JP2020170688A - Particle Beam Accelerator and Particle Beam Therapy System - Google Patents

Abstract

To provide a particle beam accelerator capable of accelerating a beam further stably and a particle beam therapy system including the particle beam accelerator.SOLUTION: In a magnet device 1 that generates the main magnetic field of an accelerator 1004, an upper magnetic pole 8 and a lower magnetic pole 9 form a magnetic field distribution such that the orbits of the accelerating beam are dense on an exit channel 1019 side, and the vertical spacing of coils 6A and 6B on the exit channel 1019 side is narrower than the vertical spacing at a position symmetrical with respect to the center of the beam orbit region of the accelerator 1004.SELECTED DRAWING: Figure 5

Description

The present invention relates to a particle beam accelerator and a particle beam therapy system.

For the purpose of providing a variable energy and compact accelerator, Patent Document 1 describes a pair of magnets forming a magnetic field between them, an ion source in which ions are incident between the magnets, and an accelerating electrode for accelerating the ions. It has a beam emission path that takes out ions to the outside, and a plurality of annular beam orbits formed by a pair of magnets, in which ions of different energies orbit each, are aggregated on one side, and a high frequency applied to the ions by an accelerator electrode. It is described that the frequency of the electric field is modulated by the orbit around the beam.

WO2018 / 173240

In recent years, the particle beam therapy system used for particle beam therapy has been miniaturized.

Generally, a particle beam accelerator called a synchrocyclotron is an incident device containing an ion source, a main magnetic field magnet that generates a main magnetic field to stably orbit the beam, and an acceleration cavity that accelerates the beam in the circumferential direction by applying a high-frequency electric field. It is equipped with a gradient magnet that acts on the beam with a magnetic field that intentionally displaces the beam from the equilibrium orbit, and an exit channel that takes the beam displaced from the equilibrium orbit out of the accelerator and guides it to the downstream beam transport system.

The mechanism by which the beam is accelerated by the synchrocyclotron is as follows.

First, the beam incident from the ion source orbits due to the main magnetic field. The beam is accelerated to a predetermined energy by adjusting the phase of the high-frequency electric field for acceleration so that the orbiting beam passes through the gap of the acceleration cavity. Since the orbital frequency of the beam differs depending on the energy, the frequency of the high-frequency electric field for acceleration is also modulated accordingly.

Here, as described in Patent Document 1, the orbit on the high energy side of the orbit of the beam is formed on the opposite side of the extraction port and the aggregation region where the orbits on the high energy side are densely gathered on the extraction region side to the outside of the accelerator. Consider the magnetic field generated by the circular coil and the return yoke in an accelerator of the type having an enlarged region where the beam trajectory is sparse.

The circular coil and return yoke draw concentric contour lines where the magnetic field gradually weakens from the center of the circle. On the other hand, in the orbit of the beam described in Patent Document 1, the incident point is closer to the outlet side than the center, and the beam orbit is eccentric, so that the contour lines of the beam or magnetic field intersect. That is, the magnetic field along the beam trajectory is not a constant value.

An object of the present invention is to provide a particle beam accelerator capable of accelerating a beam more stably and a particle beam therapy system including the particle beam accelerator.

The present invention includes a plurality of means for solving the above problems. For example, a particle beam accelerator, an accelerating cavity capable of modulating the frequency of a high-frequency electric field for accelerating a beam, and a main magnetic field. The magnet device includes a magnet device for generating, and the magnet device has a pair of upper and lower main coils, a return yoke, a pair of upper and lower magnetic poles, and an emission channel for taking the accelerated beam out of the particle beam accelerator. Form a magnetic field distribution so that the orbital orbit of the accelerating beam is dense on the exit channel side, and the main coil has a vertical distance on the exit channel side at the center of the beam orbit region of the particle beam accelerator. On the other hand, it is characterized in that it is narrower than the vertical distance at a symmetrical position.

According to the present invention, it is possible to accelerate the beam more stably. Issues, configurations and effects other than those mentioned above will be clarified by the description of the following examples.

It is a figure which shows typically the ideal beam trajectory in an accelerator in which the orbit of the beam is eccentric to one side of the accelerator, and the contour line of the magnetic field formed by the coil and the return yoke. It is a figure which showed the change of the magnetic field which the beam traveling along the ideal orbit shown in FIG. 1 receives. It is a block diagram of the particle beam therapy system in the particle beam therapy system of Example 1 of this invention. It is a perspective view of the main magnetic field magnet arranged in the accelerator of the particle beam therapy system in Example 1. FIG. It is sectional drawing in the vertical plane of the main magnetic field magnet in Example 1. FIG. It is sectional drawing by another vertical plane of the main magnetic field magnet in Example 1. FIG. It is a figure which represented typically the side surface of the coil of the main magnetic field magnet in Example 1. FIG. It is a figure which compared and showed the strength of the magnetic field which the beam traveling in an orbit in the accelerator in Example 1 receives, and the intensity of the magnetic field which a beam traveling in an orbit in a conventional accelerator receives. FIG. 5 is a plan view of the main magnetic field magnet in the first embodiment as viewed from an intermediate plane. It is sectional drawing in the vertical plane of the main magnetic field magnet in the particle beam therapy system of Example 2 of this invention. It is a figure which represented typically the side surface of the coil of the main magnetic field magnet in Example 2. FIG. It is sectional drawing in another vertical plane of the main magnetic field magnet in Example 2. FIG. It is sectional drawing in the vertical plane of the main magnetic field magnet in the particle beam therapy system of Example 3 of this invention. It is sectional drawing by another vertical plane of the main magnetic field magnet in Example 3. FIG. It is sectional drawing in the vertical plane of the main magnetic field magnet in the modification of Example 3 of this invention. It is sectional drawing by another vertical plane of the main magnetic field magnet in the modification of Example 3. FIG. It is sectional drawing in the vertical plane of the main magnetic field magnet in the particle beam therapy system of Example 4 of this invention.

Hereinafter, an embodiment of a small particle beam accelerator with variable energy of the present invention and a particle beam therapy system including the same will be described with reference to the drawings.

