Cyclotron including multifoil stripping assembly for stripping charged particles at intermediate energies

Abstract

A particle acceleration and extraction system includes a cyclotron having a stripping assembly and a target. The cyclotron includes an acceleration chamber and is operable to generate a magnetic field and an electric field in the acceleration chamber such that charged particles in the acceleration chamber are accelerated along a spiral path extending outward and at increasing energies from an initial energy E1 to a final energy E2, E2 being greater than E1. The target defines a target location outside of the acceleration chamber. The stripping assembly is positioned in the acceleration chamber and is operable to extract a charge from the charged particles at an intermediate location of the outward spiral path whereby the post-stripping assembly particles are directed towards the target location. The charged particles have an intermediate energy E3 at the intermediate location that is between E1 and E2.

Description

CYCLOTRON INCLUDING MULTIFOIL STRIPPING ASSEMBLY FORSTRIPPING CHARGED PARTICLES AT INTERMEDIATE ENERGIESCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application Serial No. 63 / 645655 filed May 10, 2024, the disclosure of which is hereby incorporated by reference in its entirety.FIELD

[0002] The field relates generally to particle accelerators, and more particularly, to cyclotrons that accelerate charged particles over an outwardly directed spiral path, extract a charge from the charged particles, and redirect the particles towards a target.BACKGROUND

[0003] Particle accelerators have various industrial, medical, and research applications. For example, particle accelerators may be used to produce radioisotopes (also called radionuclides), which have uses in medical therapy, imaging, and research, as well as other applications that are not medically related. Systems that produce radioisotopes typically include a cyclotron that accelerates and guides charged particles within an acceleration chamber along a spiral trajectory at increasing energies. To produce the radioisotopes, the cyclotron forms an energized particle beam of the charged particles, strips the charged particles of a charge producing energized protons, and directs the beam of energized protons out of the acceleration chamber and toward a target that includes a starting radioisotope material. The energized protons impinge the target material thereby generating radioisotopes.

[0004] The radioisotopes produced by the protons impinging the target material depends on the nuclear reaction behavior of the starting material andthe energy of the protons. Depending on the proton energy, undesired radioisotopes (also referred to as impurities) may be produced, leading to operational inefficiencies and reduced yield. There is an ongoing need in particle accelerator technology for improvements that facilitate better control of the proton energy to produce the desired radioisotopes and to do so in a cost-effective manner while reducing complexities of the particle accelerator.

[0005] This section is an introduction to various aspects of the present disclosure, which are described and / or claimed below. This discussion provides supporting information for better understanding of the various aspects of the present disclosure. Accordingly, these statements are to be read in this light, and not as admissions of prior art.BRIEF SUMMARY

[0006] One aspect is a particle acceleration and extraction system. The system comprises a cyclotron and a target. The cyclotron comprises a housing defining an acceleration chamber, the housing including a peripheral wall with an opening. The cyclotron comprises a stripping assembly positioned in the acceleration chamber defined by the housing. The cyclotron is operable to generate a magnetic field in the acceleration chamber in a direction parallel to the central axis and to generate an electric field in the acceleration chamber in a direction perpendicular to the central axis, such that charged particles in the acceleration chamber are accelerated along a spiral path extending outward from the central axis of the acceleration chamber towards the peripheral wall and at increasing energies from an initial energy Ei at a location proximate the central axis to a final energy E2 at a location proximate the peripheral wall, E2 being greater than Ei. The target defines a target location outside of the acceleration chamber. The target location is connected to the opening of the peripheral wall. The stripping assembly is operable to extract a charge from the charged particles at an intermediate location of the outward spiral path whereby the post-stripping assembly charged particles are directed towards the opening and the target location. The intermediate location is on an intermediate orbitof the outward spiral path such that the charged particles have an intermediate energy E3 at the intermediate location that is between Ei and E2.

[0007] Another aspect is a cyclotron for accelerating charged particles over an outwardly directed spiral path and for extracting a charge from the charged particles. The cyclotron comprises a peripheral wall defining an acceleration chamber. The peripheral wall includes an opening. A magnetic field system includes two poles on opposite sides of the acceleration chamber and is operable to generate a magnetic field in the acceleration chamber. An electric field system is operable to generate an electric field in the acceleration chamber. The magnetic field system and the electric field system are cooperatively operable to accelerate charged particles in the acceleration chamber along an outward spiral path from the center axis of the acceleration chamber towards the peripheral wall and bring the charged particles from an initial energy Ei at a first location proximate the center axis to a final energy’ E2 at a second location proximate the opening in the peripheral wall. E2 is greater than Ei. A stripping assembly includes a plurality of rotatable support arms and a plurality of stripper foils. Each of the plurality' of stripper foils is connected to one of the plurality of rotatable support arms wherein one of the plurality of stripper foils is located at an intermediate location of the outward spiral path to extract a charge from the charged particles at the intermediate location. The intermediate location is located a radial distance from the center axis that is less than a radial distance of the second location from the center axis but greater than a radial distance of the first location from the center axis. The charged particles have an intermediate energy E3 at the intermediate location that is between Ei and E2 wherein, upon extracting the charge from the charged particles at the intermediate location, the post-stripping assembly charged particles is directed towards the opening of the peripheral wall.

