Partial ionization plasma centrifuge for fusion power

Abstract

A plasma centrifuge is provided that is suitable for processing material for use as fuel in a fusion generator. The centrifuge system includes one or more centrifuges including a central cylindrical chamber, a plurality of electrodes arranged to generate a partially-ionzied plasma within the chamber, and an electromagnetic field generator configured to generate an electromagnetic field within the chamber. The plasma centrifuge system causes ions of materials having different atomic weights to exit the central chamber at various outlets based upon their atomic weights.

Description

Docket No. 165704-00021 OUSPARTIAL IONIZATION PLASMA CENTRIFUGE FOR FUSION POWERCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a non-provisional of, and claims the priority benefit of U.S. Provisional Patent Application No. 63 / 695,487, filed September 17, 2024, the disclosure of which is incorporated by reference in its entirety for all purposes.BACKGROUND

[0002] A fusion reactor is a device that provides electricity from heat generated during nuclear fusion reactions in which two atomic nuclei fuse into a heavier nucleus in a process that releases energy. Fusion reactors typically use a fuel in a plasma state, which is held in a confined environment. Initiating and maintaining a fusion reaction at sufficient levels to produce usable electricity requires a large energy input. Achieving a sufficient combination of input energy, fuel density, and temperature has proven to be challenging. To date, no fusion reactors have achieved a sustained fusion reaction that produces more usable energy than is required to initiate and maintain the fusion reaction.BRIEF DESCRITION OF THE DRAWINGS

[0003] The accompanying drawings, which are included to provide a further understanding of the disclosed subject matter, are incorporated in and constitute a part of this specification. The drawings also illustrate implementations of the disclosed subject matter and together with the detailed description explain the principles of implementations of the disclosed subject matter. No attempt is made to show structural details in more detail than can be necessary for a fundamental understanding of the disclosed subject matter and various ways in which it can be practiced.

[0004] FIG. 1 shows a side cut-away view of an example plasma centrifuge as disclosed herein.

[0005] FIG. 2A shows a side view of a hollow electrode as disclosed herein, which is suitable for use in a plasma centrifuge as shown in FIG. 1. FIG. 2B shows an end schematic view of the same.Docket No. 165704-00021 OUS

[0006] FIG. 3 shows a schematic view of an example plasma centrifuge as shown in FIG. 1, which includes multiple successive stages in a cascade arrangement as disclosed herein.

[0007] FIG. 4 shows an example fusion generator system incorporating a plasma centrifuge system as disclosed herein.DETAILED DESCRIPTION

[0008] Fusion devices have a unique set of engineering requirements compared to more conventional power-generating systems, such as complex requirements around the fuel processing systems needed for fusion power plants. For example, recycling the exhaust of these devices and breeding new fuel to sustain the reaction can be challenging problems.

[0009] Exhaust recycling may be important to the overall fuel cycle. For example, many fusion reactor designs use deuterium- deuterium (D-D) fusion, in which two deuterium nuclei fuse to produce either a tritium nucleus and a proton or a helium-3 nucleus and a free neutron; or deuterium-tritium (D-T) fusion, in which one deuterium nucleus fuses with one tritium nucleus to produce a helium-4 nucleus and a free neutron in addition to the desired energy production. Conventional D-T fusion devices often have a relatively low tritium burn efficiency (TBE), meaning that most (often 95% or more) of injected fuel is exhausted from the device before being burned. Accordingly, deuterium-tritium burning devices may require relatively large mass flow rates of tritium, and rapid recycling may be desirable to minimize the total tritium required in the system (the “tritium inventory”) to an acceptable level. Fusion systems that use deuterium and helium-3 as fuel can have an analogous challenge with He-3 processing in various examples, such as separation of He-3 from He-4, which may be a challenging process due to the lack of chemical effects to distinguish between the isotopes as well as the lack of chemical reactivity more broadly that could otherwise provide some isotope effects to allow for separation. Of particular interest in gaseous fuel processing is rebalancing of light isotopes such as those of hydrogen and helium.

[0010] Many fusion reactor designs, both conventional and as disclosed herein, include a fuel “breeding blanket,” which is a region of material near, around, or forming a part of the plasma containment device, that serves multiple purposes in maintaining the fusion reactor. Typically,Docket No. 165704-00021 OUS the breeding blanket is designed to do one or more of the following: absorb neutrons generated in the reactor to generate tritium from lithium; increase the total neutron flux in the system through neutron multiplication reactions; provide cooling for the reactor; and shield the exterior of the reactor from radiation, including neutrons, produced during the fusion reaction.

