JP2007101193A - Radioisotope manufacturing device and target recycling method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radioisotope manufacturing device for performing stable supply with a high yield and also lengthening the useful life of a target, as to a radioisotope manufacturing device used for performing PET diagnosis for cancer examination and metabolism test on a brain or a heart. <P>SOLUTION: This target 20 is filled with material water W, which generates a radioisotope when irradiated with an ion beam R accelerated by an accelerator. This target 20 comprises a transmitting foil 22 forming a boundary between a vacuum domain U and the material water W while transmitting the ion beam, and a body substrate 24 for forming a space S filled with the material water W together with the transmitting foil 22. The body substrate 24 and the transmitting foil 22 are characterized in that their space S side surfaces are made of at least one noble metal material selected from a group comprising gold, platinum, and radium. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a radioisotope production apparatus for producing a radiopharmaceutical to be injected into a patient in cancer screening or PET diagnosis for examining brain and heart metabolism, and in particular, a raw material for obtaining ¹⁸ F radioisotope. ^This is a technique related to a target that encloses ¹⁸ O concentrated water (raw water) and is irradiated with an ion beam (proton beam).

^{18 F} radioisotope (hereinafter referred to as F-18) using positron emission, diagnosis by tomographic patients (hereinafter, PET (Positron Emission Tomography) of diagnosis) by implementing, enables effective cancer diagnosis It is known that For this reason, PET diagnosis has begun to be used in many fields in the nuclear medicine field in Japan in addition to the United States and Europe.
Radiopharmaceuticals including F-18 to be injected into a patient irradiate a target enclosing ¹⁸ O water (hereinafter referred to as O-18 water (raw water)) with an ion beam obtained by accelerating hydrogen ions with an accelerator. ¹⁸ O (p, n) ¹⁸ F reaction.
Radioisotope production capable of stably supplying F-18 in a high yield as the number of hospitals and medical centers that introduce PET diagnostic equipment in response to the increasing needs of PET diagnosis has increased in recent years. A device is sought.

  By the way, in order to improve the yield of F-18, it is conceivable to increase the output of the ion beam irradiated to the target. However, when the output of the ion beam is increased, a part of O-18 water (raw material water) is vaporized and boils, so that voids (bubbles) are formed. When many such voids are generated inside the target or grow large, O-18 water (raw water) that cannot be subjected to beam irradiation due to being pushed away by the voids increases, so that the concentration of F-18 is increased. There arises a problem that the rate decreases.

This problem is particularly prominent when using a thin target with a reduced capacity by reducing the space in which O-18 water is sealed for the purpose of reducing the amount of expensive O-18 water (raw water) used. .
That is, when O-18 water (raw material water) boils inside the target and vapor voids are generated, its diameter may be larger than the width of the space inside the target. It may pass through the region where O-18 water (raw water) does not exist without participating in any reaction.
In particular, O-18 water is excluded in the partial region of the target space where the central portion of the ion beam having high energy is irradiated, and not only the energy of the ion beam is effectively used but also the yield of F-18 is reduced. The problem is that it contributes greatly.

In order to prevent the yield of F-18 from being lowered in this way, the conventional target uses O-18 water (raw material water) that has been heated using silver, niobium material, aluminum, or the like having a high thermal conductivity. ) Cooling characteristics, or pressurizing O-18 water enclosed in a space with Ar or He gas to raise its boiling point to 200 ° C. or higher. Efforts have been made to reduce the generation as much as possible.
US Pat. No. 5,917,874 (second row, pages 56-58, FIG. 3)

However, it is impossible to completely prevent the occurrence of voids in the O-18 water (raw water) sealed in the target. For this reason, if the silver or niobium material on the space wall surface is exposed to water vapor in the void and is irradiated with an ion beam for a long time, the wall surface corrodes (oxidizes) and elutes in O-18 water. As a result, fine particles are deposited.
As described above, when the oxidation reaction by water vapor on the space wall surface inside the target proceeds, the decomposition (reduction) of water proceeds as a side reaction at the same time, and a new decomposition gas (hydrogen gas) is generated. As a result, voids were further grown, and the reduction in the yield of F-18 was spurred, and the target pressure rapidly increased, making it difficult to continue ion beam irradiation.

