WO2022155462A1

WO2022155462A1 - Plasma injection and confinement systems and methods

Info

Publication number: WO2022155462A1
Application number: PCT/US2022/012502
Authority: WO
Inventors: Raymond Golingo; Jean-christoph BTAICHE; Paul Harris; Ayan CHOUDHURY; Zahra SEIFOLLAHI MOGHADAM; Pierre TOCHON; Alex MCDONALD
Original assignee: Fuse Energy Technologies Corp.
Priority date: 2021-01-15
Filing date: 2022-01-14
Publication date: 2022-07-21

Abstract

Plasma processing systems and methods suitable for use in fusion power applications are disclosed. The system can include a plasma confinement device having a first compression electrode and a second compression electrodes spaced apart from each other along Z-pinch axis to define a reaction chamber therebetween; a precursor supply device including an inner precursor supply unit configured to supply, through an inner injector thereof, an inner precursor plasma or gas into the reaction chamber, and an outer precursor supply unit configured to supply, through an outer injector thereof disposed radially outwardly of the inner injector with respect to the Z-pinch axis, an outer precursor plasma into the reaction chamber; and a power supply configured to apply a voltage between the first and second compression electrodes to energize and compress the inner precursor plasma or gas and the outer precursor plasma into a Z-pinch plasma having a radially sheared axial flow.

Description

PLASMA INJECTION AND CONFINEMENT SYSTEMS AND METHODS

CROSS-REFERENCE TO RELATED PATENT APPLICATION(S)

[0001] The present application claims priority to U.S. Provisional Patent Application No. 63/137,987 filed on January 15, 2021, the disclosure of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

[0002] The technical field generally relates to techniques to generate and confine plasmas, and more particularly, to the use of such techniques to produce nuclear fusion energy.

BACKGROUND

[0003] Nuclear fusion energy is energy produced by a nuclear fusion process in which two or more lighter atomic nuclei are joined to form a heavier nucleus whose mass is less than the sum of the masses of the lighter nuclei. The difference in mass is released as energy, which can be harnessed to produce electricity. Fusion reactors are devices whose function is to harness fusion energy. One type of fusion reactors relies on magnetic plasma confinement. Such fusion reactors aim to confine high-temperature plasmas to sufficiently high-density with prolonged stability. Non-limiting examples of magnetic plasma confinement approaches include Z-pinch-configurations, magnetic mirror configurations, and toroidal configurations, for example, the tokamak and the stellarator. In Z-pinch configurations, a plasma column with an axial current flowing through it generates an azimuthal magnetic field that radially compresses the plasma, resulting in an increase of the fusion reaction rate. Z-pinch reactors are attractive due to their simple geometry, absence of magnetic field coils for plasma confinement and stabilization, inherent compactness, and relatively low cost. Conventional Z-pinch reactors suffer from instabilities that limit plasma lifetimes. Recent research has found that stabilization of the plasma with a sheared flow can help reduce these instabilities, opening up the possibility of producing and sustaining stable Z-pinches over longer timescales. However, despite these advances, challenges remain in the field of Z-pinch-based fusion devices.

SUMMARY

[0004] The present description generally relates to plasma injection and confinement techniques for use, for example, in fusion power generation.

[0005] In accordance with an aspect, there is provided plasma processing system including: a plasma confinement device including: a reaction chamber having a first end, a second end, and a Z-pinch axis extending longitudinally between the first end and the second end; a first compression electrode provided at the first end of the reaction chamber, and a second compression electrode provided at the second end of the reaction chamber; a precursor supply device coupled to the plasma confinement device and including: an inner precursor supply unit including an inner injector, the inner precursor supply unit being configured to supply, through the inner injector, an inner precursor medium into the reaction chamber; and an outer precursor supply unit including an outer injector disposed radially outwardly of the inner injector with respect to the Z-pinch axis, the outer precursor supply unit being configured to supply, through the outer injector, an outer precursor plasma into the reaction chamber at an outer velocity; and a main power supply configured to supply power to the plasma confinement device to apply a compression voltage between the first compression electrode and the second compression electrode configured to energize and compress the inner precursor medium and the outer precursor plasma into a Z-pinch plasma having a radially sheared axial flow along the Z-pinch axis.

[0006] In some embodiments, the outer precursor supply unit includes an outer plasma generator configured to generate the outer precursor plasma.

[0007] In some embodiments, the outer plasma generator includes an inner electrode, and an outer electrode surrounding the inner electrode to define a plasma formation region for forming the outer precursor plasma and a plasma transport channel extending from the plasma formation region to the outer injector. In some embodiments, the outer precursor supply unit includes an outer process gas supply unit configured to supply an outer process gas to the plasma formation region of the outer plasma generator, an outer plasma formation power supply configured to apply a voltage between the inner electrode and the outer electrode of the outer plasma generator to energize the outer process gas into the outer precursor plasma and cause the outer precursor plasma to flow along the plasma formation region and through the plasma transport channel of the outer plasma generator to reach the outer injector for injection of the outer precursor plasma into the reaction chamber. In some embodiments, the outer process gas includes deuterium, tritium, hydrogen, or helium, or any combination thereof.

[0008] In some embodiments, the outer plasma generator includes a plurality of outer plasma generators, each outer plasma generator being configured to generate a respective portion of the outer precursor plasma, and wherein the outer injector includes a plurality of outer injectors, each outer injector corresponding to a respective one of the outer plasma generators and being configured to inject the respective portion of the outer precursor plasma into the acceleration region.

[0009] In some embodiments, the outer velocity of the outer precursor plasma has a magnitude ranging from about 70 km/s to about 200 km/s. In some embodiments, the outer velocity of the outer precursor plasma is substantially axial upon entering the reaction chamber. In some embodiments, the outer velocity of the outer precursor plasma has an axial component and a radial component upon entering the reaction chamber. [0010] In some embodiments, the inner precursor medium is an inner precursor plasma, and the inner precursor supply unit is configured to supply the inner precursor plasma into the reaction chamber at an inner velocity different from the outer velocity of the outer precursor plasma. In some embodiments, the inner precursor supply unit includes an inner plasma generator configured to generate the inner precursor plasma. In some embodiments, the inner plasma generator includes an inner electrode, and an outer electrode surrounding the inner electrode to define a plasma formation region therebetween for forming the inner precursor plasma, the outer electrode extending beyond the inner electrode along a plasma formation axis to enclose a plasma transport channel extending from the plasma formation region to the inner injector along the plasma formation axis. In some embodiments, the inner precursor supply unit includes an inner process gas supply unit configured to supply an inner process gas to the plasma formation region of the inner plasma generator, and an inner plasma formation power supply configured to apply a voltage between the inner electrode and the outer electrode of the inner plasma generator to energize the inner process gas into the inner precursor plasma and cause the inner precursor plasma to flow along the plasma formation region and through the plasma transport channel of the inner plasma generator to reach the inner injector for injection of the inner precursor plasma into the reaction chamber. In some embodiments, the inner process gas includes deuterium, tritium, hydrogen, or helium, or any combination thereof.

