Patent ID: 12232245

While the disclosed subject matter is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the disclosed subject matter to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosed subject matter as defined by the appended claims.

DETAILED DESCRIPTION

The following detailed description illustrates embodiments of the present disclosure. These embodiments are described in sufficient detail to enable a person of ordinary skill in the art to practice these embodiments without undue experimentation. It should be understood, however, that the embodiments and examples described herein are given by way of illustration only, and not by way of limitation. Although specific embodiments of the present invention will now be described with reference to the drawings, it should be understood that such embodiments are by way of example only and merely illustrative of but a small number of the many possible specific embodiments which can represent applications of the principles of the present invention. Various changes and modifications obvious to one skilled in the art to which the present invention pertains are deemed to be within the spirit, scope and contemplation of the present invention as further defined in the appended claims.

As used herein, the terms “coupled” or “couple” include both a direct connection and an indirect connection between components. With respect to components that direct fluids from one component to another, the terms “couple” or “coupled” includes connections via a pipe or other ducting to provide fluid communication between components.

Further, in the figures and the description, like numerals are intended to represent like elements.

With reference toFIG.1, an illustrative embodiment of an Ra-226 target insert100is shown. In certain illustrative embodiments, the Ra-226 target insert100is designed to be mounted to the target receptacle of a cyclotron (not shown). A person of skill in the art having the benefit of the present disclosure would recognize that various shapes for Ra-226 target insert100may be chosen to fit a particular cyclotron target or a cyclotron from a particular manufacturer. While the Ra-226 target insert100ofFIG.1is one shape shown for illustrative purposes, one of skill in the art would recognize that other shapes may be chosen for compatibility with different manufactures and models of particle accelerators. For example, the Ra-226 target insert100may be shaped as a disk/coin, oval, or rectangle or other polygon. In certain embodiments, the Ra-226 target insert100may include a protective layer101, a crimp ring102and a target insert body103. The protective layer101may be disposed on the target insert body103, as is described in further detail herein. The crimp ring102may be disposed so as to substantially affix the protective layer101to the target insert body103, as is describe in more detail herein. The protective layer101may be constructed of any suitable material as would be appreciated by those of ordinary skill in the art, having the benefit of the present disclosure. For example, in certain illustrative embodiments, the protective layer101may be constructed of materials such as Copper foil, Gold foil, Aluminum foil, and alloy foils such as Havar. As described in further detail inFIG.2, an Ra-226 layer104(not shown inFIG.1) may be disposed on a portion of the target insert body103between target insert body103and the protective layer101, as shown inFIG.2. In particular embodiments, the Ra-226 layer104may be deposited by electroplating, micro-sputtering, boiling, or other methods of depositing thin films as would be recognized by those of skill in the art with the benefit of the present disclosure.

Specifically,FIG.2provides an exploded view200of the Ra-226 target insert100shown inFIG.1. As shown inFIG.2, the Ra-226 layer104is disposed onto a portion of the surface of target insert body103between the target insert body103and the protective layer101. When the protective layer101is affixed to the target insert body103, as is described herein, the Ra-226 layer is disposed into a sealed compartment formed between the protective layer101and the target body103during the process of affixing the protective layer101to the target body103as is described more detail herein. The protective layer101may be placed over the Ra-226 layer104and held in place on target insert body103by a crimp ring102. As discussed in more detail herein, the crimp ring102may be disposed in a manner to substantially seal the protective layer101to the target insert body103. The protective layer101provides an airtight barrier that protects the Ra-226 layer104and prevents portions of the Ra-226 layer104from being released into the environment surrounding the Ra-226 target insert100during irradiation of Ra-226.

