Vacuum duct and accelerator

Abstract

To provide a vacuum duct and an accelerator that can pass charged particles in directions crossing each other without three-dimensionally crossing a plurality of ducts different in the degree of vacuum.SOLUTION: A vacuum duct 10 comprises: a first duct 21 that forms a first beam trajectory 11 of charged particles; a vacuum vessel 15 that is provided by cutting the middle of a linear portion of the first duct 21; and a second duct 22 that forms a second beam trajectory 12 intersecting the first beam trajectory 11 inside the vacuum vessel 15.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] SUMMARY OF THE INVENTION Embodiments of the present invention relate to vacuum ducts and accelerators for passing charged particles. [Background technology]

[0002] Research is underway into the application of charged particle beams, which are created by supplying charged particles (ions) to an accelerator and accelerating them to a high-energy state, in a wide range of fields, including engineering and medicine. Accelerator systems currently in widespread use are roughly composed of an ion source, a linear accelerator, and a circular accelerator, which accelerate the charged particles in this order. When the charged particles circulating in the circular accelerator reach a predetermined energy, an extraction control device is activated, and the charged particle beam is redirected from its orbit and extracted into a beam transport system.

[0003] If gas molecules exist in the area through which charged particles pass in a circular accelerator, the accelerated charged particles will be scattered and dissipated due to interactions with them. For this reason, the area through which charged particles pass in a circular accelerator is formed inside a vacuum duct set to an ultra-high vacuum.

[0004] On the other hand, the beam transport system connecting the ion source to the circular accelerator does not require a high degree of vacuum compared to the circular accelerator. This is because, while charged particles pass through the circular accelerator repeatedly, they pass through the beam transport system only once and at a slower speed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-012776 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, the miniaturization of circular accelerators has progressed, and it has become necessary to place the ion source and linear accelerator, which were previously located inside the circular accelerator, outside it. As a result, it is sometimes necessary to create an overpass between the circular accelerator and the beam transport system for equipment layout reasons. In this case, it is necessary to install additional bending magnets in the vacuum duct to bend the beam trajectory of the charged particle beam passing through the beam transport system.

[0007] The embodiments of the present invention have been made taking these circumstances into consideration, and aim to provide a vacuum duct and accelerator that allows charged particles to pass in directions that intersect with each other without having multiple ducts with different vacuum levels intersect each other. [Means for solving the problem]

[0008] The vacuum duct according to the embodiment is characterized by comprising a first duct that forms a first beam orbit of charged particles, a vacuum vessel that is provided by dividing the straight portion of the first duct midway, and a second duct that forms a second beam orbit that intersects with the first beam orbit inside the vacuum vessel. [Effects of the Invention]

[0009] According to an embodiment of the present invention, a vacuum duct and an accelerator are provided that allow charged particles to pass in directions that intersect with each other without multiple ducts with different vacuum levels intersecting each other. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a system top view of an accelerator equipped with a vacuum duct according to an embodiment of the present invention. [Figure 2] 1A is a horizontal cross-sectional view of a vacuum duct according to a first embodiment, and FIG. 1B is a vertical cross-sectional view thereof. [Figure 3] 10A and 10B are horizontal cross-sectional views of a vacuum duct provided with a focusing lens element for a charged particle beam in each embodiment; [Figure 4] FIG. 10 is a horizontal cross-sectional view of a vacuum duct provided with an opening and closing valve for a charged particle beam in each embodiment. [Figure 5] FIG. 10 is a horizontal cross-sectional view of a vacuum duct according to a second embodiment. [Figure 6] FIG. 10 is a horizontal cross-sectional view of a vacuum duct according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] (First embodiment) Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a system top view of an accelerator 30 equipped with a vacuum duct 10 according to an embodiment of the present invention. As described above, the accelerator 30 is a system composed of an ion source 35, a linac 36 which is a linear accelerator, and a synchrotron 20 which is a circular accelerator, and these components accelerate a charged particle beam 24 (24a, 24b) in stages in this order. Then, when the charged particles orbiting the synchrotron 20 reach a predetermined energy, the extraction device 29 is operated while maintaining that energy, and the charged particle beam 24c, which has been changed in its traveling direction from the orbit, is extracted into a beam transport line 28.