[0011] As a result, in addition to hydrogen and helium separations, lithium separation can play an important role for fusion energy overall and for the efficiency of the individual reactor. Most of the tritium generated in a typical fusion blanket of conventional fusion reactors results from a reaction of a thermal neutron, typically generated in the reactor fuel plasma, with a Li-6 nucleus. As the natural abundance of Li-6 is only about 7.5%, significant improvements in tritium breeding efficiency may be achieved through enrichment of lithium to have higher concentrations of Li-6.

[0012] In various examples of at least some of the above separations, isotopes of light elements may need to be separated. These isotopes can have minimal usable chemical effects that can make the separation especially challenging in some examples. For example, separation of He-3 from He-4 has nearly no chemically useful properties to enable separation, with existing methods relying on mass based effects or superfluid effects. A less extreme example is for lithium isotope separation, where small chemical effects are present and can be used to achieve separation in processes like the column exchange (COLEX) process, but where single stage separation factors are exceedingly small, requiring cascades with hundreds or thousands of stages to achieve a desired target enrichment. As disclosed herein, it has been found that use of a partial ionization plasma centrifuge may be well-suited to achieving such physical separations of low mass species, thus improving the efficiency of the fusion blanket and / or the overall fusion reactor.

[0013] The basic principle of a plasma centrifuge is to make use of a physical separation mechanism similar to an ultracentrifuge approach used in uranium isotope separation, but using a “plasma rotor” to drive an azimuthal flow of ions in the plasma through JxB forces. Within a rotating plasma subjected to an electromagnetic field, the ions experience a force in the direction of the cross product of the electric (J) and magnetic (B) forces caused by the interaction of the ion with the field, i.e., perpendicular to the direction of both the ion velocity and magnetic fieldDocket No. 165704-00021 OUS operating on each ion. In this arrangement, ions in a partially ionized plasma transfer their momentum to a mostly neutral background gas. Centrifugal forces create a gradient in the radial pressure profde, causing heavier ions (i.e., ions having a higher atomic weight) to move more toward the outer regions of the rotating plasma than lighter ions.

[0014] A separation factor R can be defined for any two gas species within the plasma:where rhi is the mass flow of species 1; rh is the total mass flow; r = 0 corresponds to the axis of the device and r = a corresponds to the outer radius of the device, both at the outlet of the centrifuge; v represents the azimuthal velocity of the gas, and mi, m2 are the atomic masses of the two isotopes being separated.

[0015] A high R value is desirable to efficiently separate isotopes in the plasma centrifuge. To achieve a high R, it may be necessary to increase the azimuthal velocity while decreasing the temperature. However, there is a limit at which the kinetic energy of an ion is equal to the ionization potential of the neutral gas (the “Alfven ionization velocity”):- 1mv7= eVionthe kinetic energy of the ion at the ionization velocity v, and Vton is the ionization potential of the neutral gas,Rewriting the separation factor R using the Alfven ionization velocity gives the following:where mt, mm is the mass of the more-readily ionized species based on its combination of mass and ionization energy.Docket No. 165704-00021 OUS

[0016] While higher velocities may be achieved in a fully ionized plasma in principle, higher temperatures limit separation factors and can introduce significant engineering challenges. Accordingly, it may be preferable for embodiments disclosed herein to reduce heating while driving and enabling engineering improvements.

[0017] The unique properties of a plasma centrifuge approach may be well suited to low mass species as disclosed herein. In various separation examples, the mass difference mi-n is fixed; as such, the exponent in the separation factor R is inversely proportional to the mass of the easiest to ionize species in the system. The viscous shear heating in a plasma centrifuge also may be strongly influenced by the ratio of the viscosity and the conductivity, which can be proportional to mass for neutral monatomic gases. As such, in some examples, viscous heating that drives increased temperatures can be mitigated, and this can provide a reason why low-mass separations can be a suitable application for this approach. Fusion energy may have a particular need for many of the separations described herein. In addition, these properties can mean that plasma centrifuges as disclosed herein can have poor properties for separation of isotopes with large masses, and thus can be inherently resistant to proliferation.