FIG. 1 schematically shows an ideal beam trajectory in an accelerator in which the orbit of the beam is eccentric to one side of the accelerator and contour lines of the magnetic field formed by the coil and the return yoke. With respect to the ideal eccentric orbitals A, B, and C shown by the solid line in FIG. 1, the contour lines of the magnetic fields generated by the coil and the return yoke are concentric as shown by the dotted line in FIG.

Therefore, when the accelerating beam travels in the orbit from the aggregation region to the expansion region, or from the expansion region to the aggregation region, it not only travels in a region where the magnetic field strength hardly changes, but also contour lines of the magnetic field. Will proceed while crossing. In the vicinity of crossing the contour lines of the magnetic field in this way, the magnetic field strength changes significantly as shown in FIG.

Here, it would be good if the shape of the main magnetic pole could be adjusted so as to reduce the region where the magnetic field strength changes significantly, but the magnetization of the iron constituting the main magnetic pole is limited and cannot be adjusted. Sex can occur.

Therefore, it has been clarified by the present inventor's study that if possible, the magnetic field formed by the coil and the return yoke should be as close to the ideal eccentric orbit as possible, thereby making the beam acceleration more stable.

<Example 1>
The particle beam accelerator of the present invention and the first embodiment of the particle beam therapy system including the particle beam accelerator will be described with reference to FIGS. 3 to 9.

FIG. 3 is a block diagram of the particle beam therapy system according to the first embodiment. FIG. 4 is a perspective view of a main magnetic field magnet arranged in the accelerator. FIG. 5 is a cross-sectional view of the main magnetic field magnet in the vertical plane 3. FIG. 6 is a cross-sectional view taken along the vertical plane 3A. FIG. 7 is a diagram schematically showing the side surface of the coil. FIG. 8 is a diagram showing a comparison between the strength of the magnetic field received by the beam traveling in the orbit in the accelerator in this embodiment and the strength of the magnetic field received by the beam traveling in the orbit in the conventional accelerator. FIG. 9 is a plan view of the main magnetic field magnet as viewed from an intermediate plane.

First, the overall configuration of the particle beam therapy system will be described with reference to FIG. In FIG. 3, the particle beam therapy system 1001 is installed on the floor surface of a building (not shown). The particle beam therapy system 1001 includes an ion beam generator 1002, a beam transport system 1013, a rotating gantry 1006, an irradiation device 1007, and a control system 1065.

The ion beam generator 1002 has an ion source 1003 that generates ions, and an accelerator 1004 to which the ion source 1003 is connected and accelerates ions incident from the ion source 1003. Details of the accelerator 1004 will be described later. The ion source 1003 is arranged closer to the exit channel 1019 than the center of the accelerator 1004.

The ion beam emitted from the accelerator 1004 is transported to the irradiation device 1007 by the beam transport system 1013. The beam transport system 1013 has a beam path 1048, and the beam path 1048 is connected to an emission channel 1019 provided in the accelerator 1004. The beam path 1048 includes a quadrupole electromagnet 1046, a deflection electromagnet 1041, a plurality of quadrupole electromagnets 1047, a deflection electromagnet 1042, a plurality of quadrupole electromagnets 1049, 1050, and a deflection electromagnet 1043, 1044 from the accelerator 1004 toward the irradiation device 1007. It is configured by being arranged in order.

A part of the beam path 1048 of the beam transport system 1013 is installed in the rotating gantry 1006, and the deflecting electromagnets 1042, the quadrupole electromagnets 1049, 1050 and the deflection electromagnets 1043, 1044 are also installed in the rotating gantry 1006.

The rotary gantry 1006 is configured to be rotatable around a rotary shaft 1045, and is a rotary device that rotates the irradiation device 1007 around the rotary shaft 1045.

The irradiation device 1007 includes two scanning electromagnets 1051, 1052, a beam position monitor 1053, and a dose monitor 1054. The scanning electromagnets 1051, 1052, the beam position monitor 1053, and the dose monitor 1054 are arranged along the central axis of the irradiation device 1007. The scanning electromagnets 1051, 1052, the beam position monitor 1053, and the dose monitor 1054 are arranged in the casing (not shown) of the irradiation device 1007.

The beam position monitor 1053 and the dose monitor 1054 are arranged downstream of the scanning electromagnets 1051 and 1052. The scanning electromagnet 1051 and the scanning electromagnet 1052 each deflect an ion beam and scan the ion beam in a direction orthogonal to each other in a plane perpendicular to the central axis of the irradiation device 1007. The beam position monitor 1053 measures the passing position of the irradiated beam. The dose monitor 1054 measures the dose of the irradiated beam.

The irradiation device 1007 is attached to the rotating gantry 1006 and is arranged downstream of the deflection electromagnet 1044.

On the downstream side of the irradiation device 1007, a treatment table 1055 on which the patient 1056 lies is arranged so as to face the irradiation device 1007.

The control system 1065 includes a central control device 1066, an accelerator / transport system control device 1069, a scanning control device 1070, a rotation control device 1088, and a database 1072.

The central control device 1066 has a CPU (central processing unit) 1067 and a memory 1068 connected to the CPU 1067. The accelerator / transport system control device 1069, the scanning control device 1070, the rotation control device 1088, and the database 1072 are connected to the CPU 1067 in the central control device 1066.

The particle beam therapy system 1001 further includes a treatment planning device 1073, which is connected to the database 1072. In the particle beam therapy system 1001, the irradiation energy and irradiation angle of the particle beam are created as a treatment plan by the treatment planning device 1073 prior to the irradiation of the particle beam, and the irradiation is executed based on this treatment plan.

The CPU 1067 of the central control device 1066 reads various operation control programs related to irradiation of each device constituting the particle beam therapy system 1001 from the treatment plan stored in the database 1072, executes the read programs, and executes the accelerator. -By outputting a command via the transport system control device 1069, the scanning control device 1070, and the rotation control device 1088, the operation of each device in the particle beam therapy system 1001 is controlled.

The operation control process to be executed may be integrated into one program, may be divided into a plurality of programs, or may be a combination thereof.

