Patent Application
20200305268
The content of Japanese Patent Application No. 2019-054739, on the basis of which priority benefits are claimed in an accompanying application data sheet, is in its entirety incorporated herein by reference.
A certain embodiment of the present invention relates to a liquid target device.
As a technique in the related art, a liquid target device as described in the related art has been known. A target liquid is accommodated in the liquid target device and the target liquid is irradiated with a charged particle beam accelerated by a particle accelerator such that a radioisotope (RI) of the target liquid is generated.
According to an aspect of the present invention, there is provided a liquid target device including a liquid accommodation portion in which a target liquid is accommodated, a beam passage through which a charged particle beam emitted from a particle accelerator passes to reach the liquid accommodation portion, a target foil that separates the beam passage and the liquid accommodation portion from each other, and a vacuum foil that separates a vacuum region provided upstream of the beam passage and the beam passage from each other. The beam passage is provided with a first gas chamber into which a cooling gas is supplied at a position on the vacuum foil side and a second gas chamber into which a cooling gas is supplied at a position closer to the target foil side than the first gas chamber and the first gas chamber and the second gas chamber are separated from each other by an intermediate foil.
Ina liquid target device, a so-called target foil covers an opening upstream of an accommodation portion of a target. In the case of such a device configuration, a target foil may be damaged during irradiation with a charged particle beam. When the target foil is damaged, the target liquid may flow into a particle accelerator side.
It is desirable to provide a liquid target device in which a target liquid is prevented from flowing out toward a particle accelerator side even when a target foil is damaged.
According to the liquid target device, a vacuum foil and an intermediate foil that partition a beam passage are provided between the target foil of a liquid accommodation portion and a vacuum region. Therefore, even in a case where the target foil is damaged and a target liquid held in a liquid accommodation portion flows out toward a second gas chamber, the movement thereof is restricted by the intermediate foil and thus the target liquid is prevented from moving to the vacuum region via a first gas chamber. Therefore, even when the target foil is damaged, the target liquid can be prevented from flowing out toward the particle accelerator side.
Here, a flow system for the cooling gas relating to the first gas chamber and a flow system for the cooling gas relating to the second gas chamber may be independent of each other.
According to such a configuration, even when the target liquid flows out to the second gas chamber and the target liquid is discharged to the outside of a system along with movement of the cooling gas, the target liquid can be prevented from being erroneously supplied to the first gas chamber or the like since the flow system for the cooling gas relating to the second gas chamber and the flow system for the cooling gas relating to the first gas chamber are independent of each other.
The liquid target device may further include a pipe through which a fluid discharged from the second gas chamber flows and a recovery unit that is provided in the pipe and recovers a foreign substance contained in the fluid.
In a case where a configuration, in which the recovery unit that recovers the foreign substance contained in the fluid is provided in the pipe through which the fluid discharged from the second gas chamber flows, is adopted, even when the target liquid leaks into the second gas chamber and flows to the pipe along with movement of the cooling gas, the target liquid can be recovered in the recovery unit and thus the target liquid can be prevented from flowing out to a subsequent stage.
A flow system for the cooling gas relating to the first gas chamber maybe shared with another liquid target device that is different from the liquid target device.
In a case where one particle accelerator is provided with a plurality of liquid target devices, a flow system for a cooling gas may be shared with another liquid target device. In such a case, when a foreign substance such as the target liquid which is different from a cooling gas intrudes into the shared flow system, the influence thereof may become wide-ranging. However, when a configuration in which the flow system for the cooling gas relating to the first gas chamber that is on a side distant from the liquid accommodation portion in which the target liquid is accommodated is shared with the other liquid target device is adopted, the other liquid target device can be prevented from being influenced even in a case where the target foil is damaged.
Hereinafter, an embodiment of the present invention will be described in detail with reference to attached drawings. Note that, the same reference numerals are assigned to the same constituent elements in description of the drawings and repetitive descriptions thereof will be omitted.
The RI manufacturing system includes a particle accelerator in addition to the liquid target device 1. The particle accelerator is an accelerator that emits the charged particle beam B. Examples of charged particles include protons and heavy particles (heavy ions). Note that, as the particle accelerator, for example, a cyclotron, a linear accelerator (linac), or the like is used. As the charged particle beam, for example, a proton beam, a deuteron beam, an α-beam, or the like is used. In the following description, words such as “upstream side” and “downstream side” will be used corresponding to the upper stream and the lower stream of the charged particle beam emitted from a particle accelerator 3.
The liquid target device 1 is mounted into a manifold 90 that is provided in a port for emission of the charged particle beam, the port being provided in the cyclotron. The cyclotron adjusts the trajectory of the charged particle beam in an acceleration space such that the charged particle beam is extracted from the port. The extracted charged particle beam is incident into the manifold 90 and reaches the liquid target device 1.