[0008] Y et another aspect is a cyclotron for accelerating charged particles over an outwardly directed spiral path and for extracting a charge from the charged particles. The cyclotron comprises a peripheral wall defining an acceleration chamber. The peripheral wall includes an opening. A magnetic field system includes two magnets with poles on opposite sides of the acceleration chamber. The magnetic field system is operable to generate a magnetic field in the acceleration chamber. Anelectric field system is operable to generate an electric field in the acceleration chamber. The magnetic field system and the electric field system are cooperatively operable to accelerate negatively charged particles in the acceleration chamber along a spiral trajectory' outward from the center axis of the acceleration chamber towards the peripheral wall and bring the charged particles from an initial energy Ei at an inner orbit of the spiral trajectory’ proximate the center axis to a final energy E2 at an outer orbit of the spiral trajectory proximate the peripheral wall. E2 is greater than Ei. A stripping assembly' comprises a rotatable axle mounted to one of the two magnets within the acceleration chamber, a plurality7of support arms extending from the rotatable axle, and a plurality’ of stripper foils connected to each of the plurality of support arms. One of the plurality of stripper foils is positioned at an intermediate orbit of the spiral trajectory to intercept and modify the negatively charged particles by stripping the negatively charged particles of electrons at an intermediate location of the intermediate orbit wherein the intermediate orbit is between the inner orbit and the outer orbit of the spiral trajectory’ and wherein the negatively charged particles have an intermediate energy E3 at the intermediate location that is between Ei and E2. Upon extracting the charge from the negatively charged particles at the intermediate orbit, the modified particles are directed towards the opening of the peripheral wall to bombard a target material.

[0009] Various refinements exist of the features noted in relation to the above-mentioned aspects. Further features may also be incorporated in the above- mentioned aspects as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to any of the illustrated embodiments may be incorporated into any of the above-described aspects, alone or in any combination.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 is a schematic block diagram of a particle acceleration and extraction system.

[0011] FIG. 2 is a schematic cross-section of a cyclotron of the system of FIG. 1.

[0012] FIG. 3 is a schematic top view of a portion of the cyclotron of FIG. 2, and depicts a spiral trajectory' traveled by charged particles in the cyclotron at increasing energies from an initial energy to a final energy.

[0013] FIG. 4 is a similar view as shown in FIG. 3, and depicts a location on the spiral trajectory' at which charged particles are extracted out of the cyclotron at intermediate energy that is between the initial and final energies.

[0014] FIGS. 5-9 depict various examples of a stripping assembly that is used to extract the charged particles at the intermediate energy location shown in FIG. 4.

[0015] FIG. 10 is a plot of the cross section of the64Ni(p,n)64Cu reaction vs. proton energy.

[0016] FIG. 11 is a plot of the cross section of the58Ni(p,a)55Co reaction vs. proton energy.

[0017] Corresponding reference numerals used throughout the drawings indicate corresponding elements.DETAILED DESCRIPTION

[0018] The present disclosure relates to particle acceleration and extraction systems that include a cyclotron operable to accelerate charged particles at increasing energies, strip a charge from energized charged particles to produce energized protons, and direct the energized protons towards a target material that includes a radioisotope starting material. The energized protons impinge the target material at a suitable energy to generate radioisotopes. The energy of the protons directed into impingement with the target material is controlled to achieve a high probability that a desired radioisotope will be produced while reducing or minimizing the probability that impurities (e.g., undesired radioisotopes) are produced.

[0019] Known cyclotrons include a stripping assembly that operates to strip the charge from the energized charged particles as the particles traverse a spiral trajectory during acceleration. Typically, a stripping assembly intercepts the charged particles along the outer orbit of the spiral trajectory. At this location, the charged particles are at final, or near final, energy. The final energy is typically determined based on the operational conditions of the cyclotron (e.g.. magnetic flux, and / or frequency and voltage of the electric field). In some cases, the final energy that the cyclotron is capable of achieving is not the desired energy level of protons impinging the target material, since it increases the probability of generating reactions with the target material that produce impurities rather than the desired radioisotope.