[0011] In some embodiments, the inner velocity of the inner precursor plasma has a magnitude ranging from about 0 km/s to about 60 km/s. In some embodiments, the inner velocity of the inner precursor plasma is substantially axial upon entering the reaction chamber. In some embodiments, a velocity magnitude difference between the outer velocity of the outer precursor plasma and the inner velocity of the inner precursor plasma ranges from about 50 km/s to about 200 km/s.

[0012] In some embodiments, upon entering the reaction chamber, the inner precursor plasma has a cylindrical geometry centered about the Z-pinch axis, and the outer precursor plasma is coaxially arranged around the inner precursor plasma.

[0013] In some embodiments, the inner precursor medium is an inner precursor gas, and the inner precursor supply unit includes an inner precursor gas source configured to store the inner precursor gas, and an inner precursor gas supply line configured to transport the inner precursor gas from the inner precursor gas source to the inner injector for injection of the inner precursor gas into the reaction chamber. In some embodiments, the inner precursor gas includes deuterium, tritium, hydrogen, or helium, or any combination thereof.

[0014] In some embodiments, the inner precursor supply unit is configured to start by supplying the inner precursor medium as an inner precursor gas, and switch to supplying the inner precursor medium as an inner precursor plasma. In some embodiments, a time duration between starting to supply the inner precursor medium as the inner precursor gas and switching to supplying the inner precursor medium as the inner precursor plasma ranges from about 0.5 millisecond to about 5 milliseconds. [0015] In some embodiments, the inner precursor supply unit is configured to start supplying the inner precursor medium into the reaction chamber at the same time as the outer precursor supply is configured to supply the outer precursor plasma into the reaction chamber. In some embodiments, the inner precursor supply unit is configured to start supplying the inner precursor medium into the reaction chamber before or after the outer precursor supply is configured to supply the outer precursor plasma into the reaction chamber. In some embodiments, the precursor supply device is configured to start supplying the inner precursor medium and the outer precursor plasma into the reaction chamber before the main power supply is configured to start supplying power to the plasma confinement device. In some embodiments, the precursor supply device is configured to start supplying the inner precursor medium and the outer precursor plasma into the reaction chamber at the same time as or after the main power supply is configured to start supplying power to the plasma confinement device. In some embodiments, the precursor supply device is configured to continue supplying the inner precursor medium and the outer precursor plasma into the reaction chamber during a sustainment phase after formation of the Z-pinch plasma, the sustainment phase having a duration ranging from about 5 microseconds to about 10 milliseconds.

[0016] In some embodiments, the inner injector is disposed at one of the first end and the second end of the plasma confinement device, and wherein the outer injector is disposed at the same one of the first end and the second end of the plasma confinement device. In some embodiments, the inner injector is disposed at one of the first end and the second end of the plasma confinement device, and wherein the outer injector is disposed at the other one of the first end and the second end of the plasma confinement device. In some embodiments, In some embodiments, the inner injector is centered on the Z-pinch axis, and wherein the outer injector is disposed at a radial distance from the Z-pinch axis, the radial distance ranging from about from about few centimeters to about a few tens of centimeters. In some embodiments, the inner injector and the outer injector are each formed through the first compression electrode or the second compression electrode.

[0017] In some embodiments, the inner injector is a single inner injector. In some embodiments, the outer injector includes a plurality of outer injectors azimuthally distributed about the Z-pinch axis and around the inner injector. In some embodiments, ,a number of the outer injectors ranges from about two to about fifty.

[0018] In some embodiments, the precursor supply device further includes an intermediate precursor supply unit including an intermediate plasma generator configured to generate an intermediate precursor plasma, and an intermediate injector disposed radially between the inner injector and the outer injector with respect to the Z-pinch axis, the intermediate injector being configured to inject the intermediate precursor plasma into the reaction chamber at an intermediate velocity different from the outer velocity of the outer precursor plasma.

[0019] In some embodiments, the main power supply is a pulsed-DC power supply including a capacitor bank and a switch. [0020] In some embodiments, the Z-pinch plasma is configmed to undergo nuclear fusion reactions in response to compression of the Z-pinch plasma. In some embodiments, the nuclear fusion reactions include neutronic fusion reactions.

[0021] In some embodiments, the radially sheared axial flow is uniform. In some embodiments, the radially sheared axial flow is nonuniform.

[0022] In some embodiments, the reaction chamber has a substantially cylindrical shape centered about the Z-pinch axis.

[0023] In some embodiments, the plasma processing system further includes a control and processing device operatively coupled at least to the precursor supply device and the main power supply, the control and processing device including a processor and a non-transitory computer readable storage medium having stored thereon computer readable instructions that, when executed by the processor, cause the processor to perform operations, the operations including controlling the inner precursor supply unit of the precursor supply device to supply, through the inner injector, the precursor medium (inner precursor gas or inner precursor plasma) into the reaction chamber; controlling the outer precursor supply unit of the precursor supply device to supply, through the outer injector, the outer precursor plasma into the reaction chamber; and controlling the main power supply to supply power to the plasma confinement device to apply a compression voltage between the first compression electrode and the second compression electrode configured to energize and compress the inner precursor medium and the outer precursor plasma into the radially sheared Z-pinch plasma.

[0024] In accordance with another aspect, there is provided a plasma processing method including: providing a plasma confinement device including: a reaction chamber having a Z-pinch axis; a first compression electrode; and a second compression electrode longitudinally spaced apart from the first compression electrode along the Z-pinch axis; supplying, through an inner injector, an inner precursor medium into the reaction chamber; supplying, through an outer injector disposed radially outwardly of the inner injector with respect to the Z-pinch axis, an outer precursor plasma into the reaction chamber at an outer velocity; and supplying power to the plasma confinement device to apply a compression voltage between the first compression electrode and the second compression electrode configured to energize and compress the inner precursor medium and the outer precursor plasma into a Z-pinch plasma having a radially sheared axial flow along the Z-pinch axis.

