Patent Publication Number: US-2018033496-A1

Title: Systems, methods, and devices for inertial electrostatic confinement

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of U.S. Provisional Application No. 62/367,410, filed Jul. 27, 2016, which is hereby incorporated by reference herein in its entirety. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
     This invention was made with government support under NNX13AL44H awarded by the National Aeronautics and Space Administration (NASA). The government has certain rights in the invention. 
    
    
     FIELD 
     The present disclosure generally relates to nuclear fusion, and, more particularly, to fusion by inertial electrostatic confinement using a device with continuous walls. 
     SUMMARY 
     In embodiments, a continuous electrode (CE) inertial electrostatic confinement (IEC) device employs sidewalls with substantially continuous surfaces radially extending from a central core to define radial particle paths. Electrodes coupled to the sidewalls provide an electric field that varies along each particle path to accelerate ions within the particle paths toward the core. Interaction of the ions within the core can result in nuclear fusion, which may be used for electricity generation or for spacecraft propulsion. The CE-IEC device can include one or more features designed to decrease distances between ions, for example, by compacting ion bunches as they travel along the particle paths and/or neutralizing space charge of ion bunches within the core using a population of electrons captured therein. 
     In one or more embodiments, a device comprises a central core region, particle paths, sidewalls, electrodes, and a control module. Each particle path can radially extend from the central core region and can have a corresponding particle path aligned therewith on an opposite side of the central core region. The sidewalls can extend in a radial direction. Each particle path can be bounded by a corresponding set of the sidewalls. The electrodes can be coupled to the sidewalls so as to provide an electric field that varies along each particle path from a cathode region proximal to the central core region to an anode region remote from the central core region. The control module can control the electrodes to provide the electric field. Each sidewall can provide a continuous surface radially extending from the cathode region to the anode region. 
     In one or more embodiments, a fusion method comprises directing ion bunches along particle paths that radially extend from a central core region. Each particle path can be bounded by a corresponding set of radially extending sidewalls and can have a corresponding particle path aligned therewith on an opposite side of the central core region. Each sidewall can provide a continuous surface radially extending from a cathode region proximal to the central core region to an anode region remote from the central core region. The method can further comprise generating an electric field that varies along each particle path from the cathode region to the anode region such that the ion bunches are accelerated toward the central core region, and fusing ions from the ion bunches within the central core region. The method can also comprise allowing fusion products to travel from the central core region to beyond the anode region via the particle paths. 
     Objects and advantages of embodiments of the disclosed subject matter will become apparent from the following description when considered in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments will hereinafter be described with reference to the accompanying drawings, which have not necessarily been drawn to scale. Where applicable, some features may not be illustrated or otherwise simplified to assist in the illustration and description of underlying features. Throughout the figures, like reference numerals denote like elements. 
         FIG. 1A  is an isometric view of a CE-IEC device employing a square configuration, according to one or more embodiments of the disclosed subject matter. 
         FIG. 1B  is a view of  FIG. 1A  along one of the particle paths, according to one or more embodiments of the disclosed subject matter. 
         FIG. 1C  is a cross-sectional view of a CE-IEC device, according to one or more embodiments of the disclosed subject matter. 
         FIG. 1D  is a graph of an exemplary electrical potential profile along one of the particle paths of  FIG. 1C , according to one or more embodiments of the disclosed subject matter. 
         FIG. 1E-1G  are cross-sectional views of a CE-IEC device with ion bunches traveling and interacting to produce fusion products, according to one or more embodiments of the disclosed subject matter. 
         FIG. 2A  is a cross-sectional view of a CE-IEC device employing sidewalls with variable resistivity, according to one or more embodiments of the disclosed subject matter. 
         FIG. 2B  is a cross-sectional view of a CE-IEC device employing sidewalls with segments having different electric potentials applied thereto, according to one or more embodiments of the disclosed subject matter. 
         FIG. 3A  is a cross-sectional view showing construction of a sidewall in a CE-IEC device that has a permanent magnet therein, according to one or more embodiments of the disclosed subject matter. 
         FIG. 3B  is a cross-sectional view showing construction of a sidewall in a CE-IEC device that is formed of a permanent magnet, according to one or more embodiments of the disclosed subject matter. 
         FIG. 3C  shows exemplary magnetic field lines for a CE-IEC device employing the sidewall construction of either  FIG. 3A  or  FIG. 3B . 
         FIG. 4A  is a cross-sectional view showing construction of a sidewall in a CE-IEC device that has multiple permanent magnets therein, according to one or more embodiments of the disclosed subject matter. 
         FIG. 4B  is a cross-sectional view showing construction of a sidewall in a CE-IEC device that is formed of multiple permanent magnets, according to one or more embodiments of the disclosed subject matter. 
         FIG. 4C  shows exemplary magnetic field lines for a CE-IEC device employing the sidewall construction of either  FIG. 4A  or  FIG. 4B . 
         FIG. 5  is a magnified cross-sectional view of a CE-IEC device employing protective standoffs, according to one or more embodiments of the disclosed subject matter. 
         FIG. 6  is an isometric view of a CE-IEC device employing a square configuration with conduits at vertices between adjacent sidewalls, according to one or more embodiments of the disclosed subject matter. 
         FIG. 7A  is a cross-sectional view showing an exemplary configuration for electrical coupling for a variable resistivity sidewall via a conduit, according to one or more embodiments of the disclosed subject matter. 
         FIG. 7B  is a cross-sectional view showing an exemplary configuration for electrical coupling for a variable resistivity sidewall via a conduit with a permanent magnet, according to one or more embodiments of the disclosed subject matter. 
         FIG. 7C  is a cross-sectional view showing an exemplary configuration for electrical coupling for a segment of a sidewall via a conduit, according to one or more embodiments of the disclosed subject matter. 
         FIG. 7D  is a cross-sectional view showing an exemplary configuration for electrical coupling for multiple segments of sidewalls via a conduit, according to one or more embodiments of the disclosed subject matter. 