[0020] In the examples of this disclosure, a stripping assembly is positioned to intercept the charged particles at an intermediate location on the spiral trajectory that is inboard of the outer, or final energy, orbit. The charged particles at the intermediate location are at an intermediate energy, smaller than the final energy. The intermediate energy at which the charged particles are intercepted and impinge the target material suitably increases the probability7of generating reactions with the target material that produce the desired radioisotope rather than impurities. As one example, the target material is enriched Nickel-64 (64Ni) and the desired radioisotope is Copper-64 (64Cu), and the cyclotron is operable to accelerate the charged particles to a final energy of greater than 16 MeV. This final energy risks production of impurities rather than64Cu as will be described below with reference to FIGS. 10 and 11. Accordingly, the stripping assembly is located to intercept the charged particles at an intermediate energy of 16 MeV or smaller, which diminishes the probability of a reaction with the nickel-64 or other nickel isotopes in the enrich target material to produce an impurity7, while maintaining a high probability that the 64-copper isotope is produced (see FIGS. 10 and 11). Intercepting the charged particles at the lower intermediate energy also reduces thermal load on the stripping assembly, which facilitates better heat dissipation and longer lifetime of the stripping assembly parts (e.g., a stripper foil).

[0021] Additional advantages are also provided by the stripping assemblies described below. The stripping assemblies enable extracting the chargedparticles at intermediate energy while using a full beam current capability of the cyclotron. For example, the stripping assemblies are used with cyclotrons operable using a beam current of between 270 pA to 300 pA. This is a significant advantage over other methods of reducing energy7such as beam degraders, which are limited by cooling requirements, are prone to failure due to high heat loads, and can only operate at about 150 pA or lower. The stripping assemblies described can be used in conjunction with lower beam currents as necessary, and in this way provide a wide operational range for the cyclotron while efficiently and effectively producing the desired radioisotope with limited impurities. The stripping assemblies described also include multiple stripper foils which enable longer runtimes of the cyclotron without having to shut down the equipment for replacement of the foils. In particular, the stripping assemblies include a rotatable axle that rotates to locate one stripper foil at the intermediate location and to replace the stripper foils with another stripper foil after it is spent or damaged. Longer runtimes reduce downtime and labor costs, increases throughput, and improves safety by limiting the exposure to radiation during replacement of the foils.

[0022] Referring now to the drawings, FIG. 1 is schematic block diagram of a particle acceleration and extraction system, indicated at 100. The system 100 includes a cyclotron 102, a controller 104, a cooling system 106, an external target 108, and a vacuum system 110. The cyclotron 102 can be an isochronous cyclotron or a synchrocyclotron. The cyclotron 102 includes an ion source 112 that injects charged particles such as. for example, negatively charged Hydrogen ions (e.g., H ) or Deuterons into an acceleration chamber 204 (see FIG. 2) of the cyclotron. The cyclotron 102 also includes a magnetic field system 114 that generates a magnetic field in the acceleration chamber 204, and an electric field system 116 that generates an electric field in the acceleration chamber 204. The magnetic field and the electric field generated by the systems 114, 116 are regulated or controlled by the controller 104, and cooperate to accelerate the charged particles along an outward spiral path or trajectory7118 at increasing energies. The vacuum system 110 draws a vacuum in the acceleration chamber 204, which reduces pressure and removes other particles that can interfere with the spiral trajectory of the charged particles.

[0023] A stripping assembly 120 is positioned in the acceleration chamber and includes a stripper foil 222 (e.g.. a carbon / graphite foil), shown in FIG. 2, that intercepts the charged particles at a point along the spiral trajectory 118. The stripper foil 222 extracts electrons from the charged particles, and producing protons that have an opposite charge. The protons are diverted along a path 122 as a result of the electric field in the acceleration chamber. The protons travel along the path 122 towards and impinge or bombard the target 108.

[0024] The target 108 includes a radioisotope starting material (e.g., enriched Ni-64) that produces radioisotopes (e.g., Cu-64) when bombarded with the protons. The radioisotope starting material is at one or more locations defined by the target 108. The radioisotope starting material suitably produces radioisotopes used in diagnostic nuclear medicine, such as in nuclear medicine imaging and / or positron emission tomography (PET) imaging. Alternatively, the radioisotope starting material produces radioisotopes useful in any suitable application, such as other scientific research or analysis purposes. The radioisotope starting material suitably includes enriched64Ni that produces the64Cu radioisotope. Other radioisotope starting materials may be used, such as Yttrium-89 (used to produce the radioisotope Zirconi um-89).