[0025] In some embodiments, supplying the outer precursor plasma into the reaction chamber includes: generating the outer precursor plasma, including: supplying an outer process gas into a plasma formation region of an outer plasma generator; and supplying power to the outer plasma generator to apply a voltage across the plasma formation region of the outer plasma generator configured to energize the outer process gas into the outer precursor plasma; and flowing the outer precursor plasma from the plasma formation region to the outer injector for injection of the outer precursor plasma into the reaction chamber.

[0026] In some embodiments, the outer plasma generator includes an inner electrode, and an outer electrode surrounding the inner electrode to define therebetween the plasma formation region. In some embodiments, the outer process gas includes deuterium, tritium, hydrogen, or helium, or any combination thereof. In some embodiments, supplying the outer precursor plasma into the reaction chamber includes controlling a magnitude of the outer velocity of the outer precursor plasma in a range from about 70 km/s to about 200 km/s. In some embodiments, supplying the outer precursor plasma into the reaction chamber includes controlling the outer velocity of the outer precursor plasma to be substantially axial upon entering the reaction chamber. In some embodiments, supplying the outer precursor plasma into the reaction chamber includes controlling the outer velocity of the outer precursor plasma to have an axial component and a radial component upon entering the reaction chamber.

[0027] In some embodiments, supplying the inner precursor medium into the reaction chamber includes supplying, as the inner precursor medium, an inner precursor plasma into the reaction chamber at an inner velocity different from the outer velocity of the outer precursor plasma.

[0028] In some embodiments, supplying the inner precursor plasma into the reaction chamber includes: generating the inner precursor plasma, including: supplying an inner process gas into a plasma formation region of an inner plasma generator; and supplying power to the inner plasma generator to apply a voltage across the plasma formation region of the inner plasma generator configured to energize the inner process gas into the inner precursor plasma; and flowing the inner precursor plasma from the plasma formation region to the inner injector for injection of the inner precursor plasma into the reaction chamber

[0029] In some embodiments, the inner plasma generator includes an inner electrode, and an outer electrode surrounding the inner electrode to define therebetween the plasma formation region. In some embodiments, the inner process gas includes deuterium, tritium, hydrogen, or helium, or any combination thereof.

[0030] In some embodiments, supplying the inner precursor plasma into the reaction chamber includes controlling a magnitude of the inner velocity of the inner precursor plasma in a range from about 0 km/s to about 60 km/s. In some embodiments, supplying the inner precursor plasma into the reaction chamber includes controlling the inner velocity of the inner precursor plasma to be substantially axial upon entering the reaction chamber. In some embodiments, the method further includes controlling a velocity magnitude difference between the outer velocity of the outer precursor plasma and the inner velocity of the inner precursor plasma in a range from about 50 km/s to about 200 km/s.

[0031] In some embodiments, supplying the inner precursor medium into the reaction chamber includes supplying, as the inner precursor medium, an inner precursor gas into the reaction chamber. In some embodiments, the inner precursor gas includes deuterium, tritium, hydrogen, or helium, or any combination thereof.

[0032] In some embodiments, supplying the inner precursor medium into the reaction chamber includes starting by supplying the inner precursor medium as an inner precursor gas during a first phase of operation, and switching to supplying the inner precursor medium as an inner precursor plasma during a second phase of operation of the plasma processing system. In some embodiments, a duration between starting to supply the inner precursor medium as the inner precursor gas and switching to supplying the inner precursor medium as the inner precursor plasma ranges from about 0.5 millisecond to about 5 milliseconds.

[0033] In some embodiments, the step of supplying the inner precursor medium into the reaction chamber and the step of supplying the outer precursor plasma into the reaction chamber are initiated at the same time. In some embodiments, the step of supplying the inner precursor medium into the reaction chamber is initiated before or after the step of supplying the outer precursor plasma into the reaction chamber is initiated. In some embodiments, the step of supplying the inner precursor medium and the outer precursor plasma into the reaction chamber is initiated before the step of supplying power to the plasma confinement device is initiated. In some embodiments, the step of supplying the inner precursor medium and the outer precursor plasma into the reaction chamber is initiated at the same time as or after the step of supplying power to the plasma confinement device is initiated.

[0034] In some embodiments, the method further includes continuing to supply the inner precursor medium and the outer precursor plasma into the reaction chamber during a sustainment phase after formation of the Z-pinch plasma, the sustainment phase having a duration ranging from about 5 microseconds to about 10 milliseconds.

[0035] In some embodiments, the inner injector is formed through one of the first compression electrode and the second compression electrode, and the outer injector is formed through the same one of the first compression electrode and the second compression electrode. In some embodiments, the inner injector is formed through one of the first compression electrode and the second compression electrode, and the outer injector is formed through the other one of the first compression electrode and the second compression electrode. [0036] In some embodiments, the inner injector is a single inner injector. In some embodiments, the outer injector includes a plurality of outer injectors azimuthally distributed about the Z-pinch axis and around the inner injector.

[0037] In some embodiments, the method further includes supplying, through an intermediate injector disposed radially between the inner injector and the outer injector with respect to the Z-pinch axis, an intermediate precursor plasma into the reaction chamber at an intermediate velocity different from the outer velocity of the outer precursor plasma.

[0038] In some embodiments, the method further includes generating nuclear fusion reactions inside the Z-pinch plasma in response to compression of the Z-pinch plasma. In some embodiments, the nuclear fusion reactions include neutronic fusion reactions.

[0039] In accordance with another aspect, there is provided a plasma processing system for nuclear fusion generation, including: a plasma confinement device; and a plasma formation and injection device disposed outside the plasma confinement device and configured to form an initial plasma and inject the initial plasma inside the plasma confinement device with a radially sheared axial velocity, wherein the plasma confinement device is configured to compress the initial plasma into a sheared flow Z-pinch plasma at fusion conditions.

[0040] In accordance with another aspect, there is provided a plasma processing method for nuclear fusion generation, including: forming an initial plasma; injecting the initial plasma inside a plasma confinement device with a radially sheared axial velocity; and compressing the initial plasma into a sheared flow Z-pinch plasma to reach fusion conditions.