  In addition, conventional targets composed of silver and niobium materials often require maintenance to smooth the surface by rubbing the surface with an abrasive to remove corrosion products (fine particles) that have accumulated on the surface due to corrosion. There is a problem that the target needs to be worn and the life is shortened due to wear of the target. Moreover, when this corrosion product accumulates in the piping which takes out O-18 water, the piping was clogged.

  An object of the present invention is to solve the above-mentioned problems and to stably supply a radioisotope in a high yield by improving the material constituting the target enclosing the radioisotope raw material water. An object of the present invention is to provide a radioisotope production apparatus which can be used and has a long target life.

  In order to solve the above-described problems, the present invention provides a radioisotope manufacturing apparatus, an ion source for emitting an ion beam, an accelerator having a vacuum region in which the ion beam emitted from the ion source is accelerated, and an acceleration A target in which raw water that generates a radioisotope is enclosed when irradiated with the ion beam, and the target forms a boundary between the vacuum region and the raw water and transmits the ion beam. And a body substrate that forms a space in which the raw water is enclosed together with the transmission foil, and the body substrate is made of at least one noble metal material selected from the group consisting of gold, platinum, and palladium. It is characterized by that.

  Since the present invention has such a configuration, the wall surface in contact with the raw water sealed in the target is made of a noble metal material having high corrosion resistance against water vapor. Thereby, since a void does not grow large in raw material water, raw material water can receive irradiation of an ion beam over the whole.

  According to the present invention, when producing a radiopharmaceutical for use in PET diagnosis, even if the raw material water (O-18 water) sealed in the target is irradiated with an ion beam, the radioisotope is stably produced in a high yield. A radioisotope manufacturing apparatus that can be supplied and has a long target life is provided.

A radioisotope production apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings as appropriate.
As shown in FIG. 1, a radioisotope production apparatus 10 of this embodiment includes an ion source 11, a radio frequency quadrupole linear accelerator (hereinafter referred to as RFQ) 12a, a drift tube linear accelerator (Drift). Tube Linac (hereinafter referred to as DTL) 12b and target 20. The accelerator 12 in the present invention is formed by a combination of the RFQ 12a and the DTL 12b.

The ion source 11 serves to ionize a source material (in this case, hydrogen gas) that becomes ions and extract it as a positive ion beam R, and around the ion source 11 selectively extracts only desired ions by mass. An electrostatic lens (not shown) that shapes the magnet and the ion beam R, an ion beam generation unit, and the like are provided.
As the ion source 11, a hot cathode type duoplasmatron type ion source or a PIG type ion source can be used. A microwave discharge ion source that can generate a large current with a long lifetime can also be used.

The RFQ 12a is provided at the subsequent stage of the ion source 11, and accelerates the ion beam R emitted from the ion source 11 to a predetermined energy. A vacuum chamber having a wavy quadrupole electrode is provided inside the RFQ 12a. The quadrupole electrode forms a quadrupole electric field in a direction perpendicular to the traveling direction of the ion beam R, and the ion beam R is accelerated while being focused.
In place of the RFQ 12a used here, a multi-electrode type high-frequency accelerator having an even number of magnetic poles of six or more poles may be used, and other high-frequency accelerators may be used.

The DTL 12b receives the ion beam R accelerated by the RFQ 12a and further accelerates it. A plurality of drift tubes 14 are arranged in the axial direction at the center inside the DTL 12b. A quadrupole electromagnet (not shown) is incorporated in the drift tube 14, and the ion beam R is converged when passing through the drift tube 14. The ion beam R is accelerated between the drift tubes 14 and 14.
Such RFQ 12a and DTL 12b are combined to function as a linear accelerator (accelerator) 12 that finally generates an ion beam R having a high energy of about 7 MeV. The accelerator used in this embodiment is not limited to such a linear accelerator, and a cyclotron may be used.

  The target shield 13 stores the target 20 in the center thereof, and plays a role of preventing radiation harmful to the human body generated at the same time as the ion beam R is incident on the target 20 from being leaked to the outside.

  As shown in FIG. 2A, the target 20 includes a support grid 21, a transmission foil 22, a body substrate 24, and a cylindrical body 28.

