JP2019068870A - Neutron capture therapy device and target for neutron capture therapy - Google Patents

Abstract

To provide a neutron capture therapy device and a target for neutron capture therapy that are capable of enlarging irradiation area with a neutron beam while ensuring strength while inhibiting generation of a blistering in the target.SOLUTION: A target 8 has a sectional form protruding along an irradiation axis A of a charged particle beam L in the case of being viewed from a longer direction D1 orthogonal to the irradiation axis A and has a shape extending so that sectional forms continue along the longer direction D1. According to the shape, the target 8 can be thinned while securing the target's strength. Therefore, the charged particle beam L's Bragg peak can be easily shifted to a position on the downstream side of the target 8. Therefore, generation of blistering in the target 8 can be inhibited. Capability of increasing area of the target 8 without increasing the target 8's curvature enables security of the strength while increasing the area.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a neutron capture therapy device and a target for neutron capture therapy.

  BACKGROUND ART Conventionally, boron neutron capture therapy (BNCT: Boron Neutron Capture Therapy) using a boron compound is known as a neutron capture therapy for irradiating a neutron beam to kill cancer cells. In boron neutron capture therapy, boron which has been incorporated into cancer cells in advance is irradiated with neutrons, and the cancer cells are selectively destroyed by scattering of heavy charged particles generated thereby.

  As an apparatus used in such a neutron capture therapy, for example, an apparatus having an accelerator for emitting a charged particle beam and a target for generating a neutron beam by irradiating the charged particle beam is disclosed in Patent Document 1 Have been described. The target of this neutron capture therapy apparatus secures its strength by protruding hemispherically along the irradiation axis of the charged particle beam. Since it becomes possible to make it thin by making it a shape that can ensure strength in this way, by positioning the Bragg peak of the charged particle beam in the cooling section downstream of the target, blistering due to hydrogen retention is suppressed. doing.

JP, 2015-073783, A

  Here, it is required to widen the area of the target in order to widely irradiate the neutron beam to the object to be irradiated. However, since the above-mentioned target has a hemispherical shape, it has been difficult in some cases to secure the strength while increasing the area.

  Therefore, an object of the present invention is to provide a neutron capture therapy apparatus and a target for neutron capture therapy that can increase the irradiation area of neutron beams while securing strength while suppressing occurrence of blistering in the target. .

  In order to solve the above problems, a neutron capture therapy apparatus according to the present invention is a neutron capture therapy apparatus for irradiating a neutron beam to an irradiated object, which is an accelerator for accelerating charged particles to emit charged particle beams, and an accelerator A target for generating a neutron beam by being irradiated with a charged particle beam emitted from the target, and a mounting portion on which an object to be irradiated with a neutron beam is mounted, the target being a charged particle beam When viewed from a first direction orthogonal to the irradiation axis, it has a cross-sectional shape that protrudes or is recessed along the irradiation axis, and a shape that extends so that the cross-sectional shape is continuous along the first direction There is no.

  In the neutron capture therapy apparatus according to the present invention, the target has a cross-sectional shape projecting or recessed along the irradiation axis when viewed from the first direction orthogonal to the irradiation axis of the charged particle beam, It has an elongated shape so that the cross-sectional shape is continuous along the direction 1. According to the shape, the Bragg peak of the charged particle beam can be easily positioned downstream of the target or at a position where the Bragg peak in the target can be suppressed because the target can be thinned while securing the strength of the target. . Therefore, the occurrence of blistering in the target can be suppressed. In addition, since the area of the target can be increased, the irradiation area of the neutron beam can be increased. Furthermore, since the area of the target can be increased without increasing the curvature of the target, it is possible to secure the strength while increasing the area. As mentioned above, the irradiation area of a neutron beam can be enlarged, securing intensity | strength, suppressing generation | occurrence | production of blistering in a target.

  In the neutron capture therapy apparatus according to the present invention, the target includes a first layer and a second layer in order from the upstream side to the downstream side in the irradiation direction of the charged particle beam, and the hydrogen of the second layer The storage performance may be higher than that of the first layer. In this case, even if hydrogen is generated in the target, the occurrence of blistering can be suppressed by storing hydrogen in the second layer having high hydrogen storage performance.