[0025] The type of radioisotopes produced from the radioisotope starting material depends on the energy of the protons bombarding the target 108, which in turns depends on the location along the spiral trajectory at which the charged particles are intercepted by the stripping assembly 120. As will be described below, the stripping assembly 120 is positioned to intercept the charged particles at suitable energy7to produce the desired radioisotope from the target 108 while reducing or eliminating production of impurities (e.g., undesired radioisotopes).

[0026] Bombardment of the charged particles within the acceleration chamber and / or bombardment of the protons at or near the target 108 generates heat. The cooling system 106 circulates a coolant (e.g., water) that absorbs generated heat from the cyclotron 102 and / or the target 108.

[0027] The controller 104 controls various aspects and parameters of the system 100 during operation. The controller 104 is communicatively connected to various components of the system 100, such as the cyclotron 102, the cooling system 106, the target 108, and / or the vacuum system 110. The controller 104 is a computer system that includes one or more processors and one or more memory devices that store programs or instructions that are executable by the processor(s) to perform the functions described for the controller 104. Although a single controller 104 is shown and described, the controller 104 may include multiple controllers 104 that may be centralized or decentralized. The controller 104 includes a communication interface to communicatively couple the controller 104. via one or more connections, to one or more components of the system 100 via a wired and / or wireless connection.

[0028] In one example, the ion source 112 injects negatively charged Hydrogen ions (e.g., H ) into the acceleration chamber 204. These ions gain energy as they accelerate along orbits of the outward spiral trajectory 118 due to the magnetic field and the accelerating electric field until they are intercepted at an intermediate energy E3 by the stripper foil 222 at an intermediate location 404 (FIG. 4) on an intermediate orbit 402 (FIG. 4) of the spiral trajectory 118. In this example, the stripper foil 222 extracts electrons from the H ions (e.g., strips the H ions of electrons), converting the negatively charged ions into positively charged ions (or protons), and guides the protons out of the acceleration chamber 204 (via opening 208, FIG. 2) towards the target 108 to bombard the target 108. The target 108 may include enriched Ni-64 and the protons (e.g., proton beam) may be used to initiate a nuclear reaction with the target 108, such as the64Ni(p,n)64Cu reaction, to produce radioisotopes, such as Copper-64 (64Cu).

[0029] FIG. 2 is a schematic cross-section of the cyclotron 102. The cyclotron 102 includes a housing 202 defining the acceleration chamber 204 extending between a peripheral wall 206. An opening 208 is defined in the peripheral wall to allow the protons to exit the acceleration chamber 204 and travel towards the target 108 after being stripped of charge using the stripping assembly 120.

[0030] The magnetic field system 114 of the cyclotron 102 includes two magnets 210, 212 that are located on opposite sides of the acceleration chamber 204. The magnets 210, 212 each include a pole that faces the pole of the other magnet across the acceleration chamber 204. The magnets 210, 212 also include magnet coils surrounding the respective pole. The magnets 210, 212 are operable (e.g., using the controller 104) to generate the magnetic field in a direction of a central axis A of the acceleration chamber 204, between the poles of the magnets 210, 212.

[0031] The electric field system 116 of the cyclotron 102 includes two electrodes or “dees” 214, 216 that are located between the magnets 210, 212. The electrodes include radio frequency (RF) electrodes in some examples. The electrodes 214, 216 are spaced apart from each other, creating a gap at the central axis A. The electrodes 214, 216 are operable (e.g., using the controller 104) to generate the electric field in a direction perpendicular to the central axis A, across the gap between the two electrodes 214. 216.

[0032] Depending on the ty pe of cyclotron 102, the direction of the electric field between the electrodes 214, 216 oscillates or alternates and the direction of the magnetic field between the magnets 210, 212 is held constant to accelerate the charged particles along the spiral trajectory. Alternatively, the direction of the electric field between the electrodes 214, 216 is held constant and the direction of the magnetic field alternates. Oscillation and / or alternating of the electric field or the magnetic field is controlled using the controller 104. The magnets 210, 212 and the electrodes 214, 216 are shown as separate components, but electromagnets can also be used to generate the electric field and the magnetic field.

[0033] The ion source 112 is located at or near the central axis A and between the electrodes 214, 216. The charged particles are injected into the acceleration chamber 204 via the ion source 112, and during operation the charged particles travel along the spiral trajectory' from the ion source 112 towards the peripheral wall 206 with increasing energies.

[0034] The stripping assembly 120 includes a rotatable center axle 218 mounted within the acceleration chamber 204. For example, the center axle 218 is mounted to one of the magnets 210, 212, but can be mounted to any suitable structure of the cyclotron 102.

