Patent Description:
Fusion is a process which can be harnessed to release the nuclear energy in abundant fuels, without emissions of greenhouse gases and with significantly lower and shorter-lived radioactive waste than conventional fission nuclear reactors. Fusion fuels fuse only at extremely high temperature, at which all materials are in the plasma state.

Magnetic fusion devices aim to confine a fusing plasma using magnetic fields. The two leading magnetic fusion approaches are the tokamak and the stellarator, both of which utilize a magnetic field which has the topology of a torus.

Stellarators have the advantage over tokamaks of operating in steady state and requiring no additional electrical current to be driven within the plasma itself. Prior stellarator designs have included non-planar electromagnetic coils which have a complex, 3D curvature. These electromagnetic coils are difficult to design, fabricate, integrate, and maintain. Some stellarator designs include electromagnetic coils which link other electromagnetic coils, akin to the links of a chain. These electromagnetic coils cannot be fabricated separately and then assembled; they must be fabricated together, which further increases the difficulty of their fabrication, integration, and maintenance.

One example of a stellarator employing complex electromagnetic coils is the Large Helical Device (LHD) experiment operated by the Japanese National Institute for Fusion Science (<NPL>. These electromagnetic coils are helical coils, which are non-planar and interlock the plasma and the other helical coils. These electromagnetic coils must be wound with electrical wire on-site. Stellarators employing such electromagnetic coils are termed Torsatrons or Heliotrons.

Another example of a stellarator employing complex electromagnetic coils is the Wendelstein <NUM>-X (W7-X) experiment operated by the German Max Planck Institute for Plasma Physics (<NPL>. With reference to <FIG>, W7-X uses a combination of external planar coils <NUM> and modular coils <NUM>. The external planar coils are planar <NUM>, interlock the plasma, and do not interlock any other coils. The modular coils <NUM> are non-planar, interlock the plasma, and do not interlock any other coils. Stellarators employing this kind of coils can be termed Heliases or, more generally, modular coil stellarators.

The National Compact Stellarator Experiment (NCSX) was a proposed experiment that was canceled during its construction. A few different designs were proposed (<NPL>. A proposed "saddle coil design" which utilized (i) Toroidal Field (TF) coils, which are planar coils that interlock the plasma, but which do not interlock any other coils; and (ii) saddle coils, which are non-planar coils that do not interlock the plasma, but do not interlock any other coils. An alternative design, referred to as the "optimized background coils and conformal coils design" utilized (i) background coils which are planar, interlock the plasma, and that interlock other background coils; and (ii) saddle coils, which are planar, do not interlock the plasma, and which do not interlock any other coils.

Several experimental designs, such as W7-X and NCSX, incorporate planar trim coils (<NPL>. Planar trim coils are planar, do not interlock the plasma, and do not interlock with any other coils. Planar trim coils are part of a control system rather than a magnetic field generation system. As such, their purpose is to correct a magnetic field which is off nominal in some way (e.g., due to some imprecision in construction or due to plasma behavior). At the nominal operating point, planar trim coils are designed to be inactive. <FIG> illustrates the planar trim coils <NUM> as utilized in the W7-X design. Notably, the planar trim coils <NUM> positioned on the "outboard side" of the stellarator, away from the center of the device; and also positioned outside to the external planar coils. It is also notable that the planar trim coils <NUM> are comprised of copper; and are not comprised of a superconducting material like the external planar coils <NUM> and the modular coils <NUM> utilized in the W7-X design. It is also notable that the planar trim coils <NUM> are much larger than the minor radius of the plasma, and almost the size of the major radius of the plasma.

An article by T. Todd in <NUM> (<NPL>) and an experiment built at Columbia University in <NUM>, called the Columbia Non-neutral Torus (CNT, <NPL>. ) describe stellarators which use planar coils. The Todd <NUM> article describes a <NUM>-coil stellarator, both of which are planar and interlock the plasma. With reference to <FIG>, the CNT uses Inter-Locking (IL) <NUM> coils and Poloidal Field (PF) <NUM> coils. The IL coils are planar and interlock each other and the plasma. The PF coils are planar and do not interlock the plasma, themselves, or any other coils.

