conductance of the second path can be reduced.

[0012] The second path may be longer than the first path, which allows the second path to have a smaller conductance than the first path.

[0013] The degassing source may be a coil that controls the beam. In this case, if gas is generated from the coil arranged in the vacuum space, the gas can be prevented from moving toward the beam orbit.

[0014] The degassing source may include a resin, which tends to generate gas, but can prevent the gas from traveling toward the beam orbit.

[0015] The beam transport system may be a system selected from a linear accelerator, a beam duct, and an ion source. In this case, a decrease in beam current in the linear accelerator, the beam duct, and the ion source can be suppressed. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a beam transport system capable of suppressing a decrease in beam current. [Brief explanation of the drawings]

[0017] [Figure 1]1 is a schematic cross-sectional view showing a beam transport system according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram showing the main chamber as viewed from the axial direction. [Figure 3] 2 is an enlarged view showing the storage chamber and the suction means in FIG. 1. FIG. [Figure 4] FIG. 1 is a cross-sectional view showing a specific configuration of an ion source device to which a beam transport system is applied. [Figure 5] FIG. 10 is a schematic cross-sectional view showing a beam transport system according to a comparative example. [Figure 6] FIG. 10 is a schematic cross-sectional view showing a beam transport system according to a modified example. [Figure 7] FIG. 10 is a schematic cross-sectional view showing a beam transport system according to a modified example. [Figure 8] FIG. 10 is a diagram showing a configuration in which a beam transport system is applied to a beam duct. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments, which are merely examples for explaining the present invention. In the description, the same elements or elements having the same functions will be designated by the same reference numerals, and redundant description will be omitted.

[0019] A beam transport system 1 according to an embodiment of the present invention will be described with reference to Fig. 1. The beam transport system 1 is a system that transports a beam having a predetermined energy, such as an ion beam or a proton beam. In this embodiment, an example of the beam transport system 1 applied to an ion source device will be described. Note that Fig. 1 is a schematic cross-sectional view showing the schematic configuration of the beam transport system 1.

[0020] The ion source device 100 is a device that generates negative ions in an ion source and extracts the generated negative ions as a beam B. The beam transport system 1 transports the beam B generated by the ion source device 100. As shown in FIG. 1 , the beam transport system 1 includes a vacuum chamber 2, a beam orbit 3, a suction means 4, a degassing source 6, and an inhibition unit 7.

[0021] The vacuum chamber 2 is a chamber for forming a vacuum space SP inside. The vacuum chamber 2 is configured to extend along the traveling direction of the beam B. The center line of the vacuum chamber 2 is referred to as the "center line CL1." The beam B travels on and along the center line CL1. The direction in which the center line CL1 extends is referred to as the "traveling direction D1" in which the beam B travels. An ion source is provided upstream of the traveling direction D1 (left side in Figure 1). A cyclotron that uses the beam B is provided downstream of the traveling direction D1 (right side in Figure 1). In the following description, when simply referred to as "upstream" and "downstream," this refers to upstream and downstream in the traveling direction D1. The direction around the center line CL1 is referred to as the "circumferential direction D2."

[0022] The beam orbit 3 is a path along which the beam B travels within the vacuum space SP. The beam orbit 3 is formed in a region along the center line CL1 in the vacuum space SP of the vacuum chamber 2. In this embodiment, the beam orbit 3 includes an extraction electrode 11 that extracts negative ions as the beam B, and a cylindrical beamline 12 that extends downstream of the extraction electrode 11 along the traveling direction D1.

[0023] The suction means 4 is a means for sucking gas from the vacuum space SP and discharging the gas from the vacuum space SP. The suction means 4 includes a vacuum pump 13 provided for the vacuum chamber 2 and a communication part 14 that connects the vacuum pump 13 to the vacuum space SP. The communication part 14 is connected to a side wall of the vacuum chamber 2 and has an opening 14a that opens into the vacuum space SP. The communication part 14 is provided at a position corresponding to the degassing source 6 in the traveling direction D1.

[0024] The degassing source 6 is a component at least partially disposed within the vacuum space SP, which generates gas within the vacuum space SP. In the example shown in FIG. 1, the entire degassing source 6 is disposed within the vacuum space SP. In this embodiment, the degassing source 6 includes a steering coil 16 that controls the beam B. The degassing source 6 is configured in an annular shape on the outer periphery of the beam line 12, surrounding the entire beam line 12 in the circumferential direction D2. The steering coil 16 adjusts the position of the beam B in order to adjust the injection position into the cyclotron. The degassing source 6 includes a resin. Examples of the resin of the degassing source 6 include an adhesive applied to the steering coil 16 and a cylindrical member that supports the steering coil 16.