[0035] The center axle 218 is rotatable using a motor controlled by the controller 104. Foil support arms 220 extend from the center axle 218, and one or more stripper foils 222 are connected to each support arm 220. The center axle 218 is positioned a radial distance from the central axis A such that one of the stripper foil 222 connected to one of the support arms 220 is located at a desired location for intercepting the charged particles along the spiral trajectory. The center axle 218 may be positioned at a radial distance from the central axis A such that the stripper foil 222 located within the spiral trajectory7is positioned at an intermediate location along an intermediate orbit of the spiral trajectory. In one example, the cyclotron 102 is operable to accelerate the particles to a final energy E2 of 18 MeV or greater. In this example, the center axle 218 may be positioned such that one of the stripper foil 222 is along an intermediate orbit that is associated with an energy' of 16 MeV or lower (e.g., between 12 MeV to 16 MeV), such that this stripper foil 222 intercepts the charged particles along the intermediate orbit rather than the outer orbit of the spiral trajectory'. The support arms 220 have suitable angular spacing (e.g., at least 72° or at least 90°) such that the other stripper foils 222 connected to the support arms 220 are located out of the spiral trajectory7and do not interfere with charged particles. When the stripper foil 222 located for intercepting the charged particles is spent or damaged, the center axle 218 is rotated to move the support arms 220 and bring a fresh stripper foil 222 into location for intercepting the charged particles.

[0036] Mounting the center axle 218 to structure(s) of the cyclotron 102, such as one of the magnets 210, 212. requires appropriate tuning of the magnetic field and RF harmonics of the cyclotron 102. Accordingly, in some examples, iterative analysis is performed to tune the magnetic and electrical characteristics of the cyclotron 102. The iterative analysis is also performed to ensure that the location of the stripper foil 222 is at the appropriate location for intercepting the charged particles at the desired energy.

[0037] Referring to FIG. 3, in operation of the cyclotron, the magnetic field and the electric field are generated in the acceleration chamber to guide and accelerate the charged particles along a spiral trajectory 300. Over the spiral trajectory' 300, the charged particles travel along orbits of increasing radius from the central axis A (shown in FIG. 2). In each orbit, the energy' of the charged particles increases. The charged particles have an initial energy Ei at or near the ion source 112 and a final energy E2 in an outermost orbit 302 proximate the peripheral wall 206. The final energy E2 depends on the type of charged particles as well as the operating conditions of the cyclotron (e.g., the accelerating frequency of the electric field).

[0038] The example cyclotron 102 is operable to accelerate the particles to a final energy' E2 of greater than 16 MeV, such as 18 MeV or greater. The final energy' E2 may be, for example, from greater than 16 MeV to 500 MeV, such as from 18 MeV to 500 MeV. The final energy’ E2may also be greater than 500 MeV. The cyclotron 102 may operate using a beam current of the charged particles that is greater than 150 pA, such as a beam current of between 270 pA to 300 pA. Lower beam currents may also be used, such as beam currents smaller than 150 pA. Additionally and / or alternatively, the cyclotron 102 may be operable to achieve a relatively lower final energy E2, include a final energy’ E2 that is smaller than 18 MeV, or smaller than 16 MeV. The examples described can be implemented in any type of cyclotron 102 operable to achieve any final energy E2 and / or using any beam current.

[0039] In conventional cyclotrons, a stripping assembly is positioned such that a stripper foil intercepts the charged particles at a point (indicated by "‘X” 304 in FIG. 3) along the outermost orbit 302, at which point 304 the charged particles are at the final energy' E2. However, for the production of some radioisotopes, it is not desirable to intercept the charged particles at the final energy E2 since this can increase the amount of impunties. or undesired radioisotopes, produced. This is because the energy' at which the protons bombard the target 108 affects the radioisotopes produced. Depending on the type of radioisotope starting material included in the target, increased energy of bombardment may undesirably lead to the production of other radioisotopes than the desired type of radioisotopes, increasing the amount of impurities produced. The increased energy of the protons also generatesunwanted heat and reduces the useful life of the stripper foil. The cyclotron 102 may be operated at lower accelerating frequency to reduce the energy in the outermost orbit 302 where the stripper foil is located, but this is disadvantageous since it adds complexity to the system and increases costs.

