JP7763142B2 - Accelerators and neutron capture therapy devices - Google Patents

Description

The present invention relates to an accelerator and a neutron capture therapy device.

Boron neutron capture therapy (BNCT) using boron compounds is known as a type of neutron capture therapy that uses neutron beams to kill cancer cells. In boron neutron capture therapy, boron that has been incorporated into cancer cells in advance is irradiated with neutron beams, and the resulting heavy charged particles selectively destroy the cancer cells. To generate neutron beams, an accelerator is used to accelerate charged particles and irradiate the target as a particle beam.

Japanese Patent Application Laid-Open No. 2020-146119

The accelerators used in neutron capture therapy do not transmit RF power using coaxial tubes due to the large beam loading, but instead couple a vacuum tube amplifier to the acceleration electrode. This eliminates the need to consider the effects of reflected waves on the transmission line even when the beam loading changes, but it does result in a decrease in the efficiency of the vacuum tube. To change the operation of the vacuum tube (to increase efficiency), the coupling must be changed, and the area of the coupling capacitor electrode may be adjusted for this purpose. However, this method has the problem of changing the resonant frequency.

Therefore, an object of the present invention is to provide an accelerator and a neutron capture therapy device that can suppress changes in the resonant frequency.

The accelerator according to the present invention comprises an electrode for accelerating charged particles, a vacuum tube amplifier for supplying power to the electrode, a coupler for transmitting power from the vacuum tube amplifier to the electrode, and an adjustment mechanism for adjusting the distance between the vacuum tube amplifier and the coupler.

In the accelerator of the present invention, the vacuum tube amplifier can supply power to the electrode via the coupler. This allows the electrode to accelerate charged particles. Here, the accelerator is equipped with an adjustment mechanism that can adjust the distance between the vacuum tube amplifier and the coupler. In this case, when the beam loading changes, the adjustment mechanism adjusts the distance between the vacuum tube amplifier and the coupler to an appropriate value, thereby preventing a decrease in vacuum tube efficiency. Furthermore, adjusting the distance using the adjustment mechanism can prevent changes in resonant frequency, unlike methods that involve adjusting the area of the capacitor electrodes.

The adjustment mechanism may have a contact portion that allows the vacuum tube amplifier to slide relative to the coupler while in contact with the coupler. In this case, the adjustment mechanism can easily prevent a decrease in vacuum tube efficiency without requiring extensive work, simply by sliding the vacuum tube amplifier while maintaining contact of the contact portion with the coupler.

The coupler may have a first cylindrical portion, and the adjustment mechanism may have a second cylindrical portion arranged on the outer periphery of the first cylindrical portion, and a contact portion fixed to the second cylindrical portion and in contact with the first cylindrical portion. In this case, by sliding the second cylindrical portion along the first cylindrical portion while keeping the contact portion in contact with the outer periphery of the first cylindrical portion, it is possible to easily suppress a decrease in the efficiency of the vacuum tube.

The distance between the coupler and the electrode may be fixed. In this case, the adjustment mechanism can be used to prevent a decrease in the efficiency of the vacuum tube while maintaining the structure of the coupling portion between the coupler and the electrode.

A pair of capacitor electrodes with a fixed distance between them may be provided between the coupler and the electrode. In this case, the coupler and the electrode can be coupled by a C-couple.

The accelerator may have at least a vacuum region in which the electrodes are arranged, and an atmospheric pressure region, and the adjustment mechanism may be arranged in the atmospheric pressure region. In this case, the adjustment mechanism can adjust the distance in the atmospheric pressure region without affecting the configuration of the vacuum region.

The vacuum tube amplifier may have a guide mechanism that guides its movement relative to the coupler. In this case, the guide mechanism allows the vacuum tube amplifier to slide smoothly, allowing the distance between it and the coupler to be adjusted.

The neutron capture therapy device according to the present invention comprises the above-described accelerator and a neutron beam generation unit that generates a neutron beam by irradiating a target with a particle beam emitted from the accelerator.

This neutron capture therapy device can achieve the same effects and aims as the accelerator described above.

The present invention provides an accelerator and a neutron capture therapy device that can suppress changes in resonant frequency.