[0041] In accordance with another aspect, there is provided a plasma processing system, including: a plasma confinement device having a longitudinal axis and including a first compression electrode and a second compression electrode spaced apart from each other and defining a compression region therebetween; and a plasma formation and injection device provided externally of the compression region, the plasma formation and injection device being configured to form an initial plasma outside the compression region and inject the initial plasma in the compression region with a plasma velocity that is radially sheared along the longitudinal axis, wherein applying, with a power supply, an electric potential difference between the first compression electrode and the second compression electrode causes the initial plasma injected in the compression region to be compressed into a Z-pinch plasma with an embedded sheared axial flow. [0042] In some embodiments, the Z-pinch plasma is compressed sufficiently to generate nuclear fusion reactions therein. In some embodiments, the nuclear fusion reactions produce neutrons.

[0043] In some embodiments, the plasma formation and injection device may include a first plasma formation and injection unit and a second plasma formation and injection unit. The first plasma formation and injection unit may be configured to form a first portion of the initial plasma and inject the first portion of the initial plasma into the compression region with a first plasma velocity. The second plasma formation and injection unit may be configured to form a second portion of the initial plasma and inject the second portion of the initial plasma into the compression region with a second plasma velocity different from the first plasma velocity. The first and second plasma velocities may be different from each other in magnitude and/or direction to provide the shear axial velocity of the initial plasma. In some embodiments, the first portion of the initial plasma may be injected in the compression region via one or more first injection ports formed through one of the first and second compression electrodes, and the second portion of the initial plasma may be injected in the compression region via one or more second injection ports formed through the same or the other one of the first and second compression electrodes. More plasma formation and injection units may be provided in other embodiments.

[0044] In some embodiments, the plasma formation and injection device may include an inner plasma formation and injection unit and an outer plasma formation and injection unit. The inner plasma formation and injection unit may be centrally located on the longitudinal axis and the outer plasma formation and injection unit may be azimuthally distributed around the inner plasma formation and injection unit. The inner plasma formation and injection unit may be configured to form an inner portion of the initial plasma and to inject the inner portion of the initial plasma in the compression region with an inner velocity. The outer plasma formation and injection unit may be configured to form an outer portion of the initial plasma and to inject the outer portion of the initial plasma in the compression region with an outer velocity different from the inner velocity. Depending on the application, the inner and outer velocities may differ in magnitude, direction, or both. In some embodiments, the inner initial plasma portion may be injected in the compression region by the inner plasma formation and injection unit with a substantially cylindrical shape centered about the longitudinal axis, and the outer initial plasma portion may be injected in the compression region by the outer plasma formation and injection unit with a substantially annular shape centered about the longitudinal axis and surrounding the inner initial plasma portion. In such a configuration, injecting the inner initial plasma portion and the outer initial plasma portion with different plasma velocity profiles and from different radial positions with respect to the longitudinal axis can induce an overall sheared flow profile in the initial plasma injected in the compression region prior to its compression into a sheared flow Z-pinch plasma.

[0045] In accordance with another aspect, there is provided a plasma process method, including: forming an initial plasma; injecting the initial plasma with a radially sheared axial velocity into a compression region extending along a longitudinal axis and defined between a first compression electrode and a second compression electrode spaced apart from each other; and applying an electric potential difference between the first compression electrode and the second compression electrode to compress the initial plasma injected in the compression region into a Z- pinch plasma with an embedded sheared axial flow.

[0046] In accordance with another aspect, there is provided a plasma processing method for use as a neutron source in nuclear fusion power generation and other fields and applications requiring neutrons. The method can include steps of forming an initial plasma, injecting the initial plasma inside a plasma confinement device with a radially sheared axial velocity, and compressing the initial plasma into a sheared flow Z-pinch plasma at fusion conditions. The method may be implemented in a plasma processing system that includes a plasma confinement device and a plasma formation and injection device disposed outside the plasma confinement device and configured to form an initial plasma and inject the initial plasma inside the plasma confinement device with a radially sheared axial velocity. The plasma confinement device is configured to compress the initial plasma into a sheared flow Z-pinch plasma capable of reaching fusion conditions.

[0047] Other method and process steps may be performed prior, during, or after the steps described herein. The order of one or more steps may also differ, and some of the steps may be omitted, repeated, and/or combined, as the case may be.

[0048] Other objects, features, and advantages of the present description will become more apparent upon reading of the following non-restrictive description of specific embodiments thereof, given by way of example only with reference to the appended drawings. Although specific features described in the above summary and in the detailed description below may be described with respect to specific embodiments or aspects, it should be noted that these specific features may be combined with one another unless stated otherwise.

BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figs. 1 to 5 are schematic representations of a conventional Z-pinch plasma confinement device at five different stages of the Z-pinch formation.

[0050] Fig. 6 is a flow diagram of a plasma processing method, in accordance with an embodiment.

[0051] Fig. 7 is a schematic perspective view of a plasma processing system, in accordance with an embodiment.

[0052] Fig. 8 is a partially cutaway perspective view of the plasma processing system of Fig. 7. [0053] Fig. 9 is a schematic longitudinal cross-sectional view of the plasma processing system of Fig. 7, taken along section line 9-9 in Fig. 7.

[0054] Fig. 10 is a schematic longitudinal cross-sectional view of a plasma processing system, in accordance with another embodiment.

[0055] Fig. 11 is a schematic longitudinal cross-sectional view of a plasma processing system, in accordance with another embodiment.

[0056] Fig. 12 is a schematic longitudinal cross-sectional view of a plasma processing system, in accordance with another embodiment.

[0057] Figs. 13A and 13B are schematic longitudinal cross-sectionals view of a plasma processing system, in accordance with another embodiment, depicted at two different operation stages.

[0058] Figs. 14A to 14D depict four different stages of a method of operating a plasma processing system to generate a sheared-flow Z-pinch plasma, in accordance with another embodiment.

DETAILED DESCRIPTION

[0059] In the present description, similar features in the drawings have been given similar reference numerals. To avoid cluttering certain figures, some elements may not be indicated if they were already identified in a preceding figure. The elements of the drawings are not necessarily depicted to scale, since emphasis is placed on clearly illustrating the elements and structures of the present embodiments. Furthermore, positional descriptors indicating the location and/or orientation of one element with respect to another element are used herein for ease and clarity of description. Unless otherwise indicated, these positional descriptors should be taken in the context of the figures and should not be considered limiting. Such spatially relative terms are intended to encompass different orientations in the use or operation of the present embodiments, in addition to the orientations exemplified in the figures. Furthermore, when a first element is referred to as being “on”, “above”, “below”, “over”, or “under” a second element, the first element can be either directly or indirectly on, above, below, over, or under the second element, respectively, such that one or multiple intervening elements may be disposed between the first element and the second element.