[0025] Here, in order to increase the current of the beam B, the power input to the ion source is increased. In addition, the beam B itself hits the beam line 12, heating the beam line 12. Due to the influence of this increase in power and the heating of the beam line 12, the area around the steering coil 16 is heated, which causes outgassing.

[0026] The inhibition section 7 inhibits gas generated from the degassing source 6 from moving toward the beam orbit 3 and guides the gas toward the suction means 4. The inhibition section 7 is constituted by a storage chamber 20 that stores the degassing source 6 within the vacuum space SP. The storage chamber 20 is configured in an annular shape by providing wall members on the outer periphery of the beam line 12. Specifically, the storage chamber 20 includes a pair of end walls 21 and an outer periphery wall 23. The pair of end walls 21 are annular walls that expand from the beam line 12 toward the outer periphery. The pair of end walls 21 are disposed so as to face each other and spaced apart in the traveling direction D1. The outer periphery wall 23 is a cylindrical wall that connects the outer peripheries of the pair of end walls 21.

[0027] As a result, the accommodation chamber 20 sandwiches the degassing source 6 between the pair of end wall portions 21 on both sides of the traveling direction D1, thereby inhibiting the flow of gas generated in the degassing source 6 in the traveling direction D1. Also, the accommodation chamber 20 connects the inner peripheral ends of the pair of end wall portions 21 to the beamline 12 without any gaps, thereby inhibiting the gas generated in the degassing source 6 from leaking from both ends of the beamline 12. Also, the accommodation chamber 20 surrounds the degassing source 6 with the outer peripheral wall portion 23, thereby inhibiting the flow of gas generated in the degassing source 6 toward the outer periphery.

[0028] The storage chamber 20 has an outlet 20a that discharges gas generated in the degassing source 6 to the outside of the storage chamber 20. The outlet 20a is formed in a partial region of the outer wall 23 in the traveling direction D1. The outlet 20a only needs to be located at a position that at least partially overlaps with the opening 14a in the traveling direction D1. However, the outlet 20a may be located at a position offset from the opening 14a in the traveling direction D1. In this case, it is desirable to maintain a relationship in which the conductance between the outlet 20a and the opening 14a is greater than the conductance between the outlet 20a and the beam orbit 3.

[0029] As shown in FIG. 2(a), the outlet 20a is formed in a partial region of the outer peripheral wall 23 in the circumferential direction D2. The outlet 20a of the storage chamber 20 is formed at a position corresponding to the suction means 4 in the circumferential direction D2 around the beam B. For example, a line connecting the center of the opening 14a of the suction means 4 and the center of the outer peripheral wall 23 is defined as a reference line SL1, and a line passing through the center of the outer peripheral wall 23 perpendicular to the reference line SL1 is defined as a reference line SL2. The outlet 20a may be formed at a position closer to the suction means 4 than the reference line SL2 in the circumferential direction D2. The outlet 20a may be formed at a position and in a range including the reference line SL1 in the circumferential direction D2. For example, the range obtained by projecting the opening 14a onto the outer peripheral wall 23 along the reference line SL1 is defined as a "projection range PE1." In this case, the outlet 20a may be formed at a position and in a range that at least partially overlaps with the projection range PE1.

[0030] Next, referring to FIG. 3, the flow path of the gas generated in the degassing source 6 will be described. As shown in FIG. 3, a first path PL1 and a second path PL2 are formed within the vacuum space SP. The first path PL1 is a path that connects the outlet 20a and the suction means 4. The terminal of the first path PL1 is the opening 14a of the suction means 4. The opening 14a is the portion of the suction means 4 that generates a suction force to the vacuum space SP. The second path PL2 is a path that connects the outlet 20a and the beam trajectory 3. The terminal of the second path PL2 is the irradiation axis of the beam B (here, the center line CL1). The starting ends of the first path PL1 and the second path PL2 are the outer circumferential surface of the degassing source 6 that is closest to the outlet 20a.

[0031] The first path PL1 includes a path from the outer peripheral surface of the degassing source 6 toward the outlet 20a, a path that passes through the outlet 20a, and a path from the outlet 20a toward the opening 14a. The second path PL2 includes a path from the outer peripheral surface of the degassing source 6 toward the outlet 20a, a path that passes through the outlet 20a, a path from the outlet 20a to the opening 26 between the outer peripheral wall 23 and the inner peripheral surface of the vacuum chamber 2, and a path from the opening 26 toward the center line CL1.