1 is a schematic diagram illustrating a neutron capture therapy device and an accelerator according to an embodiment of the present invention. FIG. 2 is a perspective view showing a part of the accelerator. FIG. 1 is a schematic plan view showing a part of an accelerator. FIG. 1 is a schematic cross-sectional view showing a part of an accelerator. FIG. 4 is an enlarged cross-sectional view of the adjustment mechanism. FIG. 4 is an enlarged cross-sectional view of the adjustment mechanism. 10 is a graph showing measurement results of the load impedance of the accelerator, etc. 1A is a graph showing the measurement results of load impedance, etc. of a comparative example, and FIG. 1B is a graph showing the measurement results of load impedance, etc. of an example. 1 is a graph showing the relationship between voltage, current, and impedance.

A preferred embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic diagram showing a neutron capture therapy device 100 and an accelerator 2 according to an embodiment of the present invention. The neutron capture therapy device 100 is a device that performs therapy using a neutron beam generated as a particle beam by a neutron beam generator 1. The neutron beam generator 1 is used as a neutron capture therapy device that performs cancer treatment using boron neutron capture therapy (BNCT). First, the configuration of the neutron capture therapy device 100 will be described with reference to FIG. 1. The neutron capture therapy device 100 irradiates a neutron beam N onto a tumor in a patient 50 (treatment subject) to which, for example, boron ( ¹⁰ B) has been administered.

The neutron capture therapy device 100 is equipped with an accelerator 2. The accelerator 2 accelerates particles and emits a particle beam R. For example, a cyclotron, a linear accelerator, or the like may be used as the accelerator 2.

The particle beam R emitted from the accelerator 2 passes through a transport path 9, known as a beam duct, which is maintained in a vacuum and through which the beam can pass, and is transported to the target placement unit 30. The target placement unit 30 is where the target 10 is placed and has a mechanism for holding the target 10 in the orientation required for irradiation. The target placement unit 30 places the target 10 at a position opposite the end (exit port) of the transport path 9. The particle beam R emitted from the accelerator 2 passes through the transport path 9 and travels toward the target 10 placed at the end of the transport path 9. A plurality of electromagnets 4 (such as quadrupole electromagnets) and a scanning electromagnet 6 are provided along this transport path 9. The multiple electromagnets 4 are used, for example, to adjust the beam axis of the particle beam R.

The scanning electromagnet 6 scans the particle beam R and controls the irradiation of the particle beam R onto the target 10. This scanning electromagnet 6 controls the irradiation position of the particle beam R on the target 10.

The neutron beam generator 1 generates a neutron beam N by irradiating a target 10 with a particle beam R, and emits the neutron beam N toward a patient 50. The neutron beam generator 1 includes a target 10, a shield 8, a moderator 39, and a collimator 20.

The target 10 generates a neutron beam N when irradiated with the particle beam R. The target 10 is a solid component formed from a material that generates a neutron beam N when irradiated with the particle beam R. Specifically, the target 10 is formed from, for example, beryllium (Be), lithium (Li), tantalum (Ta), or tungsten (W), and has a solid disk shape with a diameter of, for example, 160 mm. Note that the target 10 is not limited to a disk shape and may have other shapes.

The moderator 39 slows down the neutron beam N generated by the target 10 (reducing the energy of the neutron beam N). The moderator 39 may have a layered structure consisting of a layer 39A that primarily slows down the fast neutrons contained in the neutron beam N, and a layer 39B that primarily slows down the epithermal neutrons contained in the neutron beam N.

The shielding body 8 blocks the generated neutron beam N and gamma rays and other radiation generated by the generation of the neutron beam N from being emitted to the outside. The shielding body 8 is arranged to surround the moderator 39. The upper and lower portions of the shielding body 8 extend upstream of the moderator 39 in the direction of the particle beam R.

The collimator 20 shapes the irradiation field of the neutron beam N and has an irradiation port 20a through which the neutron beam N passes. The collimator 20 is, for example, a block-shaped member with the irradiation port 20a in the center.

Next, the accelerator 2 will be described in detail with reference to Figures 2 and 3. As shown in Figures 2 and 3, the accelerator 2 is a device that accelerates charged particles incident from an ion source 11 (see Figure 3) and emits an accelerated charged particle beam. Examples of charged particles include hydrogen ions, carbon ions, and electrons. The accelerator 2 has an acceleration space 12 that is circular in plan view and through which the charged particles pass and accelerate. Here, the accelerator 2 is installed so that the acceleration space 12 extends horizontally. When terms including the concepts of "up" and "down" are used in the following description, they correspond to the top and bottom of the accelerator 2 in the state shown in Figure 2.