In an article authored by L. Boozer in <NUM> (<NPL>) describes a stellarator which uses TF coils and window pane coils. The TF coils are planar, interlock the plasma, and do not interlock any other coils. The window pane coils are depicted by Ku as being non-planar. Ku describes that they do not interlock the plasma; and that they do not interlock any other coils. Furthermore, Ku refers to the design as "difficult to implement" and qualifies the concept as an "existence proof," indicating that they did not believe the design to be practical.

Several items in the prior art use toroidal field (TF) coils. See the saddle coil design of NCSX in Neilson et al. <NUM> and the design in Ku and Boozer <NUM>. An important aspect of TF coils is that, while they are planar and encircle the plasma, their location and orientation exhibit N-fold rotational symmetry. Specifically, if the TF coil system consists of N coils, then rotating the coil system by <NUM>°/N produces the same set of TF coils. This was done in order to approximate a simple, axisymmetric magnetic field, like a tokamak.

Another stellarator example of the prior art are disclosed in document <CIT>, which in particular discloses a field-shaping coil system comprising permanent magnets disposed on structural mounting elements.

From the foregoing, it is apparent that stellarators designed to-date have incredibly complex three-dimensional design, which leads to increased costs and to difficulty controlling the distribution of the 3D magnetic field. It would be desirable to develop a stellarator having a less complex design and one which enables greater control of the generated magnetic field.

The present disclosure is directed to an improved stellarator design which has a simpler, less complex structure as compared with stellarators developed to-date. As compared with prior art stellarators, in some embodiments the stellarators of the present disclosure do not require non-planar coils. Rather, in some embodiments, the stellarators of the present disclosure utilize a plurality of planar encircling coils and a plurality of planar shaping coils. As described herein, in some embodiments the planar encircling coils encircle the plasma axis, but not any other planar encircling coil or any planar shaping coil. Moreover, in some embodiments the planar shaping coils do not encircle the plasma axis; nor do they encircle any other planar shaping coil or any planar encircling coil.

In view of the foregoing, according to claim <NUM>, the invention is directed to a stellarator comprising: (a) a field-shaping coil system including one or more field shaping units which define a void adapted to confine a plasma, wherein each field shaping unit comprises: (i) one or more structural mounting elements; and (ii) one or more planar shaping coils disposed on a surface of the one or more structural mounting elements, wherein each of the one or more planar shaping coils do not interlock with each other or the plasma confined in the void; and (b) a plurality of planar encircling coils which encircle the field-shaping coil system, wherein each planar encircling coil of the plurality of planar encircling coils do not interlock with each other, but where each individual planar encircling coil of the plurality of encircling coils interlocks the plasma confined in the void, and wherein any planar shaping coil of the one or more of planar shaping coils does not interlock with any planar encircling coil of the plurality of planar encircling coils.

In an embodiment the stellarator includes between about <NUM> and about <NUM> planar encircling coils, preferably wherein the stellarator comprises at least four planar encircling coils.

In an embodiment the plurality of planar encircling coils are comprised of one or more superconducting materials.

In an embodiment the stellarator comprises at least <NUM> field shaping units.

In an embodiment the surface of the one or more structural mounting elements faces the void.

In an embodiment each of the one or more field shaping units comprises one structural mounting element.

In an embodiment the one structural mounting element is wedge shaped.

In an embodiment each of the one or more field shaping units comprises two or more structural mounting elements.

In an embodiment a shape of each planar shaping coil of the one or more planar shaping coils is substantially rectangular, substantially rectangular with rounded corners, or substantially circular.

In an embodiment each of the one or more field shaping units comprises between about <NUM> and about <NUM> shaping coils, preferably wherein each of the one or more field shaping units comprises between about <NUM> and about <NUM> shaping coils.

In an embodiment the one or more shaping coils are comprised of a superconducting material.

In an embodiment the stellarator further comprises one or more controllers configured to control a current supplied to the one or more field shaping units.

In an embodiment the stellarator further comprises one or more additional coils.

In an embodiment the one or more additional coils are communicatively coupled to a controller to control a current supplied to the one or more additional coils.

In an embodiment each of the one or more shaping coils do not individually encircle the plasma.

For a general understanding of the features of the disclosure, reference is made to the drawings. In the drawings, like reference numerals have been used throughout to identify identical elements.