  The body substrate 24 is provided with a space S in which the raw water W is enclosed. The liquid supply flow path 26a provided in the body substrate 24 is a flow path that flows when the raw material water W is injected into the space S or when the raw material water W is recovered after being converted into a radioactive element. is there. The gas introduction path 26b is an introduction path through which argon gas for pressurizing the raw water W sealed in the space S is introduced. Further, the body substrate 24 is formed with a cooling path 25a through which the coolant E for irradiating the ion beam R and lowering the raised temperature circulates.

  The space S has a thin structure in which the diameter of the incident surface of the ion beam R is about 20 to 30 mm and the depth in the incident direction is 0.3 to 0.4 mm. Such a structure is low energy, has a short range of the ion beam R, and can adjust the beam diameter and shape (both compared with the cyclotron), and is suitable for the linear accelerator 12 as described above. The structure can be said. The reason for this is verified in the example section described later.

  Furthermore, the amount of the raw material water W enclosed in the space S is 0.5 cc or less, and it is possible to produce F-18 with a predetermined yield while suppressing the amount of the expensive raw water W used. Become. This can reduce the raw material water used to obtain the same amount of F-18 to about 1/4 compared with the thick target normally used in the cyclotron system.

  The raw material water W sealed in the space S is pressurized with argon gas (Ar) introduced from the gas introduction path 26b so that the temperature rises and bubbles due to boiling are not generated, and the cooling path 25a. , 25b is cooled by the refrigerant E circulating. Then, the water containing the converted radioisotope is recovered by the synthesizer 29 through the liquid feeding passage 26a by releasing the valve 28b under the pressure of the argon gas introduced from the gas introduction passage 26b. become.

  Moreover, in order to suppress the temperature of the raw material water W from being increased by the irradiation of the ion beam R, the target 20 is made of a material having good thermal conductivity so that the heat of the raw material water W can easily escape to the outside of the target 20. Desirably configured. Furthermore, it is desirable that the outer wall of the space S in contact with the raw water W is made of a chemically stable and highly corrosion-resistant material.

  Therefore, the body substrate 24 is composed of at least one noble metal material selected from the group of gold, platinum, and palladium. Thereby, even if the ion beam R is irradiated and the raw material water W boils as the temperature rises to generate bubbles (water vapor), the wall surface of the space S is not corroded by the water vapor. Further, it does not form a compound with the generated radioisotope.

  The transmission foil 22 forms a boundary that seals the side surface of the space S on the vacuum region U side in a sealed manner, and transmits the irradiated ion beam R. The transmission foil 22 is made of a thin film made of titanium or Havar. The wall surface forming the space S of the transmission foil 22 is coated with at least one noble metal material selected from the group of gold, platinum, and palladium. Thereby, the surface of the transmission foil 22 also does not react with the bubbles (water vapor) generated in the raw water W and the generated radioisotope (F-18).

  As shown in FIG. 2B, the support grid 21 is provided with a plurality of passage openings 27, 27,. The support grid 21 is provided in contact with the transmission foil 22 on the side of the vacuum region U, and supports the transmission foil 22 so that the transmission foil 22 does not yield due to the pressure of the raw material water W enclosed in the space S. Furthermore, the support grid 21 also serves as a heat conductor that releases the heat of the raw material water W heated by irradiation of the ion beam R to the outside.

For this reason, it is desired that the support grid 21 is made of a material having a good balance between thermal conductivity and mechanical properties at high temperatures. For example, DS Copper (alumina dispersion strengthened copper) or chromium copper is used. . Furthermore, the surface of the support grid 21 is coated with gold, thereby making it possible to improve the thermal contact with the transmission foil 22 and to suppress the activation of the support grid 21.
The cylindrical body 28 is provided with a cooling path 25 b through which the refrigerant E flows, and an end thereof is in contact with the body substrate 24 and absorbs heat of the raw water W transmitted through the support grid 21. is there.

  The raw material water W is an aqueous solution in which O-18 water is concentrated and is enclosed in the space S of the target 20 from the liquid feeding flow path 26a. When the target 20 is irradiated with the ion beam R, the ion beam R passes through the passage openings 27, 27... Of the support grid 21, the transmission foil 22, collides with the raw material water W, and O-18. Water undergoes a nuclear reaction, and F-18, which is a radioisotope, is generated as a radioisotope.