[0018] In view of the foregoing, a need exists for an improved mass-based element and isotope separation system and method, suitable for low-mass isotopes, to reduce or overcome the aforementioned obstacles and deficiencies of conventional mass-based separation methods, particularly where they have proposed the use of isotope separation schemes through the use of plasma centrifuge systems. Specifically, embodiments disclosed herein provide improved performance when implemented as part of a fusion fuel processing system through the use of optimized current profiles to reduce viscous dissipation; use of temperature controlled surfaces and / or other parameters of the system to control lithium transport in the system and improve separation of lithium isotopes; implementation of fuel processing and isotope rebalancing systems based on the plasma centrifuge, including for both deuterium-tritium and deuterium- helium-3 systems, application of ionization seeding with lithium to reduce plasma temperatures, and implementation of multiple separation stages in a single vacuum envelope to achieve a separation cascade.Docket No. 165704-00021 OUS

[0019] Embodiments disclosed herein include systems and methods for mass-based separation of light elements such as hydrogen, helium, lithium, and the like and their isotopes, based on the principle of partial ionization centrifugation. In the partial ionization regime, the plasma can be operated at lower temperature and without concern for maintaining plasma confinement to achieve full ionization, as well as relying on simpler physics for separation that make the device more reliable and robust. Additionally, a partial ionization centrifuge can be operated at significantly higher pressure and corresponding throughput than a fully ionized centrifuge, improving performance for multiple applications. They may be suited for use in, for example, fuel cycles of fusion devices, such as in the fuel reprocessing systems, for preparation of material for fusion blankets, and the like.

[0020] Embodiments disclosed herein may include approaches and subsystems that provide high throughput and high selectivity separation of elements and isotopes. For example, systems according to embodiments disclosed herein may be particularly well-suited for separations including hydrogen isotope separation, helium isotope separation, lithium isotope separation, the separation of hydrogen isotopes from helium, the separation of higher mass noble gases from hydrogen and helium, and the like.

[0021] FIG. 1 shows a side cut-away view of an example plasma centrifuge 100 according to embodiments disclosed herein. The centrifuge may include multiple separation stages within a single vacuum vessel, thus allowing for larger separation factors at the system level without the need for additional separate centrifuges, as disclosed in further detail below. This allows for more compact devices and fewer separate components to achieve separation of a larger number of isotopes or other species.

[0022] The device includes a cylindrical central chamber 101 that generates and contains the plasma. The device may include annular electrodes 103 at one or both ends of the chamber. Alternatively, the wall of the chamber itself is used as the anode. Alternatively or in addition, an axial electrode 106 may extend through the center of the chamber. Where a central axial electrode may be is used, it may have annular hollow cathode configuration, with a structure as shown in FIGS. 2A-2B. In this arrangement, a central conductor 210 is heated resistively and biased to a specified potential. The central conductor 210 may be surrounded by a thermionicDocket No. 165704-00021 OUS emitter 220 such as a tube of low work function material, for example lanthanum hexaboride or barium oxide. This tube of material is in turn surrounded by an outer jacket 230 of a high temperature tolerant material, for example a refractory metal like tungsten. In some implementations the hollow cathode can be purged directly with the working fluid gas to allow it to be operated at higher pressures. Perforations 235 allow for gas flow through the cathode.Regardless of specific configuration, the electrodes 103, 106 may be used to generate a plasma, for example by applying a sufficiently high electric field within the central chamber 101.

[0023] The central chamber 101 may be electrically connected to the anode for the arc discharge(es) that generate the plasma. This allows it to serve the additional purpose of dissipating heat from the plasma and simplifies the high-current electrical connections. Similarly, electrically non-conducting breaks, such as regions that include alumina and / or zirconia, may be used to isolate end flanges from the rest of the vessel electrically, allowing the end flanges to be electrically connected to the cathode to further improve heat dissipation and simplify electrical connections.

[0024] When operating with large plasma currents at steady-state, the central chamber 101 may be cooled by an electrically non-conducting fluid, such as deionized water, transformer oil, or the like. The coolant may flow through thermally-bonded cooling lines such as metal pipes, and / or through a cooling jacket that is integrated into the central chamber. Some embodiments may tolerate higher steady-state temperatures using a refractory anode, such as an anode made of tungsten, niobium, molybdenum, or the like, which is mechanically held in poor thermal contact with the vessel wall but sufficient electrical contact. For example, set-screws, radial plungers, garter springs, compressible shims, or the like may be used to secure the anode.