As used herein, the singular terms "a," "an," and "the" include plural referents unless context clearly indicates otherwise. Similarly, the word "or" is intended to include "and" unless the context clearly indicates otherwise. The term "includes" is defined inclusively, such that "includes A or B" means including A, B, or A and B.

Only terms clearly indicated to the contrary, such as "only one of or "exactly one of," or, when used in the claims, "consisting of," will refer to the inclusion of exactly one element of a number or list of elements. In general, the term "or" as used herein shall only be interpreted as indicating exclusive alternatives (i.e., "one or the other but not both") when preceded by terms of exclusivity, such as "either," "one of," "only one of" or "exactly one of.

The terms "comprising," "including," "having," and the like are used interchangeably and have the same meaning. Similarly, "comprises," "includes," "has," and the like are used interchangeably and have the same meaning. Specifically, each of the terms is defined consistent with the common United States patent law definition of "comprising" and is therefore interpreted to be an open term meaning "at least the following," and is also interpreted not to exclude additional features, limitations, aspects, etc. Thus, for example, "a device having components a, b, and c" means that the device includes at least components a, b, and c. Similarly, the phrase: "a method involving steps a, b, and c" means that the method includes at least steps a, b, and c. Moreover, while the steps and processes may be outlined herein in a particular order, the skilled artisan will recognize that the ordering steps and processes may vary.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment.

Electromagnetic coils may be described according to their shape and/or topology. For instance, an electromagnetic coil may have a planar shape (a coil that lines within one flat plane) or non-planar shape. Planar electromagnetic coils may be fabricated by conventional means and wound with electrical wire under tension. Topology refers to whether an electromagnetic coil links, threads, or interlocks with another coil, in the manner of chain links. Topology may also refer to whether an electromagnetic coil interlocks the plasma or not.

The present disclosure is directed to an improved stellarator design which has a simpler, less complex structure as compared with stellarators developed to-date.

Described herein are stellarators incorporating a plurality of encircling coils and a plurality of shaping coils. With reference to <FIG>, stellarators of the present disclosure comprise a field shaping system <NUM> which surrounds a void <NUM> that confines a plasma <NUM>. In some embodiments, the void <NUM> is configured such that a largest dimension from a plasma axis <NUM> of any contained plasma <NUM> to an outer edge of the contained plasma (not shown) is less than <NUM> meters, such as less than <NUM> meters, such as less than <NUM> meters, such as less than <NUM> meters, such as less than <NUM> meters, such as less than <NUM> meters, such as less than <NUM> meter, such as less than <NUM> meters, etc..

In some embodiments, the plasma <NUM> has a topology which substantially approximates that of a torus. In some embodiments, the plasma <NUM> is centered around a "plasma axis" <NUM>, which is a magnetic field line that maps onto its own origin after one toroidal rotation. In some embodiments, the plasma axis <NUM> has a topology of a loop or one that substantially approximates a loop.

The field shaping system <NUM> comprises a plurality of field shaping units <NUM>. In some embodiments, the field shaping system <NUM> may comprise at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM> field shaping units <NUM>.

In some embodiments, each of the field shaping units <NUM> includes one or more structural mounting elements <NUM> having a surface <NUM>. In some embodiments, the surface <NUM> of each field shaping unit <NUM> faces the the void <NUM>. In some embodiments, each field shaping unit <NUM> further includes one or more additional components <NUM>. The one or more additional components include, but are not limited to, a first wall to handle plasma flux, a structure which mounts to the first wall, a breeding blanket to breed radioisotopes from the fusion neutron flux, a cryostat, and/or neutron shielding.

In some embodiments, each field shaping unit <NUM> comprises a single structural mounting element <NUM>. In other embodiments, each field shaping unit <NUM> comprises two structural mounting elements <NUM>. In yet other embodiments, each field shaping unit <NUM> comprises three structural mounting elements <NUM>. In further embodiments, each field shaping unit <NUM> comprises four or more structural mounting elements <NUM>. In some embodiments, the structural mounting element <NUM> is comprised of steel. In some embodiments, the structural mounting element <NUM> comprises a metal. In some embodiments, the structural mounting element <NUM> comprises a composite material, such as G-<NUM>.