[0060] The terms “a”, “an”, and “one” are defined herein to mean “at least one”, that is, these terms do not exclude a plural number of elements, unless stated otherwise.

[0061] The term “or” is defined herein to mean “and/or”, unless stated otherwise.

[0062] Terms such as “substantially”, “generally”, and “about”, which modify a value, condition, or characteristic of a feature of an exemplary embodiment, should be understood to mean that the value, condition, or characteristic is defined within tolerances that are acceptable for the proper operation of this exemplary embodiment for its intended application or that fall within an acceptable range of experimental error. In particular, the term “about” generally refers to a range of numbers that one skilled in the art would consider equivalent to the stated value (e.g., having the same or an equivalent function or result). In some instances, the term “about” means a variation of ±10% of the stated value. It is noted that all numeric values used herein are assumed to be modified by the term “about”, unless stated otherwise. The term “between” as used herein to refer to a range of numbers or values defined by endpoints is intended to include both endpoints, unless stated otherwise.

[0063] The term “based on” as used herein is intended to mean “based at least in part on”, whether directly or indirectly, and to encompass both “based solely on” and “based in part on”. In particular, the term “based on” may also be understood as meaning “depending on”, “representative of’, “indicative of’, “associated with”, “relating to”, and the like.

[0064] The terms “match”, “matching”, and “matched” refer herein to a condition in which two elements are either the same or within some predetermined tolerance of each other. That is, these terms are meant to encompass not only “exactly” or “identically” matching the two elements but also “substantially”, “approximately”, or “subjectively” matching the two elements, as well as providing a higher or best match among a plurality of matching possibilities.

[0065] The terms “connected” and “coupled”, and derivatives and variants thereof, refer herein to any connection or coupling, either direct or indirect, between two or more elements, unless stated otherwise. For example, the connection or coupling between elements may be mechanical, optical, electrical, magnetic, thermal, chemical, logical, fluidic, operational, or any combination thereof.

[0066] The term “concurrently” refers herein to two or more processes that occur during coincident or overlapping time periods. The term “concurrently” does not necessarily imply complete synchronicity and encompasses various scenarios including time-coincident or simultaneous occurrence of two processes; occurrence of a first process that both begins and ends during the duration of a second process; and occurrence of a first process that begins during the duration of a second process, but ends after the completion of the second process.

[0067] The present description generally relates to plasma injection and confinement techniques for use in fusion power generation and various other fields and applications including, to name a few, plasma sources; ion sources; plasma accelerators; neutron sources in medicine, biology, and materials science; high-energy photon generation; materials processing; and fusion-based medical devices.

[0068] Magnetic plasma confinement is one of several approaches to achieving controlled fusion for power generation. Different types of configurations for magnetic plasma confinement have been devised and studied over the years, among which is the Z-pinch configuration. Referring to Figs. 1 to 5, there are provided schematic representations of a conventional Z-pinch plasma processing system 100’ at different stages of the Z-pinch formation. The plasma processing system 100’ includes a plasma confinement device 102’ and a power supply 106’ configured to supply power to the plasma confinement device 102’. The plasma confinement device 102’ includes an inner electrode 198’ and an outer electrode 200’. The inner electrode 198’ and the outer electrode 200’ form a coaxial electrode arrangement extending along a longitudinal Z-pinch axis 114’. In the illustrated configuration, the outer electrode 200’ extends longitudinally beyond the inner electrode 198’. The annular volume extending between the inner electrode 198’ and the outer electrode 200’ defines a plasma acceleration region 202’, while the cylindrical volume surrounded by the outer electrode 200’ and extending beyond the inner electrode 198’ defines a Z- pinch assembly region 204’. The plasma acceleration region 202’ and the Z-pinch assembly region 204’ define a reaction chamber 108’. The formation of a Z-pinch plasma involves injecting neutral gas in the acceleration region 202’ (Fig. 1), and applying, using the power supply 106’, an electric potential difference between the inner electrode 198’ and the outer electrode 200’ (Fig. 2). The neutral gas can be injected into the acceleration region 202’ via one or more gas injection ports 206’ of the plasma confinement device 102’ (e.g., formed through the peripheral surface of the outer electrode 200’), the one or more gas injection ports 206’ being connected to a gas supply system including a neutral gas source (not shown). The power supply 106’ can include a high-voltage capacitor bank and a switch. The electric potential difference applied between the inner electrode 198’ and the outer electrode 200’ is configured to ionize the neutral gas, resulting in the formation of an annular column or washer of plasma in the acceleration region 202’. The plasma column allows electric current to flow radially therethrough between the inner and outer electrodes 198’, 200’ (Fig. 2). The electric current that flows axially along the inner electrode 198’ generates an azimuthal magnetic field in the acceleration region 202’ (Fig. 3).

[0069] The interaction between the radial electric current flowing in the plasma column and the azimuthal magnetic field produces a Lorentz force in the axial direction that pushes and accelerates the plasma column axially forward along the acceleration region 202’ (Fig. 3) until the plasma column reaches the entrance of the assembly region 204’ and the Z-pinch formation begins (Fig. 4). In the assembly region 204’, the direction of the Lorentz force changes from longitudinal to radially inward, which makes the plasma column collapse inwardly toward the Z-pinch axis 114’ to complete the formation of the Z-pinch plasma (Fig. 5). The axial current flowing in the Z-pinch plasma generates an azimuthal magnetic field that exerts an inward magnetic pressure and an inward magnetic tension, which radially compress the Z-pinch plasma against the outward plasma pressure until an equilibrium is established. In this configuration, the Z-pinch plasma can continue to form and move along the Z-pinch assembly region 204’ for as long as neutral gas is supplied and ionized in the acceleration region 202’. In Figs. 1 to 5, the plasma confinement device 102’ includes a plasma exit port 138’ configured to allow part of the Z-pinch plasma to exit the plasma confinement device 102’, so as to avoid a stagnation point in the plasma flow that could create instabilities.