[0025] Microwave and / or RF heating sources may be applied separately to the plasma discharge to increase the ratio of electron to ion / neutral temperature. Where a hot electron plasma regime is employed, auxiliary increasing of the ratio of electron temperature to heavy (ion / neutral) particle temperature (the Te / Th ratio) may increase conductivity by a significant margin, in some cases up to a factor of 3-5 or more. This also may drastically reduce the power lost by joule heating in the centrifuge by the system, thereby reducing the overall power requirements to achieve the same rotational velocities and separation factors.Docket No. 165704-00021 OUS

[0026] Alternatively, the centrifuge may be operated at a lower working pressure so that electrons in the plasma are less thermalized with the ions and neutrals, akin to the behavior of a glow discharge regime, a common example of a simple DC driven plasma with an asymmetric electron / ion temperature. This operating regime may in particular be enabled by operation at high magnetic field, where lower currents may be needed in the system to achieve the desired rotation rates. Pressure control and external heating methods may be adjusted accordingly to maximize the perpendicular conductivity of the plasma, and thereby decrease the power consumption of the device.

[0027] As described above each species to be separated (whether isotopes of a single element, different elements, or combinations thereof) will be subject to a different acceleration due to its interaction with electromagnetic fields present within the central chamber 101. As a result, heavier species are pushed toward the outer edges of the chamber and exit the central chamber via exit ports 110. The lighter species may then exit the chamber at the far end exit port 112. Pumping ducts near the central chamber wall may be used to exhaust a gas mixture enriched with heavier species. Alternatively or in addition, pumping ducts may extend into the vessel near the central axis to exhaust a gas mixture depleted in heavier species. Radial ports may also be used for monitoring and management of the system, such as to extend diagnostic probes into the plasma, sample gas from different radial positions in the plasma for diagnostic purposes, enable non-invasive optical diagnostic methods, or the like.

[0028] Multiple stages of a cascade may be implemented in a single centrifuge volume by using axial dividing regions to isolate subsequent sections of the cascade from each other, and by feeding the stream enriched in the heavy species back to the inlet of the previous stage. FIG. 3 shows an example of such a system, in which each successive stage has an outlet port that feeds the fraction of the output enriched in the heavy species backwards in the cascade. As previously described, plasma within the centrifuge volume 101 flows according to the electromagnetic forces generated within the centrifuge with a flow (in this example) from bottom to top, as shown by the dashed arrows. Heavier species experience a higher force toward the outside of the centrifuge volume 301 as shown by solid arrows within the interior volume 101. Gas enters the cascade chamber through an inlet port 310, which may extend through many layers of the central centrifuge chamber 101, to a middle region as shown. In this example, the initial gas enters nearDocket No. 165704-00021 OUS the far end (top, in FIG. 3) of the chamber, but during operation of the system any of the inlet ports may be used. As the centrifuge is operated, heavier species exit via an exit port 110 as previously disclosed, in the same manner as described with respect to FIG. 1. In contrast to other arrangements in which the heavier species are transported to another system for further processing, in this example they are re-injected to the centrifuge via an earlier inlet port 330. Heavier species remaining in the plasma are again separated in the middle region, and flow from an exit port 110 to the earlier inlet port 350, as shown by flow 340.

[0029] An axial hollow electrode 106 as described earlier may span the entire system length, provided that the conductivity of the central conductor is much larger than the conductivity of the plasma pathway to the anodes. Because the required throughput at each section of the cascade centrifuge changes as more material is enriched, the stacking of successive stages in one vessel in which movable barriers are used between stages, enables each stage to be sized so that the throughput achieved in that stage is that required by the particular element of the cascade. This also simplifies the ancillary systems, reducing connections between stages as well as the total number of components that must be made for the system. More generally, a cascade system as shown in FIG. 3 may be used with any number of sections, in which each stage S has an outlet port that feeds the fraction of the output enriched in the heavy species backwards in the cascade to an earlier stage 5-1.