         FIG. 8  is a cross-sectional view showing an exemplary configuration for ion supply to the particle pathways via a conduit, according to one or more embodiments of the disclosed subject matter. 
         FIG. 9  is a cross-sectional view showing an exemplary configuration of sensors and signal communication via a conduit, according to one or more embodiments of the disclosed subject matter. 
         FIG. 10  is a simplified schematic of a CE-IEC system for particle fusion, according to one or more embodiments of the disclosed subject matter. 
         FIGS. 11A-11C  show stages in converting fusion products to electricity using standing wave direct energy conversion (SW-DEC), according to one or more embodiments of the disclosed subject matter. 
         FIG. 11D  is a simplified schematic of an RLC circuit employing SW-DEC for direct energy usage, according to one or more embodiments of the disclosed subject matter. 
         FIG. 11E  is a cross-sectional view of a CE-IEC device with SW-DEC rings in an outer power conversion region, according to one or more embodiments of the disclosed subject matter. 
         FIG. 12A  is an isometric view of a CE-IEC device employing a special irregular truncated icosahedron (SITI) configuration, according to one or more embodiments of the disclosed subject matter. 
         FIG. 12B  is a cutaway view of  FIG. 12A  showing exemplary magnetic field lines, magnets embedded in walls, and an exemplary electric potential profile. 
     
    
    
     DETAILED DESCRIPTION 
     In embodiments, an inertial electrostatic confinement (IEC) device has radially extending sidewalls that define radial particle paths emanating from a central core. Electrodes can be coupled to these sidewalls in order to provide an electric field that varies along the particle paths, for example, from a radially-outer anode region (remote from the central core) to a radially-inner cathode region (proximal to the central core). As such, embodiments employing continuous sidewalls with coupled electrodes are referred to herein as continuous electrode (CE). Although the sidewalls are referred to as continuous, this does not require that the sidewalls be monolithic or isotropic. Rather, the continuous sidewalls provide a substantially continuous surface from the anode region to the cathode region and can have different properties at different radial or azimuthal locations (e.g., formed of different material segments at different radial locations and/or having a resistivity that varies radially). 
     The electric field can accelerate ions toward the core, where the ions interact to yield nuclear fusion. Non-reacting ions can pass through the core to an opposite (aligned) particle path, where the electric field therein slows the ions to reverse direction and accelerate back toward the core for further interactions. Unlike conventional IEC devices that employ multiple independent grids of different radii centered on the core to provide an electric field, embodiments of the present disclosure employing continuous sidewalls allow the electric potential to be imposed continuously over the particle path and/or to dynamically adjust the electric potential as ions travel within the particle paths (e.g., to compact traveling ion bunches prior to introduction to the core). The continuous sidewalls can also provide a very high grid transparency (i.e., greater than 70%, for example, ˜85%) as seen from the core without otherwise sacrificing structural rigidity. 
     The sidewalls also provide real estate for conduits from external to the device toward the central core, for example, to provide electrical connections for power or signal transmission, to provide a magnetic field using permanent magnets, and/or to feed ions into the particle paths. While the sidewalls provide an additional surface area that ions could strike (representing a loss to the system) that multiple independent grids would otherwise lack, such ions would be on non-radial trajectories and thus would likely not contribute to nuclear fusion anyway. 
     Since the ions interact in the core, fusion products are only generated in the core and leave along predominantly radial paths, e.g., along the radially extending particle paths. In general, the IEC device should be as transparent as possible to these energetic particles. In other words, the construction of the IEC device (e.g., sidewalls) should subtend as little solid angle (as seen by the core) as possible. To that end, any radially outer structure that falls within the “shadow” of radially inner structures, as viewed from the device center, will not diminish the transparency of the system. Thus, in embodiments, structures are arranged to fall within this “shadow” of the innermost structure, which is designed to subtend as little solid angle as possible. In other words, the sidewalls could be considered a radially outward extrusion of the innermost edge (adjacent to the core). 
       FIG. 1A  shows an isometric view of a simplified CE-IEC device  100 .  FIG. 1B  shows a side view of the CE-IEC device  100 . The simplified CE-IEC device  100  employs a cubic configuration, where the innermost edge  104  formed by radially extending sidewalls  106  is a cube surrounding a central core region  112 . The outermost edge  102  formed by the sidewalls  106  can also be a cube. The sidewalls  106  can be continuous between the innermost edge  104  and outermost edge  102  and define three radial particle paths  108   a - 108   c . Each sidewall  106  can abut an adjacent sidewall  106  along a radially extending vertex  114 . Each particle path is bounded on four sides (defining a square face perpendicular to the radial direction) by the sidewalls  106 , such that each half of the particle path outside the core region  112  takes the form of a truncated pyramid. Note that the particle paths  108   a - 108   c  can be considered a single path that extends through the central core region  112 , or as separate but aligned paths on opposite sides of the central core region. 
     Referring to  FIGS. 1C and 1E-1G , cross-sectional views of CE-IEC device  100  are shown in order to describe various features thereof. In particular, the CE-IEC device  100  can be considered to have four main regions along the radial direction  116 : (1) an innermost core region  122 , (2) an outer core region  112  surrounding the innermost core region  122 , (3) a focusing region  110  between sidewalls  106  and along particle paths  108   a - 108   c , and (4) a power conversion region  150  beyond the sidewalls  106 . 
     The focusing region  110  is where the CE structure (i.e., sidewalls  106 ) is disposed. The open channels between facing sidewalls  106  in the focusing region  110  form the particle paths  108   a - 108   c , along which ion bunches recirculate as they pass into and out of the core. A radially outer region of the sidewalls  106  can be biased at a relatively higher voltage to form anode region  126 , while a radially inner region of the sidewalls  106  can be biased at a relatively lower voltage to form cathode region  124 . The resulting electric field in the focusing region  110  causes the ions to accelerate toward the core  112 . Since the potential profile is generated solely in the focusing region  110 , the ions will drift through the core at a constant speed. 
