TWI442412B - Target device - Google Patents

Description

Target device

The present invention relates to a target device having a target that will generate neutrons upon exposure to accelerated particles such as protons.

In the field of cancer treatment and the like, radiation therapy is highly evaluated. In particular, neutron capture Therapy (NCT: Neutron Capture Therapy) is particularly attractive for its selective treatment of cell size. In NCT therapy, a stable isotope is pre-injected into cancer cells to be treated, and this stable isotope will have a very short range and high LET (Linear Energy Trasfer) when exposed to neutrons. Heavy charged particles, etc. Then, the neutrons are irradiated again to selectively destroy only the cancer cells by utilizing the scattering of the heavily charged particles. The stable isotope system used in NCT therapy can react with neutrons to produce elements of ¹⁰ B, ⁶ Li, which are highly charged particles of high LET. For neutrons, the element has a large reaction cross-sectional area. Energy neutrons. For the time being, NCT therapy uses ¹⁰ B as well as thermal neutrons and thermal external neutrons, so it is also known as boron neutron capture therapy (BNCT: Boron NCT).

Patent Document 1 discloses a device for generating neutrons used in NCT therapy or the like. This device illuminates the target with accelerated particles to produce neutrons. When the target is used to generate neutrons, the target is irradiated with accelerated particles of very high energy intensity, so it is necessary to suppress the rise in temperature. Therefore, most of its structures are used: a heat pipe made of copper or the like, a copper pipe through which cooling water flows, and the like are disposed so as to be in close proximity to the target, thereby suppressing the temperature rise of the target.

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2006-338945

However, in the conventional device, if the accelerating particles are accumulated in the target, hydrogen gas is generated in the target, which causes a problem of the so-called "surface expansion crack phenomenon". In addition, if the thickness of the target is made thin in order to suppress the surface swelling phenomenon (Blistering) in the target, the accelerated particles after passing through the target are copper for the heat pipe and the cooling water. The surface expansion crack phenomenon is caused by the tube and the like, and as a result, the same problem still exists. Therefore, it is difficult to suppress the occurrence of the surface expansion crack phenomenon in the target.

The present invention has an object of solving the above-described technical problems, and an object of the invention is to provide a target device which can easily suppress the occurrence of a surface expansion crack phenomenon in a target.

The target device of the present invention is characterized in that it is provided with a solid target composed of a substance which generates neutrons after being irradiated by the accelerated particles, and a cooling unit for contacting the target. The cooling unit is formed with a groove that is closed by the target and through which the cooling water passes.

According to the target device of the present invention, since the flow path of the cooling water which can absorb heat from the target is placed in contact with the target, the cooling water can be used to capture the accelerated particles immediately after passing through the target. Therefore, in addition to suppressing the occurrence of the surface expansion crack phenomenon in the target, it is possible to reduce the occurrence of surface expansion cracking phenomenon caused by the acceleration of the particles entering other metal members and the like. As a result, according to the present invention, it is possible to easily suppress the occurrence of the surface expansion crack phenomenon in the target.

In addition, the target is flat, and the thickness of the target is to accelerate the thickness of the particles, that is, to reduce the necessary neutron production and to accelerate the penetration of the particles. The thickness of the target plate is made to ensure the necessary amount of neutron production and to allow the accelerated particles to penetrate the target, thereby effectively suppressing the occurrence of surface expansion and fissure.

Further, the flange portion for forming a vacuum region through which the accelerated particles pass, the one end portion formed at the end portion of the tubular portion, and the flange portion for contacting the target portion are provided to press the flange portion toward the cooling portion side Preferably, the target is sandwiched between the flange portion and the cooling portion. Since the cooling water flow path formed in the groove of the cooling portion is isolated from the vacuum region in the cylindrical portion, the cooling water does not leak into the vacuum region and thus the degree of vacuum is lowered. Therefore, it is possible to prevent the acceleration of the particles from being irradiated to the target and suppress the occurrence of the surface expansion crack phenomenon in the target.