The Ra-226 layer104may be converted to Ac-225 by irradiation of Ra-226 target insert100in a particle accelerator. To affect the conversion of Ra-226 to Ac-225, the Ra-226 target insert100may be placed into a portion of a particle accelerator (not shown), such as a cyclotron, and exposed to a beam of proton radiation having an energy of at least approximately 22.5 mega-electron volts (MeV). In some embodiments, the Ra-226 target may be placed in a holding chuck or other receptacle located in a vacuum chamber that may be coupled to the accelerator. In some embodiments the vacuum chamber, may be placed in a hot cell that is connected to an accelerator through a rabbit system (not shown). The Ra-226 target insert100is oriented in such a way that the accelerator beam may be directed onto Ra-226 layer104. After the Ra-226 target insert100is placed into the accelerator target body (not shown) it may be coupled to the accelerator beam port (not shown). The operation of a particle accelerator and associated target system would be understood by one of skill in the art having the benefit of the present disclosure. Once coupled to the accelerator beam port, the surface of Ra-226 target insert100may be exposed to a beam of radiation (i.e., a proton beam) from the particle accelerator. The proton beam may be directed at the surface of Ra-226 target insert100at any angle. In a particular embodiment the proton beam may intersect the surface of Ra-226 target insert100at an angle between approximately 0 and 180 degrees, depending on the particle accelerator model and manufacturer. In certain embodiments, the proton beam may intersect the surface of Ra-226 target insert100at an angle between approximately 1 and 90 degrees. The proton beam passes through protective layer101and contacts the Ra-226 layer104. The protective layer101may degrade the energy of the proton beam. For example, a proton beam having an energy of approximately 23.5 MeV may be degraded to an energy of approximately 22.5 MeV after passing through the protective layer101. The energy degradation caused by the protective layer101may be a function of its composition and thickness. Those having skill in the art, with the benefit of the present disclosure, would recognize the need to choose an appropriate combination of proton beam energy and protective layer101thickness and material to ensure an energy delivery of at least approximately 22.5 MeV to Ra-226 layer104, which is needed for conversion of Ra-226 to Ac-225.

Incidence of the proton beam upon the Ra-226 layer104generates heat, which must be conducted away from the Ra-226 layer104by the target insert body103to prevent overheating of the Ra-226 layer104and the Ra-226 target insert100as a whole. The target insert body103may be actively cooled to accomplish cooling of the Ra-226 layer104. For example, in certain illustrative embodiments, the target insert body103may be mounted to a cooling plate cooled by a liquid cooling. As would be understood by those of skill in the art with the benefit of this disclosure, the cooling system is generally part of a particular particle accelerator and is included with that accelerator's target system, and thus the Ra-226 target insert of the present disclosure may be configured to be compatible with the desired particle accelerator cooling system and target. For example, as would be appreciated by those of ordinary skill in the art, having the benefit of the present disclosure, most accelerator target systems in which the Ra-226 target insert100may be mounted include a liquid cooling apparatus. Alternatively, the target insert body103may be mounted in the accelerator chamber (not shown) to a device that directly or indirectly brings a cooling fluid in contact with the back of target insert body103. In some embodiments, the target insert body103may contain one or more cooling channels or a hollow portion to provide an improved contact area for the cooling fluid and facilitate flow of the cooling fluid, as shown, for example, inFIG.3. The target insert body103may be constructed from any sufficiently conductive material, including metals and ceramics. In certain embodiments, the target insert body103may be constructed from aluminum, gold, tungsten, copper, iron, nickel, palladium, platinum, titanium, and combinations and alloys thereof.

FIG.3provides an illustration of a cross section300of the exploded view200of the Ra-226 target insert100. As shown inFIG.3, the target insert body103may be formed to have a hollow portion305on the back side of the portion of the target insert body103underlying the Ra-226 layer104. The hollow portion305may include one or more channels or hollow areas to facilitate cooling fluid flow along the back of the Ra-226 target insert100. The hollow portion305decreases the distance between the irradiated Ra-226 layer104and the cooling fluid or element, enhancing heat conduction away from the Ra-226 layer104. Additionally, the implementation of the hollow portion305advantageously reduces the mass of Ra-226 target insert100, thereby increasing the efficiency of fluid cooling and reducing the weight of Ra-226 target insert100.

FIGS.4and5depict a cross section of the Ra-226 target insert100prior to compression of the crimp ring102and after the compression of the crimp ring102, respectively, according to an illustrative embodiment. Specifically, the cross section400shows a cross section of the Ra-226 target insert100prior to compression of the crimp ring102to affix the protective layer101in place. During assembly, the protective layer101is placed atop the target insert body103and the crimp ring100is aligned with the target channel206atop the protective layer101. In certain illustrative embodiments the components may be placed in an assembly chamber, for example the chamber of assembly system600illustrated inFIGS.6through9, prior to alignment or aligned within the chamber. Next, the assembly chamber may be evacuated and purged with helium before crimping takes place. Next, pressure is applied to the top of the assembly to remove any air or other material from between protective layer101and the target insert body103. The application of pressure, for example by a die, as is described in greater detail with respect toFIGS.6-9may cause crimp ring102to deform, thereby filling target channel206to seal the protective layer101to the target insert body103, as shown in cross section500ofFIG.5. In alternative embodiments, the crimp ring102may be welded to the protective layer101and the target insert body103to provide a seal. In yet other embodiments, the protective layer101may be welded directly to the target insert body103along the circumference of the target channel206. In certain embodiments, there area of target channel206may by level with the perimeter of target insert body103to provide a flat surface for spot welding (not shown).