The liquid target device 1 is configured to include a cooling unit 10 and a target holding unit 20. Note that, although the cooling unit 10 and the target holding unit 20 will be described separately in the present embodiment, the way in which the units are classified can be appropriately changed.
The cooling unit 10 is provided in a state of protruding from the manifold 90 of the cyclotron. The cooling unit 10 includes a beam passage 11, through which the charged particle beam B passes, at a position corresponding to an irradiation axis of the charged particle beam B. The beam passage 11 is formed to have a circular section with the irradiation axis of the charged particle beam B as a center line and is formed to extend along the irradiation axis.
The cooling unit 10 includes two sets of foils on the beam passage 11. By a vacuum foil 31, a region in the beam passage 11 that is upstream of the vacuum foil 31 is kept vacuum. In other words, a region upstream of the vacuum foil 31 is a vacuum region A1. In addition, an intermediate foil 32 is provided downstream of the vacuum foil 31 in the beam passage 11. The vacuum foil 31 and the intermediate foil 32 are thin circular foils formed of metal such as titanium and chromium or an alloy thereof and the thickness thereof is approximately 10 μm to 100 μm. As a foil, for example, a Havar foil or the like containing iron, cobalt, nickel, chromium, molybdenum, manganese, tungsten, or the like can be used. However, the foil is not limited thereto. In addition, the intermediate foil 32 may be provided by stacking two foils as described above.
In addition, the cooling unit 10 includes two sets of cooling flow paths 12 and 13 through which a cooling gas such as helium is blown to the beam passage 11. The cooling flow path 12 is configured to include a pair of cooling flow paths 12a and 12b. In addition, the cooling flow path 13 is configured to include a pair of cooling flow paths 13a and 13b.
The cooling flow path 12 is provided between the vacuum foil 31 and the intermediate foil 32 on the beam passage 11. The cooling flow paths 12a and 12b are provided to face each other with the beam passage 11 interposed therebetween. In addition, each of the cooling flow paths 12a and 12b branches into a portion facing an upstream side and a portion facing a downstream side. A cooling gas is blown to the vacuum foil 31 on the upstream side through a portion of the cooling flow path 12a that faces the upstream side and the cooling gas is blown to the intermediate foil 32 through a portion of the cooling flow path 12a that faces the downstream side (refer to
The cooling flow path 13 is provided downstream of the intermediate foil 32 on the beam passage 11. The cooling flow paths 13a and 13b are provided to face each other with the beam passage 11 interposed therebetween. In addition, each of the cooling flow paths 13a and 13b branches into a portion facing an upstream side and a portion facing a downstream side. A cooling gas is blown to the intermediate foil 32 on the upstream side through a portion of the cooling flow path 13a that faces the upstream side and the cooling gas is blown to a target accommodation portion 23 (liquid accommodation portion) through a portion of the cooling flow path 13a that faces the downstream side (refer to
The target holding unit 20 has an approximately columnar shape and includes a target foil 33, a target container portion 21, and a cooling mechanism 22. The target holding unit 20 is connected to the cooling unit 10 at a position downstream of the cooling flow path 13.
The target container portion 21 is disposed on an upstream side of the target holding unit 20. The target foil 33 is interposed between the target container portion 21 and the cooling unit 10 on the upstream side. Note that, a configuration in which the target foil 33 is supported by being interposed between members constituting the target holding unit 20 may also be adopted and a configuration in which the target foil 33 is supported by being interposed between members constituting the cooling unit 10 as shown in
In the case of a configuration as shown in
The target container portion 21 includes the target accommodation portion 23 that is formed at a center portion as seen in front view and in which the target liquid T can be accommodated and a buffer portion 24 that is positioned above the target accommodation portion 23 and communicates with the target accommodation portion 23. The target accommodation portion 23 and the buffer portion 24 are configured as a closed space formed when a front surface side of the target container portion 21 is closed by the target foil 33. A portion of the closed space is the target accommodation portion 23 in which the target liquid T is stored and a portion of the closed space that is above the liquid surface of the target liquid T is the buffer portion 24. In other words, the target foil 33 separates the beam passage 11 from the target accommodation portion 23 and the buffer portion 24. The target liquid T is supplied to the target accommodation portion 23 through a pipe 41 such that the target accommodation portion 23 is filled with the target liquid T and the target liquid T after processing is recovered through the pipe 41 again.