Further, the connection portion has a screw hole formed in the cooling portion and a bolt portion that passes through the flange portion and is screwed into the screw hole, and a clearance fitting hole through which the bolt portion can be inserted is formed in the target portion. It is appropriate. Even if the target thermally expands as the temperature rises, the amount of expansion of the target can be absorbed by the gap between the clearance fitting hole and the bolt portion, thereby preventing the vacuum caused by the misalignment of the target. Reduced vacuum in the field or leakage of cooling water.

The cooling portion has a plate shape, has a surface on one side in contact with the target, and a surface on the other side of the back side of the one side surface; the other side surface is formed with: a groove An introduction groove for introducing cooling water into the groove, and a discharge groove for communicating the cooling water from the groove, and further comprising: being mounted on the other side of the cooling portion The lid portion of the surface is preferably used for occluding the introduction groove and the discharge groove. The introduction path of the cooling water is provided in the introduction groove formed on the other surface of the cooling unit, and the discharge path is provided in the discharge groove. Therefore, it is not necessary to provide another piping or the like to the side of the cooling unit in order to provide the introduction path and the discharge path, so that the obstacle can be reduced. As a result, when the target device approaches the neutron reduction device (also referred to as "reducer") from the cooling portion side, it is not easily hindered, so that the target and the neutron reduction device can be further brought closer. Therefore, the loss of the neutron generated from the target as a low-energy neutron when irradiated to the patient can be reduced.

According to the present invention, it is possible to easily suppress the occurrence of the surface expansion crack phenomenon in the target.

[Best way to implement the invention]

The preferred embodiment of the target device of the present invention will now be described with reference to the drawings. Fig. 1 is a side view of a BNCT apparatus including a target device of the present embodiment. Figure 2 is a cross-sectional view of the target device. Fig. 3 is a cross-sectional view taken along line III-III of Fig. 2; Fig. 4 is a cross-sectional view taken along line IV-IV of Fig. 2; Fig. 5 is a cross-sectional view showing an enlarged upper portion of a target mounted on a target device. In the description of the drawings, the same or equivalent elements are denoted by the same reference numerals, and the repeated description thereof is omitted.

As shown in Fig. 1, the BNCT apparatus 1 is a device for treating cancer or the like using neutron capture therapy (NCT: Neutron Capture Therapy). The BNCT apparatus 1 includes a treatment table 3 for the patient to ride while performing treatment, and a high-speed proton (hereinafter referred to as "proton line") L (refer to FIG. 2) manufactured by the centrifugal accelerator. A target device 5 for generating neutrons; a neutron reduction device (also referred to as a "reducer") 7 that illuminates the patient by decelerating the neutron N generated by the target device 5 into a low-energy neutron. The proton line L corresponds to the accelerated particles.

As shown in FIGS. 2 to 5, the target device 5 is detachably attached to the end portion of the particle beam guide 9 that is laid to be connected to the centrifugal accelerator. The target device 5 is composed of a target 10 that will generate neutron N after being irradiated by the proton line L, and a target support 11 for holding the target 10. The target 10 is formed into a disk shape, and the target holder 11 has a flanged short tube (tube portion) 13 for holding the target 10 and a cooling plate (cooling portion) 15. The flanged short tube 13 is fixed to the particle beam guide 9. The proton line L after passing through the flanged short tube 13 will illuminate the end face 10a on one side of the target 10. When the target 10 is irradiated with the proton beam L, neutrons will be generated, and these neutrons will be released from the back surface 10b of the target 10, that is, the end face side of the other side in contact with the cooling plate 15. On the back surface 10b of the target 10, there is an anodizing treatment which acts to prevent corrosion.

The cooling plate 15 is formed of copper (Cu) or graphite. On the side of the end face 15a of one side of the cooling plate 15 which is in contact with the target 10, a plurality of spiral grooves 17 through which the cooling water W can pass are formed (refer to Fig. 4). Further, on the back side of the end surface 15a of one of the cooling plates 15, that is, on the other end surface 15b side, an introduction groove 19 for introducing the cooling water W (refer to FIG. 5) is formed and used. The discharge groove 21 of the cooling water is discharged.