     Over time, the traveling ions self-assemble into bunches  120  due to two-stream instability. Moreover, due to cross-talk, the bunches  120  synchronize between different particle paths  108   a - 108   c , as shown in  FIG. 1E , such that the bunches  120  arrive at the inner core region  122  at substantially the same time, as shown in  FIG. 1F . Alternatively or additionally, ions could be introduced into the particle paths  108   a - 108   c  in a pulsed manner (i.e., at different times), thereby forming preliminary ion bunches. The formation of bunches and the synchronization results in a beneficial situation since the ion bunches  120  only cross in the inner core  122 . 
     Low angle scattering between counter-streaming ions, which would normally result in the rapid global thermalization of the ion population, is suppressed by local thermalization within each of the bunches  120  near the anode region  126 . Moreover, the low-angle collisions among opposing bunches within the core merely reshuffle the specific radial trajectories among the particle paths  108   a - 108   c  that the individual ions will follow to exit the inner core  122 . Upon refocusing (in focusing region  110 ), the velocity distribution in the azimuthal direction  118  within each bunch  120  should be indistinguishable from the start of the previous pass, cancelling any azimuthal momentum growth. Low angle scatters among non-opposing ion bunches can introduce both azimuthal and radial (energy) scattering. However, on average these scattering events will both up-scatter and down-scatter the ions equally. Upon refocusing (in focusing region  110 ), the net ion energy within each bunch  120  due to low angle ion-ion collisions should remain the same. 
     High angle scatters are confined to the core where the resulting ion trajectories will still be approximately radial. In other words, if the scattering angle of the ion does not otherwise cause it to collide with the inner edge of a sidewall  106 , the ion should simply end up in a different channel (proceeding along a different particle path  108   a - 108   c ) rather than being lost. Upon refocusing (in focusing region  110 ), the ion will be merged into the traveling ion bunch  120 . Thus, the electric potential within the particle pathways can help keep scattered ions from being lost. 
     To increase the density of ion bunches as they pass into the core  112 , where the bulk coulomb repulsion of the ions would tend to push them apart, a population of electrons is confined to the core of the device in order to neutralize the space charge of the ions. For example, an electron population can be generated within the core by completely ionizing the fusion fuel (e.g., boron), which may be only singly ionized initially prior to injection. For example, any remaining electrons of the fusion fuel can be stripped, either through collisions with other ions passing through the core or as a result of a nuclear fusion event. Alternatively or additionally, electrons can be injected directly into the core, for example, to replenish those that might be lost over time and that would otherwise not be replenished by further ionizing the fusion fuel. 
     To help confine the electrons to the core, the sidewalls  106  may further provide another anode region  128  adjacent to the core (i.e., radially between the cathode region  124  and the outer core  112 ). The resulting electric field can create a reversed potential well for electrons that keeps them from escaping the core along particle pathways. For example,  FIG. 1D  shows a graph of an exemplary electric potential  130  along one of the particle paths  108   a - 108   c . Region  132  represents a confinement field for the ions (i.e., between the sidewalls  106  along the particle pathways) while region  134  represents the confinement field for the electrons (i.e., within the core). Alternatively or additionally, a magnetic field may be provided to keep electrons from escaping along the particle paths  108   a - 108   c , as described in further detail elsewhere herein. 
     The ions thus travel from the anode region  126  to the cathode region  124  (see  FIG. 1E ) and on to the outer core region  112  (see  FIG. 1F ), which is a transition region where the ions interact with the confined electron population. As the ions pass into the outer core  112 , the electron population responds by being attracted to the ions, thereby neutralizing their space charge and allowing the ions to further compress along their radial trajectories as they move toward the inner core region  122 . Within the inner core region  122 , the ions traveling in crossing or opposite directions along the particle paths collide, exchanging energy and momentum and in some cases undergoing nuclear fusion. In general, the central core region may be substantially empty except for the electrons confined therein, ions traveling therethrough between the particle paths, and products resulting from interaction of the traveling ions. 
     Unreacted ions  120  and/or fusion products  140  travel along substantially radial paths out of the inner core region  122  to the outer core region  112 , where they leave behind the confined electrons before passing back into the focusing region  110  (see  FIG. 1G ). The outer edge of the focusing region  110  (i.e., outermost edge of the anode region  126 ) represents the maximum radial extent to which the ion bunches  120  are allowed to reach, with only fusion products  140  being energetic enough to proceed into power conversion region  150 . 
     The fusion products  140  can thus continue through focusing region  110  and escape to power conversion region  150  beyond sidewalls  106 , where the fusion products  140  can be converted to electricity or otherwise used to generate work (e.g., to propel a spacecraft). The fusion products  140  can enter the power conversion region  150  with a nearly isotropic angular distribution and can arrive in pulses a few nanoseconds long separated by several microseconds. The pulsed output of the fusion products  140  can be converted to electricity using a direct conversion process, for example, Traveling Wave Direct Energy Conversion (TW-DEC) or Standing Wave Direct Energy Conversion (SW-DEC), as described in further detail elsewhere herein. 
     When the ions leave the outer core  112 , their self-charge will still tend to cause the bunches of ions to expand. Thus, as they travel along the particle paths  108   a - 108   c  in the focusing region  110 , the ions  120  can also be continuously refocused and compressed (due to the electric potential provided by the sidewalls  106  and/or magnetic fields from permanent magnets of the sidewalls  106 ) to combat this natural spreading due to space charge and/or low angle collisions. 
     As noted above, embodiments of the CE-IEC device can provide a potential that varies continuously in the focusing region  110 .  FIG. 2A  illustrates a configuration where the continuous sidewalls  106  can provide such an electric potential. In particular, the sidewall  106  can be formed of a material  200  that has a resistivity that varies along the radial direction  116 . Portions of the sidewall  106  at different radii can be connected to a potential difference. For example, a voltage source  204  can be connected between a radially outer portion  202  (e.g., an anode region  126 ) and a radially inner portion  206  (e.g., a cathode region  124 ). For example, the outer portion  202  can be set to ground while the inner portion  206  can be set to −50 kV. 