[0032] Here, we will explain the conductance of each path for the gas generated in the degassing source 6. Conductance indicates how easily a fluid flows; the larger the conductance, the easier it is for the fluid to flow, and the smaller the conductance, the more difficult it is for the fluid to flow. Conductance depends at least on the cross-sectional area and length of the path. A point in the path with a small cross-sectional area will cause the conductance to be small. A long path length will cause the conductance to be small. Note that the cross-sectional area of ​​a given point in the path is the area in an imaginary plane perpendicular to the gas flow direction.

[0033] In the first path PL1, the cross-sectional area is smallest at the outlet portion 20a. The cross-sectional area of ​​the outlet portion 20a is determined based on the dimension W1 of the outlet portion 20a in the direction of travel D1 and the dimension W2 of the outlet portion 20a as viewed from the direction of travel D1. In the second path PL2, the cross-sectional area is smallest at the opening 26. The cross-sectional area of ​​the opening 26 is determined based on the dimension W3 between the outer peripheral wall portion 21 and the inner peripheral surface of the chamber 2. Note that the size of the opening 26 as viewed from the direction of travel D1 is determined as the same as the dimension W2 of the outlet portion 20a, assuming that the gas exiting the outlet portion 20a immediately enters the opening 26. The dimension W3 of the opening 26 is smaller than the dimension W1 of the outlet portion 20a. Therefore, the cross-sectional area of ​​the opening 26 is smaller than the cross-sectional area of ​​the outlet portion 20a. Furthermore, the length of the outlet portion 20a as a gas path is the thickness of one piece of the outer peripheral wall portion 21. In contrast, the length of the opening 26 as a gas path is the dimension L1 between the end of the outlet 20a and the end wall 22. As described above, the cross-sectional area of ​​the opening 26 of the second path PL2 is small and the path is long, so the opening 26 is a location that causes a decrease in conductance. As a result, the conductance of the second path PL2 is smaller than that of the first path PL1.

[0034] Furthermore, the gas exiting the outlet 20a immediately reaches the opening 14a of the suction means 4, so the overall length of the first path PL1 is short. In contrast, the gas exiting the outlet 20a must pass through the opening 26 and then reach the center line CL1 in an area outside the end wall 22 of the storage chamber 20. Therefore, the overall length of the second path PL2 is longer. For these reasons, the second path PL2 is longer than the first path PL1.

[0035] Next, an example of a specific configuration of the ion source device 100 to which the beam transport system 1 is applied will be described with reference to Fig. 4. Note that the configuration of the ion source device 100 is not limited to that shown in Fig. 4. The ion source device 100 includes an ion source 102 and a vacuum box 104. The ion source 102 and the vacuum box 104 are connected by an insulating flange 106.

[0036] The ion source 102 includes a chamber 108 , a raw material gas supply unit 109 , a confining magnetic field generation unit 110 , a filter magnetic field generation unit 111 , a plasma generation unit 112 , a promoter supply unit 115 , and a plasma electrode 116 .

[0037] The chamber 108 is connected to a vacuum pump (not shown) and is capable of maintaining a vacuum state inside. The chamber 108 has a cylindrical main body 108a and a lid 108b provided at the other end of the main body 108a. The main body 108a forms the side wall of the chamber 108. A plasma generation unit 112 and a vacuum box 104 (described below) are provided at one end of the chamber 108. Outwardly protruding flanges 108c and 108d are provided at both ends of the main body 108a.

[0038] Lid 108b is detachably attached to flange 108c located on the other end side of main body 108a, and opens or closes the other end (open end) of main body 108a. A circular through-hole 108e is formed in the approximate center of lid 108b. Through-hole 108e provides communication between the inside and outside of chamber 108 when lid 108b closes the other end of main body 108a.

[0039] The raw material gas supply unit 109 includes a pipe 116b provided near the plasma electrode 116 described below, and a gas supply source 122 connected to the pipe 116b. The pipe 116b is located on the other end side of the chamber 108. The gas supply source 122 includes a raw material gas source (hydrogen gas source) and an inert gas source (argon gas source). That is, the raw material gas and the inert gas from the gas supply source 122 are supplied into the chamber 108 from the other end side of the main body 108a through the pipe 116b.