  In the neutron capture therapy apparatus according to the present invention, a cooling unit for cooling the target by flowing a cooling medium is provided downstream of the target, and the cooling passage of the cooling medium in the cooling unit is in the first direction. And a second direction orthogonal to the irradiation direction and the first direction, and the length in the first direction is larger than the length in the second direction. In this case, since the cooling passage can be made wider, cooling water is present on the back side (downstream side) of the portion of the target to which the charged particle beam is irradiated, and hydrogen is collected by the cooling water. This makes it possible to suppress the occurrence of blistering.

  Further, the target for neutron capture therapy according to the present invention is a target for neutron capture therapy that generates a neutron beam by being irradiated with a charged particle beam, and is orthogonal to a predetermined direction when viewed from a predetermined direction. It has a cross-sectional shape that protrudes or indents along the direction, and extends in such a way that the cross-sectional shape is continuous along a predetermined direction.

  According to the target for neutron capture therapy concerning the present invention, the same operation and effect as the above-mentioned neutron capture therapy apparatus can be acquired.

  ADVANTAGE OF THE INVENTION According to this invention, the irradiation area of a neutron beam can be enlarged, ensuring intensity | strength, suppressing generation | occurrence | production of blistering in a target.

It is a figure which shows arrangement | positioning of the neutron capture therapy apparatus of this embodiment. It is a figure which shows the neutron beam irradiation part vicinity in the neutron capture therapy apparatus of FIG. It is sectional drawing which shows the detail around a target with which the neutron capture therapy apparatus of FIG. 1 is provided. It is the figure which looked at the target from the other side of the irradiation direction. It is the figure which looked at the target from the short side direction. It is a figure which shows the layer structure of a target. It is a graph which shows the relationship between the thickness of a 1st layer and a 2nd layer, and the position of the Bragg peak of a charged particle beam.

  Hereinafter, a neutron capture therapy apparatus and a target for neutron capture therapy according to the present invention will be described with reference to the attached drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description.

First, an outline of the neutron capture therapy apparatus according to the present embodiment will be described using FIGS. 1 and 2. As shown in FIGS. 1 and 2, in the neutron capture therapy apparatus 1 for performing cancer treatment using boron neutron capture therapy, boron of a patient (irradiated body) S to which boron ( ¹⁰ B) was administered was accumulated. It is a device that irradiates neutrons to the site to treat cancer. The neutron capture therapy apparatus 1 has an irradiation room 2 for performing cancer treatment on a patient S by irradiating the patient S confined in the treatment table 3 with a neutron beam N.

  The preparatory work such as restraining the patient S to the treatment table 3 is performed in a preparation room (not shown) outside the irradiation room 2, and the treatment table 3 in which the patient S is restrained is moved from the preparation room to the irradiation room 2. . The neutron capture therapy apparatus 1 also includes a neutron beam generation unit 10 that generates a neutron beam N for treatment, and a neutron irradiation unit that irradiates the patient S confined in the treatment room 3 in the irradiation room 2 with the neutron beam N. And 20. Although the irradiation chamber 2 is covered by the shielding wall W, a passage and a door 45 may be provided for the patient, the worker, etc. to pass through.

  The neutron beam generation unit 10 scans the charged particle beam L by an accelerator 11 that accelerates charged particles and emits the charged particle beam L, a beam transport path 12 that transports the charged particle beam L emitted by the accelerator 11, and A charged particle beam scanning unit 13 for controlling the irradiation position of the charged particle beam L to the target 8; a target 8 for generating a neutron beam N by causing a nuclear reaction due to the irradiation of the charged particle beam L; And a current monitor 16 for measuring the current of L. The accelerator 11 and the beam transport path 12 are disposed in a chamber of a charged particle beam generation chamber 14 having a substantially rectangular shape, and the charged particle beam generation chamber 14 is a space covered with a shielding wall W made of concrete. . The charged particle beam generation chamber 14 may be provided with a passage and a door 46 for a worker for maintenance to pass. The charged particle beam generation chamber 14 is not limited to a substantially rectangular shape, and may have another shape. For example, when the path from the accelerator to the target is L-shaped, the charged particle beam generation chamber 14 may also be L-shaped. Further, the charged particle beam scanning unit 13 controls, for example, the irradiation position of the charged particle beam L to the target 8, and the current monitor 16 measures the current of the charged particle beam L irradiated to the target 8.

  The accelerator 11 accelerates charged particles such as protons to generate charged particle beams L such as proton beams. In the present embodiment, a cyclotron is employed as the accelerator 11. As the accelerator 11, instead of a cyclotron, another accelerator such as a synchrotron, a synchro cyclotron, or a linac may be used.