Further, a part or all of the program may be realized by dedicated hardware or may be modularized. Further, various programs may be installed in each device by a program distribution server or an external storage medium.

Further, each control device may be an independent device connected by a wired or wireless network, or two or more may be integrated.

The accelerator 1004 has a high frequency acceleration cavity 1037. The high-frequency power supply 1036 inputs power to the high-frequency accelerating cavity 1037 installed in the through hole 17 (see FIG. 5 and the like) in the accelerator 1004 through the waveguide 1010, and is grounded to the electrode connected to the high-frequency accelerating cavity 1037. It excites a high frequency electric field that accelerates the beam between it and the electrodes.

In the accelerator 1004 of this embodiment, it is necessary to modulate the resonance frequency of the high-frequency acceleration cavity 1037 in accordance with the energy of the beam. Inductance or capacitance may be adjusted to modulate the frequency.

A known method can be used as a method for adjusting the inductance and the capacitance. For example, when adjusting the capacitance, a variable capacitance capacitor is connected to the high frequency acceleration cavity 1037 for control.

Next, the details of the magnet device 1 constituting the accelerator 1004 will be described with reference to FIGS. 4 and later.

The magnet device 1 is a magnet that generates a static magnetic field, and has an upper return yoke 4 and a lower return yoke 5 having a substantially columnar shape when viewed from the vertical direction as shown in FIG. 4 as a main configuration. are doing.

Further, as shown in FIGS. 4, 5, 6, and 9, the magnet device 1 includes an upper return yoke 4, a lower return yoke 5, and an upper magnetic pole 8 fixed to the upper return yoke 4. It has a lower magnetic pole 9 fixed to the lower return yoke 5, a pair of upper and lower coils 6A and 6B constituting the main coil, and a high frequency kicker 40 for taking out a beam accelerated to a predetermined energy to the outside of the accelerator 1004.

The upper return yoke 4 and the lower return yoke 5 have shapes that are substantially vertically symmetrical with respect to the intermediate plane 2. The intermediate plane 2 generally passes through the center of the magnet device 1 in the vertical direction and substantially coincides with the orbital plane drawn by the accelerating beam. Further, the upper return yoke 4 and the lower return yoke 5 have a shape symmetrical with respect to the vertical plane 3 which is perpendicular to the intermediate plane 2 and generally passes through the center of the magnet device 1 with respect to the intermediate plane 2.

In FIG. 4, the intersecting portion of the intermediate plane 2 with respect to the magnet device 1 is indicated by a chain line, and the intersecting portion of the vertical plane 3 with respect to the magnet device 1 is indicated by a broken line.

An ion source 1003 is arranged on the upper return yoke 4.

As shown in FIGS. 5 and 6, in the space surrounded by the upper return yoke 4 and the lower return yoke 5, the coil 6A is on the upper return yoke 4 side and the coil 6B is on the lower return yoke 5 side in the intermediate plane 2. On the other hand, they are arranged symmetrically.

Here, FIG. 7 shows a diagram schematically showing the side surfaces of the coils 6A and 6B in this embodiment.

As shown in FIG. 7, in the coils 6A and 6B, the windings 61A and 61B are wound so as to stack the windings along a vertical plane orthogonal to the central axes 60A and 60B of the coils. Then, the coils 6A and 6B are arranged so as to incline the central axes 60A and 60B of the coils with respect to the axis of symmetry 20 perpendicular to the intermediate plane 2, that is, the central axes of the accelerator 1004 and the return yokes 4 and 5. Therefore, the distance D1 between the coil 6A and the coil 6B on the exit channel 1019 side is narrower than the distance D2 between the coil 6A and the coil 6B on the opposite side (high frequency power supply 1036 side) across the axis of symmetry 20. That is, D1 <D2.

The effect of such coil arrangement will be described with reference to FIG. The horizontal axis of FIG. 8 shows the number of times the beam makes a half-circle orbit, and the vertical axis shows the magnetic field strength in the beam orbit. In FIG. 8, it is a condition when the pair of upper and lower coils are tilted 3 degrees from the horizontal direction.

Here, the orbital region is a region through which the beam orbits and passes between the time when the beam is incident and the time when the beam is accelerated to the maximum energy. That is, the orbital region is the region inside the orbital orbit drawn by the beam of maximum energy. The center O4 of the orbiting region substantially coincides with the center of the accelerator 1004, the centers of the return yokes 4 and 5, and the centers of the magnetic poles 8 and 9. Therefore, thereafter, the center O4 of the orbiting region can be read as the center of the accelerator 1004, the center of the return yokes 4 and 5, and the center of the magnetic poles 8 and 9.

In an accelerator in which the orbit of the beam is eccentric to one side of the accelerator, the magnetic field strength changes greatly around crossing the contour line of the magnetic field as described above, but the pair of upper and lower coils are arranged in parallel without tilting as in the past. In this case, as shown in FIG. 8, it can be seen that the absolute value of the fluctuation amount of the magnetic field strength increases with each orbit.

On the other hand, as shown in FIG. 8, by arranging the pair of upper and lower coils 6A and 6B at an angle so as to narrow the outlet side instead of arranging them in parallel as in the present invention, the magnetic field crosses the contour line. It can be seen that the absolute value of the amount of change in the magnetic field strength can be made smaller than that in the conventional horizontal arrangement.

The tilt angle of the coil may be a value larger than 0, and the upper limit is not particularly limited, but it is desirable that the tilt angle from the horizontal direction is 3 degrees or less.

As shown in FIGS. 5, 6 and 9, the coil 6A described above is held by tie rods 42A1, 42A2, 42A3 arranged at intervals of 120 degrees via a holder 45A, and has a height in the horizontal direction. Is maintained.

Further, as shown in FIGS. 5, 6 and 9, the coil 6B is held by tie rods 42B1, 42B2, 42B3 arranged at intervals of 120 degrees via a holder 45B, and has a height in the horizontal direction. Is maintained.

Further, in this embodiment, the horizontal height positions of the tie rods 42A1, 42A2, 42A3 holding the coil 6A are different from those of the tie rods 42A1, 42A2, 42A3. In this embodiment, the height from the floor surface in the horizontal direction is tie rods 42A2, 42A3, 42A1 in order from the highest. This is because the coil 6A is arranged so as to be inclined with respect to the horizontal direction.