[0030] As disclosed previously, a plasma centrifuge device as disclosed herein may be particularly suited for use in separating species for use in a fusion reactor fuel processing system. FIG. 4 shows a schematic of such a system, in which a plasma centrifuge is used inside a fuel reprocessing system of a fusion device. A plasma centrifuge system 410 as disclosed herein may include one or more plasma centrifuge devices 100 as previously disclosed. The plasma centrifuge system 410 may receive raw material 401, such as fuel for the reactor necessary for operation of the reactor 420. In the example shown in FIG. 3, the plasma centrifuge system 410 receives material from the reactor 420 that includes lighter isotopes to be re-used in the fuel cycle and heavier isotopes that require additional processing or may be removed from the system as waste. The plasma centrifuge system 410 may include one or more plasma centrifuges, such as plasma centrifuge 100 described with respect to FIGS. 1-3.Docket No. 165704-00021 OUS

[0031] The material received at 401 is separated into heavier and lighter species by the plasma centrifuge(s) within the system 410 as disclosed above, which can then be provided to the appropriate component of the fuel processing system. Alternatively or in addition, one or more materials separated by the plasma centrifuge system 410 may be discarded or used by another component of the system. In the example shown in FIG. 4, lighter species are provided back to the fuel injection system 430 of the reactor 420 for further in the fusion reactor via output 411, such as via exit ports within each plasma centrifuge as previously disclosed. Heavier species may be directed to other components to be removed via a separate exhaust at 405.

[0032] As another example, in a fusion reactor system that uses a deuterium-tritium (D-T) fuel cycle, a plasma centrifuge as disclosed herein may be used to separate the deuterium and tritium fuel isotopes from impurities such as helium as well as higher mass elements like Argon or Krypton. This can be implemented directly downstream the outlet of the fusion reactor to reduce the concentration of impurities that must be handled by the processing systems, or the plasma centrifuge can be used downstream of a different separation mechanism like a metal foil pump so that the primary role of the plasma centrifuge is for hydrogen isotope separation and rebalancing before fuel reinjection, such as in the example shown in FIG. 3. Because the separation factor for heavy species like argon or krypton will be exceptionally good, in some embodiments these plasma enhancement gases may be directly reinjected back into the fusion system if the required purity can be achieved in a single stage of separation.

[0033] In this way, a fusion reactor including a plasma centrifuge as disclosed herein may implement relatively fast recycling of fuel at low upstream pressure, thereby reducing the inventory of valuable and scarce gases in the system that would otherwise be required for the system to operate.

[0034] Embodiments disclosed herein may be particularly well-suited for specific species separations that are desirable in fusion reactor systems. For example, in a reactor that uses a deuterium-He3 fuel cycle, a plasma centrifuge is used to separation He3 from He4. Because He3 is a required fuel species, and He4 is one of the components of ash in the system, it is critical to separate out the He4 to not dilute the fuel. A plasma centrifuge can be the first component after the reactor to achieve a separation of protium (the other impurity ash species) and includeDocket No. 165704-00021 OUS subsequent stages of a plasma centrifuge cascade until the desired purity is achieved for He3 to be reinjected. In some embodiments the He3 separation can be performed after a metal foil pump so that only helium species are acted on, with hydrogen separation occurring elsewhere in the system. While some approaches can include relying on differences in the superfluid point between the two isotopes, various embodiments discussed herein can be more energy efficient as well as simpler.

[0035] The centrifuge itself can include features to improve the separation of specific species. For example, in applications where hydrogen isotope separation is especially of value, the plasma centrifuge approach may be combined with separation membranes operating either diffusively-driven or driven by superpermeation, the latter process also being known as “plasma- driven permeation”. In the latter approach, the plasma used to spin up the gas can be used in various examples to split the hydrogen molecule, or alternatively this atomization may be achieved by rotation of the neutral gas at rotational kinetic energies higher than the energy of the molecular hydrogen bond. In this way, in various examples a flux of atomic hydrogen radicals can be provided that can enable separation specifically of hydrogenic species through the separation membranes, while blocking helium. As another example, by combining this effect with the rotationally-driven separation of different hydrogen masses, preferential pumping of one species over another can be achieved. By placing the separation membrane at the outer edge of the device, tritium may be preferentially separated through the membrane. Alternatively or in addition, using a membrane closer to the central axis may allow for deuterium to be preferentially separated. An example of a superpermeation pump is disclosed in co-pending Application No. , which claims priority to U.S. Provisional Application No. 63 / 695,476, fded September 17, 2024 (Docket No.165704-000210US), the disclosure of which is incorporated by reference in its entirety for all purposes.