The accelerator 2 has magnetic poles 13 arranged below and above the acceleration space 12. The magnetic pole 13 above the acceleration space 12 is not shown. The magnetic pole 13 generates a vertical magnetic field in the acceleration space 12. A coil 16 (see Figure 4) is arranged around the magnetic pole 13.

The accelerator 2 is equipped with an electrode 14, known as a D-electrode, which has a sector shape in plan view. The electrode 14 generates a radio-frequency electric field in a vacuum region 15, which is maintained at a vacuum. The electrode 14 has a cavity that penetrates in the circumferential direction, which cavity forms part of the acceleration space 12. When a vacuum tube amplifier applies radio-frequency AC power to the electrode 14 via a coupling unit 19 (see Figure 3), the electrode 14 generates a circumferential electric field in the acceleration space 12, and charged particles are accelerated by this electric field. Charged particles introduced approximately at the center of the acceleration space 12 are accelerated within the acceleration space 12 by the interaction of the magnetic field generated by the magnetic pole 13 and the electric field generated by the electrode 14, tracing a horizontal spiral orbit K within the acceleration space 12. The accelerated charged particles are ultimately emitted in the tangential direction of the orbit K.

The configuration of the accelerator 2 will be described in more detail with reference to Figure 3. Note that while Figure 4 shows electrodes 14 provided at two locations in the circumferential direction, Figure 3 shows only one of the electrodes 14 in the circumferential direction. As shown in Figure 3, the accelerator 2 comprises the above-mentioned electrode 14, a vacuum box 21, a resonator 22, a vacuum tube amplifier 23, a coupler 24, and an adjustment mechanism 26.

As mentioned above, the pair of electrodes 14 face each other at a distance in the vertical direction. The vacuum box 21 surrounds the pair of electrodes 14 from above, below, and on the outer periphery. The vacuum box 21 is positioned between the pair of magnetic poles 13 in the vertical direction. The vacuum box 21 is a container with a vacuum region 15 inside. As a result, the upper and lower electrodes 14 are each positioned within the vacuum region 15.

The resonator 22 is a mechanism for generating high-frequency waves through resonance. It comprises an outer cylinder 27 and an inner cylinder 28. The resonators 22 are provided for the upper and lower electrodes 14, respectively. The outer cylinder 27 of the upper resonator 22 extends upward from the upper wall 21a of the vacuum box 21. The lower end of the outer cylinder 27 is connected to the internal space of the vacuum box 21, and the interior of the outer cylinder 27 forms a vacuum region 15. The inner cylinder 28 of the upper resonator 22 extends vertically within the outer cylinder 27. The lower end of the inner cylinder 28 is connected to the upper electrode 14. The upper end of the inner cylinder 28 is connected to the upper end 27a of the outer cylinder 27. The lower resonator 22 is provided for the lower electrode 14 and has a vertically symmetrical configuration with the upper resonator 22.

If the capacitance of the electrode 14 is "C" and the inductance of the resonator 22 is "L", the resonant frequency of the accelerator 2 is expressed as "1/(2 x π x √LC)".

The vacuum tube amplifier 23 is a device that supplies power to the electrode 14. The vacuum tube amplifier 23 supplies RF (radio frequency) power. The vacuum tube amplifier 23 is positioned at a distance from the vacuum box 21 and the electrode 14 toward the outer periphery. The vacuum tube amplifier 23 is equipped with a vacuum tube 31 that amplifies the input electrical signal. The vacuum tube 31 supplies the amplified power to the electrode 14 via the coupler 24 and adjustment mechanism 26.

The coupler 24 is a mechanism that transmits power from the vacuum tube amplifier 23 to the electrode 14. The coupler 24 comprises an outer cylinder 32 and an inner cylinder 33 (first cylinder portion). The outer cylinder 32 extends from the outer peripheral end of the upper and lower wall portions 21a of the vacuum box 21 toward the vacuum tube amplifier 23 radially outward. The outer cylinder 32 is divided by a connection portion 34 into a member located in the vacuum region 15 and a member located in the atmospheric pressure region 35. The atmospheric pressure region 35 is an area outside the vacuum region 15 that is open to the atmosphere and is at atmospheric pressure. The portion of the outer cylinder 32 located in the vacuum region 15 and the portion near the outer peripheral end of the vacuum box 21 are covered by a wall portion 36. The inside of the wall portion 36 forms the vacuum region 15.