Similarly, the horizontal height positions of the tie rods 42B1, 42B2, 42B3 holding the coil 6B are different from those of the tie rods 42B1, 42B2, 42B3. In this embodiment, the height from the floor surface in the horizontal direction is tie rods 42B1, 42B3, 42B2 in order from the highest.

Although the case where the tie rods 42A1, 42A2, 42A3, 42B1, 42B2, 42B3 hold the coils 6A and 6B via the holders 45A and 45B has been described, the coil frames of the coils 6A and 6B are directly tilted and held. It may be configured as.

Further, although the description has been given in which the upper and lower coils 6A and 6B are held by three tie rods at 120 degree intervals as an example, the number is not limited to three at 120 degree intervals, and 2 at 180 degree intervals. There may be four books at 90 degree intervals.

Further, although the horizontal height positions of the tie rods 42A1, 42A2, and 42A3 are different from each other as an example, the tie rods 42A1 and the tie rods 42A3 have the same height, and the tie rods 42A2 have different heights from the tie rods 42A1, 42A3. It may be configured.

Similarly, the horizontal height positions of the tie rods 42B1, 42B2, and 42B3 are different from each other as an example. However, the tie rods 42B1 and the tie rods 42B3 have the same height, and the tie rods 42B2 have the same heights as the tie rods 42B1, 42B3. It may have a different configuration.

In this embodiment, the ion source 1003 is installed outside the magnet device 1 assuming an external ion source, and the through hole 24 is provided corresponding to the ion source 1003. However, the ion source 1003 is inside the magnet device 1. It may be installed in. In this case, the through hole 24 is used to supply electric power, a gas for ion generation, or the like to the ion source 1003.

The coils 6A and 6B are superconducting coils, which are installed inside a cryostat (not shown) and are cooled by a refrigerant such as liquid helium or heat transfer from a refrigerator (not shown). The coils 6A and 6B are connected to the coil excitation power supply 1057 by the coil lead-out wiring 1022 shown in FIG.

A vacuum vessel 7 is provided inside the coils 6A and 6B in the space surrounded by the upper return yoke 4 and the lower return yoke 5.

Inside the vacuum vessel 7, an upper magnetic pole 8 is arranged on a surface of the upper return yoke 4 facing the lower return yoke 5. Further, a lower magnetic pole 9 is arranged on a surface of the lower return yoke 5 facing the upper return yoke 4. The upper magnetic poles 8 and the lower magnetic poles 9 are fixed in pairs vertically and vertically, and are arranged symmetrically with respect to the intermediate plane 2.

The upper return yoke 4, the lower return yoke 5, the upper magnetic pole 8, and the lower magnetic pole 9 are made of, for example, pure iron having a reduced impurity concentration, low carbon steel, or the like. The vacuum container 7 is made of stainless steel or the like. The windings of the coils 6A and 6B are made of a superconducting wire using a superconductor such as niobium-titanium.

A space for orbiting and accelerating the ion beam is formed between the upper magnetic pole 8 and the lower magnetic pole 9.

The emission channel 1019 includes an electromagnet called a septum, and is connected to the emission channel power supply 1082 shown in FIG. 3 through the through hole 16. By energizing the electromagnet provided in the emission channel 1019 from the output channel power supply 1082, the ion beam that has reached the emission channel 1019 is arranged and sent to the beam transport system 1013.

Hereinafter, the details of the magnetic pole shape of the magnet device 1 will be described with reference to FIGS. 5 and 9. Since the magnet device 1 has a structure symmetrical with respect to the intermediate plane 2, only the lower return yoke 5 side will be described in FIGS. 5 and 9.

Recessed portions 21a, 21b, 21c, 21d and convex portions 22a, 22b, 22c, 22d are formed on the facing surfaces 10 of the upper magnetic pole 8 and the lower magnetic pole 9 facing the intermediate plane 2, respectively. As shown in 9, the concave portions 21a, 21b, 21c, 21d and the convex portions 22a, 22b, 22c, 22d are alternately arranged along the circumferential direction of the beam trajectory 26.

The concave portions 21a, 21b, 21c, 21d and the convex portions 22a, 22b, 22c, 22d may be integrally formed with the upper magnetic pole 8 and the lower magnetic pole 9, or may be formed as separate members and then the upper magnetic pole. It may be engaged with the surface of the 8 or the lower magnetic pole 9 by a known method such as welding or bolting at the time of assembly. It is desirable that the material is the same as that of the upper magnetic pole 8 and the lower magnetic pole 9.

The ion source 1003 is arranged on the exit channel 1019 side of the center of the orbital region of the accelerator 1004, and by adopting the structure of the magnetic poles 8 and 9 as described above, the beam accelerates while the orbital orbit in the orbital region is eccentric. Will be done. In other words, the distance between the orbits of the beam becomes dense on the exit channel 1019 side, and the distance between the orbits of the beam becomes sparse on the high frequency power supply 1036 side on the opposite side of the exit channel 1019 and the center O4 of the orbit region. The beam is accelerated.

Further, as shown in FIG. 9, a gradient magnetic field magnet 31 (peeler), a gradient magnetic field magnet 32 (regenerator), and a high-frequency kicker 40 are installed in the recess 21a in which the emission channel 1019 is arranged in the vicinity. There is.

The gradient magnetic field magnets 31 and 32 are coils that generate a gradient magnetic field for displacing the trajectory of the beam. Of these, the gradient magnetic field magnet 31 is preferably a coil that generates a gradient magnetic field in which the magnetic field distribution of the gradient magnetic field to be generated decreases the magnetic field strength toward the outside in the radial direction of the accelerator 1004. Further, it is desirable that the gradient magnetic field magnet 32 is a coil that generates a gradient magnetic field in which the magnetic field distribution of the gradient magnetic field to be generated increases the magnetic field strength toward the outside in the radial direction.