Next, the operation of the radioisotope manufacturing apparatus 10 configured as described above will be described with reference to FIGS.
First, when operating the radioisotope production apparatus 10, the target 20 is accommodated in the target shield 13 in advance.
When an operation switch (not shown) is operated, predetermined high-frequency power is supplied to the RFQ 12a and DTL 12b, and an electric field is formed in each of the RFQ 12a and DTL 12b. Thereafter, predetermined power is supplied to the ion source 11. As a result, the ion beam R emitted from the ion beam generator (not shown) of the ion source 11 is accelerated to a predetermined energy by the RFQ 12a. The accelerated ion beam R is emitted from the RFQ 12a, is incident on the subsequent DTL 12b, and is further accelerated by the DTL 12b.
The ion beam R accelerated to high energy in this way is irradiated to the raw material water (O-18 water) W in the target 20. And when the ion beam R irradiates O-18 water, F-18 will be produced | generated by a nuclear reaction.

  Thus, in the process in which F-18 is generated, the temperature of the raw material water W rises inside the target 20, but heat is transmitted via the body substrate 24 and the support grid 21 that are cooled by the refrigerant E. Because it escapes to the outside, the ultimate temperature is kept low. Furthermore, since the pressure in the space S is set high by an argon gas supplied from a pipe (not shown), no bubbles are generated when the temperature of the raw water W exceeds 200 degrees.

  Then, when the temperature reached by the raw water W exceeds the saturated steam temperature at the pressure in the space S, bubbles of water vapor are generated. Although the water vapor bubbles adhere to the wall surface of the space S, since the wall surface is made of a noble metal material (one or more of gold, platinum, and palladium), the water vapor does not react with the wall surface. That is, unlike the case where the wall surface of the space S is made of a silver material as in the conventional product, the wall surface is oxidized and peeled off into fine particles, or the water vapor is reduced to generate cracked gas (hydrogen gas) and further bubbles. There is no such thing as growing up.

  In this way, even if water vapor bubbles are generated inside the space S, the bubbles do not grow much larger, so the enclosed raw material water W is irradiated with the ion beam R with almost no exclusion. The yield of F-18 produced is not reduced.

  In this way, when a desired yield of F-18 is obtained, the concentrated water containing F-18 is sent from the liquid sending channel 26a to the radiopharmaceutical synthesizer 29 through the valve 28b. F-18 is extracted from the concentrated water containing. In addition, since the remaining O-18 water that did not undergo nuclear reaction to F-18 is very expensive, when a thick target used in a cyclone or the like is used, a distillation or purification process is usually performed. After that, it is collected and reused in the target 20. However, since the thin target used in this embodiment has a high conversion rate to F-18, economic efficiency is greatly increased without reusing the remaining O-18 water that has not undergone nuclear reaction to F-18. There is no loss.

In the above-described embodiment, the example in which the entire body substrate 24 in which the space S is formed is configured with a noble metal material is shown. However, as another embodiment, the body portion of the body substrate 24 is formed with a high heat transfer material, In some cases, the surface of the space S in contact with the raw material water W is composed of at least a noble metal.
Specifically, the main body of the body substrate 24 is made of a low-cost, high-thermal conductive material such as silver, copper, aluminum, or titanium, and the surface thereof is coated with a noble metal material (gold, palladium, platinum) by plating or vapor deposition. Or may be combined by pressure bonding.

  First, a case where plating is performed on the body surface of the body substrate 24 made of silver or the like will be considered. In this case, the plating thickness is desirably in the range of 10 to 100 μm from the viewpoint of extending the life of the target 20 and reducing activation. If the plating is thinner than this range, the coating effect is not sufficiently exhibited, and corrosion of the silver material on the body surface of the body substrate 24 may proceed. On the other hand, if the plating is thicker than this range, the surface becomes cloudy and rough, and the tendency for F-18 to be trapped becomes significant.

  In order to avoid such roughness of the plating surface, the plating solution used for plating is selected to be as small as possible in gold plating particles, and isotropic with respect to the plated object (the body of the body substrate 24). It is desirable to use a nozzle jet type plating apparatus so that the plating solution is applied to the surface. Further, if the plating film is made thick, the plating solution may be trapped in the film, so it is necessary to select a plating solution that does not contain a deleterious poison.

  Further, when gold deposition is performed on the body surface of the body substrate 24 made of silver or the like, gold may be deposited up to the inner walls of the holes of the liquid supply passage 26a and the gas introduction passage 26b that lead from the space S. Since it is not possible, it is necessary to use it together with plating if necessary.