[0040] The confinement magnetic field generator 110 generates a confinement magnetic field for confining plasma in a central region within the chamber 108. The confinement magnetic field generator 110 is provided in a region on the other end side of the chamber 108. The filter magnetic field generator 111 is provided on one end side of the chamber 108 and generates a filter magnetic field that blocks electrons with energy above a predetermined level. In the axial direction of the chamber 108, the confinement magnetic field generator 110 occupies a wider area than the filter magnetic field generator 111. High-energy electrons (high-temperature electrons) cannot enter the magnetic field region generated by the filter magnetic field generator 111 and are confined in the region surrounded by the confinement magnetic field generator 110. This region is referred to as the plasma generation region E1 (the region to the left of the dashed-dotted line in FIG. 1). On the other hand, electrons with energy lower than the predetermined level (low-temperature electrons) can pass through the magnetic field region surrounded by the filter magnetic field generator 111. Negative ions are easily destroyed by high-temperature electrons, but negative ions are generated in the magnetic field region of the filter magnetic field generation unit 111 because high-temperature electrons are prevented from entering the magnetic field region while low-temperature electrons are allowed to enter. Therefore, the magnetic field region generated by the filter magnetic field generation unit 111 is referred to as negative ion generation region E2 (the region to the right of the dashed dotted line in FIG. 1).

[0041] The confinement magnetic field generator 110 includes a first magnet unit 110A provided in the main body 108a of the chamber 108 and a second magnet unit 110B provided in the lid 108b. The first magnet unit 110A has multiple magnets arranged on the outer circumferential surface of the main body 108a. The first magnet unit 110A is configured by alternating south and north poles in the circumferential direction. The second magnet unit 110B is configured by alternating rows of south pole magnets and rows of north pole magnets in the lid 108b. The filter magnetic field generator 111 is configured by concentrating south poles in one region in the circumferential direction and concentrating north poles in another region in the circumferential direction.

[0042] The plasma generating unit 112 has a main body 113 provided on the lid 108b and a pair of filaments 117A, 117B extending outward from an end face of the main body 113 (toward the other end of the chamber 108, the plasma electrode 116). The main body 113 is provided in the through-hole 108e of the lid 108b and is detachable from the lid 108b (through-hole 108e). A DC power supply (not shown) is connected to the main body 113. The DC power supply applies a voltage to the filaments 117A, 117B, causing the filaments 117A, 117B to generate heat and generating a potential difference between the filaments 117A, 117B and the chamber 108 (main body 108a).

[0043] The promoter supply unit 115 includes a promoter introduction unit 114 that introduces a promoter that promotes the generation of negative ions, and a promoter supply source 118 connected to the promoter introduction unit 114. The promoter introduction unit 114 is provided on the lid 108b so as to penetrate the lid 108b. The tip of the promoter introduction unit 114 is located within the chamber 108. As the promoter, a substance that has the effect of promoting the generation of negative ions, such as cesium or other alkaline substances, may be used. The promoter may be supplied into the chamber 108 in any state, such as gas, liquid, or solid.

[0044] The plasma electrode 116 is disposed between an insulating flange 125 provided on a flange 108d located at one end of the main body 108a and the insulating flange 106 on the vacuum box 104 side. The plasma electrode 116 is connected to a variable voltage power supply (not shown). By controlling the power supply to control the magnitude of the voltage applied to the plasma electrode 116, the plasma distribution in the chamber 108 and the amount of negative ions extracted from the chamber 108 are controlled. The plasma electrode 116 has an extraction port 116a that can extract negative ions generated in the chamber 108 to the outside of the chamber 108 (to the vacuum box 104 side in this embodiment). Note that although the plasma electrode 116 according to this embodiment has a flat plate shape, the shape is not particularly limited and may be tapered or the like.

[0045] The vacuum box 104 is located downstream of the chamber 108 from where the negative ion beam is extracted (at one end of the chamber 108). Like the chamber 108, the vacuum box 104 can maintain a vacuum state inside. Note that components such as the chamber 108, insulating flange 106, and vacuum box 104 are connected to each other while ensuring airtightness, and the vacuum chamber 2 shown in FIG. 1 is configured by combining these components. The vacuum box 104 is provided with the beam orbit 3, suction means 4, degassing source 6, and inhibition unit 7 described above. Note that, with regard to these components, the explanation overlapping with that in FIG. 1 will be omitted.

[0046] A ground electrode 30 is provided at the downstream end of the beam orbit 3 in the traveling direction D1 of the beamline 12. A through-hole for passing the beam B is formed at the center of the ground electrode 30. The accommodation chamber 20 forms a long cylindrical member along the traveling direction D1. Inside the accommodation chamber 20, the steering coil 16 is arranged in a region on the downstream side in the traveling direction.