FIGS.6-9provides an illustration of an assembly apparatus600for assembly of an Ra-226 target insert100, according to an illustrative embodiment of the present disclosure. The illustrated components of assembly apparatus600includes a compression die604, one or more ejector pins605disposed under the compression die, an upper target insert die606disposed under the compression die to provide a stable base for crimping of the Ra-226 target insert, a release pneumatic/hydraulic cylinder607disposed below the upper target insert die606and the ejector pins605and coupled to the ejector pins605to provide actuation to the ejector pins605, one or more alignment pins608disposed between the upper target insert die606and the compression die604and coupled to the upper target insert die606, and a base centering plate609disposed below and coupled to a lower target insert die610which is disposed below and coupled to the upper target insert die606to provide a stable structure for upper target insert die606. The assembly apparatus600may also include one or more vacuum ports611and a gas port612coupled to the assembly chamber of assembly apparatus600, and a compression pneumatic/hydraulic cylinder613disposed above upper target insert die606and coupled to the compression die604in a manner that allows for exchange of the compression die604with other compression dies604having differing geometry or with the punch die704described herein with respect toFIGS.10-13. In some embodiments, assembly apparatus may include a plurality of vacuum ports611, for example one that may couple assembly apparatus600to a rough vacuum pump and one that may couple assembly apparatus600to a second vacuum pump, an helium gas pump, an atmospheric vent, or pressure relief valve.

The components of the Ra-226 target insert100may be inserted into assembly apparatus600as described in further detail below. These components may include: the target insert body103of the Ra-226 target insert100; the protective layer101of the Ra-226 target insert100, which as described above may be a foil in certain embodiments; the crimp ring102of the Ra-226 target insert100, which may also be a metal compression O-ring; and an electroplated Ra-226 layer104of the Ra-226 target insert100.

A method for assembly of the Ra-226 target insert by crimping is illustrated byFIG.16and described below according to an illustrative embodiment of the present disclosure. To assemble the illustrated embodiment of the Ra-226 target insert100, first, the target insert body103is placed onto the upper target insert die606within the chamber of assembly apparatus600. Next, the protective layer101is placed atop target insert body103. Next, the crimp ring102is placed atop the protective layer101and the target insert body103. This arrangement is shown inFIG.7, which illustrates the alignment of the target insert body103, the protective layer101, and the crimp ring102prior to compression.

Next, the compression die604is aligned with the crimp ring102by the alignment pins608. The compression die604may be a metal die shaped to align with the crimp ring102and transfer sufficient force from the compression hydraulic/pneumatic cylinder613to the crimp ring102to deform it to seal the protective layer101to the target insert body103as illustrated inFIGS.4and5. Next, the internal chamber of the assembly apparatus is sealed from the outside environment and is purged of air through the vacuum port611, which is used to couple assembly apparatus600to a vacuum pump (not shown). After a vacuum has been drawn inside of the assembly apparatus600through the vacuum port611, the vacuum port611may be closed by a valve, and the internal chamber of the assembly apparatus600may be filled with a desirable gas (e.g., helium) through the gas port612, which may couple assembly apparatus600to an inert gas source such as a gas tank. In certain illustrative embodiments, helium is the gas used to purge after drawing a vacuum because helium is largely transparent to cyclotron radiation, so presence of a small amount of helium between the protective layer101and target insert body103is not detrimental to conversion of Ra-226 to Ac-225.

Next, pressure is exerted on the compression die604by the compression pneumatic/hydraulic cylinder613to compress the compression crimp ring102to the protective layer101of the target insert body103, as illustrated inFIG.8. The base centering plate609and the lower insert die610provide a stable base for the upper insert die606to ensure that it is maintained in alignment during compression of the compression crimp ring102by the compression die604.

After compressing the compression crimp ring102, the compression die604may be withdrawn. After withdrawal of the compression die604, the assembled Ra-226 target insert100may be removed from the upper insert die606by the ejector pins605. The pneumatic/hydraulic cylinder607actuates the ejector pins605which provide upward pressure on the assembled Ra-226 target insert100through holes in the upper insert die606to remove or dislodge the Ra-226 target insert100from the upper insert die606. Finally, the chamber of the assembly apparatus600may be normalized to atmospheric pressure so that it can be opened and the assembled Ra-226 target insert can be removed. This process may then be repeated to manufacture additional Ra-226 targets.