The gradient magnetic field magnets 31 and 32 can be replaced with a structure integrally formed with the recess 21a instead of the coil. Examples of such a structure include a structure that is manufactured as a separate member and then engaged with the recess 21a by a known method such as welding or bolting. More specifically, a magnetic material can be further added to the surface of the recess 21a, or the surface shape of the recess 21a can be processed.

Further, in this embodiment, the case where the gradient magnetic field magnet 31 is arranged near the convex portion 22d of the concave portion 21a and the gradient magnetic field magnet 32 is arranged near the convex portion 22a of the concave portion 21a is described. This position can be reversed.

Further, since the magnetic field in the region from the outer peripheral surface of the magnetic pole to the inner peripheral surface of the yoke decreases toward the outer side in the radial direction, a gradient that generates a magnetic field in which the magnetic field strength decreases toward the outer side in the radial direction The magnetic field magnet 31 may be omitted.

Further, it is desirable that the gradient magnetic fields generated by these gradient magnetic field magnets 31 and 32 include at least a quadrupole magnetic field component, and include a multi-pole magnetic field having four or more poles or a bipolar magnetic field.

The through hole 18 is a through hole for installing the beam transport system 1013. The through hole 19 is provided so as to be plane symmetric with the through hole 18 with respect to the vertical plane 3 in order to enhance the symmetry of the main magnetic field magnet and to improve the accuracy of the magnetic field generated by the main magnetic field magnet.

The high-frequency kicker 40 is a device that applies a high-frequency electric field having a frequency different from that of the high-frequency acceleration cavity 1037, and is located in a space sandwiched between recesses 21a like the gradient magnetic field magnet 31 and the gradient magnetic field magnet 32 as shown in FIG. Have been placed.

An emission channel 1019 for taking out a beam accelerated to a predetermined energy to the outside of the accelerator 1004 is provided in the magnetic pole outer peripheral region of the recess 21a provided with the gradient magnetic field magnet 31, the gradient magnetic field magnet 32, and the high frequency kicker 40. ..

Since the configuration of the high-frequency kicker 40 is not particularly limited, details will be omitted here.

The gradient magnetic field magnet 31 and the gradient magnetic field magnet 32 are connected to the take-out electromagnet power supply 1040 from the through hole 19 by the take-out electromagnet lead wire 1023A shown in FIG. 1, and the high-frequency kicker 40 is connected to the take-out electromagnet power supply 1040 from the through hole 16 to FIG. It is connected to the take-out electromagnet power supply 1040 by the take-out electromagnet lead-out wiring 1023B shown in 1. The gradient magnetic field magnet 31 and the gradient magnetic field magnet 32 are excited at an appropriate timing by the command from the extraction electromagnet power supply 1040, the high frequency application of the high frequency kicker 40 is started, and the beam accelerated to a predetermined energy is extracted.

Next, the effects of the high-frequency kicker 40, the gradient magnetic field magnet 31, and the gradient magnetic field magnet 32 will be described.

In a synchrocyclotron having the same structure as usual, the beam accelerated to the maximum energy is affected by the gradient magnetic field generated by the gradient magnetic field magnet 31 and the gradient magnetic field magnet 32, and a resonance phenomenon occurs in the horizontal motion of the beam to balance. The displacement from the orbit increases, and the beam that reaches the exit channel 1019 is taken out of the accelerator.

At this time, it is necessary to avoid destabilizing the orbital motion of the beam having an energy lower than the maximum energy due to the gradient magnetic field formed by the gradient magnetic field magnet 31 and the gradient magnetic field magnet 32.

Therefore, for correction in the radial direction inside the gradient magnetic field magnet 31 and the gradient magnetic field magnet 32 so that the influence of the gradient magnetic field generated by the gradient magnetic field magnet 31 and the gradient magnetic field magnet 32 becomes sufficiently small inside the beam orbit of the maximum energy. It is desirable to install a magnetic material or coil (not shown).

Furthermore, in order to extract the low-energy beam, the low-energy beam that approaches the extraction energy should be destabilized in the horizontal direction, and the low-energy beam that requires more acceleration should be stably orbited to the specified extraction high energy. It is necessary to balance the two of accelerating.

Therefore, when a low-energy beam is taken out, a mechanism for selectively acting a gradient magnetic field, such as applying a gradient magnetic field generated by the gradient magnetic field magnets 31 and 32 only at that timing, is required. The mechanism for that is the high frequency kicker 40. The role of the high-frequency kicker 40 is to selectively apply the magnetic fields of the gradient magnetic field magnets 31 and 32 to the beam to be extracted.

That is, the beam incident from the ion source 1003 and accelerated gradually expands its average orbital radius, and finally passes through the inside of the high-frequency kicker 40.

When the beam reaches the desired energy to be extracted, the high-frequency power supply 1036 is turned off to cut off the high-frequency electric field excited between the electrode connected to the high-frequency acceleration cavity 1037 and the ground electrode, and the high-frequency kicker 40 Turn on.

When the beam reaches the high-frequency kicker 40 frequency f _rev orbiting the _accelerator, and .DELTA..nu the fractional part of the horizontal betatron oscillation frequency of the beam, setting the frequency of the high frequency kicker 40 substantially equal to the f _rev × .DELTA..nu Then, the high frequency electric field of the high frequency kicker 40 is applied.

As a result, the beam orbit receives a radial outward force each time it passes through the inside of the high-frequency kicker 40, and the beam orbit is gradually shifted outward in the radial direction, and finally the gradient magnetic field magnets 31 and 32 are generated. Reach the region where the gradient magnetic field acts.

The beam affected by the gradient magnetic field of the gradient magnetic field magnets 31 and 32 begins to diverge the amplitude of the horizontal betatron motion, finally reaches the exit channel 1019, and is taken out of the accelerator.

Further, the center of the orbit O4 having the highest energy and the incident point O2 do not coincide with each other, and the incident point O2 is shifted toward the beam inlet of the exit channel 1019. When the center of the beam orbit is shifted in this way, the low-energy beam orbit approaches the entrance of the exit channel 1019 on the recess 21a side, so that a region where the beam orbit becomes dense is formed on the exit channel 1019 side.