[0036] As another example, devices and systems disclosed herein may be particularly suited to separation of lithium isotopes. The relative concentration of Li-6 can be an important tool for fusion blankets, since most tritium produced in conventional fusion device blankets results from a thermal neutron reacting with a Li-6 nucleus. In some such devices, most of the benefit from lithium enrichment in fusion breeder blankets is only achieved up to approximately 20% enrichment. High-throughput separations with relatively low enrichment factors that areDocket No. 165704-00021 OUS achievable with a plasma centrifuge approach as disclosed herein may be suitable such a requirement. Lithium control in a centrifuge as disclosed herein may be achieved through control of surface temperatures to establish evaporation and condensation regions in the system and control vapor flow. Temperatures are selected to achieve the desired operating pressure in the system, and temperature differences between regions of the system are set in order to set the desired flow rates. Sufficiently high temperatures are required to prevent condensation of lithium vapor on the walls of the system when unwanted. To enable such control, heated, lithium-filled capillary porous materials may be used within the system, such as on electrode surfaces, to evaporate lithium into the chamber. Temperature control components also may be included at the vapor feed location, such as intake port 301, to regulate the local vapor pressure, and at exit ports 310, 311, 315 to force condensation of the lithium vapor onto collection surfaces. At some or all surfaces that are not used for inlet and outlet control, heating may be used to maintain the surfaces above the saturation temperature for lithium.

[0037] In some embodiments, lithium is added to a system primarily used for separation of gases in the fusion fuel processing system in order to improve the conductivity of the plasma due to its low ionization energy. Because fusion plasmas can be relatively insensitive to the presence of lithium in various examples and can even be benefited by the presence of lithium in various examples, some embodiments use this approach for a pumping system integrated with a fusion device. Lithium vapor also may be used to cool the gas in the centrifuge directly.

[0038] The driving current applied to the plasma in a centrifuge as disclosed herein may be provided by a variety of mechanisms and devices. For example, one or more external elements including injected waves may be applied to the centrifuge to produce a current. By targeting a specific radial location, local heating in various examples can cause an increased temperature and can result in a potential gradient; this potential gradient can lead to a radial current flow in some embodiments that then reacts against the axial magnetic field to produce the desired azimuthal flow. Alternatively or in addition, a desired rotation of ions and ultimately neutral molecules may be driven by any other suitable elements, including externally applied rotating magnetic fields, ion cyclotron waves, helicon waves, an ExB drift imposed on the plasma, and the like.Docket No. 165704-00021 OUS

[0039] As another example, superconducting magnets may be used to achieve higher axial magnetic fields by using coils located outside the centrifuge vessel. This approach may enable higher rotation rates and / or higher steady-state magnetic fields, without the use of higher plasma currents in the system which can lead to resistive dissipation and heating in various examples.

[0040] Regardless of the specific mechanism used to generate the interior current, optimized current profiles may be used to tune the radial profile of the azimuthal velocity, which may minimize viscous shear heating in the system. In particular, current profiles through the system may drive rotation at one radius in the plasma, as opposed to across the entire radial profile. By driving current at a single radius, regions inside that radius will spin up to a rotation profile close to a rigid body rotation profile (constant angular frequency) which does not experience viscous shear, thereby reducing viscous dissipation within the system.

[0041] In some embodiments, a compression functionality achieved in the feedstock gas can play an important role in the operation of the plasma centrifuge, enabling the use of roughing pumps downstream instead of high vacuum pumps downstream of a plasma centrifuge differential pump. Because there are no moving parts in various examples, such an arrangement in some embodiments can be desirable for processing of gases like tritium where it can be desirable in various examples to avoid some or any leakage.

[0042] It may be beneficial to include specific impurities, such as vaporized alkali metals gases (e.g., lithium, sodium, potassium) or inert gases (e.g., argon, krypton, xenon) to the input gas mixture to serve a purpose analogous to a catalyst, to “seed” ionization within the plasma and thus reduce the plasma temperature. Due to their lower ionization potential, alkali metal impurities may reduce the electric potential necessary to initiate electrical breakdown and thus to generate the plasma within the central chamber of the centrifuge. Such impurities also may increase the electrical conductivity of the plasma, thereby reducing the power required to drive the currents needed to achieve desired separation factors between the isotopes of interest. This may have the additional benefit of reducing the thermal loading on the vessel wall and plasmafacing components for a given separation factor. Any impurities added for the purpose of improving plasma properties would be selectively removed after the desired isotope separation has been achieved.Docket No. 165704-00021 OUS

[0043] Alkali metal salts also may be added to the system for easier handling of the input materials. Such a salt will be partially dissociated in the plasma and contribute alkali metal to the system that can be ionized easily, thus improving the efficiency of plasma generation within the system.