The inner cylinder 33 extends radially outward from near the outer end of the electrode 14 toward the vacuum tube amplifier 23. The inner cylinder 33 is disposed inside the outer cylinder 32. The inner cylinder 33 is divided by a connecting portion 37 into a member 33a disposed in the vacuum region 15 and a member 33b disposed in the atmospheric pressure region 35. A partition wall 38 is provided in the internal space of the outer cylinder 32 to separate the vacuum region 15 from the atmospheric pressure region 35. The partition wall 38 is provided between the connecting portion 34 and the connecting portion 37.

The distance between the coupler 24 and the electrode 14 is fixed. In this embodiment, a pair of capacitor electrodes 41, 42, with a fixed distance between them, is provided between the inner tube 33 of the coupler 24 and the electrode 14. The capacitor electrode 41 is formed in a flat plate shape that extends vertically at the outer end of the electrode 14 (see also Figure 3). The capacitor electrode 41 is formed in a flat plate shape that extends vertically at the inner end of the inner tube 33 of the coupler 24 (see also Figure 3). The capacitor electrode 41 on the electrode 14 side and the capacitor electrode 42 on the coupler 24 side face each other and are spaced apart by a fixed distance. This allows the resonator 22 and the vacuum tube amplifier 23 to be coupled by a C-couple at the coupling section 19.

The adjustment mechanism 26 is a mechanism that can adjust the distance between the vacuum tube amplifier 23 and the coupler 24. The adjustment mechanism 26 comprises an outer cylinder 43 and an inner cylinder 44 (second cylinder portion). The outer cylinder 43 extends from the housing of the vacuum tube amplifier 23 toward the electrode 14 and is connected to the outer cylinder 32 of the coupler 24. The inner cylinder 44 extends from the vacuum tube 31 toward the electrode 14 and is connected to the inner cylinder 33 of the coupler 24. The adjustment mechanism 26 is located in the atmospheric pressure region 35.

The adjustment mechanism 26 will be described in more detail with reference to Figures 5 and 6. As shown in Figures 5 and 6, the end of the inner tube 44 on the vacuum tube amplifier 23 side is fixed to the electrode portion 46 of the vacuum tube 31. The end of the inner tube 44 on the electrode 14 side is slidably connected to the inner tube 33 of the coupler 24 via a contact portion 51. The contact portion 51 is fixed to the end of the inner tube 44 on the electrode 14 side. The contact portion 51 is a member known as a contact finger, and is a member that allows the vacuum tube amplifier 23 to slide relative to the inner tube 33 while being in physical contact with the inner tube 33 of the coupler 24. The contact portion 51, together with the inner tube 44, is slidable along the outer peripheral surface F1 of the inner tube 33 while maintaining contact with the outer peripheral surface F1.

The end of the outer tube 43 facing the vacuum tube amplifier 23 is fixed to the housing 48 of the vacuum tube amplifier 23. The end of the outer tube 43 facing the electrode 14 is slidably connected to the outer tube 32 of the coupler 24 via a contact portion 52. The contact portion 52 is fixed to the end of the outer tube 43 facing the electrode 14. The contact portion 52 is a member known as a contact finger, and is a member that allows the vacuum tube amplifier 23 to slide relative to the outer tube 32 of the coupler 24 while being in physical contact with the outer tube 32. The contact portion 52, together with the outer tube 43, is slidable along the outer peripheral surface F2 of the outer tube 32 while maintaining contact with the outer peripheral surface F2.

With the above configuration, the adjustment mechanism 26 can slide the entire vacuum tube amplifier 23 together with the inner tube 44 and outer tube 43 by sliding the contact portions 51, 52 relative to the inner tube 33 and outer tube 32 of the coupler 24 from a state in which the distance between the coupler 24 and the vacuum tube amplifier 23 is short, as shown in FIG. 5. This allows the adjustment mechanism 26 to switch to a state in which the distance between the coupler 24 and the vacuum tube amplifier 23 is long, as shown in FIG. 6. To facilitate sliding of the vacuum tube amplifier 23, the vacuum tube amplifier 23 may have a guide mechanism 53 that guides its movement relative to the coupler 24, as shown in FIG. 4. The guide mechanism 53 is, for example, a rail-shaped member that extends along the direction of movement of the vacuum tube amplifier 23.