  Next, a case where the surface of the space S of the body substrate 24 made of silver or the like is formed by compounding by pressure bonding will be considered. As an example of the compounding method by this pressure bonding, there is a hot isostatic press (HIP) pressure bonding method. As a specific method of manufacturing the target 20 by compounding, the body substrate 24 and the gold member to be bonded are heated to 800 ° C. or higher and pressure-bonded at about 2,000 atmospheres, thereby forming a sufficient bonding surface. It has been confirmed that

  As described above, in the target 20 used in the present embodiment, when the wall surface with which the raw material water W contacts is formed of a noble metal substance (gold, palladium, platinum), the surface is not corroded. For this reason, the surface of the target composed of gold hardly deteriorates even after long-term use, and corrosion products do not adhere, so that cleaning is simplified by simply ultrasonically cleaning with an organic solvent, hot water, water or the like. . Therefore, the maintenance frequency and required time of the target 20 are shortened and the life of the target 20 is extended. In the unlikely event that the surface of the target 20 is scratched or a tightly adhered impurity is generated, it is preferable to regenerate by electrolytic polishing in order to remove the surface without roughening.

In the radioisotope manufacturing apparatus according to this embodiment, as described above, the wall surface portion of the space S formed by the body substrate 24 is made of a noble metal (gold, palladium, platinum) that has excellent corrosion resistance against water vapor. become. As a result, even if a void is generated in the raw water (O-18 water) sealed in the target 20 and the wall surface of the space S is exposed to water vapor, the wall surface is corroded or a new decomposition gas is generated. The void will no longer grow.
Furthermore, because the wall surface portion of the space S is composed of noble metals (gold, palladium, platinum), in addition to corrosion resistance, (1) it does not chemically react with the fluorine of F-18 produced, (2) thermal conductivity Therefore, the temperature rise of the raw material water W (O-18 water) is suppressed, (3) there is little activation due to ion beam irradiation, and (4) no metal impurities that pass through the apparatus are generated. The target 20 also has excellent characteristics.

  When the target 20 is composed of a noble metal such as gold, palladium, platinum, etc., it is inevitable to solve the problem of high cost. As described above, it can be said that the target 20 is a consumable that is deteriorated by use. Therefore, the body substrate 24 that has been used for a predetermined period of time is recycled by melting and manufacturing a new body substrate 24. Is desirable.

By the way, the radioactive isotope of mercury produced by the transmutation of a part of the contained gold by irradiating the target 20 with the ion beam R is halved every 64.1 hours. Almost all of it returns to gold and stabilizes. If it does so, it will become possible to safely perform processing, such as melting, impurity removal, casting, forging, and rolling, for recycling the target 20 containing gold at a place where work is generally performed.
In particular, when the constituent material of the body substrate 24 is gold or platinum, these constituent materials can be easily recovered and dissolved by utilizing the short decay time of the radiation intensity.
In this way, the cost of recycling is estimated to be able to recycle 10 used targets 20 for the price of purchasing one silver target material, including the replenishment gold. . The same recycling is possible with platinum, but in the case of palladium, it is difficult to recycle because a long half-life nuclide is generated.

Next, referring to FIG. 2 and other drawings as appropriate, the effect of the product of this embodiment was verified, and the effect was confirmed in comparison with the conventional product.
Here, the product of the present embodiment means that the body substrate 24 is made of gold (99.99%), and the conventional product is that made of silver-niobium alloy.
As shown in FIG. 3, the reaction probability of transmutation from O-18 water to F-18 by irradiating the raw water W with the ion beam R is maximum when the energy of the ion beam R is 5-6 MeV. It can be seen that it becomes smaller at low energy of 3 MeV or less.

  On the other hand, as shown in FIG. 4, when the target 20 is irradiated with the ion beam R, the beam energy is attenuated in the process of passing the O-18 water. Here, when the energy at the time of incidence on the target 20 is 6.5 MeV, the energy of the ion beam becomes 3 MeV when passing water having a thickness of about 0.43 mm, and in light of the result shown in FIG. It can be seen that F-18 cannot be generated in an area of about 0.43 mm or more.