     At each radial location on the sidewall, the resistivity normal to the radial direction can be very low, such that locations on the same sidewall at the same radial distance from the core can be held at substantially the same potential. In other words, portions of the sidewall  106  at the same radii would act as an isopotential conductor. Moreover, portions of different sidewalls  106  (i.e., falling along isopotential line  208  in  FIG. 2A ) can also be at substantially the same potential. Note that the isopotential line  208  connects locations on the sidewalls that are at the same potential, not between the sidewalls in the open regions of the particle paths where the potential would necessarily be different. 
     The variable resistivity material  200  may be accomplished, for example, by engineering a composite material having strips of different material layers at different radii extending in a direction perpendicular to the radial direction  116 . Adjacent strips are electrically coupled to each other along contacting faces perpendicular to the radial direction  116  to provide the radially varying resistivity, while otherwise acting as isopotential conductors in a direction perpendicular to the radial direction. The composition of the material  200  can be customized to achieve any desired radial potential profile. For example, the potential profile can monotonically decrease from the anode region to the cathode region, or can be a complex profile that does not necessarily monotonically decrease). For example, the sidewall material can be formed via 3-D printing. 
     Alternatively or additionally, a customized potential profile can be achieved using a segmented continuous sidewall structure, as illustrated in  FIG. 2B . Each sidewall  106  (or a selection of sidewalls) can include a plurality of segments  252  at different radii from the core  122 . Each segment  252  can be separated from an adjacent segment  252  in the radial direction by an insulating spacer  254 , such that each segment  252  is electrically isolated from the other segments  252  of the sidewall  106 . The segments  252  can thus be independently controlled (for example, by providing independent voltage sources  256  connected to the segments at  258 ) to provide a custom electric potential along the particle paths  108   a - 108   c . Each segment  252  can be composed of the same material or of different materials, and can act as isopotential conductors in a direction perpendicular to the radial direction. 
     Although shown in  FIG. 2B  as being the same size, the segments  252  can also be of different sizes. For example, one or more intermediate segments  252  between anode region  126  and cathode region  124  can be made smaller than the other segments  252 . These smaller segments  252  can be used to dynamically vary the potential as ion bunches pass, for example, to compact the ion bunches by providing a perturbation that slows ions at the front of the bunch and/or accelerates ions at the rear of the bunch. In addition, the number of spacers  254  and/or segments  252  illustrated in  FIG. 2B  are exemplary only, and other numbers are also possible according to one or more contemplated embodiments. 
     Moreover, the features of  FIG. 2A  and the features of  FIG. 2B  are not intended to be mutually exclusive. Rather, in some embodiments, the features of  FIGS. 2A-2B  can be combined to particular advantage. For example, one or more of the segments  252  of  FIG. 2B  can be formed of a material  200  that has a resistivity that varies along the radial direction  116 . Other combinations and variations should be readily apparent to one of ordinary skill in the art. 
     As noted above, embodiments of the CE-IEC device can provide a magnetic field to help confine electrons to the core region  112 . Since only enough electrons are needed to neutralize the traveling ions, the magnetic field requirement is relatively low and can be satisfied using permanent magnets (e.g., formed of a rare-earth material, such as neodymium, or other permanent magnetic material). For example, radially polarized permanent magnets may be incorporated into sidewalls  106  with same poles (either north or south) facing the core  112 . The resulting magnetic field has field lines  312  extending through the channels formed by the sidewalls  106 , e.g., substantially following the particle paths  108   a - 108   c , as shown in  FIG. 3C . At the core  112 , the permanent magnets form a cusped magnetic field  314 , which acts as a magnetic mirror that repels electrons from impacting ends of the sidewalls  106  facing the core  112 . Moreover, the cusped magnetic field at the intersection of the particle paths  108   a - 108   c  and the outer boundary of the core  112  keep electrons from escaping along the particle paths  108   a - 108   c.    
     The provision of permanent magnets in the sidewalls  106  allows more material to be used, thereby resulting in a stronger magnetic field, without otherwise compromising transparency to particles exiting the core  112 . For example, the permanent magnets  306  can be incorporated into each sidewall  106  between conductive panels  302  thereof, as shown in  FIG. 3A . Alternatively or additionally, the permanent magnets  310  can be conductive panels of the sidewall  106  itself and used to provide both the magnetic and potential profiles, as shown in  FIG. 3B . Depending on the desired profile of the magnetic field, the amount of magnetic material may be uniform or vary along the radial direction, and/or can be the same or different between different sidewalls at the same radius. The magnets can optionally be separated from the conductive panels  302  or other magnets  310  by an insulating spacer  304 . 
     Each magnet would have a polar orientation  308  extending radially (i.e., with one pole adjacent to the core  112 , and the opposite pole spaced at a radially outer location). Although a particular polar orientation is illustrated in  FIGS. 3A-3B , embodiments of the disclosed subject matter are not limited thereto. Indeed, a polar orientation for each magnet opposite that illustrated may be adopted with similar effect. 
     Although  FIGS. 3A-3C  illustrate a configuration with the permanent magnets extending along the length of the sidewalls, embodiments of the disclosed subject matter are not limited thereto. Indeed, in some cases, electrons that approach the cusped magnetic field with a sufficiently low pitch angle (i.e., more parallel to the field lines) may not be turned around before the point of maximum field strength. As a result, some amount of electron leakage from the core may occur. Electrons that escape the core would be accelerated by the focusing region  110  to leave the CE-IEC device, which loss would be undesirable. 