[0012] The ion source 35 may be a high frequency (including microwave) irradiation type ion source such as an ECR (Electron Cyclotron Resonance) ion source or a PIG (Penning Ionization Gauge) ion source, or a laser irradiation type ion source, but is not limited to these.

[0013] The linac 36 has a linear arrangement of multiple accelerating electric fields, each with an electric field component directed in an opposite direction to the adjacent field, and repeatedly reverses the electric field direction at a high frequency to accelerate the charged particle beam 24a passing through the accelerating electric fields in only one direction at all times. The linac 36 accelerates ions injected from the ion source 35 to a predetermined energy level and then extracts them into the synchrotron 20.

[0014] The synchrotron 20 is composed of a radio-frequency acceleration cavity 25 that accelerates charged particles injected from the linac 36 using radio-frequency power, a plurality of bending electromagnets 26 that generate a magnetic field that imparts a centripetal force to the circulating charged particles, a plurality of quadrupole electromagnets 27 that generate a magnetic field that diverges or converges the circulating charged particles and keeps them within the circulating orbit, and an extraction device 29 that extracts the charged particle beam 24b circulating in the synchrotron 20 to a transportation system 28.

[0015] The synchrotron 20 configured in this manner accelerates charged particles injected at low energy from the linac 36 while circulating them, ultimately accelerating them to an upper limit energy of 70 to 80% of the speed of light, and causes the charged particle beam 24c to pass through the beam transport system 28.

[0016] The beam transport system 28 is also provided with a quadrupole electromagnet 27 for confining the linearly traveling charged particle beam 24c within its orbit, and a bending electromagnet 26 for applying a centripetal force to the charged particle beam 24c to bend its orbit. A facility (not shown) for irradiating the charged particle beam 24c is connected to the end of the beam transport system 28.

[0017] Figure 2(A) is a horizontal cross-sectional view of the vacuum duct 10A (10) according to the first embodiment. Figure 2(B) is a vertical cross-sectional view of the vacuum duct 10A (10). As described above, the vacuum duct 10A includes a first duct 21 that forms a first beam trajectory 11 of charged particles, a vacuum vessel 15 that is provided by dividing the straight portion of the first duct 21, and a second duct 22 that forms a second beam trajectory 12 that intersects with the first beam trajectory 11 inside the vacuum vessel 15.

[0018] Here, the first duct 21 constitutes a part of the beam transport system extending from the linear accelerator side (the ion source 35 and the linac 36), and the second duct 22 constitutes a part of the circular accelerator (the synchrotron 20).

[0019] In the vacuum duct 10A, the second duct 22 penetrates the vacuum vessel 15 and is provided with openings 16 (16a, 16b) through which the first beam orbit 11 passes. The vacuum vessel 15 is configured to have a sufficiently large vertical cross section compared to the first duct 21 and the second duct 22. The openings 16 (16a, 16b) are configured to be sufficiently smaller than the vertical cross section of the second duct 22. This provides a differential pumping effect, making it possible to suppress the inflow of gas molecules from the vacuum vessel 15 connected to the first duct 21 into the second duct 22.

[0020] Here, differential pumping refers to connecting a first duct 21 with a relatively low degree of vacuum to a second duct 22 with a higher degree of vacuum by providing a vacuum vessel 15 with a volume sufficiently larger than these ducts and connecting a vacuum pump 17 with a large diameter and a short distance. This allows the conductance of the first duct 21 and the second duct 22 to be smaller than the conductance of the vacuum pump 17, suppressing the amount of gas molecules flowing into the second duct 22 with a higher degree of vacuum and stably maintaining the difference in degree of vacuum with the first duct 21 with a lower degree of vacuum. Furthermore, when crossing the first duct 21 and the second duct 22, there is no need to use an electromagnet or other such three-dimensional structure.