Therefore, the energy band of the beam orbit passing through the high-frequency kicker 40 increases. That is, the high-frequency kicker 40 passes through the beam trajectory with lower energy. Therefore, since the high-frequency electric field by the high-frequency kicker 40 can be applied to the lower-energy beam orbit, the lower-energy beam orbit is passed near the gradient magnetic field generated by the gradient magnetic field magnets 31 and 32. Can be done.

At this time, since the low-energy beam has a smaller radius of curvature than the high-energy beam, the gradient magnetic field magnet 31 and the gradient magnetic field are required to act on the low-energy beam in order for the gradient magnetic field generated by the gradient magnetic field magnet 31 and the gradient magnetic field magnet 32 to act on the low-energy beam. It is preferable that the magnet 32 is arranged in a direction in which the beam trajectory is shifted by the high-frequency kicker 40 and is close to the vertical plane 3.

That is, as described above, the gradient magnetic field magnet 31 and the gradient magnetic field magnet 32 have the smallest volume in the space sandwiched between the plurality of recesses 21a, 21b, 21c, and 21d, similarly to the high frequency kicker 40. It is preferable to arrange it in the space sandwiched between the magnets.

By arranging the gradient magnetic field magnet 31 and the gradient magnetic field magnet 32 in this way, the gradient magnetic field is surely applied to the low energy beam displaced by the high-frequency kicker 40, and the betatron vibration amplitude in the horizontal direction is increased. It expands to reach the exit channel 1019 and can be taken out of the accelerator.

Next, the effect of this embodiment will be described.

The accelerator 1004 in the particle beam therapy system 1001 of the first embodiment of the present invention described above includes an acceleration cavity 1037 capable of modulating the frequency of a high-frequency electric field that accelerates a beam, and a magnet device 1 that generates a main magnetic field. The device 1 has a pair of upper and lower coils 6A and 6B, an upper return yoke 4, a lower return yoke 5, a pair of upper magnetic poles 8, a lower magnetic pole 9, and an exit channel 1019 that takes an accelerated beam out of the accelerator 1004. The upper magnetic poles 8 and the lower magnetic poles 9 form a magnetic field distribution so that the orbital orbits of the accelerating beam are dense on the exit channel 1019 side, and the coils 6A and 6B are spaced above and below the exit channel 1019 side of the accelerator 1004. It is narrower than the vertical spacing at a position symmetrical to the center of the beam orbital region.

In particular, in this embodiment, the coils 6A and 6B have the central axes 60A and 60B of the coils 6A and 6B on the upper return yoke 4 so that the distance between the two coils 6A and 6B on the exit channel 1019 side is narrowed. It is arranged at an angle with respect to the central axis of the lower return yoke 5.

With such a configuration, when the incident point O2 of the accelerating beam is configured to form a magnetic field distribution so as to shift from the center O1 of the accelerator 1004 to the exit side, the accelerating beam crosses the contour line of the magnetic field. The absolute amount of change in the magnetic field strength received when traveling in the direction can be made smaller than in the case where the main coil is horizontally arranged as in the prior art. Therefore, the beam can be accelerated more stably.

Further, the tie rods 42A1, 42B1, the tie rods 42A2, 42B2, and the tie rods 42A3, 42B3 for holding the coils 6A, 6B from the horizontal direction are provided, and the heights of the tie rods 42A1, 42A2, 42A3, 42B1, 42B2, 42B3 in the horizontal direction are different. As a result, it is easy to adjust the positions of the coils 6A and 6B arranged so that the vertical distance on the high frequency kicker 40 side is narrower than the vertical distance at a position symmetrical with respect to the center O4 of the beam circulation region of the accelerator 1004. The effect of is obtained.

<Example 2>
The particle beam accelerator of Example 2 of the present invention and the particle beam therapy system including the particle beam accelerator will be described with reference to FIGS. 10 to 12.

As shown in FIG. 10, in the magnet device of this embodiment, the detailed structure of the upper magnetic pole 8 and the lower magnetic pole 9 is the same as that described in the first embodiment.

The difference is that the pair of upper and lower coils 6C and 6D forming the main coil in this embodiment have the coils 6A and 6B so that the axis of symmetry 20 perpendicular to the intermediate plane 2 and the central axes 60C and 60D of the coil coincide with each other. Be placed.

Here, FIG. 11 shows a diagram schematically showing the side surfaces of the coils 6C and 6D in this embodiment. The windings 61C and 61D of the coils 6C and 6D are wound diagonally with respect to the central axes 60C and 60D of the coils so that the intervals between the coils 6C and 6D are narrowed on the high frequency kicker side. Therefore, the distance D1A between the coil 6C and the coil 6D on the exit channel 1019 side is narrower than the distance D2A between the coil 6C and the coil 6D on the opposite side (high frequency power supply 1036 side) across the axis of symmetry 20. That is, D1A <D2A.

As shown in FIG. 12, the coil 6C described above is held by tie rods 42C1, 42C2, 42C3 arranged at intervals of 120 degrees via a holder 45C, and the height in the horizontal direction is maintained.

On top of that, as shown in FIGS. 10 and 12, the positions of the horizontal heights of the tie rods 42C1, 42C2, 42C3 holding the coil 6C are different from those of the tie rods 42C1, 42C2, 42C3. .. In this embodiment, the height from the floor surface in the horizontal direction is tie rods 42C2, 42C3, 42C1 in order from the highest.

Similarly, as shown in FIG. 12, the coil 6D is held by tie rods 42D1, 42D2, 42D3 arranged at 120 degree intervals via the holder 45D, and the height in the horizontal direction is maintained. ..

Further, the horizontal height positions of the tie rods 42D1, 42D2, 42D3 holding the coil 6D are different from those of the tie rods 42D1, 42D2, 42D3. In this embodiment, the height from the floor surface in the horizontal direction is tie rods 42D1, 42D3, 42D2 in order from the highest.

Further, although the description has been given in which the upper and lower coils 6C and 6D are held by three tie rods at 120 degree intervals as an example, the number is not limited to three at 120 degree intervals, and two at 180 degree intervals. There may be four each at 90 degree intervals.