The spiral groove 17 is formed by drawing a spiral from the center of the cooling plate 15 toward the outside ("planar curve" is also referred to as "scroll line"). The flow path cross section of the spiral groove 17 is substantially the same. Further, the plurality of spiral grooves 17 do not intersect each other, but are integrated at substantially the center of the cooling plate 15, and communicate with the introduction groove 19 on the back side via the center hole 23. Further, the outer end portion of the spiral groove 17 communicates with the discharge groove 21 on the back side via the through hole 25. The cooling water W passes through the introduction groove 19, passes through the center hole 23, and is divided into four spiral grooves 17. Further, the cooling water W passes through the through hole 25 from the outer end portion of the spiral groove 17, and then flows together and is discharged through the discharge groove 21 on the back side. In the present embodiment, the length of the flow path of the cooling water W is not secured by the single spiral groove 17, but the cooling water W is branched into a plurality of spiral grooves 17 to ensure the length of the flow path of the cooling water W. In comparison with the case of only one spiral groove 17, the pressure loss can be reduced.

The cooling plate 15 has a substantially circular main body portion 27 corresponding to the shape of the target 10, and projecting portions 28 and 29 which are disposed at the upper and lower opposing positions with the main body portion 27 interposed therebetween. The aforementioned spiral groove 17 is formed in the main body portion 27. Among the pair of protruding portions 28 and 29, an introduction hole 31 that communicates with the introduction groove 19 is formed in the lower protruding portion 28. Further, the protruding portion 28 is connected to the upstream pipe 33 for introducing the cooling water W by interposing the double flanged pipe 32. Further, a discharge hole 35 that communicates with the discharge groove 21 is formed in the protruding portion 29 located on the upper side. The protruding portion 29 is connected to the downstream pipe 37 for discharging the cooling water W by interposing the double flange pipe 36.

On the back surface of the cooling plate 15, a lid portion 39 having a shape corresponding to the shape of the main body portion 27 of the cooling plate 15 and the two protruding portions 28, 29 is fixed by bolts. The lid portion 39 is attached so that the introduction groove 19 and the discharge groove 21 can be closed, and an introduction path for the cooling water W is formed in the introduction groove 19, and a discharge path for the cooling water W is formed in the discharge groove 21. Further, it is also possible to form the cooling plate 15 and the lid portion 39 integrally.

The target 10 is sandwiched by a flanged short tube 13 and a cooling plate 15. The target 10 is arranged to abut against the body portion 27 of the cooling plate 15, and all of the spiral grooves 17 are closed. As shown in Fig. 5, at the edge of the target 10, a plurality of clearance fitting holes (also referred to as "recessed holes", "through holes" or "plug-in" are formed at equal intervals along the outer circumference. Hole") 10c. The clearance fitting hole 10c is a hole (insertion hole) having an inner diameter larger than the diameter of the bolt (bolt portion) 43, as long as the bolt 43 can be inserted.

A flange portion 41 is provided at both ends of the flange-attached short tube 13, and one of the flange portions 41 is formed with a plurality of clearance fitting holes that can correspond to the clearance fitting hole 10c of the target 10. 41a. On the other hand, the cooling plate 15 is formed with a plurality of screw holes 15d corresponding to the clearance fitting holes 10c of the target 10. The bolt 43 inserted from the clearance fitting hole 41a of the flange portion 41 is inserted into the clearance fitting hole 10c of the target 10, and then screwed to the screw hole 15d of the cooling plate 15. By locking a plurality of bolts 43, the flange portion 41 can be used to urge the target 10 toward the side of the cooling plate 15, and the target 10 is held between the flange portion 41 and the cooling plate 15 to be held by the flange portion 41. The status is fixed. The joint portion 44 is configured by the bolt 43 and the screw hole 15d. Further, an annular groove 47 is formed in the flange portion 41 for mounting the sealing member 45 to hermetically seal the inside of the flanged short pipe 13. Further, an annular groove 51 is formed in the cooling plate 15 for mounting the sealing member 49, and this sealing member 49 is airtight to prevent the cooling water W from leaking out.

