WO2017172815A1

WO2017172815A1 - Methods and apparatus for coincidentally forming a virtual cathode and a high beta plasma

Info

Publication number: WO2017172815A1
Application number: PCT/US2017/024605
Authority: WO
Inventors: Scott CORNISH; Paul SIECK
Original assignee: Fusion One Corporation
Priority date: 2016-03-29
Filing date: 2017-03-28
Publication date: 2017-10-05

Abstract

An inertial electrostatic confinement device is provided. The inertial electrostatic confinement device comprises a reactor chamber. Additionally, the inertial electrostatic confinement device comprises a set of inner coils within the reactor chamber. The inner coils produce magnetic field lines that extend to walls of the reactor chamber. Each magnetic field line that extends to a wall of the reactor chamber contacts the wall at an engagement point. The inertial electrostatic confinement device also comprises a set of outer coils that surround the inner coil. The outer coils modify the magnetic field lines produced by the set of inner coils. Additionally, the inertial electrostatic confinement device comprises a plurality of cathode driver plates that are placed along the walls of the reactor chamber and on device structures. Each cathode driver plate covers an engagement point along the walls of the reactor chamber and device structures.

Description

METHODS AND APPARATUS FOR COINCIDENTALLY FORMING A VIRTUAL CATHODE AND A HIGH BETA PLASMA

CROSS-REFERENCE

[1] This application claims priority to U.S. Provisional Patent Application No.

62/314,958, filed March 29, 2016, and U.S. Provisional Patent Application No. 62/329,404, filed April 29, 2016, each of which is entirely incorporated herein by reference.

BACKGROUND

[2] Inertial electrostatic confinement (IEC) describes the process of using electrostatic grids to confine and accelerate ions to fusion energies. Some examples of IEC devices include devices having a physical electrode grid or a virtual cathode. However, previous designs of IEC devices have drawbacks such as energy drainage, plasma arcing, and an inability to sustain a virtual cathode.

SUMMARY

[3] The present disclosure provides methods and devices to confine and maintain a high beta plasma with a virtual cathode so as to provide increased particle confinement due to the high beta of the plasma and for a deep potential well that is capable of confining ions to fusion energies. Previous plasma confinement schemes have been unable to achieve these effects simultaneously.

[4] A unique combination of cathode drive plates and outer magnetic field coils allow these effects to be simultaneously achieved. In particular, the device may include inner coils that drive electrons into a virtual cathode. The inner coils may generate magnetic field lines that lead from the inner coils to the walls of the device. These magnetic field lines may be oriented to terminate at points where reflectors are provided so as to reflect electrons back inside the device.

[5] In addition to the inner coils affecting the magnetic field lines, however, embodiments may be provided that have outer coils on the outside of the device. The outer coils may be used to manipulate the magnetic field between the inner coils and the wall of the device so as to orient a greater amount of the magnetic field lines to the reflector plates. In some examples, external coils may be attached directly to an outer portion of the reactor chamber. In some examples, external coils may be connected to structural reinforcements that are attached to an outer portion of the reactor camber. In some examples, some portions of external coils may be attached directly to an outer portion of the reactor chamber and some portions of the external coils may be connected to structural reinforcements that are attached to an outer portion of the reactor chamber.

[6] Additionally, the reflector plates may themselves be cathode drive plates. The cathode drive plates may be used to produce ions and electrons for the device. In some examples, the cathode drive plates may drive ions and electrons along magnetic field lines that run through the thin availability of plasma in the portion of the chamber between the inner coils and the wall. As negative voltage is applied to the cathode drive plates, the voltage in the potential well may be lowered, thereby increasing effectiveness of the IEC device.

[7] In one aspect, an inertial electrostatic confinement (IEC) device is provided. The

IEC device comprises a reactor chamber. The IEC device also comprises a set of inner coils within the reactor chamber, wherein the inner coils produce magnetic field lines that extend to walls of the reactor chamber, wherein each magnetic field line that extends to a wall of the reactor chamber contacts the wall at an engagement point. The IEC device also comprises a set of outer coils that surround the inner coils, wherein the outer coils modify the magnetic field lines produced by the set of inner coils. Additionally, the IEC device comprises a plurality of cathode driver plates that are placed along the walls of the reactor chamber and on device structures, wherein each cathode driver plate covers an engagement point along the walls of the reactor chamber and device structures.

[8] Additional aspects and advantages of the present disclosure will become readily apparent to those skilled in this art from the following detailed description, wherein only illustrative embodiments of the present disclosure are shown and described. As will be realized, the present disclosure is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the disclosure. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.