[0047] An outlet 20a is formed in the outer peripheral wall 23 of the storage chamber 20 within a range of a predetermined distance (e.g., 80 mm) from the downstream end in the traveling direction D1. The communication portion 14 of the suction means 4 is provided on the side surface of the vacuum box 104. The vacuum pump 13 of the suction means 4 is disposed outside the vacuum box 104. In the traveling direction D1, the outlet 20a is disposed so as to partially overlap with the opening 14a of the suction means 4. This allows the gas emitted from the outlet 20a to quickly reach the opening 14a and be sucked by the suction means 4. The vacuum box 104 has a partition 31 extending from the inner peripheral surface to the storage chamber 20 at the position of the downstream end wall 21 of the storage chamber 20 in the traveling direction D1. The partition 31 prevents the gas from the outlet 20a from flowing downstream in the traveling direction D1.

[0048] Next, the actions and effects of the beam transport system 1 according to this embodiment will be described.

[0049] The beam transport system 1 includes a degassing source 6 that is at least partially disposed in the vacuum space SP and generates gas in the vacuum space SP. Therefore, gas may be generated from the degassing source 6 in the vacuum space SP.

[0050] For example, a comparative example will be described with reference to FIG. 5. This comparative example does not have an inhibiting portion 7. In this case, there is little obstruction to the flow of gas between the degassing source 6 and the beam orbit 3, and the gas flows more easily into the beam orbit 3. The conductance of the path PL4 that connects the degassing source 6 and the beam orbit 3 is greater than the conductance of the path PL3 that connects the degassing source 6 and the suction means 4. This makes it easier for the gas to collide with the beam.

[0051] In contrast, the beam transport system 1 according to this embodiment is provided with an inhibiting section 7 that inhibits gas generated from the degassing source 6 from flowing toward the beam orbit 3 and directs the gas toward the suction means 4. The inhibiting section 7 inhibits the gas generated in the degassing source 6 from flowing toward the beam orbit 3. The inhibited gas is then directed toward the suction means 4. Therefore, the gas is prevented from flowing toward the beam orbit 3, and is sucked by the suction means 4 and discharged from the vacuum space SP. This inhibits collisions between the gas and the beam B. As a result, a decrease in the beam current can be suppressed.

[0052] The inhibition section 7 may be constituted by a storage chamber 20 that stores the degassing source 6 in the vacuum space SP. In this case, the degassing source 6 is covered from all sides by the walls of the storage chamber 20. Therefore, the gas generated from the degassing source 6 is prevented from moving toward the beam orbit 3 by the walls of the storage chamber 20.

[0053] The outlet 20a of the storage chamber 20 may be formed at a position corresponding to the suction means 4 in the circumferential direction D2 around the beam. In this case, the gas exiting the outlet 20a of the storage chamber 20 flows quickly toward the suction means 4. Therefore, the suction means 4 can suck the gas before it heads toward the beam orbit 3. More specifically, as shown in FIG. 2(b), if the outlet 20a is formed on the opposite side of the suction means 4, the gas G exiting the outlet 20a flows around the outside of the storage chamber 20 and is sucked into the suction means 4. In this case, while the gas G is traveling in a roundabout way toward the suction means 4, some of the gas G may flow into the beam orbit 3. On the other hand, as shown in FIG. 2(a), if the outlet 20 is formed at a position corresponding to the suction means 4, the gas G generated in the degassing source 6 flows through the storage chamber 20 to the outlet 20a and is directly sucked into the suction means 4, even if it is generated on the opposite side of the suction means 4.

[0054] Within the vacuum space SP, a first path PL1 that connects the outlet 20a with the suction means 4 and a second path PL2 that connects the outlet 20a with the beam orbit 3 are formed, and the conductance of the second path PL2 may be smaller than that of the first path PL1. In this case, gas flows more easily through the first path PL1 toward the suction means 4 than through the second path PL2 toward the beam orbit 3. This prevents gas from flowing toward the beam orbit 3 and makes it easier for the gas to be exhausted by the suction means 4. The conductance of the second path PL2 is smaller than the conductance of the path PL4 in FIG. 5.

[0055] The second path PL2 has an opening 26 that guides the gas exiting the outlet 20a to the beam trajectory 3, and the cross-sectional area of ​​the opening 26 may be smaller than the cross-sectional area of ​​the outlet 20a. In this way, by making the cross-sectional area of ​​the opening 26 of the second path PL2 smaller than that of the outlet 20a, the conductance of the second path PL2 can be reduced.