[0021] Furthermore, in FIG. 2(B), the vacuum pump 17 is provided in the vacuum duct 10A on the bottom surface of the vacuum vessel 15. However, this is not limiting, and the vacuum pump 17 may be provided on the top surface or side surface of the vacuum vessel 15, or a combination of these may be installed. Because the first duct 21 and the second duct 22 are connected to the side surface of the vacuum vessel 15 when viewed from the outside, there is a high degree of freedom in the position and number of vacuum pumps 17 to be installed. This makes it possible to avoid interference with peripheral equipment while expecting an improvement in the degree of vacuum.

[0022] Note that the vacuum chamber 15 may not necessarily be provided with the vacuum pump 17. Alternatively, the inner surface of the vacuum chamber 15 may be coated with or provided with a substance (getter pump) that has a gettering effect of adsorbing gas molecules. Such a getter pump adsorbs gas molecules without affecting the charged particle beam 24, achieving high conductance evacuation and enabling the degree of vacuum inside the vacuum chamber 15 to be maintained at a high level.

[0023] In the vacuum duct 10 incorporated in the accelerator 30 (FIG. 1) of this embodiment, the vacuum vessel 15 is provided in the first duct 21, which has a lower vacuum than the second duct 22. This prevents leakage from the vacuum vessel 15 or gas released from its inner surface from entering the duct on the higher vacuum side (second duct 22), thereby reducing the loss of the beam accelerated through this duct.

[0024] However, there is no particular need to be limited to this configuration, and the first duct 21 provided with the vacuum vessel 15 may be set to a higher vacuum than the second duct 22. Also, although the first duct 21 and the second duct 22 have different degrees of vacuum in the above example, they may have the same degree of vacuum.

[0025] 3 is a horizontal cross-sectional view of the vacuum duct 10 provided with focusing lens elements for the charged particle beam 24. As described above, the first duct 21 is provided with a pair of quadrupole electromagnets 27 (27a, 27b) as lens elements for focusing the charged particle beam 24, on both sides of the vacuum vessel 15.

[0026] In this way, by providing the quadrupole electromagnets 27 (27a, 27b) and focusing the charged particle beam 24, it is possible to reduce the diameter size of the openings 16 (16a, 16b) provided in the second duct 22. This makes it possible to suppress a decrease in the degree of vacuum in the duct on the high vacuum side (second duct 22), and further reduce the loss of the beam accelerated while passing through this duct.

[0027] 4 is a horizontal cross-sectional view of the vacuum duct 10 provided with an on-off valve 37 for the charged particle beam. In this way, the on-off valves 37 (37a, 37b) are provided in the first duct 21 on both sides of the vacuum vessel 15. By providing the on-off valves 37 (37a, 37b) in the first duct 21, which has a relatively low degree of vacuum, the on-off valve 37 can be set to open only when the beam is passing through and closed at other times. This makes it possible to suppress a decrease in the degree of vacuum in the duct on the high-vacuum side (the second duct 22), further reducing the loss of the beam accelerated while passing through this duct.

[0028] (Second embodiment) Next, a second embodiment of the present invention will be described with reference to Figure 5. Figure 5 is a horizontal cross-sectional view of a vacuum duct 10B (10) according to the second embodiment. In contrast to the configuration of the first embodiment described above, the vacuum duct 10B of the second embodiment has a configuration in which the second duct 22 is cut midway through a straight section and joined to the outer peripheral surface of the vacuum vessel 15. In Figure 5, parts having the same configuration or function as those in Figure 1 are indicated by the same reference numerals, and duplicated explanations will be omitted.

[0029] The second embodiment is a suitable configuration when there is no significant difference in the degree of vacuum between the first duct 21 and the second duct 22, when the inflow of gas molecules from one duct to the other is not a problem, etc. Furthermore, by employing the opening and closing valve 37 for the charged particle beam shown in Fig. 4, it is possible to suppress a decrease in the degree of vacuum in the duct on the high vacuum side (second duct 22), and reduce the loss of the beam accelerated while passing through this duct.

[0030] (Third embodiment) Next, a third embodiment of the present invention will be described with reference to Figure 6. Figure 6 is a horizontal cross-sectional view of a vacuum duct 10C (10) according to the third embodiment. The vacuum duct 10C of the third embodiment has a configuration in which the number N of ducts provided is 3 or more (N=3 in the illustration). In Figure 6, parts having the same configuration or function as Figure 1 are indicated by the same reference numerals, and duplicated explanations will be omitted.