[0044] The described embodiments are susceptible to various modifications and alternative forms, and specific examples thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the described embodiments are not to be limited to the particular forms or methods disclosed, but to the contrary, the present disclosure is to cover all modifications, equivalents, and alternatives. Additionally, elements of a given embodiment should not be construed to be applicable to only that example embodiment and therefore elements of one example embodiment can be applicable to other embodiments. Additionally, in some embodiments, elements that are specifically shown in some embodiments can be explicitly absent from further embodiments. Accordingly, the recitation of an element being present in one example should be construed to support some embodiments where such an element is explicitly absent.

Claims

Docket No. 165704-00021 OUSCLAIMSWhat is claimed is:

1. A plasma centrifuge system for continuous separation of gases by mass, the system comprising: a central chamber; a plurality of electrodes arranged and configured to generate a partially-ionized plasma within the central chamber; a plurality of outlets from the central chamber; and an electromagnetic field generator arranged and configured to generate an electromagnetic field within the central chamber; wherein the plasma centrifuge system causes ions of materials having different atomic weights within a plasma disposed within the central chamber to exit the central chamber through the plurality of outlets based upon the atomic weights.

2. A plasma centrifuge system as recited in claim 1, further comprising a superpermeating membrane that filters only a subset of materials from the central chamber.

3. A plasma centrifuge system as recited in claim 2, wherein the subset comprises one or more hydrogenic species.

4. A plasma centrifuge system as recited in any of claims 1 to 2, wherein the materials comprise ions of lithium isotopes.Docket No. 165704-00021 OUS5. A plasma centrifuge system as recited in claim 4, further comprising one or more controllers arranged and configured to adjust the temperature within one or more portions of the system to control a flow of lithium liquid and / or vapor.

6. A plasma centrifuge system as recited in any of claims 1, 4, and 5, wherein lithium vapor is used to cool incoming gases in order to improve separation factors in the device.

7. A plasma centrifuge system as recited in any of claims claim 1 to 2, wherein the materials comprise one or more selected from a group consisting of: deuterium, tritium, helium-3, and helium -4.

8. A plasma centrifuge system as recited in any of claims 1 to 7, wherein waves and / or rotating magnetic fields are used to drive rotation in the system.

9. A plasma centrifuge system as recited in any of claims 1 to 8, wherein the electromagnetic field generator comprises one or more superconducting magnets arranged and configured to generate an axial magnetic field within the central chamber.

10. A plasma centrifuge system as recited in any of claims 1 to 9, wherein the electromagnetic field generator comprises one or more annular electrodes disposed along and around a central axis of the central chamber.

11. A plasma centrifuge system as recited in any previous claim, wherein the central chamber comprises a plurality of regions separated by physical barriers, wherein an output in a first regionDocket No. 165704-00021 OUS of the plurality of regions feeds an input in a second region of the plurality of regions, wherein plasma within the central chamber flows from the second region to the first region during operation of the plasma centrifuge system.

12. A plasma centrifuge system as recited in any previous claim, further comprising a hollow axial electrode disposed within the central chamber.

13. A plasma centrifuge system as recited in claim 12, wherein the hollow axial electrode comprises: a central conductor; a thermionic emitter surrounding an outer cylindrical surface of the central conductor; and an outer jacket surrounding an outer cylindrical surface of the thermionic emitter.

14. A fuel processing system for a fusion generator, the fuel processing system comprising: a plasma centrifuge system as recited in any of claims 1 to 13.

15. A method of operating a fuel processing system for a fusion generator, the method comprising: receiving a gas comprising fuel material and impurities from an output of a fusion generator; generating an ionized plasma from the gas within a plasma centrifuge; operating the plasma centrifuge to separate at least a portion of the fuel material; andDocket No. 165704-00021 OUS returning the fuel material to a fuel processing component of the fusion generator for use as fuel in the fusion generator.

16. The method of claim 15, further comprising: reprocessing a portion of the plasma through a series of two or more segments of the plasma centrifuge to separate the fuel material, wherein an output of a later segment of the two or more segments feeds plasma material to an input of an earlier segment of the two or more segments.

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