[0056] The second path PL2 may be longer than the first path PL1, which allows the conductance of the second path PL2 to be smaller than that of the first path PL1.

[0057] The degassing source 6 may be a steering coil 16 (coil) that controls the beam B. In this case, when gas is generated from the steering coil 16 arranged in the vacuum space SP, the gas can be prevented from moving toward the beam orbit 3.

[0058] The degassing source 6 may contain a resin. Gas is likely to be generated from the resin, but the gas can be prevented from moving toward the beam orbit 3.

[0059] The present invention is not limited to the above-described embodiments.

[0060] For example, the structure of the inhibition unit 7 may be such that the degassing source 36 is provided at a position away from the suction means 4 in the traveling direction D1, as shown in Fig. 6 above. In this case, the inhibition unit 7 extends in the traveling direction D1 while accommodating the degassing source 36, and an outlet 36a is formed just before the suction means 4. Compared to the conductance of the path connecting the outlet 36a and the suction means 4, the conductance of the path connecting the outlet 36a and the beam orbit 3 is smaller.

[0061] As shown in FIG. 7, the outlet 20a of the storage chamber 20 may be formed on the opposite side to the suction means 4 in the circumferential direction D2.

[0062] In the above-described embodiment, the degassing source 6 is disposed entirely within the vacuum space SP of the vacuum chamber 2. However, it is sufficient that at least a portion of the degassing source 6 is disposed within the vacuum space SP, and a portion of the degassing source 6 may be disposed outside the vacuum space SP.

[0063] In the above-described embodiment, the beam transport system 1 is applied to an ion source. However, it may also be applied to a linear accelerator or a beam duct. In this case, it is possible to suppress a decrease in beam current in the linear accelerator, the beam duct, or the ion source. For example, the beam transport system 1 may be applied to a beam duct 200 as shown in FIG. 8. The beam duct 200 includes a duct section 46, bending electromagnets 41 and 43, and quadrupole electromagnets 42 and 44. A beam orbit is formed inside the duct section 46. A portion of each of the electromagnets 41, 42, 43, and 44 serves as a degassing source 6. In the vacuum space inside the duct section 46, an inhibitor is provided for each of the electromagnets 41, 42, 43, and 44. In addition, a suction unit 4 is provided in the duct section 46 at a position where gas can be easily sucked. [Explanation of symbols]

[0064] 1...beam transport system, 2...vacuum chamber, 3...beam orbit, 4...suction means, 6...degassing source, 7...inhibition section, 16...steering coil (coil), 20, 37...container chamber, 20a...exit section, 26...opening

Claims

1. a cylindrical beam orbit that is a path through which the beam passes in a vacuum space; a suction means for suctioning gas in the vacuum space and discharging the gas from the vacuum space; a degassing source, at least a portion of which is disposed on an outer circumferential side of the beam orbit in the vacuum space, for generating gas within the vacuum space; a blocking section that blocks gas generated from the degassing source from moving toward the beam orbit and guides the gas toward the suction means.

2. The beam transport system according to claim 1 , wherein the inhibiting section is configured by a chamber that accommodates the degassing source within the vacuum space.

3. 3. The beam transport system according to claim 2, wherein the accommodation chamber is configured in a ring shape around a central axis of the beam orbit by providing wall members on an outer periphery of the beam orbit.

4. 4. The beam transport system according to claim 3, wherein the outlet of the accommodation chamber is formed at a position around the beam corresponding to the suction means.

5. Within the vacuum space: a first path that connects the outlet of the storage chamber with the suction means; a second path communicating the exit portion with the beam trajectory is formed; 5. The beam transport system according to claim 2, wherein the conductance of the second path is smaller than that of the first path.

6. the second path has an opening that guides the gas exiting the outlet portion to the beam orbit; The beam transport system according to claim 5 , wherein a cross-sectional area of ​​the opening is smaller than a cross-sectional area of ​​the exit section.

7. The beam transport system according to claim 5 or 6, wherein the second path is longer than the first path.

8. 8. The beam transport system according to claim 1, wherein the degassing source is a coil for controlling the beam.

9. The beam transport system according to any one of claims 1 to 8, wherein the degassing source comprises a resin.

10. The beam transport system according to any one of claims 1 to 9, which is a system selected from the group consisting of a linear accelerator, a beam duct, and an ion source.

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