Further, in FIG. 4A, in the region of 0.43 mm or more in the depth direction, the low energy ion beam R of 3 MeV or less only heats the raw material water W (O-18 water), and causes the generation of voids. Become. Furthermore, in the region where the black peak near 0.55 mm shown in FIG. 4B exists, the amount of energy consumed to heat the raw material water W (O-18 water) is maximized, so voids are generated. Is also the largest.
Based on this verification result, as shown in FIG. 2, the target 20 has a thin structure and dimensions in the space S in which the raw water W is enclosed.

  Further, the change over time in the amount of F-18 generated inside the target 20 after the irradiation of the ion beam R is started is represented by an evaluation graph shown in FIG. According to this evaluation graph, it can be said that the generation amount of F-18 increases as the accelerator output beam current increases as 40, 60, 80, 100 μA. This evaluation graph is created with the transmittance of the ion beam R output from the accelerator 12 passing through the transmission foil 22 and the support grid 21 supporting the transmission foil 62%. From the evaluation graph of FIG. 5, it can be seen that 1 Ci (37 GBq) of F-18 is generated inside the target 20 when the accelerator output beam current of 100 μA is irradiated for 1 hour.

  Usually, at the PET diagnosis site, the production capacity of F-18 required for the radioisotope production apparatus 10 is 1 based on the relationship between the time taken for one examination and the amount of F-18 to be injected into a patient. It is said to be about 1 Ci (1 Ci / h) per hour. In order to secure such F-18 manufacturing capability, it is a necessary condition that the accelerator output beam current is applied at 100 μA from the result of the evaluation graph of FIG. ) The ion beam with a predetermined energy is effectively irradiated to the O-18 water. (2) The thickness of the O-18 water is secured to the extent of the ion beam in the O-18 water. (3) The density of O-18 water in the region irradiated with the beam is maintained. (4) It is a requirement that the produced F-18 water can be efficiently taken out from the target.

  As described above, the generation and growth of voids in the raw water W sealed in the target 20 by irradiation with the ion beam is a requirement described in (1) to (4). It can be an impediment. For this reason, it is necessary to select the material of the target 20 that can suppress the generation / growth of voids and secure the density of the raw water W (O-18) in the space S.

  FIG. 6 compares the saturation yield of F-18 produced by using the target of the conventional product and the target of the present embodiment. Here, the saturation yield of F-18 is the amount of F-18 produced and the amount of decay present in O-18 water when beam irradiation is continued for a sufficiently long time compared to the β decay time (110 minutes) of F-18. Is the amount of F-18 when the current becomes almost constant and is normalized by the incident proton beam current.

According to this, in this embodiment, even if the accelerator output beam current is increased, the saturation yield is maintained at a constant value, whereas in the conventional product 1, the saturation yield increases with the increase of the accelerator output beam current. A tendency to decrease was obtained. When the material of the support grid 21 is made of SUS material with poor heat transfer as in the configuration of the conventional product 2, more voids are generated in the raw water W, so that the saturation yield is further reduced. The result is obtained.
From this result, when the accelerator output beam current is set to 100 μA required to achieve 1 Ci / h, which is the target value of F-18 manufacturing capacity, the yield of F-18 is the theoretical value in this embodiment product. It can be seen that, in contrast to the theoretical value, the conventional example does not.

FIG. 7 shows the result of detecting the pressure change inside the target when the beam current is changed when the conventional target and the target of the present embodiment are used. As a result, in the product of this embodiment, the pressure changes linearly with respect to the beam current, whereas in the conventional example, it can be seen that the pressure rapidly increases at 60 μA as a boundary.
The linear pressure change in the product of this embodiment is considered to be due to the generation of water vapor voids accompanying the temperature rise of the raw material water W, and the pressure sudden increase curve in the conventional product is the water vapor and the wall surface of the target 20 in contact with the water vapor. This is considered to be related to the fact that the reaction gas (hydrogen gas) is generated by the reaction of (2) and the voids are further grown.

  In addition, when the target of the conventional product and the product of the present embodiment was continuously used for a predetermined period under the same conditions, adhesion of fine particles was confirmed on the surface of the target of the conventional product. Fine particles were not confirmed. As a result of component analysis of the fine particles adhering to the target of the conventional product, it was found that the particles consisted of the same components as the target and were peeled off from the target wall. Thus, in the conventional target, the raw water W and the wall surface react with each other under the irradiation of the ion beam to corrode the wall surface, but it has been proved that such a phenomenon does not occur in the present embodiment.