The target 10 is composed of beryllium (Be). When it is irradiated with 2 (mA), 30 (MeV) proton beam L, it is necessary to discharge 60 kW of heat. If it cannot efficiently dissipate heat, it will be There will be melting concerns. The target 10 of the present embodiment is arranged such that all of the spiral grooves 17 of the cooling plate 15 can be closed, and a flow path of the cooling water W is formed in the spiral groove 17, so that cooling in contact with the target 10 is formed. The flow path of water W. As a result, the target 10 can be directly cooled by the cooling water W, and the heat removal efficiency of the target 10 can be improved.

When the proton line L is irradiated onto the target 10, the air in the particle beam conduit 9 and the flanged short tube 13 is removed in advance to form a vacuum region V (please refer to FIG. 2). In the present embodiment, the flanged short tube 13 and the cooling plate 15 are arranged to sandwich the target 10, so that the vacuum region V in the flanged short tube 13 and the cooling formed in the cooling plate 15 The flow path of the water W is completely isolated by the target 10. Therefore, the cooling water W does not leak into the flanged short tube 13 and the degree of vacuum in the vacuum region V can be prevented from being lowered.

Further, the target 10 becomes a high temperature due to the irradiation of the proton line L, and a thermal expansion phenomenon occurs. In particular, since the target 10 is in the form of a plate, the degree of expansion toward the plate-like expansion direction will be greater than that toward the plate thickness direction of the target 10. In the present embodiment, the target 10 is fixed by locking the bolt 43, but the bolt 43 is simply inserted into the clearance fitting hole 10c of the target 10, and the bolt 43 is fitted into the clearance. There is still a slight gap (recess) between the inner faces of the holes 10c. Even if the target 10 expands due to thermal expansion, it is absorbed by this gap, so that a decrease in the degree of vacuum due to the misalignment of the target 10 or a leakage of the cooling water W can be prevented.

As shown in FIG. 1, the neutron reduction gear 7 is provided with a cylindrical target accommodating portion 7a that is opened to accommodate the target device 5. The neutron reduction gear 7 is movable in the front-rear direction, and the target device 5 fixed to the particle beam guide 9 can be housed in the target storage portion 7a. The neutron reduction gear 7 accommodates the target device 5 from the side of the cooling plate 15 . The spiral groove 17 for introducing the cooling water W into the cooling plate 15 and the flow path for discharging the cooling water W are constituted by the introduction groove 19 and the discharge groove 21 formed in the cooling plate 15. Therefore, it is not necessary to separately provide a piping for introducing or discharging the cooling water W on the outer periphery of the cooling plate 15, and there are few obstacles. When the neutron reduction gear 7 is moved to load the target device 5 into the target accommodating portion 7a, since there is no obstacle, the target 10 can be further brought closer to the neutron reduction device 7. As a result, the neutron generated by the target 10 is decelerated into a low-energy neutron by the neutron deceleration device 7, and the loss when the low-energy neutron is irradiated to the patient is reduced.

The energy intensity of the proton line L irradiated to the target 10 is about 30 (MeV). If the proton line L remains in the target 10, it will be converted into hydrogen gas (H ₂ ), thereby causing a surface expansion crack phenomenon. However, the plate thickness D of the target 10 is such a thickness that the desired neutron generation amount can be prevented and the proton line L can be penetrated, so that the occurrence of the surface expansion crack phenomenon in the target 10 can be suppressed. The thickness through which the proton line L can penetrate differs depending on the material of the target 10 and the energy intensity of the proton line L to be irradiated. In the present embodiment, the proton line L is only 5.8 (mm) or less in terms of its flying distance. The thickness of the plate can be penetrated. Since the fly distance is an unequal distribution value of about ±0.3 mm, if the unequal distribution value is taken into consideration, the penetrable thickness of the proton line L in the present embodiment becomes an unequal distribution value range. Below the lower limit, that is, 5.8-0.3 = 5.5 (mm) or less. On the other hand, if the plate thickness D of the target 10 is thinner, the energy lost as the neutron is generated becomes larger. Therefore, in the present embodiment, the thickness D of the target 10 is 5.5 mm. By setting the plate thickness D of the target 10 to 5.5 mm, a loss of 3% is generated. Such a degree of leakage, for example, is only a loss of about 3% with respect to a regular treatment time of about 20 minutes, which is equivalent to about 0.6 minutes, and it is only necessary to extend the treatment time slightly, so that it can be judged to be minute. difference.