[0040] To illustrate, reference is made to FIGS. 10 and 11. FIG. 10 is a plot of the cross section of the64Ni(p,n)64Cu reaction vs. proton energy. FIG. 11 is a plot of the cross section of the58Ni(p,a)55Co reaction vs. proton energy. As described above, the starting radioisotope material of the target 108 suitably includes enriched64Ni which produces the isotope64Cu via the64Ni(p,n)64Cu reaction. The64Cu isotope is advantageously used in diagnostic nuclear medicine (e.g., PET imaging) since it is a radionuclide which excellent imaging characteristics, including an average positron energy' of 278.2 keV which provides high resolution images, and has a moderate half-life (12.7 h) that is significantly longer than other common PET isotopes such as oxygen-15, nitrogen-13, carbon-11, fluorine-18, and gallium-68. which allows for production, purification, incorporation into a carrier molecule (e.g., peptide, small-molecule, antibody, etc.) and distribution to medical facilities as an end-use product before excessive radioactive decay or decomposition occurs. As shown in FIG. 10, the64Ni(p,n)64Cu reaction has a very high probability of occurring at proton energies between 12 MeV and 16 MeV, with additional probability diminishing at proton energies greater than 16 MeV.

[0041] Enriched64Ni used as the starting material in the target 108 ty pically includes other nickel isotopes, such as58Ni, which are also reactive with the protons to produce undesired isotopes (e.g., cobalt isotopes) that result in impurities and lower efficiency of the reaction product. For example,38Ni produces the55Co isotope via the58Ni(p,a)55Co reaction. As shown in FIG. 11, the58Ni(p,a)55Co reaction has a very high probability of occurring at proton energies greater than 18 MeV. Lowering the proton energy' to 16 MeV or lower, for example, greatly diminishes the probability of this reaction occurring to produce this impurity.

[0042] As can be understood from FIGS. 10 and 11. lowering the proton energy to 16 MeV or lower (e.g., between 12 MeV to 16 MeV) maintains avery' high probability that the64Ni(p.n )64Cu reaction will occur while also greatly reducing the probability that the58Ni(p,a)55Co reaction will occur. In a cyclotron that is operable to achieve a final energy E2 of greater than 16 MeV, such as 18 MeV or greater, therefore, it would be advantageous to strip the charged particles at an intermediate energy E3 that is lower than the final energy E2, such as an intermediate energy E3 that is between 12 MeV to 16 MeV. In some embodiments, the charged particles are stripped at an intermediate energy E that is between 13 MeV to 15 MeV.

[0043] Referring to FIGS. 2 and 4, the stripping assembly 120 is located such that one of the stripper foils 222 intercepts the charged particles at an intermediate location (indicated by “X” 404 in FIG. 4) along an intermediate orbit 402 of the spiral trajectory 300. The charged particles at this intermediate location 404 are at the intermediate energy E3 that is smaller than E2. The stripping assembly 120 is positioned to locate the stripper foil 222 for intercepting the charged particles at any suitable intermediate location 404. along any intermediate orbit 402. In this regard, the intermediate energy E3 is between 5% and 95% of the final energy E2, depending on the intermediate location 404 of the stripper foil 222 that intercepts the charged particles. For example, the intermediate energy E3 is betw een 10% to 90% of the final energy’ E2, such as between 50% to 90% of the final energy E2, between 60% to 90% of the final energy E2, betw een 70% to 90% of the final energy E2, betw een 80% to 90% of the final energy E2, between 50% to 80% of the final energy E2, between 60% to 80% of the final energy' E2, between 70% to 80% of the final energy E2, between 50% to 70% of the final energy E2, between 50% to 60% of the final energy E2, or between 60% to 70% of the final energy' E2. The intermediate energy E3 in various examples in less than 95% of the final energy E2, such as less than 90%, or less than 88.8% of the of the final energy' E2.

[0044] The intermediate energy E3 is suitably tuned for the production of the desired radioisotope w hile reducing production of impurities that form at higher energies. In this regard, the value(s) selected for the intermediate energy E3 will vary depending on the desired radioisotope and reactive behavior of the radioisotope starting material included in the target 108. For example, referring again to FIGS. 10 and 1 1 , the intermediate energy E3 is between 12 MeV and 16 MeVto optimize balancing an increased probability that the64Ni(p,n)64Cu reaction will occur and a reduced the probability that the58Ni(p,a)55Co reaction will occur. Additionally, with the stripping assembly 120 positioned for intercepting the charged particles at the intermediate location 404, the cyclotron 102 can be run at full capacity, and complex controls and equipment for varying the final energy E2 of the cyclotron 102 are not required.