[0031] The vacuum duct 10C comprises a first duct 21 that forms a first beam trajectory 11 of charged particles, a first vacuum vessel 151 that is provided by dividing the straight portion of the first duct 21, and a second duct 22 that forms a second beam trajectory 12 that intersects with the first beam trajectory 11 inside the first vacuum vessel 151. The vacuum duct 10C further comprises a second vacuum vessel 152 that is provided by dividing the straight portion of the second duct 22, and a third duct 23 that forms a third beam trajectory 13 that intersects with the second beam trajectory 12 inside the second vacuum vessel 152.

[0032] Furthermore, the vacuum duct 10C of the third embodiment can be expanded to define the number of ducts as N (N≧3). In this case, for all natural numbers n in the range of 3 to N, the vacuum duct 10C includes an (n-1)th vacuum vessel provided by dividing the straight portion of the (n-1)th duct midway, and an n-th duct that forms an n-th beam orbit that intersects with the (n-1)th beam orbit inside the (n-1)th vacuum vessel.

[0033] This allows a number N of ducts with different vacuum degrees (N=3 or more) to intersect while suppressing changes in the vacuum degree. In this case, the vacuum duct 10C can be configured as a first duct 21 with the lowest vacuum degree, a second duct 22 with the next lowest vacuum degree, and an Nth duct with the highest vacuum degree.

[0034] According to at least one of the vacuum duct embodiments described above, the first duct and the second duct are connected to the vacuum vessel so that the first beam trajectory of the first duct and the second beam trajectory of the second duct intersect inside the vacuum vessel, making it possible to provide a vacuum duct and accelerator that allows charged particles to pass in directions that intersect with each other without having multiple ducts with different degrees of vacuum intersect with each other.

[0035] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, modifications, and combinations can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as the inventions described in the claims and their equivalents. [Explanation of symbols]

[0036] 10 (10A, 10B, 10C)...vacuum duct, 11...first beam orbit, 12...second beam orbit, 13...third beam orbit, 15...vacuum vessel, 151...first vacuum vessel, 152...second vacuum vessel, 16...opening, 17...vacuum pump, 20...synchrotron, 21...first duct, 22...second duct, 23...third duct, 24 (24a, 24b, 24c)...charged particle beam, 25...radio frequency acceleration cavity, 26...bending electromagnet, 27...quadrupole electromagnet, 28...beam transport system, 29...extraction equipment, 30...accelerator, 35...ion source, 36...linac, 37...opening / closing valve.

Claims

1. a first duct for forming a first beam trajectory of the charged particles; a vacuum vessel provided by dividing the straight portion of the first duct; a second duct forming a second beam trajectory that intersects with the first beam trajectory inside the vacuum vessel;

2. 2. The vacuum duct according to claim 1, The second duct is a vacuum duct that penetrates the vacuum vessel and has an opening through which the first beam orbit passes.

3. 3. The vacuum duct according to claim 2, The first duct is a vacuum duct in which lens elements for focusing the beam of charged particles are provided on both sides of the vacuum vessel.

4. 2. The vacuum duct according to claim 1, The second duct is a vacuum duct whose straight portion is cut off midway and joined to the outer peripheral surface of the vacuum vessel.

5. The vacuum duct according to any one of claims 1 to 4, A vacuum duct in which a vacuum pump is provided in the vacuum vessel.

6. The vacuum duct according to any one of claims 1 to 4, The first duct and the second duct are vacuum ducts having different vacuum degrees.

7. The vacuum duct according to any one of claims 1 to 4, The first duct is a vacuum duct in which open / close valves are provided on both sides of the vacuum vessel.

8. The vacuum duct according to any one of claims 1 to 4, Set the number of ducts N (N≧3), and for all natural numbers n in the range of 3 to N, an (n-1)th vacuum vessel provided by dividing the straight portion of the (n-1)th duct; a vacuum duct comprising: an nth duct for forming an nth beam orbit that intersects with the n-1th beam orbit inside the n-1th vacuum vessel;

9. An accelerator comprising the vacuum duct according to any one of claims 1 to 4.

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