  One end (upstream end) of the beam transport path 12 is connected to the accelerator 11. The beam transport path 12 includes a beam adjustment unit 15 that adjusts the charged particle beam L. The beam adjustment unit 15 includes a horizontal steering electromagnet and a horizontal vertical steering electromagnet for adjusting the axis of the charged particle beam L, a quadrupole electromagnet for suppressing the divergence of the charged particle beam L, and four directions for shaping the charged particle beam L. It has a slit or the like. The beam transport path 12 may have a function of transporting the charged particle beam L, and the beam adjustment unit 15 may be omitted.

  The charged particle beam L transported by the beam transport path 12 is irradiated on the target 8 with its irradiation position controlled by the charged particle beam scanning unit 13. The charged particle beam scanning unit 13 may be omitted, and the same portion of the target 8 may be always irradiated with the charged particle beam L.

  The target 8 generates a neutron beam N by being irradiated with the charged particle beam L. The target 8 is made of, for example, beryllium (Be), lithium (Li), tantalum (Ta) or tungsten (W), and has a plate shape (however, details of the material of the target 8 will be described later). To do). The neutron beam N generated by the target 8 is irradiated toward the patient S in the irradiation chamber 2 by the neutron beam irradiation unit 20.

  The neutron beam irradiation unit 20 includes a moderator 21 that decelerates the neutron beam N emitted from the target 8 and a shield 22 that shields radiation such as the neutron beam N and gamma rays from being emitted to the outside. A moderator is configured by the moderator 21 and the shield 22.

  The moderator 21 has, for example, a laminated structure composed of a plurality of different materials, and the material of the moderator 21 is appropriately selected according to various conditions such as the energy of the charged particle beam L. Specifically, for example, when the output from the accelerator 11 is a proton beam of 30 MeV and a beryllium target is used as the target 8, the material of the moderator 21 can be lead, iron, aluminum or calcium fluoride.

  The shield 22 is provided so as to surround the moderator 21 and has a function of shielding the radiation N such as neutron rays N and gamma rays generated with the generation of the neutron rays N from being emitted to the outside of the shield 22. Have. The shield 22 may or may not be at least partially embedded in the wall W1 separating the charged particle beam generation chamber 14 and the irradiation chamber 2. Further, between the irradiation chamber 2 and the shield 22, a wall 23 forming a part of the side wall surface of the irradiation chamber 2 is provided. The wall 23 is provided with a collimator mounting portion 23 a which is an output port of the neutron beam N. A collimator 31 for defining an irradiation field of the neutron beam N is fixed to the collimator attachment portion 23a. In addition, the collimator 31 may be attached to the treatment table 3 described later without providing the collimator attachment portion 23 a on the wall body 23.

  In the above-described neutron beam irradiation unit 20, the charged particle beam L is irradiated to the target 8, and the target 8 generates the neutron beam N accordingly. The neutron beam N generated by the target 8 is decelerated while passing through the moderator 21, and the neutron beam N emitted from the moderator 21 passes through the collimator 31 to the patient S on the treatment table 3. It is irradiated. Here, as the neutron beam N, a thermal neutron beam or an epithermal neutron beam having a relatively low energy can be used.

  The treatment table 3 functions as a mounting table used in the neutron capture therapy, and can be moved from the preparation room (not shown) to the irradiation room 2 while the patient S is placed. The treatment table 3 includes a base portion 32 which forms a base of the treatment table 3, a caster 33 which allows the base portion 32 to move on the floor surface, a top plate 34 on which the patient S is placed, and a top plate 34. And a drive unit 35 for moving the base unit 32 relative to the base unit 32. The base portion 32 may be fixed to the floor without using the caster 33.

  Next, the structure around the target 8 provided in the neutron capture therapy apparatus 1 according to the present embodiment will be described in detail with reference to FIG. FIG. 3 is a cross-sectional view showing details of the vicinity of the target provided in the neutron capture therapy apparatus of the present embodiment. As shown in FIG. 3, the target 8 is detachably attached to the downstream end of the beam transport path 12 by a target holder 19. The target holder 19 is composed of a flanged short pipe 17 and a cooling plate 18. The target holder 19 holds and holds the target 8 by the flanged short tube 17 and the cooling plate 18. The flanged short tube 17 is fixed to the downstream end of the beam transport path 12.