INCORPORATION BY REFERENCE

[9] All publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference. To the extent publications and patents or patent applications incorporated by reference contradict the disclosure contained in the specification, the specification is intended to supersede and/or take precedence over any such contradictory material. BRIEF DESCRIPTION OF THE DRAWINGS

[10] The novel features of the invention are set forth with particularity in the appended claims. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings (also "figure" and "FIG." herein), of which:

[11] FIG. 1 illustrates an inertial electrostatic confinement (IEC) device having a physical grid cathode, as provided in the prior art.

[12] FIG. 2 illustrates a polywell IEC device having coil interconnects, as provided in the prior art.

[13] FIG. 3 illustrates a polywell IEC device having coils mounted on walls, as provided in the prior art.

[14] FIG. 4 illustrates an IEC device having a cubic inner coil arrangement in a square vacuum chamber, square outer coils, and a plurality of cathode drive plates, in accordance with embodiments of the invention.

[15] FIG. 5 illustrates a magnetic field cubic inner coil geometry, as provided in the prior art.

[16] FIG. 6 illustrates a magnetic field of cubic inner coil geometry with additional outer coils in a cubic reactor chamber, in accordance with embodiments of the invention.

[17] FIG. 7 illustrates an IEC device having a cubic inner coil arrangement in a spherical vacuum chamber, circular outer coils, and a plurality of cathode drive plates, in accordance with embodiments of the invention.

[18] FIG. 8 illustrates another IEC device having a cubic inner coil arrangement in a spherical vacuum chamber, circular outer coils, and a plurality of cathode drive plates, in accordance with embodiments of the invention.

[19] FIG. 9 illustrates an IEC device having a cubic inner coil arrangement in a spherical vacuum chamber, circular outer coils attached to structural reinforcements, and a plurality of cathode drive plates, in accordance with embodiments of the invention.

[20] FIG. 10 illustrates another magnetic field of cubic inner coil geometry with additional outer coils in a spherical reactor chamber, in accordance with embodiments of the invention. DETAILED DESCRIPTION

[21] While various embodiments of the invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions may occur to those skilled in the art without departing from the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed.

[22] Inertial electrostatic confinement (IEC) describes the process of using electrostatic grids to confine and accelerate ions to fusion energies. An example of a prior art IEC device that uses a hollow electrode grid structure is seen in FIG. 1. In particular, FIG. 1 illustrates an inertial electrostatic confinement (IEC) device having a physical grid cathode, as provided in the prior art that comprises an anode 401, a cathode 402, and ions 403. Generally, a hollow electrode grid is given a negative bias of high voltage. This creates an electrostatic potential well in which ions are trapped and may eventually undergo fusion reactions.

However, the amount of fusion capable of such a grid-based IEC device is limited to the transparency of the grid to confined ions. Due to asymmetries in the potential well caused by the presence of the physical wires that compose the grid, ions may typically only make a few passes through the grid before they collide with it and lose their energy. This loss of power due to ion collisions with the grid prevents gridded IEC devices from achieving a net gain of fusion power.

[23] In another example of an IEC device, a physical grid cathode may be replaced with a virtual cathode. A virtual cathode may be made up of a space charge of negative electrons. In examples, a virtual cathode may be formed by confining electrons in a magnetic null region of a cusp geometry of magnetic fields. An example of the magnetic field geometry that may be used to create a virtual cathode is illustrated in FIG. 5. FIG. 5 illustrates a magnetic field produced by a cubic inner coil geometry, as provided in the prior art. In particular, FIG. 5 illustrates inner coils 500, cathode driver plats 501, and magnetic field lines 503. By using this geometry, the electrical current in each magnetic coil is made to be in the same direction and magnitude so that the magnetic field cancels in the interior of the device. This geometry may lead to a magnetic null in the center and a high magnetic field region at the edges of the device, effectually creating a magnetic well.

[24] Another prior art construction of a device used to create a magnetic field having a geometry as depicted in FIG. 5 is shown in FIG. 2. FIG. 2 illustrates a polywell IEC device having coil interconnects, as provided in the prior art. In particular, FIG. 2 illustrates inner coils 101, coil interconnects 112, and supporting legs 104. The device shown in FIG. 2 has an interconnecting structure that mechanically joins the individual coils. Devices that are similar to the device illustrated in FIG. 2 have been shown to produce deep potential wells via the formation of a virtual cathode. However, as plasma density is increased, the interconnecting structure of a device as illustrated in FIG. 2 may become the site of plasma arcing, due to magnetic field lines that directly channeled plasma to this section of the device. In particular, as plasma density is increased, plasma arcing may worsen.