The protons that have penetrated the target 10 are mainly captured by the cooling water W in the spiral groove 17. Even if the proton line L is caught in the cooling water W, the surface expansion crack phenomenon does not occur. Therefore, it is difficult for the proton line L after penetrating the target 10 to cause a problem of a so-called surface expansion crack phenomenon in other metal members and the like. As a result, the target 10 can be easily suppressed to a level below the proton-permeable thickness, and the occurrence of surface expansion cracking in the target 10 can be reduced.

The present invention has been specifically described above based on the embodiments of the present invention, but the present invention is not limited to the above embodiments.

The target 10 is not limited to the use of beryllium (Be), and tantalum (Ta) or the like may also be used. Further, the permeable thickness of the target 10 varies depending on the material used for the target 10 and the energy of the accelerated particles to be irradiated, and can be appropriately selected and used. For example, in the case of the target 10 composed of tantalum (Ta), in the case of irradiating the proton line L of energy intensity of about 30 (MeV), the thickness that can be penetrated becomes 1.2 (mm).

10. . . Target

10c. . . Clearance fitting hole formed on the target

13. . . Short tube with flange (tube)

15. . . Cooling plate (cooling section)

15d. . . a threaded hole formed in the cooling plate

17. . . Spiral groove

19. . . Leading groove

twenty one. . . Drainage

39. . . Cover

41. . . Flange portion of flanged short tube

43. . . Bolt (bolt part)

44. . . Conclusion department

L. . . Proton line

D. . . Target thickness

V. . . Vacuum field

W. . . Cooling water

Fig. 1 is a side view showing a BNCT apparatus in which a target device according to an embodiment of the present invention is mounted.

Fig. 2 is a cross-sectional view showing a target device of the present embodiment.

Fig. 3 is a cross-sectional view taken along line III-III of Fig. 2;

Fig. 4 is a cross-sectional view taken along line IV-IV of Fig. 2;

Fig. 5 is a cross-sectional view showing an enlarged upper portion of a target mounted on a target device.

5. . . Target device

9. . . Particle beam catheter

10. . . Target

10a. . . Clearance fitting hole formed on the target

10b. . . The back of the target 10

11. . . Target support

13. . . Short tube with flange (tube)

15. . . Cooling plate (cooling section)

15a. . . An end face of one side of the cooling plate 15 that is in contact with the target 10

15b. . . The back side of the end face 15a of one of the cooling plates 15

17. . . Spiral groove

19. . . Leading groove

twenty one. . . Drainage

twenty three. . . Central hole

28. . . Protruding

29. . . Protruding

31. . . Import hole

32. . . Double flange tube

33. . . Upstream tube

35. . . Drain hole

36. . . Double flange tube

37. . . Downstream tube

39. . . Cover

L. . . Proton line

V. . . Vacuum field

N. . . neutron

Claims (3)

A target device comprising: a solid target composed of a substance that generates neutrons after being irradiated by the accelerated particles; and a cooling portion in contact with the target; and the acceleration is formed a cylindrical portion of a vacuum region through which the particles pass; and a flange portion formed at one end of the tubular portion for contacting the target; and a flange portion for pushing the flange portion toward the cooling portion side to a target portion that is fixed between the flange portion and the cooling portion, and the cooling portion has a groove that is formed on a surface contacting the target and is closed by the target and that allows cooling water to pass therethrough. The connection portion includes a screw hole formed in the cooling portion, and a bolt portion penetrating the flange portion and screwed into the screw hole; and the target system is formed with a clearance fitting hole through which the bolt portion is inserted . The target device according to claim 1, wherein the target is a flat plate, and a plate thickness of the target is a thickness through which the accelerated particles can penetrate. The target device according to claim 1 or 2, wherein the cooling unit has a plate shape, and has a surface on one side in contact with the target and a back side on a side of the one side. One side of the face, On the other side surface, an introduction groove communicating with the groove for introducing the cooling water into the groove, and a communication groove communicating with the groove for discharging the cooling water from the groove are formed And a cover portion attached to the other side surface of the cooling unit for closing the introduction groove and the discharge groove.