  The target 8 has a plate shape, and is integrally formed, for example, by pressing a sintered body. The target 8 has a protrusion 8 c and a flange 8 d. The protrusion 8 c protrudes in the irradiation direction of the charged particle beam L. The irradiation axis A means an axis through which the beam center of the charged particle beam L passes when the charged particle beam L is irradiated without deflection. The irradiation direction is a direction in which the irradiation axis A extends and the charged particle beam L is irradiated.

  Here, the target 8 according to the present embodiment has a rectangular shape when viewed from the irradiation direction, and has a longitudinal direction D1 (first direction, predetermined direction) and a transverse direction D2 . FIG. 4 is a view of the target 8 viewed from the side opposite to the irradiation direction. FIG. 5 is a view of the target 8 as seen from the short side direction D2. FIG. 3 is a cross-sectional view of the target 8 viewed from the longitudinal direction D1.

  The protrusion 8 c of the target 8 has a cross-sectional shape that curves so as to protrude convexly toward the beam transport path 12 side along the irradiation axis A when viewed from the longitudinal direction D1. Curvature means smoothly curved and not linear.

  Further, the projecting portion 8c of the target 8 has a shape extended so that the cross-sectional shape is continuous along the longitudinal direction D1. Thus, the protrusion 8c has a curved arch-like shape with a radius of curvature that can ensure sufficient strength. Even when the projection 8c of the target 8 is cut at any position in the longitudinal direction D1, it has the same cross-sectional shape when viewed from the longitudinal direction D1. However, depending on the position in the longitudinal direction D1, the shape (size, radius of curvature, etc.) of the protrusion 8c may be different.

  Moreover, the both ends in the longitudinal direction D1 of the protrusion part 8c are sealed by the side wall part 8e. In addition, as shown in FIG. 4, the protrusion part 8c has comprised the rectangular shape extended along the longitudinal direction D1.

  The protrusion 8 c may protrude in a range covering at least a scanning range of the charged particle beam scanning unit 13, that is, a range to which the charged particle beam L is irradiated. The protrusion 8c has a front surface 8a and a back surface 8b. The surface 8 a is a surface on the side of the flanged short pipe 17. When the charged particle beam L passes through the flanged short tube 17, the surface 8a is irradiated. The target 8 generates a neutron beam N when irradiated with the charged particle beam L. The back surface 8 b is a surface in contact with the cooling plate 18 by the cooling water. The neutron beam N generated from the target 8 is emitted from the back surface 8 b of the protrusion 8 c. The back surface 8b may be subjected to anodizing treatment for corrosion protection.

  The protrusion 8c has both the front surface 8a and the back surface 8b protruding. The back surface 8b protrudes so as to follow the protruding shape of the surface 8a. In the present embodiment, the front surface 8a and the back surface 8b are separated such that the thickness of the protruding portion 8c is substantially constant. Here, the thickness of the protrusion 8c is the shortest distance from an arbitrary point on the surface 8a to the back surface 8b, that is, the thickness of the protrusion 8c. Hereinafter, this is simply referred to as "plate thickness".

  The plate thickness of the protruding portion 8c may be equal to or less than the maximum thickness (predetermined value) through which the charged particle beam L can pass. For example, the thickness may be such that the thickness (hereinafter simply referred to as “irradiation thickness”) of the protrusion 8 c in the irradiation direction of the charged particle beam L is equal to or less than the range of the charged particle beam L. However, the protrusion amount of the protrusion 8 c is an amount that can sufficiently ensure structural strength in relation to the thickness of the target 8.

  The shape of the projecting portion 8c as viewed in the longitudinal direction D1 is not limited to the above-described shape as long as the structural strength is satisfied. For example, it may be a semi-elliptic body, a polygonal shape or the like. In addition, the projecting portion 8c can have various shapes such as an ellipse and an oval when viewed from the irradiation direction.

  The flange portion 8 d extends so as to extend around the entire circumference of the projecting portion 8 c. In the present embodiment, when viewed from the irradiation direction, the projecting portion 8c has a rectangular shape extending in the longitudinal direction D1, so the flange portion 8d has a rectangular frame shape extending in the longitudinal direction D1 in accordance with the projecting portion 8c. It has the shape of The seal portion 50 can be arranged on the flange portion 8 d so as to surround the entire circumference of the projecting portion 8 c. The flange portion 8 d is attached so as to be sandwiched between the flanged short pipe 17 and the cooling plate (cooling portion) 18.