     To avoid such electron losses, additional cusps  414  can be provided within the focusing region  106  along the particle paths  108   a - 108   c , as shown in  FIG. 4C . Electrons escaping the core  112  that encounter the cusp  414  can be guided to the sidewall  106  by the magnetic field  312 , and thus absorbed at a potential that is closer to that of the core  112 . The cusps  414  may be repeated along the radial direction—due to randomization of electron velocities between null regions of the magnetic fields, an electron that makes it through one cusp  414  may not necessarily make it through a subsequent cusp  414 . As a result, power loss by escaping electrons can be reduced. In addition, these magnetic field lines can help ions from spreading too far in the azimuthal direction and potentially impacting the sidewalls  106 . Moreover, the periodic magnetic field (experienced by the ion bunches as they recirculate along the particle paths  108   a - 108   c ) can help to compress the ion bunches in the azimuthal direction. 
     Such cusped magnetic fields can be generated by incorporating multiple separate magnets in the sidewalls along the radial direction. For example, radially polarized permanent magnets  402 A- 402 C may be incorporated into sidewalls  106 , with polar orientations  404 A- 404 C alternating along the radial direction, as shown in  FIG. 4A . Alternatively or additionally, the permanent magnets  406 A- 406 C can be conductive panels of the sidewall  106  itself and used to provide both the magnetic and potential profiles, as shown in  FIG. 4B . The magnets can optionally be separated from the conductive panels  302  or other magnets  406 A by insulating spacers  304  and/or  410 . The innermost magnet  402 C of the sidewalls  106  can have the same pole facing the core. 
     Each magnet would have a polar orientation  404 A- 404 C extending radially (i.e., with one pole closer to the core  112 , and the opposite pole spaced at a radially outer location). The resulting magnetic field lines  312  extend through the channels formed by the sidewalls, but with cusped regions  414  directed toward the sidewalls. Although a particular polar orientation is illustrated in  FIGS. 4A-4B , embodiments of the disclosed subject matter are not limited thereto. Indeed, a polar orientation for each magnet opposite that illustrated may be adopted with similar effect. Although an alternating polar orientation is illustrated in  FIGS. 4A-4B , in certain embodiments, the polar orientation of each magnet  402 A- 402 C of the sidewall  106  can be the same (i.e., non-alternating, with a north pole facing the south pole of the adjacent magnet). 
     Moreover, the features of  FIG. 3A-4C  are not intended to be mutually exclusive. Rather, in some embodiments, the features of  FIGS. 3A, 3B, 4A , and/or  4 B can be combined to particular advantage. For example, one or more sidewalls can be formed of a permanent magnet, while other sidewalls can be formed of permanent magnet segments. Other combinations and variations should be readily apparent to one of ordinary skill in the art. 
     Although the magnetic field configurations of  FIGS. 3A-4C  have been separately illustrated from the electric field configurations of  FIGS. 2A-2B , embodiments of the disclosed subject matter can employ both techniques, for example, to cooperatively contain electrons within the core. For example, the electrons can be prevented from hitting ends of the sidewalls  106  facing the core  112  by the cusped magnetic field  314  provided by the permanent magnets, despite the field generated by inner anode region  128  of sidewalls  106 . Meanwhile, electrons that are able to escape the core and enter the particle paths  108   a - 108   c  between sidewalls  106  can be turned back by the electric field generated by the cathode region  124  of the sidewalls  106 . 
     Despite the provision of a cusped magnetic field, high-angle scattered ions and/or fusion products can impact the edges of the sidewalls  106  facing the core  112 . These impacts can cause undesirable heating of the sidewall  106  and its components (e.g., permanent magnets, embedded electrodes, sensors, etc.). Heating of the permanent magnets is especially undesirable as it may lead to de-magnetization. To avoid damaging the sidewalls  106 , protective standoffs  502  (i.e., shields) can be provided at the innermost edge of the sidewalls  106 , as shown in  FIG. 5 , to absorb impacts from the ions and fusion products. Since energetic particles impacting the standoff  502  will deposit both energy and momentum, which will cause both heating and sputtering, the standoffs  502  can be formed of a material having a very high melting point (e.g., greater than 2000K) and be resistant to sputtering. For example, the standoff  502  can be formed of tungsten or carbon. 
     Instead of forming the standoff  502  from the heat-resistant material, the standoff  502  can be coated with a layer of the heat-resistant material. For example, the heat-resistant material could be flowed through a pipe extending along sidewall  106 , for example, via expanded channel  604  of  FIG. 6  (or temporarily along the particle paths  108   a - 108   c  between the sidewalls  106 ), to coat the radially inner surface of the standoff  502 . This material could be allowed to sputter away as a result of particle impacts, which can provide a mechanism for heat removal in addition to protecting the standoff  502  and the sidewalls  106  from erosion. 
     Any heat absorbed by the standoff  502  may be passively radiated away or actively cooled by a separate mechanism (e.g., a heat transfer fluid circulating through the standoff  502 ). The standoff  502  can also be formed of sufficient thickness (or coated with sufficient thickness) such that any sputtering that does occur would still allow for a sufficient lifetime of operation before failure. For example, if sputtering resulted in loss of approximately 0.013 monolayers/second, a standoff  502  having a 1 cm thick layer of carbon could have a lifetime of several years. 
     In embodiments, transparency of the CE-IEC device can be maintained by taking advantage of otherwise unused real estate of the sidewall structures for various functions, such as, but not limited to, electrical connections for voltage or signals, supporting permanent magnets, feeding fuel (e.g., ions) for fusion, and coating standoffs. For example, one or more of the vertices  602  between adjacent sidewalls  106  can be expanded into channel  604  to accommodate an electrical feed line  606 , as shown in  FIG. 6 . The electrical feed line  606  can be coupled to one or more sidewalls  106  at an internal attachment point  608  to provide a bias to the sidewall  106  to generate the radially varying potential field. Outside of the coupling  608 , the feed line  606  within the channel  604  can be electrically isolated so as to avoid impacting the potential profile. 