Further, although the horizontal height positions of the tie rods 42C1, 42C2, and 42C3 are different from each other as an example, the tie rods 42C1 and the tie rods 42C3 have the same height, and the tie rods 42C2 have different heights from the tie rods 42C1, 42C3. It may be configured.

Similarly, the horizontal height positions of the tie rods 42D1, 42D2, and 42D3 are different from each other as an example. However, the tie rods 42D1 and the tie rods 42D3 have the same height, and the tie rods 42D2 have the same heights as the tie rods 42D1, 42D3. It may have a different configuration.

Other configurations and operations are substantially the same as those of the particle beam accelerator of Example 1 described above and the particle beam therapy system provided with the accelerator, and details thereof will be omitted.

As in the second embodiment of the present invention, in the coils 6C and 6D, the central axes 60C and 60D of the coils 6C and 6D coincide with the central axes of the upper return yoke 4 and the lower return yoke 5, and the centers of the coils 6C and 6D are aligned. Even if the windings 61C and 61D are formed so as to be wound diagonally with respect to the shafts 60C and 60D, substantially the same effect as that of the first embodiment can be obtained.

Further, by winding the windings 61C and 61D diagonally, the space for installing the coils 6C and 6D can be reduced as compared with the case where the coils 6A and 6B are tilted and arranged as in the first embodiment. it can. Therefore, the accelerator 1004 can be made smaller. It should be noted that winding diagonally as in Example 2 requires more spacers and the like than in the normal winding method as in Example 1. Therefore, the first embodiment has an advantage that the coil can be easily manufactured as compared with the second embodiment.

<Example 3>
The particle beam accelerator of Example 3 of the present invention and the particle beam therapy system including the particle beam accelerator will be described with reference to FIGS. 13 to 16.

As shown in FIG. 13, in the magnet device of this embodiment, the detailed structure of the upper magnetic pole 8 and the lower magnetic pole 9 is the same as that described in the first embodiment.

As a difference, as shown in FIGS. 13 and 14, two split coils 6E1 and 6E2 are arranged on the upper return yoke side, and two split coils 6F1 and 6F2 are arranged on the lower return yoke side. In this embodiment, the pair of the two split coils 6E1 and 6E2 and the set of the two split coils 6F1 and 6F2 form a pair of upper and lower main coils.

The distance between the split coil 6E2 and the split coil 6F1 on the exit channel 1019 side is narrower than the gap between the split coil 6E2 and the split coil 6F1 on the opposite side (high frequency power supply 1036 side) with the center of the circumferential region in between.

The split coils 6E1, 6E2 and the split coils 6F1, 6F2 may be arranged so that the central axis of the coil is tilted as in the first embodiment, or the central axis of the coil is made vertical as in the second embodiment and wound. The wire may be wound diagonally.

Further, the divided coils 6E1, 6E2, 6F1, 6F2 have a common coil frame, and are held by tie rods 42E1, 42E2, 42E3 or tie rods 42F1, 42F2, 42F3 via holders 45E, 45F.

Other configurations and operations are substantially the same as those of the particle beam accelerator of Example 1 described above and the particle beam therapy system provided with the accelerator, and details thereof will be omitted.

A particle beam accelerator and a particle beam therapy system provided with the particle beam accelerator as in Example 3 of the present invention can also obtain substantially the same effects as in Example 1 described above.

When the number of divided coils is two or more, the case is not limited to the case where the divided coils are held in a common coil frame, and the main coil is divided into two divided coils 6G1, 6G2, respectively, as shown in FIGS. 15 and 16. , It can be assumed that it is formed from the split coils 6H1 and 6H2. In this case, the two split coils 6G1, 6G2, 6H1, 6H2 have separate coil frames, and the tie rods 42G11, 42G12, 42G13 and the like via the holders 45G1, 45G2 or the holders 45H1, 45H2, respectively. It can be assumed that it is held by the tie rods 42G21, 42G22, 42G23, or 42H11, 42H12, 42H13 or the tie rods 42H21, 42H22, 42H23.

With such a configuration, it is possible to obtain an advantage that the degree of freedom in design can be increased as compared with the third embodiment and other embodiments. That is, by dividing the coil in this way, when the coil central axis is tilted and arranged, the space required for coil installation is reduced, and the accelerator can be reduced. In addition, even when the coil center axis is tilted or the coil winding is wound diagonally, by dividing the coil, the position of the coil can be finely adjusted by the tie rod, so that the magnetic field can be adjusted. There is an advantage that the degree of freedom of is increased.

Further, the number of upper or lower coils constituting the main coil is not limited to two, and may be three or more, and the number of coils may be different between the upper side and the lower side. .. Further, one of the upper or lower coils constituting the main coil may be one, and the other may be plural.

<Example 4>
The particle beam accelerator of Example 4 of the present invention and the particle beam therapy system including the particle beam accelerator will be described with reference to FIG.

As shown in FIG. 17, the detailed structure of the upper magnetic pole 8 and the lower magnetic pole 9 is the same as that described in the first embodiment.

The difference is that the pair of upper and lower coils 6I, 6J have a common coil frame 6K, and the tie rods 42I1, 42I2, 42I3 for holding the coil frame 6K from the horizontal direction are provided, and the tie rods 42I1, 42I2, are provided. The horizontal height position of 42I3 is the same for all tie rods, and three tie rods 42J for holding the coil frame 6K from the vertical direction are provided.

Although the tie rods 42I1 and 42I2 are not shown in FIG. 17, the tie rods 42I1 and 42I2 have the same horizontal height position as the tie rod 42I3 and the same plane position as the tie rod 42A1 or the like or the tie rod 42A2 or the like, respectively. However, it is omitted for convenience of illustration.

Other configurations and operations are substantially the same as those of the particle beam accelerator of Example 1 described above and the particle beam therapy system provided with the accelerator, and details thereof will be omitted.

As in the fourth embodiment of the present invention, the pair of upper and lower coils 6I, 6J have a common coil frame 6K, and at least two tie rods 42I1, 42I2, 42I3 for holding the coil frames 6K from the horizontal direction are provided. Even when a particle beam accelerator is provided in which the horizontal height positions of at least two or more tie rods 42I1, 42I2, 42I3 are the same for all tie rods 42I1, 42I2, 42I3, the same as in the first embodiment described above. The effect is obtained.