[0045] Referring to FIGS. 5-9, various examples of the stripping assembly 120 are shown, respectively indicated at 120a-e. Each stripping assembly 120a-e includes multiple support arms 220, and each support arm 220 is connected to one or more stripper foils 222. As described above, the support arms 220 are moveable by rotation of the center axle 218 to replace a spent or damaged stripper foil 222 connected to one of the support arms with a fresh stripper foil 222 connected to an adjacent support arm 220. The FIG. 5 is an example stripping assembly 120a that includes four support arms 220 spaced angularly by 90°. FIG. 6 is an example stripping assembly 120b that includes four support arms 220 spaced angularly by 90°, similar to the stripping assembly 120a, and also includes two stripper foils 222 connected to each one support arm 220 at different radial locations. The configuration of the stripping assembly 120b can extend the runtime of the cyclotron without stopping by providing a backup foil (radially inward foil 222) that intercepts the charged particles even when the primary foil is spent or damaged. FIG. 7 is an example stripping assembly 120c that includes two support arms 220 spaced angularly by 180°. FIG. 8 is an example stripping assembly 120d that includes three support arms 220 spaced angularly by 120°. FIG. 9 is an example stripping assembly 120e that includes five support arms 220 spaced angularly by 72°. Other configurations of the stripping exist and the stripping assembly 120 is not limited to the examples depicted in FIGS. 5-9.

[0046] When introducing elements of the present invention or the embodiment(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.

[0047] Unless otherwise indicated, approximating language, such as “generally ' “substantially,” and “about.” as used herein indicates that the term so modified may apply to only an approximate degree, as would be recognized by one of ordinary skill in the art, rather than to an absolute or perfect degree. Accordingly, a value modified by a term or terms such as “about,” “approximately,” and “substantially” is not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Additionally, unless otherwise indicated, the terms “first,” “second,” etc. are used herein merely as labels, and are not intended to impose ordinal, positional, or hierarchical requirements on the items to which these terms refer. Moreover, reference to. for example, a “second” item does not require or preclude the existence of, for example, a “first” or lower-numbered item or a “third” or higher-numbered item.

[0048] As used herein, the terms “processor” and “computer” and related terms, e.g., “processing device,” “computing device,” and “controller” are not limited to just those integrated circuits referred to in the art as a computer, but instead refer broadly to a microcontroller, a microcomputer, a programmable logic controller (PLC), an application specific integrated circuit, and / or other programmable circuits, and such terms are used interchangeably herein. In the embodiments described herein, memory may include, but is not limited to, a computer-readable medium, such as a random access memory7(RAM), and a computer-readable non-volatile medium, such as flash memory7. Alternatively, a floppy disk, a compact disc - read only memory (CD-ROM), a magneto-optical disk (MOD), and / or a digital versatile disc (DVD) may also be used. Also, in the embodiments described herein, additional input channels may be, but are not limited to only being, computer peripherals associated with an operator interface such as a mouse and a keyboard. Alternatively, other computer peripherals may also be used such as, but not limited to, a scanner. Furthermore, in the embodiments described herein, additional output channels may include, but are not limited to only being, an operator interface monitor.

[0049] This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art topractice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.

Claims

WHAT IS CLAIMED IS:

1. A particle acceleration and extraction system, the system comprising: a cyclotron comprising: a housing defining an acceleration chamber, the housing including a peripheral wall with an opening; and a stripping assembly positioned in the acceleration chamber defined by the housing, wherein the cyclotron is operable to generate a magnetic field in the acceleration chamber in a direction parallel to a central axis and to generate an electric field in the acceleration chamber in a direction perpendicular to the central axis, such that charged particles in the acceleration chamber are accelerated along a spiral path extending outward from the central axis of the acceleration chamber towards the peripheral wall and at increasing energies from an initial energy Ei at a location proximate the central axis to a final energy E2 at a location proximate the peripheral wall, E2 being greater than Ei; a target defining a target location outside of the acceleration chamber, the target location being connected to the opening of the peripheral wall; and wherein the stripping assembly is operable to extract a charge from the charged particles at an intermediate location of the outward spiral path whereby the post-stripping assembly charged particles are directed towards the opening and the target location, the intermediate location being on an intermediate orbit of the outward spiral path such that the charged particles have an intermediate energy E3 at the intermediate location that is between Ei and E2.

2. The system of claim 1, wherein the stripping assembly includes support arms moveable about a rotation axis parallel to the central axis, and stripper foils each connected to one of the support arms, wherein one of the stripper foils is located at the intermediate location of the outward spiral path and movement of thesupport arms is controlled to replace the one of the stripper foils with another stripper foil at the intermediate location.

3. The system of claim 2, wherein each support arm is spaced angularly from each adjacent support arm an arc measure of 72° or greater.

4. The system of claim 2, wherein each support arm is spaced angularly from each adjacent support arm an arc measure of 90° or greater.