The field shaping unit <NUM> may have any size and shape. In some embodiments, the field shaping unit <NUM> defines an extruded circular annulus cross section structure. In other embodiments, the field shaping unit <NUM> has an arbitrary shape, such as a shape having a non-constant crosssection. For example, and as illustrated in <FIG>, in some embodiments, the field shaping unit <NUM> has a wedge shape (as seen from a perspective perpendicular to the plasma axis and the direction of curvature, arranged such that the narrower portion of the wedge faces the direction of plasma axis curvature, and the wider portion of the wedge faces opposite the direction of plasma axis curvature). In some embodiments, the field shaping unit <NUM> is substantially wedge shaped. In other embodiments, the field shaping unit <NUM> has a shape similar to or the same as a cross sectional shape of the plasma at that location. In other embodiments, the field shaing unit has about the cross sectional shape of the plasma, with some constant normal offset distance.

In some embodiments, one or more shaping coils <NUM> are disposed on the surface <NUM> of each of the one or more structural mounting elements <NUM>. It is believed that the one or more shaping coils <NUM> of the present disclosure are relatively easy to manufacture, assemble, and integrate into a field shaping unit. Moreover, it is beleved that the one or more field shaping coils <NUM> allow precise control over the shape of the plasma.

Each of the one or more shaping coils <NUM> are planar coils. A "planar" coil is one whose shape substantially lies within one flat plane. In some embodiments, each of the shaping coils <NUM> individually do not encircle the plasma axis <NUM>. Said another way, any one shaping coil <NUM> does not encircle the plasma <NUM> or the plasma axis <NUM>. For instance, and as depicted in <FIG> and <FIG>, the shaping coils <NUM> or <NUM> are disposed on surface <NUM> or <NUM> of a structural mounting element <NUM> or <NUM>, respectively, and each individual shaping coil <NUM> or <NUM> does not encircle the plasma axis.

While any individual shaping coil <NUM> does not encircle the plasma axis <NUM>, collectively an array including a plurality of shaping coils <NUM> mounted on the surfaces <NUM> of one or more structural mounting elements <NUM> would encircle the plasma axis <NUM>. This is illustrated in <FIG> which shows a plurality of shaping coils <NUM> arranged on a surface <NUM> of a structural mounting element <NUM>. As depicted, no one shaping coil <NUM> encircles the plasma confined in the void <NUM>. However, the collective of all shaping coils <NUM> as arranged on the surface <NUM> of the one or more structural mounting elements <NUM> does encircle the plasma and/or the void <NUM>. This concept is further illustrated in <FIG>, which again illustrates that no one shaping coil <NUM> encircles the plasma confining void <NUM>. In some embodiments, individual shaping coils <NUM> may be positioned on opposite sides of the plasma or on different faces of the void.

Each of the one or more shaping coils <NUM>, <NUM> or <NUM> do not interlock with any other shaping coil, such as illustrated in at least <FIG>, <FIG> and <FIG>. Additionally, each of the one or more shaping coils do not interlock with any of the encircling coils <NUM> described herein (see <FIG>, <FIG>, and <FIG>). In some embodiments, the one or more shaping coils <NUM> are removably coupled to the surface <NUM> of the one or more surface mounting elements <NUM>.

In some embodiments, the planar shaping coils have a mean coil radius which is smaller than a major radius of the plasma and smaller than a minor radius of the plasma. As used herein, the "major radius" of the plasma is the mean distance between the plasma axis and the geometric center of the stellarator. As used herein, the "minor radius" of the plasma is the mean closest distance between each point on the plasma boundary and the plasma axis. The plasma boundary is sometimes represented by a set of toroidal Fourier amplitudes; for this case, the major radius is represented by the amplitude of the mode with toroidal mode number <NUM> and poloidal mode number <NUM>; and the minor radius is represented by the amplitudes of the mode with toroidal mode number <NUM> and poloidal mode number <NUM>.