[0070] By increasing the axial current to compress the Z-pinch plasma to sufficiently high density and temperature, fusion reactions can be achieved within the pinch, resulting in an exothermic energy release. In many applications, fusion reactions release their energy in the form of neutrons. A commonly used fusion reaction is the deuterium-tritium reaction, or D-T reaction, in which the fusion of one deuterium nucleus and one tritium nucleus produces one alpha particle and one neutron. Being chargeless, neutrons can escape from the magnetically confined plasma pinch and transfer their kinetic energy into thermal energy after they exit the confinement region. This thermal energy can be converted into electricity, for example, by transferring the heat generated to a working fluid used by a heat engine for generating electrical energy. The remaining fusion products have kinetic energy that can contribute more energy to the fusion process.

[0071] Conventional Z-pinch configurations are unstable due to the presence of magnetohydrodynamic (MHD) instabilities. A challenge in Z-pinch fusion research is devising ways of improving the control of instabilities to keep Z-pinch plasmas confined long enough to sustain ongoing fusion reactions. Techniques such as close fitting walls, axial magnetic fields, and pressure profile control have been proposed, with mitigated results. Recent advances have demonstrated that sheared plasma flows — that is, plasma flows with a radius-dependent axial velocity — can provide a promising stabilization approach to achieving and sustaining fusion conditions in Z-pinch configurations. One of the keys to unlocking the potential of sheared-flow-stabilized Z-pinch fusion devices as these devices are scaled up in power input — and thus in power output — is to mitigate, circumvent, or otherwise control instabilities, turbulence, heat transfer, and other factors limiting plasma lifetime. This is because once the reaction becomes unstable, the pinch ceases, neutron production stops, and power generation shuts down. Researchers have theorized that fusion conditions resulting in viable net power output that can be met at high power input are achievable when the flow shear exceeds a certain threshold above which the Z-pinch is stable, this threshold depending on the magnetic field strength and the plasma density. It is appreciated that the theory, instrumentation, implementation, and operation of conventional sheared-flow-stabilized Z-pinch plasma confinement devices are generally known in the art and need not be described in detail herein other than to facilitate an understanding of the present techniques. Reference is made in this regard to international patent application PCT/US2018/019364 (published as WO 2018/156860) as well as the following doctoral dissertation: Golingo, Raymond, Formation of a Sheared Flow Z-Pinch (University of Washington, 2003). The contents of these two documents are incorporated herein by reference in their entirety.

[0072] Referring to Fig. 6, there is illustrated a flow diagram of a plasma processing method 600, in accordance with an embodiment. The method 600 of Fig. 6 may be implemented in a plasma processing system 100 such as the ones depicted in Figs. 7 to 14D, or another suitable plasma processing system. The method 600 of Fig. 6 includes a step 602 of providing a plasma confinement device including: a reaction chamber having a Z-pinch axis; a first compression electrode; and a second compression electrode longitudinally spaced apart from the first compression electrode along the Z-pinch axis. The method 600 also includes a step 604 of supplying, through an inner injector of an inner precursor supply unit of a precursor supply device, an inner precursor medium into the reaction chamber, and a step 606 of supplying, through an outer injector of an outer precursor supply unit of the precursor supply device, an outer precursor plasma into the reaction chamber, the outer injector being disposed radially outwardly of the inner injector with respect to the Z-pinch axis. Depending on the application, the inner precursor medium can be an inner precursor plasma or an inner precursor gas. The method 600 further includes a step 608 of supplying power to the plasma confinement device to apply a compression voltage between the first compression electrode and the second compression electrode configured to energize and compress the inner precursor medium and the outer precursor plasma into a Z-pinch plasma having a radially sheared axial flow along the Z-pinch axis. In the present description, a Z-pinch plasma having a radially sheared axial flow, or simply a sheared- flow Z-pinch plasma, refers to a Z-pinch plasma having an embedded plasma flow with an axial velocity v_z whose magnitude varies has a function of the radius r of the Z-pinch plasma, such that dv_z/dr 0). In embodiments where the inner precursor medium is an inner precursor plasma, the inner precursor plasma and the outer precursor plasma can be injected into the reaction chamber at different velocities in order to control the sheared axial flow embedded inside the Z-pinch plasma for stabilization. For example, in some embodiments, the magnitude of the velocity of the outer precursor plasma can be controlled to be significantly larger than the magnitude of the velocity of the inner precursor plasma in order to provide sheared flow stabilization.

[0073] Referring to Figs. 7 to 9, there are illustrated schematic views of a plasma processing system 100, in accordance with an embodiment. The plasma processing system 100 can be used for generating thermonuclear fusion reactions, for example, neutronic fusion reactions, for use in various applications, including fusion power generation. The plasma processing system 100 of Figs. 7 to 9 generally includes a plasma confinement device 102, a precursor supply device 104, and a main power supply 106. It is noted that certain components of the plasma processing system 100 that are depicted in Fig. 9 have been omitted in Figs. 7 and/or 8 for clarity and ease of illustration.

[0074] The plasma confinement device 102 includes a reaction chamber 108 having a first end 110, a second end 112, and a Z-pinch axis 114 extending longitudinally between the first end 110 and the second end 112. The plasma confinement device 102 also includes a first compression electrode 116 provided at the first end 110 of the reaction chamber 108, and a second compression electrode 118 provided at the second end 112 of the reaction chamber 108. The precursor supply device 104 includes an inner precursor supply unit 120 and an outer precursor supply unit 122. The inner precursor supply unit 120 includes an inner injector 124 and is configured to supply, through the inner injector 124, an inner precursor medium 126 into the reaction chamber 108. Depending on the application, the inner precursor medium 126 can be an inner precursor plasma, as in Figs. 7 to 9, or an inner precursor gas, as in Fig. 10. In the illustrated embodiment, the inner precursor supply unit 120 includes a single inner injector 124, although other embodiments can include multiple inner injectors 124. The outer precursor supply unit 122 includes four outer injectors 128 disposed radially outwardly of the inner injector 124 with respect to the Z-pinch axis 114. In other embodiments, the number of outer injectors 128 can be smaller or larger than four. The outer precursor supply unit 122 is configured to supply, through the four outer injectors 128, an outer precursor plasma 130 into the reaction chamber 108. The main power supply 106 is configured to supply power to the plasma confinement device 102 to apply a compression voltage between the first compression electrode 116 and the second compression electrode 118 configured to energize and compress the inner precursor medium 126 and the outer precursor plasma 130 into a Z-pinch plasma 132 having a radially sheared axial flow along the Z-pinch axis 114. In some applications, the plasma processing system 100 is configured to compress and heat the Z-pinch plasma 132 sufficiently to reach fusion conditions, that is, plasma density and temperature conditions at which nuclear fusion reactions occur inside the Z-pinch plasma 132. In such applications, the energy produced by the fusion reactions, which typically involve the generation of neutrons, exceeds the input energy required to establish fusion conditions. In fusion power applications, the energy of the neutrons thus generated can be converted into electricity.