5. The system of any one of claims 1 to 4, wherein the final energy E2 is greater than 16 MeV.

6. The system of any one of claims 1 to 5, wherein the intermediate energy E3 is 16 MeV or less.

7. The system of any one of claims 1 to 5, wherein the intermediate energy E3 is between 12 MeV and 16 MeV.

8. The system of any one of claims 1 to 5, wherein the intermediate energy E3 is between 13 MeV and 15 MeV.

9. The system of any one of claims 1 to 8, wherein the cyclotron is operable to accelerate the charged particles along the outward spiral path using a beam current of greater than 150 pA.10 The system of claim 9, wherein the cyclotron is operable to accelerate the charged particles along the outward spiral path using a beam current of between 270 pA and 300 pA.

11. The system of claim 1, wherein the intermediate energy E3 is less than 90% of the final energy E2.

12. A cyclotron for accelerating charged particles over an outwardly directed spiral path and for extracting a charge from the charged particles, the cyclotron comprising:a peripheral wall defining an acceleration chamber, the peripheral wall including an opening; a magnetic field system including two poles on opposite sides of the acceleration chamber, the magnetic field system operable to generate a magnetic field in the acceleration chamber; an electric field system operable to generate an electric field in the acceleration chamber, the magnetic field system and the electric field system cooperatively operable to accelerate charged particles in the acceleration chamber along an outward spiral path from a center axis of the acceleration chamber towards the peripheral wall and bring the charged particles from an initial energy Ei at a first location proximate the center axis to a final energy E2 at a second location proximate the opening in the peripheral wall, E2 being greater than Ei; and a stripping assembly including a plurality of rotatable support arms and a plurality of stripper foils, each of the plurality of stripper foils being connected to one of the plurality of rotatable support arms, wherein one of the plurality of stripper foils is located at an intermediate location of the outward spiral path to extract a charge from the charged particles at the intermediate location, the intermediate location being located a radial distance from the center axis that is less than a radial distance of the second location from the center axis but greater than a radial distance of the first location from the center axis; the charged particles having an intermediate energy E3 at the intermediate location that is between Ei and E2, wherein, upon extracting the charge from the charged particles at the intermediate location, the post-stripping assembly charged particles is directed towards the opening of the peripheral wall.

13. The cyclotron of claim 12, wherein the plurality of rotatable support arms is moveable about a rotation axis parallel to the center axis, and wherein movement of the plurality of rotatable support arms is controlled to replace the one of the stripper foils with another stripper foil at the intermediate location.

14. The cyclotron of claim 12, wherein each of the plurality of rotatable support arms is spaced angularly from each adjacent support arm by an arc measure of 72° or greater.

15. The cyclotron of any one of claims 12 to 14, wherein the final energy E2 is greater than or equal to 18 MeV.

16. The cyclotron of any one of claims 12 to 14, wherein the intermediate energy E3 is 16 MeV or less.

17. The cyclotron of any one of claims 12 to 14, wherein the intermediate energy E3 is between 12 MeV and 16 MeV.

18. The cyclotron of any one of claims 12-17, wherein the cyclotron is operable to accelerate the charged particles along the outward spiral path using a beam current of between 270 pA and 300 pA.

19. The cyclotron of any one of claims 12-17, wherein the intermediate energy E3 is less than 90% of the final energy E2.

20. A cyclotron for accelerating charged particles over an outwardly directed spiral path and for extracting a charge from the charged particles, the cyclotron comprising: a peripheral wall defining an acceleration chamber, the peripheral wall including an opening; a magnetic field system including two magnets with poles on opposite sides of the acceleration chamber, the magnetic field system operable to generate a magnetic field in the acceleration chamber; an electric field system operable to generate an electric field in the acceleration chamber, the magnetic field system and the electric field system cooperatively operable to accelerate negatively charged particles in the acceleration chamber along a spiral trajectory outward from the center axis of the acceleration chamber towards the peripheral wall and bring the charged particles from an initialenergy Ei at an inner orbit of the spiral trajectory proximate the center axis to a final energy E2 at an outer orbit of the spiral trajectory proximate the peripheral wall, E2 being greater than Ei; and a stripping assembly comprising: a rotatable axle mounted to one of the two magnets within the acceleration chamber; a plurality of support arms extending from the rotatable axle; and a plurality7of stripper foils connected to each of the plurality' of support arms; wherein one of the plurality of stripper foils is positioned at an intermediate orbit of the spiral trajectory, to intercept and modify the negatively charged particles by stripping the negatively charged particles of electrons at an intermediate location of the intermediate orbit, wherein the intermediate orbit is between the inner orbit and the outer orbit of the spiral trajectory', and wherein the negatively charged particles have an intermediate energy E3 at the intermediate location that is between Ei and E2; and wherein upon extracting the charge from the negatively charged particles at the intermediate orbit, the modified particles are directed towards the opening of the peripheral wall to bombard a target material.

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