The shaping coils <NUM> may have different sizes and shapes. For instance, and with reference to <FIG>, in some embodiments the shaping coils <NUM> may be circular or substantially circular. In other embodiments, the shaping coils may be rectangular or substantially rectangular (<FIG>). In yet other embodiments, the shaping coils may be rectangular with rounded corners or substantially rectangular with rounded corners (<FIG>). In some embodiments, each field shaping unit <NUM> may comprise one or more coils having different shapes. For instance, a field shaping unit <NUM> may comprise <NUM> shaping coils where <NUM> of the shaping coils may have a substantially circular shape, <NUM> of the shaping coils may have a substantially rectangular shape, and <NUM> of the coils may have a substantially rectangular shape with rounded corners (not depicted).

In some embodiments, the stellarator of the present disclosure may include between about <NUM> and <NUM>,<NUM> shaping coils. In other embodiments, the stellarator of the present disclosure may include between about <NUM> and <NUM>,<NUM> shaping coils. In yet other embodiments, the stellarator of the present disclosure may include between about <NUM> and <NUM>,<NUM> about shaping coils. In further embodiments, the stellarator of the present disclosure may include between about <NUM> and <NUM>,<NUM> about shaping coils. In yet further embodiments, the stellarator of the present disclosure may include between about <NUM> and <NUM>,<NUM> about shaping coils. In even further embodiments, the stellarator of the present disclosure may include between about <NUM> and <NUM>,<NUM> about shaping coils. In even further embodiments, the stellarator of the present disclosure may include between about <NUM> and <NUM>,<NUM> about shaping coils.

In some embodiments, a field shaping unit <NUM> may include between about <NUM> and about <NUM> shaping coils <NUM>. In other embodiments, a field shaping unit <NUM> may include between about <NUM> and about <NUM> shaping coils <NUM>. In yet other embodiments, a field shaping unit <NUM> may include between about <NUM> and about <NUM> shaping coils <NUM>. In further embodiments, a field shaping unit <NUM> may include between about <NUM> and about <NUM> shaping coils <NUM>. In even further embodiments, a field shaping unit <NUM> may include between about <NUM> and about <NUM> shaping coils <NUM>. In yet even further embodiments, a field shaping unit <NUM> may include between about <NUM> and about <NUM> shaping coils <NUM>. In yet even further embodiments, a field shaping unit <NUM> may include between about <NUM> and about <NUM> shaping coils <NUM>. In yet even further embodiments, a field shaping unit <NUM> may include between about <NUM> and about <NUM> shaping coils <NUM>. In yet even further embodiments, a field shaping unit <NUM> may include between about <NUM> and about <NUM> shaping coils <NUM>. In yet even further embodiments, a field shaping unit <NUM> may include between about <NUM> and about <NUM> shaping coils <NUM>. In yet even further embodiments, a field shaping unit <NUM> may include between about <NUM> and about <NUM> shaping coils <NUM>.

With reference to <FIG>, the stellarator of the present disclosure also includes a plurality of encircling coils <NUM> which encircle the plasma axis <NUM>. Each of the encircling coils <NUM> are arranged around an exterior of the field shaping system <NUM> and encircle it. This is further illustrated in <FIG> and <FIG> which show encircling coils <NUM> and <NUM> encircling the plasma and/or void <NUM> or <NUM>, respectively; but where the encircling coils <NUM> and <NUM> are exterior to any field shaping unit <NUM> or <NUM>.

Each encirlcing coil <NUM> of the plurality of encircling coils are planar. Moreover, each encircling coil <NUM> of the plurality of encircling coils are non-interlocking with any other encircling coil <NUM>. Additionally, each encircling coil <NUM> of the plurality of encircling coils are do not interlock with any of the shaping coils <NUM>. Said another way, any encirlcing coil <NUM> does not interlock with any other planar encircling coil <NUM> or with any other shaping coil <NUM>, such as depicted in <FIG>, <FIG>, and <FIG>. In some embodiments, each encircling coil <NUM> is supported by a structural component <NUM>. In some embodiments, the structural componnent <NUM> and the field shaping units <NUM> may be coupled to other structural members <NUM> which react to unbalanced forces and torques.

In some embodiments, the encircling coils do not exhibit the N-fold rotational symmetry of toroidal field (TF) coils. If the encircling coils are N-fold rotationally symmetric, like TF coils in the prior art, then the planar shaping coils require some irreducible quantity of current length (Amperes*meters) in order to correct this field. If the encircling coils are allowed to not be N-fold rotationally symmetric, the current-length requirements of the planar shaping coils can be reduced by a large factor. It is believed that this requirement may be reduced by nearly a factor of <NUM> by allowing the encircling coils to be positioned more favorably.