     The channel  604  may accommodate a single electrical feed line  606 , for example, to set a potential at a single radial location. For example,  FIG. 7A  illustrates a configuration of the vertex channel  604  where a single feed line  606  is coupled to adjacent sidewalls  106  at internal attachment points  608 . The feed line  606  is insulated along its length outside of attachment point  608  by insulating wall  702 . Such a configuration may be employed, for example, when the sidewall is formed of a material that has a resistivity that varies along  704 , i.e., the radial direction, although the configuration can also be applied to a sidewall formed of multiple segments  252 , as illustrated in  FIG. 7C   
     Alternatively or additionally, the channel  604  may accommodate multiple electric feed lines  606  to set potentials on different sidewalls, while also having a permanent magnet therein. For example,  FIG. 7B  illustrates a configuration of the vertex channel  604  where multiple feed lines  606  are disposed around an embedded permanent magnet  306  and separated therefrom by insulating material  702 . Each feed line  606  can be coupled to a respective sidewall  106  at a corresponding attachment point  608 . Again, the feed line  606  may be insulated along its entire length outside of attachment point  608  by insulating material  702 . 
     Alternatively or additionally, the channel  604  may accommodate multiple electric feed lines  606 , for example, to set potentials at more than one radial location. For example,  FIG. 7D  illustrates a configuration of the vertex channel  604  where multiple feed lines  606  extend to different radial depths and are separated from each other and the sidewalls  106  by insulating material  702 . 
     The features of  FIGS. 7A-7D  are not intended to be mutually exclusive. Rather, in some embodiments, the features of  FIGS. 7A-7D  can be combined to particular advantage. For example, some vertex channels  604  may have the configuration of  FIG. 7C , while other feed channels may have the configuration of  FIG. 7D , especially if the number of available vertices may be otherwise limited. Other combinations and variations should be readily apparent to one of ordinary skill in the art. 
     The vertex channels  604  could also be used to provide fuel to the CE-IEC device for fusion. For example, protons and boron ions can be generated at appropriate radial locations within a particle path so that the relative energy matches the fusion cross-section resonance, and so that the center mass of the reaction is stationary at the device core (i.e., zero net momentum). To achieve this, neutral atoms can be fed into the device to an appropriate radius prior to ionization. If the feed tubes were placed within the particle paths, they would be subject to fusion product bombardment. To avoid such bombardment, the feed tubes  804  are placed between the sidewalls  106 , for example, at the vertices  602  between adjacent sidewalls, for example, as shown in  FIG. 8 . Non-ionized fuel  810  is introduced at inlet  802  of the fuel feed tube  804 , where it is conveyed down to an appropriate radius before being ionized by ionizer  806 . The resulting ions can then be injected transversely to the particle path via outlets  808  extending through sidewalls  106 . The injected ions  812  mix with existing ions and join the ion bunches traveling along the particle paths. Injection slightly above the required energy level can allow for energy losses and for the ion to approach the resonance peak from above. 
     The vertex channels  604  could also be used to convey signals to/from locations within the sidewalls  106 , for example, to convey sensor signals. As discussed above, the potential may be dynamically controlled to compact ion bunches as they travel along the particle paths. In some embodiments, the potential may be controlled without feedback (i.e., open loop), for example, by establishing a time-varying profile and allowing the traveling ion bunches to synchronize to the profile. 
     Alternatively, one or more sensors  902 , as illustrated in  FIG. 9 , may be disposed along the sidewalls  106  to monitor the ion bunches as they travel along the particle path. The profile can then be dynamically adjusted in real time to compact the ion bunches or for any other purpose (e.g., to transfer energy to the ion bunch). The sensors  902  may be disposed on a surface of the sidewalls  106  (as shown), within the sidewalls  106 , or behind the sidewalls  106  (i.e., within channel  604 ). Other sensor types and configurations are also possible according to one or more contemplated embodiments, for example, to monitor variable indicative of operation of CE-IEC device, such as temperature, electron population in core, standoff thickness, etc. Signals from the sensors  902  can be communicated via signal wires  904  for subsequent use, for example, by controller  1006 . Although shown as extending along vertex channel  604 , it is also possible for the signal wires  904  to be disposed between adjacent panels of sidewalls  106  away from the vertex  602 . 
     Referring to  FIG. 10 , an overview of a system  1000  including a CE-IEC device  100  is shown. When the CE-IEC device  100  is used in a space environment, the CE-IEC device  100  may be housed in an enclosure  1002  that may be open to the environment (i.e., vacuum). Otherwise, the enclosure  1002  of the CE-IEC device  100  is a chamber that maintains a vacuum environment. 
     The CE-IEC device  100  can be coupled to a controller  1006  that controls operation thereof. Such control by the controller  1006  can include providing a static potential and/or a dynamic potential (e.g., to compact ion bunches) to the sidewalls  106  using voltage source  1008 . Although shown as a single component, voltage source  1008  can include multiple voltage sources and/or be capable of generating multiple independent voltages (for example, as needed for the multiple sidewall segments of  FIG. 2B ). The controller  1006  can also control fuel supply  1004  to supply non-ionized fuels to the CE-IEC device  100 , for example, to be ionized in situ as in  FIG. 8 . The control by the controller  1006  may be responsive to feedback from one or more sensor signals  1010 , for example, the sensors of  FIG. 9 . 
     The fusion products  1012  can be directed from the focusing region  110  of the CE-IEC device  100  for subsequent use, for example, directly utilized  1014  (e.g., propulsion of a spacecraft) and/or converted for use  1016  (e.g., converted to electricity using electrostatic deceleration and/or dynamically oscillating potentials). In the latter utility, the kinetic energy of the fusion products can be directly converted into electrical energy. Alternatively or additionally, the fusion products can be used to charge a conducting plate, which resulting charge can be used to drive a high impedance load. 
     For example,  FIGS. 11A-11C  show aspects of a 1-D version of a standing wave direct energy conversion (SW-DEC) process  1100  for converting the fusion products to electricity. The fusion products  140  pass along the particle paths  108   a - 108   c  and are energetic enough to escape the focusing region  110  and reach the power conversion region  150 . In the power conversion region  150 , a plurality of ring-shaped electrodes  1102 - 1108  are sequentially disposed along a path collinear with one of the particle paths  108   a - 108   c . Alternating ring electrodes are coupled together, such that odd numbered electrodes are in-phase with each other, and the even numbered electrode are 180° out of phase with the odd numbered electrodes. 