As shown in FIG. 9, based on the above verification, as a material constituting the body substrate 24 of the target 20, as a result of comparative examination from the viewpoint of corrosion resistance against water vapor, thermal conductivity, and compound formation with F (fluorine), Gold was the best, followed by palladium and platinum. Note that it is considered that even the platinum having the lowest thermal conductivity among these three materials can secure the same level of cooling performance as that of currently used niobium materials.
Here, ◎ indicates extremely excellent properties, ◯ indicates that it can be used, Δ indicates that the performance is unsatisfactory, × indicates that it cannot be used, and? Indicates that no experiment was conducted.

It is sectional drawing of the radioisotope manufacturing apparatus which concerns on embodiment of this invention. (A) It is side surface sectional drawing of the target used by this invention, (b) is a front view which shows the front of a target. It is a graph showing the production | generation nucleus reaction cross section of F-18 with respect to the intensity | strength of beam energy. (A) It is a graph showing the intensity | strength of the energy attenuate | damped with respect to the distance which permeate | transmits when an ion beam passes O-18 water. (B) It is a graph showing the attenuation amount per unit distance of energy. It is a graph showing the production | generation amount of F-18 with respect to the time when the accelerator output beam current which shows a different value of 100, 80, 60, 40 microamperes is irradiated. It is a graph which shows the change of the saturation yield with respect to an accelerator output beam current compared with the case where the target of this invention and the conventional target are used. It is a graph which shows the pressure change inside a target with respect to the accelerator output beam current compared with the case where the target of this invention and the conventional target are used. It is data which shows the component analysis result of the microparticles | fine-particles adhering to the surface when using the conventional target. It is a table | surface which shows the result of having examined about the optimal material for comprising the target of the radioisotope manufacturing apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Radioisotope production apparatus 11 Ion source 12 Accelerator 20 Target 21 Support grid 22 Transmission foil 24 Body substrate 27 Passage port R Ion beam S Space U Vacuum region W Raw material water

Claims (7)

An ion source that emits an ion beam;
An accelerator having a vacuum region in which the ion beam emitted from the ion source is accelerated;
A target in which raw water for generating a radioisotope is encapsulated when irradiated with the accelerated ion beam; and
The target is
A transmissive foil that forms a boundary between the vacuum region and the raw material water and transmits the ion beam;
A body substrate that forms a space in which the raw water is enclosed together with the transmission foil, and
The body substrate is
A radioisotope manufacturing apparatus comprising at least one noble metal material selected from the group consisting of gold, platinum and palladium. An ion source that emits an ion beam;
An accelerator having a vacuum region in which the ion beam emitted from the ion source is accelerated;
A target in which raw water for generating a radioisotope is encapsulated when irradiated with the accelerated ion beam; and
The target is
A transmissive foil that forms a boundary between the vacuum region and the raw material water and transmits the ion beam;
A body substrate that forms a space in which the raw water is enclosed together with the transmission foil, and
The body substrate is
A main body made of at least one high thermal conductive material selected from the group consisting of silver, copper, aluminum, titanium and niobium;
The radioisotope manufacturing apparatus characterized in that at least a surface of the main body portion on which the space is formed is formed of at least one noble metal material selected from the group of gold, platinum, and palladium.   The radioisotope manufacturing apparatus according to claim 2, wherein the noble metal material is provided on the surface of the main body by any one of plating, vapor deposition, and pressure bonding.   4. The surface of the transparent foil that forms the space is coated with at least one noble metal material selected from the group consisting of gold, platinum, and palladium. The radioisotope production apparatus according to item 1. A support grid that supports the transmission foil from the vacuum region side and is provided with a plurality of passage openings through which the ion beam passes,
The radioisotope manufacturing apparatus according to claim 1, wherein a surface of the support grid is coated with gold.   A target body characterized in that the used body substrate used in the radioisotope production apparatus according to any one of claims 1 to 5 is collected, and its surface is electropolished and regenerated. Recycling method.   A used body substrate used in the radioisotope manufacturing apparatus according to any one of claims 1 to 5 is collected, and after undergoing a step of dissolving it, a new body substrate is manufactured. A target recycling method characterized by being used as a raw material for the purpose.

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