The cooling mechanism 22 is provided rearward of a rear wall 43 constituting the target accommodation portion 23 and the buffer portion 24. The cooling mechanism 22 cools the target accommodation portion 23 and the buffer portion 24 by supplying a cooling water that comes into contact with the rear wall 43. The cooling mechanism 22 includes a rear water path 45 that is immediately rearward of the rear wall 43, a water introduction path 47 through which the cooling water is introduced into the rear water path 45, and a water discharge path 49 through which the cooling water is discharged from the rear water path 45. The cooling water is supplied from the outside through a cooling water supply pipe connected to the water introduction path 47. By the cooling mechanism 22 as described above, the target liquid T in the target accommodation portion 23 is cooled. In addition, when the buffer portion 24 is cooled by the cooling mechanism 22, vapor evaporated from the target liquid T in the target accommodation portion 23 is condensed in the buffer portion 24 and returns to the target accommodation portion 23 due to the own weight thereof. Note that, the pressure in the target accommodation portion 23 and the buffer portion 24 is increased by an inert gas (for example, He) supplied through a pipe 51 and thus the boiling point of the target liquid T increases.
As described above, in the liquid target device 1, the vacuum foil 31, the intermediate foil 32, and the target foil 33 form two gas chambers on the beam passage 11 through which a cooling gas passes. That is, a first gas chamber R1 into which a cooling gas is supplied from the cooling flow path 12 (12a and 12b) and a second gas chamber R2 into which a cooling gas is supplied from the cooling flow path 13 (13a and 13b) are formed on the beam passage 11. The first gas chamber R1 and the second gas chamber R2 are separated from each other by the intermediate foil 32.
Next, the flow of cooling gases supplied to the first gas chamber R1 and the second gas chamber R2 will be described with reference to
In
In this case, a cooling gas supplied to the first gas chamber R1 on the upstream side can be shared between the adjacent liquid target devices 1. That is, a flow system S1 for the cooling gas supplied to the first gas chamber R1 is shared with another liquid target device. In the case of an example shown in
Meanwhile, a flow system S2 for a cooling gas to the second gas chamber R2 can be provided to be independent of an adjacent liquid target device 1.
Note that, a cooling gas discharged from the second gas chamber R2 via the cooling flow path 13b is returned to the helium cooling and pressurizing device 61 via a pipe L4. Note that, on the pipe L4, a gas-water separation device 62 and a filter 63 are provided. The gas-water separation device 62 and the filter 63 function as a recovery unit that recovers a foreign substance including the target liquid T in a case where the target foil 33 is damaged and the target liquid T flows into the pipe L4. Here, the “foreign substance” refers to all substances different from a cooling gas which is a fluid supposed to flow through the flow systems S1 and S2. The only fluid supposed to flow through the pipe L4 is a helium gas.
The gas-water separation device 62 is provided to prevent the target liquid T from flowing to the subsequent stage in a case where a fluid (helium gas) flowing through the pipe L4 contains the target liquid T with the target foil 33 being damaged. Although the configuration of a device for gas-water separation is not particularly limited, a configuration in which gas-water separation can be performed by changing the shape of a tank as shown in
The filter 63 is provided to remove water vapor and the like contained in a gas flowing through the pipe L4. In addition, in a case where a gas of which a component is different from the helium gas is contained in the gas, a filter that can adsorb the component may be used.
A gas flowing from the second gas chamber R2 is returned to the helium cooling and pressurizing device 61 via the gas-water separation device 62 and the filter 63 on the pipe L4. Since the gas passes through the gas-water separation device 62 and the filter 63, the target liquid T flowing in can be removed even in a case where the target foil 33 is damaged. Therefore, the helium cooling and pressurizing device 61 can be prevented from being damaged.
As described above, in the liquid target device 1 according to the present embodiment, the vacuum foil 31 and the intermediate foil 32 that partition the beam passage 11 are provided between the target foil 33 defining the target accommodation portion 23 (liquid accommodation portion) and the vacuum region A1 on the upstream side. Therefore, even in a case where the target foil 33 is damaged and a target liquid held in the target accommodation portion 23 flows out toward the second gas chamber R2, the movement thereof is restricted by the intermediate foil 32. Therefore, the target liquid is prevented from moving to the vacuum region on the upstream side via the first gas chamber R1. Therefore, even when the target foil 33 is damaged, the target liquid can be prevented from flowing out toward the particle accelerator side.
In a configuration in the related art, no intermediate foil 32 is provided and a gas chamber through which a cooling gas passes is configured as one chamber. Therefore, in a case where the target foil 33 is damaged and the target liquid T leaks into the gas chamber, the target liquid T may flow to a position downstream of the vacuum foil 31. In this case, the target liquid T may flow to the vacuum region A1 on the upstream side when the vacuum foil 31 is damaged. When the target liquid T flows to the vacuum region A1, the particle accelerator on the upstream side maybe influenced. Particularly, in a case where an acidic target liquid T is used, the vacuum region A1 may be corroded by an acid, which results in a serious influence. With regard to this, in the liquid target device 1 according to the present embodiment, the beam passage 11 is provided with the two gas chambers separated from each other by the intermediate foil 32 such that the leakage of the target liquid T is prevented from reaching the vacuum foil 31. Therefore, even when the target foil 33 is damaged, the target liquid T moving toward the particle accelerator can be suppressed.