FIG.9provides an illustration of a close-up exploded view900of components of the assembly apparatus600for assembly of Ra-226 target insert100, according to an illustrative embodiment of the present disclosure. The illustration provided inFIG.9includes the same components as described with respectFIGS.6-8and the illustrated components of assembly apparatus600include a compression die604, ejector pins605, upper target insert die606, release pneumatic/hydraulic cylinder607, alignment pins608, base centering plate609, and lower target insert die610, vacuum port611, gas port612, and compression pneumatic/hydraulic cylinder613. The components of Ra-226 target insert100may be inserted into assembly apparatus600as described above with respect toFIGS.6-8.

FIGS.10-13illustrate a punch apparatus700which may be used to remove the protective foil101from the Ra-226 target insert100after irradiation of the Ra-226 layer104to convert the Ra-226 layer to Ac-225 according to an illustrative embodiment of the present disclosure. Specifically,FIG.10depicts punch apparatus700during punch contact with the irradiated Ra-226 target insert100to remove the protective foil101andFIG.11depicts punch apparatus700after removal of the protective foil101.FIG.12depicts an exploded illustration of the Ra-226 target insert100after punching to remove protective layer101from Ra-226 target insert100andFIG.13depicts an exploded illustration1300of the internal components of the punch apparatus700.

Punch apparatus700includes a punch704coupled to a punch pneumatic/hydraulic cylinder713and disposed above an upper target insert die706and one ore more alignment pins alignment pins708that are coupled to the upper target insert die706. An upper target insert die706is disposed above one or more ejector pins705which are coupled to an ejection pneumatic/hydraulic cylinder707. A Lower target insert die710is disposed below and coupled to the upper target insert die706. A base centering plate709is disposed below and coupled to the lower target insert die710to provide structural rigidity for upper target insert die706. The punch apparatus700also may include a one or more vacuum ports711and a gas port712that are coupled to the chamber of assembly apparatus700.

To remove the foil from an irradiated Ra-226 target100to allow access to the Ac-225, first the irradiated Ra-226 target100is inserted into the upper insert die706. The internal chamber of the punch apparatus700is next sealed to the outside environment and a vacuum may be drawn in the chamber of punch apparatus700through vacuum port711, which may couple the punch apparatus700to a vacuum pump (not shown). After a vacuum is drawn on the interior of punch apparatus700, it may be filled with a desirable gas (e.g., helium) through the gas port712, which may couple punch apparatus700to a helium or other inert gas source such as a tank (not shown). In some embodiments, the same apparatus may be used for assembly apparatus600and punch apparatus700by simply substituting the compression die604with the punch704.

Next the punch704is aligned with the portion of the protective foil101corresponding to the electroplated area104(which has been converted from Ra-226 to Ac-225 by irradiation in a particle accelerator) by the alignment pins708. Punch720is shaped in a manner to apply pressure sufficient to break protective layer101along the perimeter of the electroplated area104of target100to allow for removal of a portion of the protective layer101covering irradiated electroplated area104. Pressure is exerted on the punch704by punch pneumatic/hydraulic cylinder713to provide pressure to protective foil101, which may cause the protective foil101to separate from the irradiated Ra-226 target insert100. Next, the punch704is withdrawn from the surface of the irradiated Ra-226 target insert100, as shown inFIG.11. In some embodiments, a vacuum may be drawn on the interior of punch704to cause the punched portion of the protective foil101to adhere to the punch704for removal form irradiated Ra-226 target insert100. Next the punched, irradiated Ra-226 target100may be removed from the punch apparatus by ejector pins708in a manner similar to that described above with respect to assembly apparatus600. Finally, the chamber of the punch apparatus700may be normalized to atmospheric pressure so that it can be opened and the exposed, irradiated Ra-226 target insert can be removed.

Alternatively, the protective layer101may be spot welded to the target insert body103instead of being crimped into place as described above. If the protective layer101is spot welded to target insert body103then crimp ring102does not need to be present and instead protective layer101may be directly fused to the target insert body103around the perimeter of the electroplated Ra-226 area104, for example in channel206. However, in some embodiments, the crimp ring102may be spot welded to the protective layer101and target insert body103after being crimped.