[25] The same magnetic field coil geometry is depicted in FIG. 3. FIG. 3 illustrates a polywell IEC device having coils mounted on walls, as provided in the prior art. In particular, FIG. 3 illustrates inner coils 102, coil mounting legs 109, and inner coil electric feed-through 110. However, in this device the magnetic field coils are held by legs that join the walls of the surrounding vacuum chamber and are individually powered through these legs. This eliminates the interconnects shown in FIG.2 and associated arcing and coil damage. The geometry depicted in FIG. 3 has been used to confine very dense, high beta plasma without arcing. However, due to the fact that none of the magnetic field lines that emerge from the cusps end up on a surface with an applied voltage, a virtual cathode in the center of the inner coils cannot be maintained with such a structure.

[26] Additionally, an inner set of magnetic field coils may create an imperfect confinement of electrons. Magnetic field lines may emanate from the inner magnetic field coils, which lost electrons may travel along. In examples, cathode driver plates may be placed in locations where these magnetic field lines intersect with structures of the device and or the vacuum chamber that encloses the device. Additional magnetic field coils are added to modify the magnetic field lines emanating from the inner coils so that they impinge on a smaller surface area of the device structures and vacuum chamber and are better correlated to the cathode driver plates.

[27] In examples, a plurality of magnetic field coils may be suspended from the walls of a vacuum chamber. These magnetic field coils may form a magnetic well. In some examples, these coils can be electrically connected to the vacuum chamber walls. In some examples, these magnetic field coils can be insulated from the walls. An example of a cubic geometry of coils is depicted in FIG. 4. In particular, FIG. 4 provides an IEC device having a cubic inner coil arrangement in a square sided vacuum chamber, square outer coils, and a plurality of cathode drive plates, in accordance with embodiments of the invention. In particular, FIG. 4 illustrates outer coils 300, cathode driver plates 301, inner coils 302, and coil mounting legs 303. Additionally, FIG. 7 illustrates an IEC device having a cubic inner coil arrangement in a spherical vacuum chamber, circular outer coils, and a plurality of cathode drive plates, in accordance with embodiments of the invention. In particular, FIG. 7 illustrates outer coils 700, cathode driver plates 701, inner coils 702, and coil mounting legs 703. Additionally, FIG. 8 illustrates another IEC device having a cubic inner coil arrangement in a spherical vacuum chamber, circular outer coils 710, and a plurality of cathode drive plates 711, in accordance with embodiments of the invention. FIG. 8 also illustrates inner coils 712 and coil mounting legs 713. Further, FIG. 9 illustrates an IEC device having a cubic inner coil arrangement in a spherical vacuum chamber, circular outer coils 720 attached to structural reinforcements 724, and a plurality of cathode drive plates 721, in accordance with embodiments of the invention. FIG. 9 also provides inner coils 722 and coil mounting legs 723.

[28] A series of electrically isolated cathode drive plates may extend around the locations where magnetic field lines intersect the device structure and vacuum chamber. The cathode drive plates may be used to inject electrons into the inner coil region and reflect escaping electrons. In order to provide electrons to the device, a negative bias voltage, relative to the ground potential of the chamber and inner coils, may be placed on the cathode drive plates. Alternatively, if the coils are insulated from the chamber, they may be biased with a positive voltage and the cathode drive plates held at ground potential along with the chamber. Another alternative is negative bias applied to the cathode drive plates and a positive bias applied to the coils and a ground or other potential applied to the vacuum chamber. In each of these examples, the cathode driver plates have the most negative potential relative to other components of the device. In examples, these cathode drive plates may form a boundary condition that allows the formation of a virtual cathode within the inner coils. An example of a cubic geometry of inner coils within a cubic reactor chamber is depicted in FIG. 4. Examples of a cubic geometry of inner coils within a spherical reactor chamber is depicted in FIGs. 7-9.

[29] The position of the cathode drive plates may correspond to locations where the magnetic field created by the inner coils impinges on the surfaces of the vacuum chamber and other supporting structures within the vacuum chamber. These magnetic field lines generally impinge on surfaces of the vacuum chamber which correspond to locations where the magnetic field lines pass through the center of the inner coils impinge on the vacuum chamber walls, and where the magnetic field between the coils extends to the chamber walls. The position of these plates in the case of a cubic geometry of inner coils within a cubic reactor chamber is depicted in FIG. 4. Examples of the position of these plates in the case of a cubic geometry of inner coils within a spherical reactor chamber is depicted in FIGs. 7-9. [30] Other shapes of vacuum chamber may be used in examples of an IEC device as described herein. Some examples of other shapes that may be used include a spherical chamber, a cylindrical chamber, or other shapes of chambers. In examples of a cubic geometry of inner coils that are centrally located within a spherical vacuum chamber, the edge reflector plates may follow great circles on the inner surfaces of the vacuum chamber rather than the square shapes depicted in FIG. 4. Examples of a cubic geometry of inner coils that are centrally located within a spherical vacuum chamber are illustrated in FIGs. 7-9.