  The cooling plate 18 is formed of copper (Cu) or graphite. The cooling plate 18 has a main body portion 28 and a pair of projecting portions 29 and 30 provided at opposing positions so as to sandwich the main body portion 28. The main body portion 28 has a front surface 18 a and a back surface 18 b. The main body 28 includes a protrusion 18 c and a flange 18 d. The protrusion 18 c is shaped to be in contact with the protrusion 8 c of the target 8 on the surface 18 a side. A groove 24 through which the cooling water passes is formed on the surface 18 a side of the protrusion 18 c. That is, the cooling plate 18 is a cooling plate having a cooling passage through which a cooling medium (for example, cooling water) flows so as to be in contact with the target 8.

  The groove 24 which constitutes the cooling passage of the cooling medium of the cooling plate 18 constitutes a wide space extending in the longitudinal direction D1 and the transverse direction D2. Further, in the grooves 24 of the cooling passage, the length L2 in the short direction is smaller than the length L1 in the longitudinal direction D1. Although the grooves 24 extending in both the longitudinal direction D1 and the lateral direction D2 are formed in this embodiment, the invention is not limited to this as long as the target 8 can be cooled.

  The flange portion 18 d of the cooling plate 18 is shaped such that a portion thereof is in contact with the flange portion 8 d of the target 8 on the surface 18 a side. The flange portion 8d of the target 8 is sandwiched and fixed between the flange portion 18d and the flanged short pipe 17. The lid portion 42 is bolted on the back surface 18b side of the flange portion 18d. The lid portion 42 has a shape corresponding to the shapes of the main body portion 28 and the projecting portions 29 and 30. The lid 42 is attached to close the introduction groove 25 and the discharge groove 26. The lid portion 42 forms an introduction passage of the cooling water in the introduction groove 25, and forms a discharge passage of the cooling water in the discharge groove 26. The cooling plate 18 and the lid 42 may be integrally formed.

  An introduction hole 36 communicating with the introduction groove 25 is formed in the lower overhanging portion 29 of the pair of overhanging portions 29 and 30 of the cooling plate 18. Furthermore, the overhanging portion 29 is connected to the upstream pipe 38 laid for the introduction of the cooling water through both flange pipes 37. Further, a discharge hole 39 communicating with the discharge groove 26 is formed in the upper overhang portion 30. The overhanging portion 30 is connected via a flange tube 40 to a downstream pipe 41 laid for discharging the cooling water.

  Next, the layer configuration of the target 8 will be described with reference to FIG. The target 8 includes a first layer 8A and a second layer 8B from the upstream side to the downstream side in the irradiation direction of the charged particle beam L. Further, the hydrogen storage performance of the second layer 8B is higher than that of the first layer 8A. By enhancing the hydrogen storage performance of the second layer 8B on the side to be cooled, even if hydrogen is generated on the back surface side of the target 8, the second layer 8B can store hydrogen. Specifically, as described above, beryllium (Be), lithium (Li), tantalum (Ta) or tungsten (W) may be employed as the first layer 8A. A material containing Ti may be employed as the second layer 8B. For example, Ti-6Al-4V may be employed. The material also contributes to the improvement of the strength of the target 8 because the material also has high tensile strength. Alternatively, a barber foil (SUS alloy) may be employed as the second layer 8B.

  FIG. 7 is a graph showing the relationship between the thickness of the first layer 8A and the second layer 8B and the position of the Bragg peak of the charged particle beam L. As shown in FIG. For example, when the thickness of the first layer 8A is t1 and the thickness of the second layer 8B is "t2-t1", the position P of the Bragg peak is in the cooling medium on the back side of the target 8 . In this case, the generation of hydrogen inside the target 8 can be suppressed. On the other hand, even if the thickness of the first layer 8A is t1 and the thickness of the second layer 8B is "t3-t1", the position P of the Bragg peak is the position of the second layer 8B. Therefore, even if hydrogen is generated in the target 8, it can be absorbed by the second layer 8B.

  Next, the operation and effects of the neutron capture therapy apparatus 1 and the target 8 in the present embodiment will be described.