     As the fusion products  140  approach the first electrode  1102  in  FIG. 11A , the first and third electrodes  1102 ,  1106  are rising toward their peak potential, while the second and fourth electrodes  1104 ,  1108  are falling toward their minimum potential. The potential  1110  along the axis seen by the fusion products  140  has a positive gradient, which decelerates the fusion products. As the fusion products  140  pass through the first electrode  1102  in  FIG. 11B , the potential is approximately zero as the potentials reverse. Once past the first electrode  1102 , the first and third electrodes  1102 ,  1106  are falling toward their minimum potential, while the second and fourth electrodes  1104 ,  1108  are rising toward their peak potential, as shown in  FIG. 11C . Thus, the fusion products continue to experience a positive gradient that further causes deceleration. The process of  FIGS. 11A-11C  continues for each subsequent ring, extracting additional energy with the passing of each subsequent electrode. Although illustrated as equally spaced in  FIGS. 11A-11C , it is also possible to place consecutive rings closer together to compensate for reduced velocity of the fusions products. 
     For example, the electrodes  1102 - 1108  can form the capacitive element of a tuned resistor-inductor-capacitor (RLC) circuit  1120 , as shown in  FIG. 11D . The first and third electrodes  1102 ,  1106  can be connected together as one plate of the capacitor while the second and fourth electrodes  1104 ,  1108  can be connected together as the opposing plate of the capacitor. A resistor  1122  and an inductor  1124  can be connected in series between the plates of the capacitor. As the fusion products  140  lose kinetic energy passing through electrodes  1102 - 1108 , a corresponding amount of energy is pumped into the circuit  1120 , thereby increasing its oscillation amplitude. The resistive element  1122  of the circuit  1120  can be a load, which could be operating equipment or an energy storage device. 
     The description of  FIGS. 11A-11D  is for a simplified 1-D SW-DEC configuration. An SW-DEC configuration applied to practical embodiments of the CE-IEC device would necessarily be more complex, with ring or wire mesh electrodes provided at each end of particle paths  108   a - 108   c  to capture energy of fusion products emanating therefrom. For example, to implement the SW-DEC configuration in the power conversion region  150  of the CE-IEC, each electrode ring can be at a separate radius from the central core. However, instead of individual rings, each radial layer would be thin walled 3-D honeycomb structure, similar to the construction of the sidewalls forming the particle path channels. Such a configuration would maintain the high transparency of the CE-IEC, while allowing the fusion products to strongly couple to the electrodes. At the outermost radius of the SW-DEC, the fusion products can be driven into an electrode (not shown) where they would be neutralized and allowed to pass out into space. The charging of this electrode due to electron loss could also potentially be used to convert any remaining percentage of the kinetic energy of the fusion products into electricity. 
     An exemplary configuration of a 3-D SW-DEC is illustrated in the cross-sectional view of  FIG. 11E , where ring electrodes  1102 - 1108  are disposed along common radial lines in the power conversion region  150 . The ring electrodes  1102 - 1108  may be supported in position with respect to each other by supports  1132 , which may also connect the ring electrodes  1102 - 1108  to the sidewalls  106  of the CE-IEC device  100 . The supports  1132  may also provide electrical connectivity between the various ring electrodes and/or other components. Other configurations are also possible according to one or more contemplated embodiments. For example, although four electrodes (rings in  FIGS. 11A-11D , cubes in  FIG. 11E ) have been illustrated, fewer or greater number of electrodes may be provided for the SW-DEC system. 
     Although a cubic configuration for the CE-IEC device  100  is illustrated in  FIGS. 1-11 , this is merely the simplest configuration for explanation of the features of the present disclosure and embodiments are not limited to such geometries. For example, the innermost edge  104  and/or the outermost edge  102  can lie on a sphere, such that each half of the particle path outside the core region  112  takes the form of a truncated cone (defining a circular face perpendicular to the radial direction). 
     Indeed, practical embodiments of the disclosed subject matter may employ other configurations with different particle path geometries and/or number of particle paths. To this end, the sidewall structure can be formed by radial extrusion of the edges of any polyhedron, so long as the faces of the polyhedron come in diametrically opposed pairs in order to create the aligned particle paths on opposite sides of the core. For example, the number of particle pathways can be increased and the geometry of the innermost edge  104  and/or outermost edge  102  can be more complex, such as a truncated icosahedron (e.g., soccer ball geometry), as described in further detail below with respect to  FIGS. 12A-12B . Accordingly, geometries other than those specifically illustrated are also possible according to one or more contemplated embodiments. 
     An entire family of highly symmetric CE options is provided by the geometry of fullerenes—carbon molecules that form closed polyhedral cages. Fullerenes are labeled as C N , where N is the number of carbon atoms in the molecule. Of particular interest are those of icosahedral (−I h ) symmetry, such as C 20 , C 60 , C 80 , C 240 , etc., where a necessary condition is that N must be a multiple of 20. For each of these, 12 faces are always pentagons and the rest are always hexagons. A regular truncated icosahedron (RTI) has edges of equal length, but the hexagonal faces have an area that is about 60% larger than the pentagons. This is the geometry of the C 60  molecule (and the soccer ball). However, the truncation of the icosahedron can be done in such a way that instead of ending up with the edges all the same length, one can achieve a geometry where the two types of faces can be inscribed by circles having substantially the same area. This makes the resulting particle paths more equivalent.  FIG. 12A  shows an exemplary CE-IEC device  1200  employing such geometry, which is referred to as the special irregular truncated icosahedron (SITI).  FIG. 12B  shows a cutaway version of the CE-IEC device  1200  and illustrates exemplary magnetic field lines and an exemplary electric potential as well as other hidden components (e.g., internal permanent magnets). 