FIG.14depicts an exploded view of a spot welding apparatus800for a spot welded Ra-226 target insert100wherein the protective layer101is spot welded to the target insert body103. Similar to the assembly apparatus600and the punch apparatus700, the spot welding apparatus800includes one ore more ejector pins805, an upper target insert die806, an ejection pneumatic/hydraulic cylinder807, one or more alignment pins808, a base centering plate809, a lower target insert die810and these components perform the same functions as in assembly apparatus600and punch apparatus700, holding the Ra-226 target insert100in place, providing alignment of the components of Ra-226 target insert100during spot welding, and providing for ejection of Ra-226 target insert100from spot welding apparatus800after completion of spot welding of protective layer101to target insert body103. In some embodiments, the spot welding apparatus800ofFIG.14may be operated in the same chamber as the assembly apparatus600and the punch apparatus700and pictured inFIGS.6-8and10-12.

Spot welding apparatus800may also include a negative electrode804having a corresponding negative lead814and a positive electrode803having a corresponding positive lead813. The positive and negative electrodes (803,804) are disposed above and below the Ra-226 target insert100and provide electrical current to spot weld the protective layer101to the target insert body103. The negative lead814is coupled to the negative electrode804and electrically couples the negative electrode804to a negative terminal of an electrical source (not shown), such as a welding generator or capacitor bank. The positive lead813is coupled to the positive electrode803and electrically couples the positive electrode803to a positive terminal of an electrical source (not shown), such as a welding generator or capacitor bank. In some embodiments, the positive electrode803may be disposed below the target insert body103and the negative electrode804may be disposed on top of the protective layer101, as is illustrated inFIG.14. In other embodiments, the orientation of the negative electrode804and the positive electrode803may be reversed from what is illustrated inFIG.14and the negative electrode804may be disposed below the target insert body103and the positive electrode803may be disposed on top of the protective layer101.

A method for assembly of the Ra-226 target insert by spot welding is illustrated byFIG.17and described below according to an illustrative embodiment of the present disclosure. To spot weld the illustrated embodiment of Ra-226 target insert100, first, the target insert body103is placed onto the upper target insert die806within the chamber of the spot welding apparatus800, such as the chamber illustrated with respect to assembly apparatus600. Next, the protective layer101is placed atop the target insert body103. Next, a Teflon shim802is placed atop the protective layer101and the target insert body103. The Teflon shim802is a non-conductive polymer cap that insulates the portion of the target insert body103having the electroplated area104and the portion of the protective layer101that covers the electroplated area104from electrical current supplied through the negative electrode804and the positive electrode803. Because these portions of the target insert body103and the protective layer101are insulated from electrical current, they do not heat up and fuse (weld) during spot welding.

Next, the negative electrode804is aligned with the perimeter of the protective layer101and over the Teflon shim802by the one or more alignment pins808. Next, the internal chamber of the spot-welding apparatus800is sealed from the outside environment and is purged of air through a vacuum port such as vacuum port611ofFIG.6. After a vacuum has been drawn inside of the chamber containing the spot-welding apparatus800through the vacuum port611, the vacuum port611may be closed by a valve (not shown) and the chamber may be filled with an inert gas (e.g., helium) through a gas port, such as gas port612ofFIG.6. Next, pressure may be exerted on the negative electrode804by a compression pneumatic/hydraulic cylinder such as the pneumatic/hydraulic cylinder613to provide compressive force to the negative electrode804, which helps insure even spot welding around the perimeter of the protective layer101. Next, a current is applied through the positive electrode803and the negative electrode804. Because Teflon shim802insulted the central portion of Ra-226 target insert100from this current, the current is conducted through the perimeter of the protective layer101and the target insert body103, which causes them to heat and fuse, thereby welding the protective layer101to the target insert body103. After welding, the assembled Ra-226 target may be ejected from the spot welding apparatus800by force applied to the ejector pins805through the pneumatic/hydraulic cylinder807, which actuates the ejector pins805in an upward direction and causes separation of the assembled Ra-226 target insert100from the upper plate806. Finally, the chamber of the spot welding apparatus800may be normalized to atmospheric pressure so that it can be opened and the spot welded Ra-226 target insert can be removed.

After irradiation of a spot welded Ra-226 target insert100, the protective layer101may be removed from the target insert100by punch apparatus700in the same manner as described with respect to a crimped Ra-226 target insert100.

The particular embodiments disclosed above are illustrative only, as the disclosed subject matter may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the disclosed subject matter. Accordingly, the protection sought herein is as set forth in the claims below.