  In the neutron capture therapy apparatus 1 according to the present embodiment, the target 8 has a cross-sectional shape projecting along the irradiation axis A when viewed from the longitudinal direction D1 orthogonal to the irradiation axis A of the charged particle beam L It has a shape extended so that the cross-sectional shape is continuous along the longitudinal direction D1. According to the shape, the Bragg peak of the charged particle beam L can be reduced to the downstream side of the target 8 or the Bragg peak in the target can be suppressed because the target can be thinned while securing the strength of the target 8 (here In the second layer). Therefore, the occurrence of blistering in the target 8 can be suppressed. Moreover, since the area of the target 8 can be increased, the irradiation area of the neutron beam N can be increased. Furthermore, since the area of the target 8 can be increased without increasing the curvature of the target 8, it is possible to secure the strength while increasing the area. As mentioned above, the irradiation area of the neutron beam N can be enlarged, securing intensity | strength, suppressing generation | occurrence | production of the blistering in the target 8. FIG. Moreover, by enlarging the area of the target 8, the irradiation field at the time of irradiating the neutron beam N to a patient can be taken widely.

  Further, in the neutron capture therapy apparatus 1 according to the present embodiment, the target 8 includes the first layer 8A and the second layer 8B from the upstream side to the downstream side in the irradiation direction of the charged particle beam L. . Further, the hydrogen storage performance of the second layer 8B is higher than that of the first layer 8A. In this case, even if hydrogen is generated in the target 8, the occurrence of blistering can be suppressed by storing hydrogen in the second layer 8B having high hydrogen storage performance.

  Further, in the neutron capture therapy apparatus 1 according to the present embodiment, a cooling plate 18 for cooling the target 8 by flowing a cooling medium is provided downstream of the target 8 in the irradiation direction of the charged particle beam L. The grooves 24 constituting the cooling passage of the cooling medium of the cooling plate 18 extend in the irradiation direction and the short direction D2. In this case, since the cooling passage can be made wider, cooling water is present on the back side (downstream side) of the portion of the target 8 to which the charged particle beam L is irradiated, and hydrogen is captured by the cooling water. It becomes possible to collect and to suppress the occurrence of blistering.

  Further, the target 8 according to the present embodiment is a target that causes a nuclear reaction by irradiation of the charged particle beam L to generate a neutron beam N, and when viewed from the longitudinal direction D1, the irradiation axis A is It has a cross-sectional shape protruding along the extending direction, and has a shape extended so that the cross-sectional shape is continuous along the longitudinal direction D1.

  According to the target 8 according to the present embodiment, the same operation and effect as those of the above-described neutron capture therapy apparatus 1 can be obtained.

  In the above embodiment, the projection 8 c of the target 8 projects toward the beam transport path 12. However, the projection 8 c may project to the opposite side of the beam transport path 12.

  In the above embodiment, the target 8 is configured of the first layer and the second layer, but may be configured in more layers. Alternatively, it may be composed of a single layer.

  The longitudinal direction and the lateral direction of the target may be reversed, and the target may be square.

DESCRIPTION OF SYMBOLS 1 ... Neutron capture therapy apparatus, 8 ... target, 8A ... 1st layer, 8B ... 2nd layer, 11 ... accelerator, 18 ... Cooling plate (cooling part), 24 ... groove (cooling passage), A ... Irradiation axis .

Claims (4)

A neutron capture therapy apparatus for irradiating an irradiated body with neutrons, comprising:
An accelerator that accelerates charged particles and emits charged particle beams;
A target for generating a neutron beam by being irradiated with the charged particle beam emitted from the accelerator;
A mounting unit on which the irradiation target to which the neutron beam is irradiated is mounted;
The target is
When viewed from a first direction orthogonal to the irradiation axis of the charged particle beam, it has a cross-sectional shape projecting or recessed along the irradiation axis,
A neutron capture therapy device, wherein the cross-sectional shape is extended so as to be continuous along the first direction. The target includes a first layer and a second layer in order from the upstream side to the downstream side in the irradiation direction of the charged particle beam,
The neutron capture therapy device according to claim 1, wherein the hydrogen storage capacity of the second layer is higher than that of the first layer. In the irradiation direction of the charged particle beam, a cooling unit for cooling the target by flowing a cooling medium is provided downstream of the target,
The cooling passage of the cooling medium in the cooling unit is
While extending in the first direction, and extending in a second direction orthogonal to the irradiation direction and the first direction,
The length in the first direction is greater than the length in the second direction,
The neutron capture therapy device according to claim 1 or 2. It is a target for neutron capture therapy that generates neutrons by being irradiated with charged particle beams,
When viewed from a predetermined direction, it has a cross-sectional shape projecting or recessed along a direction orthogonal to the predetermined direction,
A target for neutron capture therapy, wherein the cross-sectional shape is extended so as to be continuous along the predetermined direction.

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