     Embodiments of the CE-IEC device can employ various nuclear fusion fuels. For example, the CE-IEC device can employ the deuterium-tritium (D-T) reaction or the deuterium-deuterium (D-D) reaction. For single species fuel, such as D-D, only two diametrically opposed ion bunches  120  will be present along each particle path at any given time, one bunch on each side of the core. While the burning of D-T has the highest cross-section, it may suffer from the production of highly energetic neutrons, which can be absorbed into the nuclei of other materials and create unstable radioactive isotopes. In addition, scattering of these neutrons can dislocate atoms from their lattices resulting in structural degradation over time. 
     In another example, the CE-IEC device uses an aneutronic fuel such as p- 11 B, which is the fusion of a hydrogen atom with the most common isotope of boron. The result of the fusion process is three helium nuclei (alpha particles) with a total energy of about 8.7 MeV. For two-species fuel such as p- 11 B, four diametrically opposed bunches  120 —one pair for each of the two species—will be present along each particle path at any given time, two bunches on each side of the core, separated radially. 
     Although features of the various figures have been separately illustrated, embodiments of the disclosed subject matter can combine one or more of the separately illustrated features. For example, embodiments can include the sidewall geometry features of  FIGS. 1A-1C or 12A-12B , the continuous electrode features of  FIGS. 2A-2B , the permanent magnet features of  FIGS. 3A-4C , the protective standoff features of  FIG. 5 , the electric feed line features of  FIGS. 6-7D , the fuel feed features of  FIG. 8 , the sensor features of  FIG. 9 , the control features of  FIG. 10 , and/or the power generation features of  FIGS. 11A-11C . Accordingly, embodiments of the disclosed subject matter are not limited to the configurations specifically illustrated. 
     Moreover, although the above description has focused on the use of the CE-IEC device for nuclear fusion, embodiments of the disclosed subject matter are not necessarily limited thereto. Indeed, aspects of the disclosed subject matter may be employed in other applications that have traveling ions. 
     It will be appreciated that the aspects of the disclosed subject matter can be implemented, fully or partially, in hardware, hardware programmed by software, software instruction stored on a computer readable medium (e.g., a nontransitory computer readable medium) or a combination of the above. 
     For example, components of the disclosed subject matter, including components such as a controller, processor, or any other feature, can include, but are not limited to, a personal computer or workstation or other such computing system that includes a processor, microprocessor, microcontroller device, or is composed of control logic including integrated circuits such as, for example, an application specific integrated circuit (ASIC). 
     Features discussed herein can be performed on a single or distributed processor (single and/or multi-core), by components distributed across multiple computers or systems, or by components co-located in a single processor or system. For example, aspects of the disclosed subject matter can be implemented via a programmed general purpose computer, an integrated circuit device (e.g., ASIC), a digital signal processor (DSP), an electronic device programmed with microcode (e.g., a microprocessor or microcontroller), a hard-wired electronic or logic circuit, a programmable logic circuit (e.g., programmable logic device (PLD), programmable logic array (PLA), field-programmable gate array (FPGA), programmable array logic (PAL)), software stored on a computer-readable medium or signal, an optical computing device, a networked system of electronic and/or optical devices, a special purpose computing device, a semiconductor or superconductor chip, a quantum computing chip or device, a software module or object stored on a computer-readable medium or signal. 
     When implemented in software, functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. The steps of a method or algorithm disclosed herein may be embodied in a processor-executable software module, which may reside on a computer-readable medium. Instructions can be compiled from source code instructions provided in accordance with a programming language. The sequence of programmed instructions and data associated therewith can be stored in a computer-readable medium (e.g., a nontransitory computer readable medium), such as a computer memory or storage device, which can be any suitable memory apparatus, such as, but not limited to quantum-based memory, read-only memory (ROM), programmable read-only memory (PROM), electrically erasable programmable read-only memory (EEPROM), random-access memory (RAM), flash memory, disk drive, etc. 
     As used herein, computer-readable media includes both computer storage media and communication media, including any medium that facilitates transfer of a computer program from one place to another. Thus, a storage media may be any available media that may be accessed by a computer. By way of example, and not limitation, such computer-readable media may comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, quantum-based storage, or any other medium that may be used to carry or store desired program code in the form of instructions or data structures and that may be accessed by a computer. 
     Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a transmission medium (e.g., coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave), then the transmission medium is included in the definition of computer-readable medium. Moreover, the operations of a method or algorithm may reside as one of (or any combination of) or a set of codes and/or instructions on a machine readable medium and/or computer-readable medium, which may be incorporated into a computer program product. 
     One of ordinary skill in the art will readily appreciate that the above description is not exhaustive, and that aspects of the disclosed subject matter may be implemented other than as specifically disclosed above. Indeed, embodiments of the disclosed subject matter can be implemented in hardware and/or software using any known or later developed systems, structures, devices, and/or software by those of ordinary skill in the applicable art from the functional description provided herein. 
     In this application, unless specifically stated otherwise, the use of the singular includes the plural, and the separate use of “or” and “and” includes the other, i.e., “and/or.” Furthermore, use of the terms “including” or “having,” as well as other forms such as “includes,” “included,” “has,” or “had,” are intended to have the same effect as “comprising” and thus should not be understood as limiting. 
     Any range described herein will be understood to include the endpoints and all values between the endpoints. Whenever “substantially,” “approximately,” “essentially,” “near,” or similar language is used in combination with a specific value, variations up to and including 10% of that value are intended, unless explicitly stated otherwise. 
     It is thus apparent that there is provided in accordance with the present disclosure, systems, methods, and devices for inertial electrostatic confinement. Many alternatives, modifications, and variations are enabled by the present disclosure. While specific examples have been shown and described in detail to illustrate the application of the principles of the present invention, it will be understood that the invention may be embodied otherwise without departing from such principles. For example, disclosed features may be combined, rearranged, omitted, etc. to produce additional embodiments, while certain disclosed features may sometimes be used to advantage without a corresponding use of other features. Accordingly, Applicant intends to embrace all such alternatives, modifications, equivalents, and variations that are within the spirit and scope of the present invention.