[0075] More details regarding the structure, configuration, and operation of these components and other possible components of the plasma processing system 100 are provided below. It is appreciated that Figs. 7 to 9 are simplified schematic representations that illustrate certain features and components of the plasma processing system 100, such that additional features and components that may be useful or necessary for its practical operation may not be specifically depicted. Non-limiting examples of such additional features and components can include, to name a few, power supplies, electrical connections, gas sources, gas supply lines (e.g., conduits, such as pipes or tubes), pressure and flow control devices (e.g., pumps, valves, regulators, restrictors), operation monitoring and diagnostic devices (e.g., sensors), processors and controllers, and other standard hardware and equipment.

[0076] In the embodiment illustrated in Figs. 7 to 9, the Z-pinch axis 114 is the longitudinal axis of the reaction chamber 108 of the plasma confinement device 102 along which the Z-pinch plasma 132 is formed and sustained. The term “Z-pinch plasma” broadly refers herein to a plasma that has an electric current flowing substantially along the longitudinal or axial direction Z of a cylindrical coordinate system. The axial electrical current generates an azimuthal magnetic field that radially compresses, or pinches, the plasma by the Lorentz force. It is appreciated that in some instances, terms such as “Z-pinch”, “zeta pinch”, “plasma pinch”, “pinch”, “plasma arc” may be used interchangeably with the term “Z-pinch plasma”.

[0077] In the illustrated embodiment, the reaction chamber 108 has a substantially cylindrical shape centered about the Z-pinch axis 114, and the first and second compression electrodes 116, 118 are shaped as flat circular discs that define the opposite end walls of the reaction chamber 108. The reaction chamber 108 also has a tubular lateral wall 134 that extends longitudinally between the first and second compression electrodes 116, 118. The lateral wall 134 can be made of any suitable material, such as various metals and metal alloys. The lateral wall 134 is electrically insulated from the first and second compression electrodes 116, 118 by electrical insulators 136. The electrical insulator 136 can be made of any suitable electrically insulating material, for example, glass, ceramic, and glass-ceramic materials. In some embodiments, the reaction chamber 108 may have a length ranging from about 25 cm to about 3 m and a radius ranging from about 5 cm to about 50 cm, although other chamber dimensions may be used in other embodiments.

[0078] The first and second compression electrodes 116, 118 can each be made of any suitable electrically conductive material, such as various metals and metal alloys. Non-limiting examples include, to name a few, tungsten-coated copper and graphite. The first and second compression electrodes 116, 118 can each have a radius that matches the radius of the reaction chamber 108. In the illustrated embodiment, both the first and second compression electrodes 116, 118 are flat, although non-flat geometries are possible. In some embodiments, the first compression electrode 116 and/or the second compression electrode 118 may define not only the end walls of the reaction chamber 134, but also at least part of the lateral wall 134. It is appreciated that the size, shape, composition, structure, and arrangement of the first and second compression electrodes 116, 118 can be varied depending on the application.

[0079] In some embodiments, the plasma confinement device 102 may include a plasma exit port 138 configured to allow part of the Z-pinch plasma 132 to exit the plasma confinement device 102, so as to avoid a stagnation point in the plasma flow that could create instabilities and destroy the Z-pinch plasma 132. In the illustrated embodiment, the plasma exit port 138 is provided as a hole formed on the Z- pinch axis 114 through the second compression electrode 118. In other embodiments, the plasma exit port 138 may provided at other locations of the plasma confinement device 102, for example, through the first compression electrode 116, as in Fig. 10, or through the lateral wall 134 of the reaction chamber 108. In yet other embodiments, a plurality of plasma exit ports 138 may be provided, as in Fig. 10.

[0080] It is appreciated that the plasma confinement device 102 depicted in Figs. 7 to 9 is provided by way of example only, and that various other structures and configurations are possible in other embodiments.

[0081] Referring still to Figs. 7 to 9, the main power supply 106 is connected to the first compression electrode 116 and the second compression electrode 118 via appropriate electrical connections. The term “power supply” refers herein to any device or combination of devices configured to supply electrical power into a form usable by another device or combination of devices. It is appreciated that while the main power supply 106 depicted as a single entity for illustrative purposes, the term “power supply” should not be construed as being limited to a single power supply and, accordingly, in some embodiments the main power supply 106 may include a plurality of power supply units. In some instances, the main power supply 106 coupled to the plasma confinement device 102 may be referred to as an “compression power supply” to more clearly distinguish it from other power supplies of the plasma processing system 100.

[0082] In some embodiments, the main power supply 106 may be a switching pulsed-DC power supply and may include an energy source (e.g., a capacitor bank, such as in Figs. 7 to 9), a switch (e.g., a spark gap, an ignitron, or a semiconductor switch), and a pulse shaping network (including, e.g., inductors, resistors, diodes, and the like). Depending on the application, the main power supply 106 may be voltage- controlled or current-controlled. In other embodiments, other suitable types of power supplies may be used, including DC and AC power supplies. Non-limiting examples include, to name a few, DC grids, voltage source converters, and homopolar generators. The main power supply 106 is configured to supply power to the plasma confinement device 102 in order to apply a voltage between the first and second compression electrodes 116, 118. The voltage is configured to generate an electric field across the reaction chamber 108 that causes the inner precursor medium 126 and the outer precursor plasma 130 to be energized and compressed into the Z-pinch plasma 132. In the illustrated embodiment, the first and second compression electrodes 116 act as current source and current retan electrodes, respectively. In some embodiments, the voltage applied between the first and second compression electrodes 116, 118 may range from about 1 kV to about 40 kV, although other voltage values may be used in other embodiments. In some embodiments, the voltage may be applied as a voltage pulse of duration ranging from 20 microseconds to about 1 to 10 milliseconds, although other pulse duration values may be used in other embodiments. The operation of the main power supply 106 may be selected in view of the parameters of the inner precursor medium 126 and the outer precursor plasma 130, and the configuration and operating conditions of the plasma confinement device 102 in order to favor the formation and sustainment of the sheared-flow Z-pinch plasma 132 in the reaction chamber 108. Depending on the application, the operation of activating the main power supply 106 to supply power to the plasma confinement device 102 can be initiated before, at the same time as, or after initiating the operation of supplying the inner precursor medium 126 and the outer precursor plasma 130 into the reaction chamber 108.