Next, the functions and effects of the accelerator 2 and neutron capture therapy device 100 according to this embodiment will be described.

Because accelerators used in neutron capture therapy have large beam loading, they do not transmit RF power via coaxial tubes; instead, they couple vacuum tube amplifiers to the acceleration electrodes. This eliminates the need to consider the effects of reflected waves from the transmission line when the beam loading changes, but it also reduces the efficiency of the vacuum tubes. For example, Figure 7(a) shows the results of measurements of the accelerator's load impedance and other parameters when there is no beam, assuming a design load impedance of 550 Ω (anode RF voltage = 13 kV/anode peak current = 24 A). Graph G1 in Figure 7(a) shows the load impedance. The horizontal axis represents frequency, while the vertical axis on the left represents load impedance (Ω). Figure 7(b) shows the results of measurements of the accelerator's load impedance and other parameters when there is a beam, without adjustments to the capacitor electrode area or adjustment mechanism. As shown in graph G1 in Figure 7(b), the load impedance has dropped to approximately 300 Ω, confirming a decrease in the vacuum tube's conversion efficiency. In this case, the load on the vacuum tube increases, potentially resulting in damage.

To change the operation of the vacuum tube (to increase efficiency), the coupling must be changed, and for this purpose, the area of the coupling capacitor electrode within the vacuum region may be changed. Specifically, the area of the capacitor electrode 42 is increased, as shown by the phantom lines in Figures 2 and 3. In this case, as shown in Figure 8(a), the load impedance with the beam present can be maintained at approximately 550 Ω. However, this method has the problem that replacing the capacitor electrode 42 with one of a larger area requires the extensive work of opening the vacuum region to the atmosphere and raising the yoke. Another problem with this method is that it changes the resonant frequency. As shown in Figure 8(a), the frequency at the peak of graph G1, i.e., the resonant frequency, is lower than those in Figures 7(a) and (b).

In contrast, in the accelerator 2 according to this embodiment, the vacuum tube amplifier 23 can supply power to the electrode 14 via the coupler 24. This allows the electrode 14 to accelerate the charged particles. The accelerator 2 is equipped with an adjustment mechanism 26 that can adjust the distance between the vacuum tube amplifier 23 and the coupler 24. In this case, when the beam loading changes, the adjustment mechanism 26 adjusts the distance between the vacuum tube amplifier 23 and the coupler 24 to an appropriate value, thereby preventing a decrease in the efficiency of the vacuum tube 31. Furthermore, adjusting the distance using the adjustment mechanism 26 can suppress changes in the resonant frequency, unlike the method of adjusting the area of the capacitor electrode 42. Specifically, as shown in Figure 8(b), the load impedance can be maintained at approximately 550 Ω, and the resonant frequency can be kept equivalent to that shown in Figures 7(a) and 7(b).

This diagram shows how load impedance can be changed by adjusting the appropriate distance between the vacuum tube amplifier 23 and the coupler 24. Figure 9 shows the current distribution (graph G3) and voltage distribution (graph G4) within the coaxial line. The horizontal axis of Figure 9 represents distance (unit: cm) from a certain location. The right vertical axis represents current, and the left vertical axis represents voltage. When the resonant frequency is 73 MHz, the wavelength is approximately 30,000/73 ≒ 411 cm, and the current and voltage distribution within the coaxial line are sinusoidal waves with one period equal to the wavelength. The impedance at a certain location on the horizontal axis (graph G5) is expressed as "Z = V/I." For example, if the point where the voltage is zero is taken as the reference position SP and the initial position of the vacuum tube 31, then the impedance Z increases as the vacuum tube 31 is moved away from the coupler from the reference position, i.e., as the horizontal axis moves to the left. In the accelerator 2, there is an appropriate impedance Z for the operation of the vacuum tube 31, depending on the size and output power of the vacuum tube 31. Therefore, the adjustment mechanism 26 can adjust the distance between the coupler 24 and the vacuum tube amplifier 23 to adjust the impedance Z to a value appropriate for the operation of the vacuum tube 31.