In some embodiments, the stellarators of the present disclosure include between about <NUM> and about <NUM> encircling coils. In other embodiments, the stellarators of the present disclosure include between about <NUM> and about <NUM> encircling coils. In yet other embodiments, the stellarators of the present disclosure include between about <NUM> and about <NUM> encircling coils. In further embodiments, the stellarators of the present disclosure include between about <NUM> and about <NUM> encircling coils. In yet further embodiments, the stellarators of the present disclosure include between about <NUM> and about <NUM> encircling coils. In even further embodiments, the stellarators of the present disclosure include between about <NUM> and about <NUM> encircling coils. In yet even further embodiments, the stellarators of the present disclosure include between about <NUM> and about <NUM> encircling coils. In some embodiments, the spacing between each encircling coil may range from between abhout <NUM> to about <NUM>.

The shaping coils <NUM> and the encircling coils <NUM> may be comprised of one or more superconducting materials. A superconductor is a material that achieves superconductivity. Superconductivity is the property of certain materials to conduct direct current (DC) electricity without energy loss when they are cooled below a critical temperature (referred to as Tc). An electric current in a superconductor can persist indefinitely. Exemplary superconducting materials include, but are not limited to, Nb-Ti, Nb<NUM>Sn, MgB<NUM>, LaBaCuOx, LSCO (e.g., La<NUM>-xSrxCuO<NUM>, etc.), YBCO (e.g., YBa<NUM>Cu<NUM>Ox or YBa<NUM>Cu<NUM>O<NUM>), REBCO, bismuth-based cuprate superconductors (BSCCO) (including Bi<NUM>Sr<NUM>CaCu<NUM>O<NUM> (Bi-<NUM>) and Bi<NUM>Sr<NUM>Ca<NUM>Cu<NUM>O<NUM> (Bi-<NUM>)), TBCCO (e.g., Tl<NUM>Ba<NUM>Ca<NUM>Cu<NUM>O<NUM> or TlmBa<NUM>Can-<NUM>CunO2n+m+<NUM>+δ), HgBa<NUM>Ca<NUM>Cu<NUM>Ox, and other mixed-valence copper-oxide perovskite materials. In some embodiments, the shaping coils and the encircling coils may be comprised on the same materials. In other embodiments, the shaping coils and the encircling coils may be comprised on different materials.

With reference to <FIG> and <FIG>, in some embodiments, the stellarators of the present disclosure further include one or more additional coils <NUM>, such as one or more control coils and/or one or more saddle coils. In some embodiments, the control coils and/or the saddles are planar. In some embodiments, the control coils and/or the saddles are non-planar. In some embodiments, the control coils and/or the saddles are superconducting. In some embodiments, the control coils and/or the saddles are non-interlocking and, in particular, they do not interlock any other of the disclosed coils (e.g., encircling coils, shaping coils) or the plasma axis. In some embodiments, the control coils and/or the saddle coils are disposed between the plasma boundary and the field shaping system. In some embodiments, the control coils and/or the saddle coils are disposed outward of the field shaping system, on the non-plasma-axis-facing side. Control coils are coils included as a contingency against unexpected sources of error. These errors may arise from errors in assembly of the magnet system, or from unexpected plasma physics. Before the error is measured, the correct electrical current for the control coils is not known. During normal operation of the stellarator, if the stellarator and plasma are operating at their design points, the control currents have zero electric current. The design of the stellarator magnetic field does not include contributions from the control coils.

In some embodiments, the stellarator is communicatively coupled to one or more controllers. In some embodiments, the one or more controllers are configured to control each of the one or more field-shaping units and optionally the one or more encircling coils. In some embodiments, one or more controllers are adapted to control a subset of the shaping coils disposed on a surface of a field shaping unit. In some embodiments, one or more controllers may be adapted to control one or more of the optional control coils and/or the optional saddle coils. In some embodiments, the one or more controllers include one or more power supplies which may be configured to increase or decrease the electrical current flowing in a subset of the encircling coils and/or the shaping coils. In some embodiments, the one or more controllers include a switching system which may be configured to connect one or more power supplies to certain subsets of encircling coils and/or shaping coils.