In addition, the flow system S1 for a cooling gas relating to the first gas chamber R1 and the flow system S2 for a cooling gas relating to the second gas chamber R2 can be made independent of each other. According to such a configuration, even when the target liquid T flows out to the second gas chamber R2 and the target liquid T is discharged to the outside of a system via the flow system S2 along with movement of a cooling gas, the target liquid T can be prevented from being erroneously supplied to the first gas chamber R1 or the like since the flow system S2 for the cooling gas relating to the second gas chamber R2 and the flow system S1 for the cooling gas relating to the first gas chamber R1 are independent of each other. That is, only the second gas chamber R2 comes into contact with the target liquid T and the first gas chamber R1 can be prevented from coming into contact with the target liquid T and thus the target liquid T can be prevented from moving toward the particle accelerator.
In addition, the pipe L4 through which a fluid discharged from the second gas chamber R2 flows and the gas-water separation device 62 and the filter 63 as the recovery unit that is provided in the pipe L4 and recovers a foreign substance contained in the fluid may further be provided. According to such a configuration, even when the target liquid T leaks into the second gas chamber R2 and flows to the pipe L4 along with movement of the cooling gas, a foreign substance relating to the target liquid T can be recovered in the recovery unit and thus the target liquid T can be prevented from flowing out to a subsequent stage. That is, the foreign substance relating to the target liquid T can be prevented from being discharged out of the system and a pump, a pipe, and the like for supply of a cooling gas to the second gas chamber R2 like the helium cooling and pressurizing device 61 can be prevented from coming into contact with a substance relating to the target liquid T.
In addition, as described above, the flow system S1 for the cooling gas supplied to the first gas chamber R1 is shared with another liquid target device different from the liquid target device. In a case where one particle accelerator is provided with a plurality of liquid target devices, a flow system for a cooling gas may be shared with another liquid target device. In such a case, when a foreign substance such as the target liquid T which is different from a cooling gas intrudes into the shared flow system, the influence thereof may become wide-ranging. However, when a configuration in which the flow system for the cooling gas relating to the first gas chamber R1 that is on a side distant from the target accommodation portion 23 is shared with another liquid target device is adopted as in the case of the liquid target device 1 described above, the other liquid target device can be prevented from being influenced even in a case where the target foil 33 is damaged.
Starting with the above-described embodiment, the present invention can be carried out in various modes that are variously modified and improved on the basis of the knowledge of those skilled in the art. In addition, modification examples can also be configured using technical features described in the above-described embodiment. The configurations of each embodiment may be appropriately combined with each other.
For example, the shape or the like of each part constituting the liquid target device 1 can be appropriately changed. For example, although the second gas chamber R2 has been described as a portion of the cooling unit 10, a configuration relating to the second gas chamber R2 may be configured as a portion of the target holding unit 20.
In addition, a structure or the like supporting the foils is not limited to that described in the above-described embodiment. In addition, the intermediate foil 32 does not need to be formed by stacking two foils and may be configured by using one foil.
In addition, the number of gas chambers provided in the beam passage 11 may be three or more. However, since the number of members separating gas chambers from each other (members corresponding to intermediate foil 32) increases as the number of gas chambers increases, the efficiency of irradiation of the target liquid T with a charged particle beam may be lowered.
In addition, a configuration in which the flow system S1 for the cooling gas relating to the first gas chamber R1 and the flow system S2 for the cooling gas related to the second gas chamber R2 are not independent from each other may also be adopted. However, for example, when a configuration in which a cooling gas discharged from the second gas chamber R2 is prevented from being directly supplied to the first gas chamber R1 is adopted, a foreign substance relating to the target liquid T can be prevented from flowing to the first gas chamber R1 in a case where the target liquid T leaks into the second gas chamber R2 as described above. In addition, a configuration in which the flow system S1 for the cooling gas relating to the first gas chamber R1 is not shared with another liquid target device 1 may also be adopted.
In addition, the gas-water separation device 62 and the filter 63 as the recovery unit maybe in a state of not exhibiting a function as the recovery unit when there is no abnormality in the liquid target device 1, that is, the target foil 33 is not damaged. In this case, when a configuration in which control is performed such that the function as the recovery unit is exhibited when some abnormality is detected is adopted, the function as the recovery unit described in the above-described embodiment can be realized.
It should be understood that the invention is not limited to the above-described embodiment, but may be modified into various forms on the basis of the spirit of the invention. Additionally, the modifications are included in the scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-054739 | Mar 2019 | JP | national |