The adjustment mechanism 26 may have contact portions 51, 52 that allow the vacuum tube amplifier 23 to slide relative to the coupler 24 while in contact with the coupler 24. In this case, the adjustment mechanism 26 can easily suppress a decrease in the efficiency of the vacuum tube 31 without requiring extensive work, simply by sliding the vacuum tube amplifier 23 while maintaining contact between the contact portions 51, 52 and the coupler 24.

The coupler 24 has an inner tube 33, and the adjustment mechanism 26 may have an inner tube 44 arranged on the outer periphery of the inner tube 33, and a contact portion 51 fixed to the inner tube 44 and in contact with the inner tube 33. In this case, by sliding the inner tube 44 along the inner tube 33 with the contact portion 51 in contact with the outer periphery F1 of the inner tube 33, it is possible to easily suppress a decrease in the efficiency of the vacuum tube 31.

The distance between the coupler 24 and the electrode 14 may be fixed. In this case, the adjustment mechanism 26 can suppress a decrease in the efficiency of the vacuum tube 31 while maintaining the structure of the coupling portion 19 between the coupler 24 and the electrode 14.

A pair of capacitor electrodes 41, 42 with a fixed distance between them may be provided between the coupler 24 and the electrode 14. In this case, the coupler 24 and the electrode 14 can be coupled by a C-couple.

The accelerator 2 has a vacuum region 15 in which at least the electrodes 14 are arranged, and an atmospheric pressure region 35, and the adjustment mechanism 26 may be arranged in the atmospheric pressure region 35. In this case, the adjustment mechanism 26 can adjust the distance in the atmospheric pressure region 35 without affecting the vacuum region 15 by opening it to the atmosphere.

The vacuum tube amplifier 23 may have a guide mechanism 53 that guides its movement relative to the coupler 24. In this case, the guide mechanism 53 allows the vacuum tube amplifier 23 to slide smoothly, allowing the distance between it and the coupler 24 to be adjusted.

The neutron capture therapy device 100 according to this embodiment includes the accelerator 2 described above and a neutron beam generator 1 that generates a neutron beam by irradiating a target with a particle beam emitted from the accelerator 2.

This neutron capture therapy device 100 can achieve the same effects and benefits as the accelerator 2 described above.

The coupling between the coupler 24 and the electrode 14 is not limited to a C-couple, and may be an L-couple. In this case, it is preferable that the coupling point be a low-voltage point, such as the end 27a of the outer tube 27, rather than the high-voltage capacitor electrode 41.

The configuration of the accelerator and vacuum tube amplifier described above is merely an example, and may be modified as appropriate without departing from the spirit and scope of the present invention.

The accelerator's use is not particularly limited, and it may be used for purposes other than neutron capture therapy devices.

2...Accelerator, 14...Electrode, 15...Vacuum region, 23...Vacuum tube amplifier, 24...Coupler, 26...Adjustment mechanism, 33...Inner cylinder (first cylinder part), 35...Atmospheric pressure region, 44...Inner cylinder (second cylinder part), 51, 52...Contact parts, 100...Neutron capture therapy device.

Claims (8)

an electrode for accelerating the charged particles;
a vacuum tube amplifier for supplying power to the electrodes;
a coupler for transmitting power from the vacuum tube amplifier to the electrode;
an adjustment mechanism capable of adjusting a load impedance by adjusting the distance between the vacuum tube amplifier and the coupler. The accelerator of claim 1, wherein the adjustment mechanism has a contact portion that allows the vacuum tube amplifier to slide relative to the coupler while in contact with the coupler. the coupler has a first cylindrical portion;
3. The accelerator according to claim 2, wherein the adjustment mechanism includes a second cylindrical portion disposed on an outer circumferential side of the first cylindrical portion, and the contact portion fixed to the second cylindrical portion and in contact with the first cylindrical portion. The accelerator described in any one of claims 1 to 3, wherein the distance between the coupler and the electrode is fixed. The accelerator of claim 4, wherein a pair of capacitor electrodes having a fixed distance from each other are provided between the coupler and the electrode. The device has a vacuum region in which at least the electrodes are disposed and an atmospheric pressure region,
The accelerator according to any one of claims 1 to 5, wherein the adjustment mechanism is disposed in an atmospheric pressure region. The accelerator described in any one of claims 1 to 6, wherein the vacuum tube amplifier has a guide mechanism that guides movement relative to the coupler. The accelerator according to any one of claims 1 to 7;
a neutron beam generating unit that generates a neutron beam by irradiating a target with the particle beam emitted from the accelerator.