Embodiments of the subject matter and the operations described in this disclosure may be implemented in digital electronic circuitry, or in computer software, firmware, or hardware, including the structures disclosed in this specification and their structural equivalents, or in combinations of one or more of them. Embodiments of the subject matter described in this disclosure may be implemented as one or more computer programs, i.e., one or more modules of computer program instructions, encoded on computer storage medium for execution by, or to control the operation of, data processing apparatus.

In some embodiments, the controller includes a processor and a non-transitory computer readable storage medium operably coupled to the processor. A computer storage medium can be, or can be included in, a computer-readable storage device, a computer-readable storage substrate, a random or serial access memory array or device, or a combination of one or more of them. Moreover, while a computer storage medium is not a propagated signal, a computer storage medium can be a source or destination of computer program instructions encoded in an artificially generated propagated signal. The computer storage medium can also be, or can be included in, one or more separate physical components or media (e.g., multiple CDs, disks, or other storage devices). The operations described in this disclosure may be implemented as operations performed by a data processing apparatus on data stored on one or more computer-readable storage devices or received from other sources. In some embodiments, the non-transitory computer readable storage medium contains instructions that, when executed by the processor, cause the processor to adjust a strength of a field generated by one or more coils in order to contain plasma within the magnetic fields.

In some embodiments, a method is provided for designing a stellarator using shaping and encircling coils. As seen in <FIG>, the method <NUM> may include determining <NUM> a continuous surface dipole or surface current potential distribution that produces any required fields for confining a plasma using a surface current, given an optimized plasma target and an encircling coil array as in Merkel <NUM> (<NPL>. ) or Landreman <NUM> (<NPL>). The method may also include receiving parameters and then defining <NUM> a configuration of shaping coils by discretizing the continuous surface dipole or current potential distribution. Non-limiting examples of parameters that may be received are the resolution of the surface to be discretized into coils, a cutoff current below which a coil is removed from the design, and/or the maximum coil linear dimension. The method may also include modeling <NUM>, e.g., via a simulation, a reconstructed plasma, and comparing <NUM> properties of the reconstructed model plasma to the optimized plasma target. In some embodiments, the reconstructed model plasma is modeled using a free-boundary plasma solver.

In some embodiments, the method may include optimizing the target plasma properties and magnetic field coil requirements via an iterative process. After the comparing step <NUM>, the method may include adjusting <NUM> a parameter used to define (determine) the configuration of shaping coils, then repeating <NUM> the steps of defining <NUM>, generating <NUM>, and comparing <NUM>, until an acceptable comparison is achieved. The iteratively defining the configuration of shaping coils, generating the reconstructed model plasma, comparing properties, and adjusting a parameter used to define the configuration of shaping coils.

After the comparing step <NUM>, the method may include defining <NUM> forces on a subset of the coils, such as any of the encircling coils and/or any of the shaping coils or any subset thereof. Once the force on a subset of the coils has been defined, the method may also include designing <NUM> one or more structural members <NUM> and/or structural components <NUM> to react to the forces on a subset of the coils.

Claim 1:
A stellarator comprising:
(a) a field-shaping coil system (<NUM>) including one or more field shaping units (<NUM>,<NUM>,<NUM>) which define a void (<NUM>,<NUM>,<NUM>) adapted to confine a plasma, wherein each field shaping unit comprises:
(i) one or more structural mounting elements (<NUM>,<NUM>,<NUM>); and
(ii) one or more planar shaping coils (<NUM>,<NUM>,<NUM>) disposed on a surface of the one or more structural mounting elements, wherein each of the one or more planar shaping coils do not interlock with each other or the plasma confined in the void; and
(b) a plurality of planar encircling coils (<NUM>,<NUM>,<NUM>) which encircle the field-shaping coil system, wherein each planar encircling coil of the plurality of planar encircling coils do not interlock with each other, but where each individual planar encircling coil of the plurality of encircling coils interlocks the plasma confined in the void, and wherein any planar shaping coil of the one or more of planar shaping coils does not interlock with any planar encircling coil of the plurality of planar encircling coils.