In this embodiment, the case where the pair of upper and lower coils 6I and 6J have the same shape as the main coil shown in the second embodiment has been described, but the shape of the pair of upper and lower main coils is not particularly limited, and the first and second embodiments It can have the same shape as the main coil of any of the third embodiment and those modifications.

<Others>
The present invention is not limited to the above examples, and includes various modifications. The above-mentioned examples have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the described configurations.

It is also possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to add / delete / replace a part of the configuration of each embodiment with another configuration.

For example, in the above description of the first embodiment and the like, the number of concave portions and convex portions provided on the upper magnetic pole 8 and the lower magnetic pole 9 is four, respectively, but the number of concave portions and convex portions is not limited to four. With the above integers, it is possible to generate a magnetic field in which the beam orbits stably.

Furthermore, in the above description of Examples 1 to 4, the particles to be accelerated are not particularly specified. That is, regardless of whether protons are supplied from the ion source 1003 or carbon ions are supplied from the ion source 1003, the beam is stably accelerated or circulated by adjusting the frequency of the high-frequency acceleration cavity 1037 according to each of the accelerating particles. Can be made to. Further, the accelerating particles are not limited to the above-mentioned protons and carbon ions, and can be heavy particle ions other than carbon ions such as helium ions.

Further, although the case where the particle beam therapy system 1001 is provided with the beam transport system 1013 has been described, the particle beam therapy system directly connects the ion beam generator to the rotating gantry or the irradiation device without providing the beam transport system. Can be done.

Further, although the case where the rotating gantry 1006 is used as the device for irradiating the particle beam used for the treatment has been described, a fixed irradiation device can be used. Further, the number of irradiation devices is not limited to one, and a plurality of irradiation devices can be provided.

Further, the case of the scanning method using scanning electromagnets 1051 and 1052 as the irradiation method has been described, but after expanding the distribution of particle beams such as the wobbler method and the double scatterer method, the particle beam is adjusted to the shape of the target by using a collimator or a bolus. The present invention can also be applied to an irradiation method for forming a dose distribution.

Further, although the case where the accelerator is used for particle beam therapy has been described, the use of the accelerator is not limited to particle beam therapy, and it can be used for high energy experiments, PET (Positron Emission Tomography) drug production, and the like.

1 ... Magnet device 2 ... Intermediate plane 3, 3A ... Vertical plane 4 ... Upper return yoke 5 ... Lower return yoke 6A, 6B, 6C, 6D, 6I, 6J ... Coil 6E1, 6E2, 6F1, 6F2, 6G1, 6G2, 6H1 , 6H2 ... Split coil 6K ... Coil frame 7 ... Vacuum container 8 ... Upper magnetic pole 9 ... Lower magnetic pole 10 ... Facing surfaces 16, 17, 18, 19, 24 ... Through holes 20 ... Axis of symmetry 21a, 21b, 21c, 21d ... Recessed 22a, 22b, 22c, 22d ... Convex part 26 ... Beam orbit 31, 32 ... Gradient magnetic field magnet 40 ... High frequency kicker 42A1, 42A2, 42A3, 42B1, 42B2, 42B3, 42C1, 42C2, 42C3, 42D1, 42D2, 42D3, 42E1 , 42E2, 42E3, 42F1, 42F2, 42F3, 42G11, 42G12, 42G13, 42G21, 42G22, 42G23, 42H11, 42H12, 42H13, 42H21, 42H22, 42H23, 42I1, 42I2, 42I3, 42J ... Tie rods 45A, 45B, 45C, 45D, 45E, 45F, 45G1, 45G2, 45H1, 45H2 ... Holders 60A, 60B, 60C, 60D ... Central axes 61A, 61B, 61C, 61D ... Winding 1001 ... Particle beam therapy system 1004 ... Accelerator (particle beam accelerator)
1019 ... Emission channel 1036 ... High frequency power supply 1037 ... High frequency acceleration cavity

Claims (7)

It ’s a particle beam accelerator,
Acceleration cavities that can modulate the frequency of high-frequency electric fields that accelerate the beam,
Equipped with a magnet device that generates a main magnetic field,
The magnet device has a pair of upper and lower main coils, a return yoke, a pair of upper and lower magnetic poles, and an exit channel for taking the accelerated beam out of the particle beam accelerator.
The magnetic poles form a magnetic field distribution so that the orbit of the accelerating beam becomes dense on the exit channel side.
The main coil is a particle beam accelerator characterized in that the vertical distance on the emission channel side is narrower than the vertical distance at a position symmetrical with respect to the center of the beam orbiting region of the particle beam accelerator. In the particle beam accelerator according to claim 1,
The main coil is characterized in that the central axis of the main coil is tilted with respect to the central axis of the return yoke so that the vertical distance between the two coils on the exit channel side is narrowed. Particle beam accelerator. In the particle beam accelerator according to claim 1,
The main coil is characterized in that the central axes of the two coils constituting the main coil coincide with the central axis of the return yoke, and the winding is wound obliquely with respect to the central axis of the main coil. Particle beam accelerator. In the particle beam accelerator according to claim 1,
A first tie rod that holds the main coil from the horizontal direction and a second tie rod that holds the main coil from the horizontal direction are provided.
A particle beam accelerator characterized in that the horizontal height of the first tie rod and the horizontal height of the second tie rod are different. In the particle beam accelerator according to claim 1,
The pair of upper and lower main coils have a common coil frame.
A third tie rod that holds the coil frame from the horizontal and vertical directions and a fourth tie rod that holds the coil frame from the horizontal and vertical directions are provided.
A particle beam accelerator characterized in that the horizontal height of the third tie rod and the horizontal height of the fourth tie rod are the same. In the particle beam accelerator according to claim 1,
The pair of upper and lower main coils is a pair of an upper coil and a lower coil.
At least one of the upper coil and the lower coil is formed of two or more split coils.
A particle beam accelerator, characterized in that at least two or more coils each have a different coil frame. A particle beam therapy system comprising the particle beam accelerator according to any one of claims 1 to 6.

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