[31] In additional examples, a set of outer magnetic field coils may be provided that are outside the inner coils. The outer coils may be placed within the vacuum chamber, outside of the vacuum, or both inside and outside the vacuum chamber. These coils may be used to modify the magnetic field created by the inner coils. An example of a cubic geometry of inner coils within a cubic reactor chamber is depicted in FIG. 4, whereas examples of a cubic geometry of inner coils within a spherical reactor chamber are illustrated in FIG. 7-9.

[32] The outer coils may have little effect on the field within the inner coils, but may affect the field that extends between the inner field coils and the walls of the external vacuum chamber. This region of the magnetic field may be modified such that the magnetic field exiting the inner coils is better guided towards the cathode driver plates, effectively coupling the magnetic field created by the inner coils to the cathode driver plates. This effect can be seen in FIG. 6 for the case of a cubic inner coil geometry and circular outer coils within a cubic reactor chamber. Additionally, this effect can be seen in FIG. 10 for the case of a cubic inner coil geometry and circular outer coils within a spherical reactor chamber.

[33] Additionally, multiple sets of outer coils corresponding to a single inner coil may be used. An example of two sets of outer coils is shown in FIG. 4, while an example with a single set is shown in FIG. 6. FIG. 6 illustrates a magnetic field of cubic inner coil geometry with additional outer coils attached to a cubic reactor chamber, in accordance with embodiments of the invention. In particular, FIG. 6 illustrates inner coils 600, outer coils 601, cathode driver plates 602, and magnetic field lines 603. Additionally, FIG. 10 illustrates a magnetic field of cubic inner coil geometry with additional outer coils attached to a spherical reactor chamber, in accordance with embodiments of the invention. In particular, FIG. 10 illustrates inner coils 800, outer coils 801, cathode driver plates 802, and magnetic field lines 803.

[34] A high beta plasma may also be maintained in this way as the electrons emitted from the cathode driver plates can be made to ionize the background gas found in the vacuum chamber. This source of ions may be additional to other sources such as ion guns. In this way, the cathode driver plates may provide additional plasma density to the region inside the inner coils. This combination of external magnetic field coil and cathode driver plates may have the effect of efficiently creating boundary conditions so that a potential well can be maintained in the center of the device along with a high beta plasma.

[35] While preferred embodiments of the present invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. It is not intended that the invention be limited by the specific examples provided within the specification. While the invention has been described with reference to the aforementioned specification, the descriptions and illustrations of the embodiments herein are not meant to be construed in a limiting sense. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the invention. Furthermore, it shall be understood that all aspects of the invention are not limited to the specific depictions, configurations or relative proportions set forth herein which depend upon a variety of conditions and variables. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is therefore contemplated that the invention shall also cover any such alternatives, modifications, variations or equivalents. It is intended that the following claims define the scope of the invention and that methods and structures within the scope of these claims and their equivalents be covered thereby.

Claims

CLAIMS WHAT IS CLAIMED IS:

1. An inertial electrostatic confinement device, comprising: a reactor chamber; a set of inner coils within the reactor chamber, wherein the inner coils produce magnetic field lines that extend to walls of the reactor chamber, wherein each magnetic field line that extends to a wall of the reactor chamber contacts the wall at an engagement point; a set of outer coils that surround the inner coils, wherein the outer coils modify the magnetic field lines produced by the set of inner coils; and

a plurality of cathode driver plates that are placed along the walls of the reactor chamber and on device structures, wherein each cathode driver plate covers an engagement point along the walls of the reactor chamber and device structures.

2. The device of claim 1, wherein each of the inner coils in the set of inner coils is outside the reactor chamber.

3. The device of claim 1, wherein each of the outer coils in the set of outer coils is within the reactor chamber.

4. The device of claim 1, wherein each of the outer coils in the set of outer coils is outside the reactor chamber.

5. The device of claim 1, wherein a first portion of the set of outer coils are within the reactor chamber, and wherein a second portion of the set of outer coils are outside the reactor chamber.

6. The device of claim 1, wherein the reactor chamber is substantially spherical.

7. The device of claim 1, wherein the reactor chamber is spherical.

8. The device of claim 1, wherein the reactor chamber is substantially cubical.

9. The device of claim 1, wherein the reactor chamber is cubical.

10. The device of claim 1, wherein the outer rings are substantially circular.

11. The device of claim 1, wherein a portion of the outer rings are circular.

12. The device of claim 1, wherein the outer rings are attached directly to the reactor chamber.

13. The device of claim 1, wherein the outer rings are connected to structural

reinforcements that are attached directly to the reactor chamber.