[0083] Referring still to Figs. 7 to 9, the precursor supply device 104 is configured to supply to the reaction chamber 108 the precursor elements that are to be energized and compressed into the sheared-flow Z-pinch plasma 132. The precursor elements supplied by the precursor supply device 104 are the inner precursor medium 126, which is an inner precursor plasma in the illustrated embodiment, and the outer precursor plasma 130. The precursor supply device 104 includes an inner precursor supply unit 120 and an outer precursor supply unit 122. The inner precursor supply unit 120 includes an inner plasma generator 140, and the inner injector 124 introduced above. The inner plasma generator 140 is configured to generate the inner precursor plasma 126, and the inner injector 124 is configured to inject the inner precursor plasma 126 into the reaction chamber 108 at an inner velocity v,. The outer precursor supply unit 122 includes four outer plasma generators 142, and the four outer injectors 128 introduced above. The outer plasma generators 142 are configured to generate the outer precursor plasma 130, and the four outer injectors 128 are configured to inject the outer precursor plasma 130 into the reaction chamber 108 at an outer velocity v₀. Thus, each generator-injector unit of the outer precursor supply unit 122 is configured to provide a respective portion of the outer precursor plasma 130 injected in the reaction chamber 108 of the plasma confinement device 102. As described in greater detail below, the outer velocity v₀ of the outer precursor plasma 130 is different from the inner velocity v, of the inner precursor plasma 126. In the illustrated embodiment, both the inner injector 124 and the four outer injectors 128 are disposed at the first end 110 of the reaction chamber 108 and are formed through the first compression electrode 116. However, in other embodiments, the inner injector 124 may be disposed at one of the first and second ends 110, 112 of the reaction chamber 108, while the outer injectors 128 may be disposed at the other one of the first and second ends 110, 112. An example of such a configuration is depicted in the embodiment of the plasma processing system 100 illustrated in Fig. 11, which is discussed in greater detail below.

[0084] Returning to Figs. 7 to 9, the inner plasma generator 140 and the inner injector 124 are disposed on the Z-pinch axis 114, while the four outer plasma generators 142 and the four outer injectors 128 are azimuthally distributed about the Z-pinch axis 114 to surround the inner plasma generator 140 and the inner injector 124. In such a configuration, the inner precursor plasma 126 is configured to enter the reaction chamber 108 via the inner injector 124 with a cylindrical geometry centered about the Z-pinch axis 114, while the outer precursor plasma 130 is configured to enter the reaction chamber 108 via the outer injectors 128 with a coaxial geometry around the inner precursor plasma 126. In some embodiments, the outer injectors 128 may be disposed at a radial distance from the Z-pinch axis 114 that range from about few centimeters to about a few tens of centimeters, although other radial distance values may be used in other embodiments. In the illustrated embodiment, the four outer plasma generators 142 and the four outer injectors 128 are symmetrically spaced apart azimuthally at a same radial distance from the Z-pinch axis 114. This is not a requirement, however, and both the inner precursor supply unit 120 and the outer precursor supply unit 122 may have less symmetrical or otherwise different arrangements in other embodiments, including any suitable number of inner and outer plasma generators 140, 142 and any suitable number of inner and outer injectors 124, 128. In some embodiments, the number of outer plasma generators 142 and the number of outer injectors 128 may each range from two to about fifty or even a hundred or more. In other embodiments, the outer precursor supply unit 122 may include a single outer plasma generator 142 and a single outer injector 128. For example, some embodiments may include a single annular outer injector 128 disposed at a radial distance from the Z-pinch axis 114 and surrounding a single inner injector 124 centered on the Z-pinch axis 114. In other embodiments, it is the inner injector 124 that may have an annular shape, in addition to or instead of the outer injector(s) 128. In some embodiments, both the inner injectors 124 and the outer injectors 128 may be arranged in an azimuthal distribution about the Z-pinch axis 114, where the azimuthal distribution of outer injectors 128 is disposed radially outwardly of the azimuthal distribution of inner injectors 124 with respect to the Z-pinch axis 114. It is appreciated that the number of inner plasma generator(s) 140 may be smaller than, equal to, or larger than the number of inner injector(s) 124, and that the number of outer plasma generator(s) 142 may be smaller than, equal to, or larger than the number of outer injector(s) 128. Depending on the application, the different inner and outer plasma generators 140, 142 may or may not be identical to one another, and likewise for the different inner and outer injectors 124, 128.

[0085] Depending on the application, the inner velocity v, of the inner precursor plasma 126 and the outer velocity v₀ of the outer precursor plasma 130 can differ from each other in magnitude, in direction, or in both magnitude and direction. It is appreciated that injecting the inner precursor plasma 126 and the outer precursor plasma 130 with different velocities and from injectors 124, 128 having different radial positions with respect to the Z-pinch axis 114 can allow the formation and sustainment of a radially sheared axial flow within the Z-pinch plasma 132, which in turn can provide stabilization to the Z-pinch plasma 132 and increase its lifetime. Depending on the application, the radially sheared axial flow imparted to the Z-pinch plasma 132 by the flow of the inner and outer precursor plasmas 126, 130 can be uniform (dv_zldr = constant) or nonuniform (dv_z/dr constant) over the radial extent of the Z-pinch plasma 132.

[0086] In some embodiments, the inner velocity v, of the inner precursor plasma 126 injected into the reaction chamber 108 can have a magnitude ranging from about 0 km/s (e.g., less than 1 km/s, for example, 0.1 km/s) to about 60 km/s, while the outer velocity v₀ of the outer precursor plasma 130 injected into the reaction chamber 108 can have a magnitude ranging from about 70 km/s to about 200 km/s. In some embodiments, a velocity magnitude difference between the outer velocity v₀ of the outer precursor plasma 130 and the inner velocity v, of the inner precursor plasma 126 can range from about 50 km/s to about 200 km/s, with the magnitude of v₀ being generally larger than the magnitude of v,, although embodiments where the magnitude of v₀ is smaller than the magnitude of v, are contemplated as well. It is appreciated these velocity values are provided by way of example only, and that velocity values outside these ranges can be used in other embodiments.

[0087] In the illustrated embodiment, the inner precursor supply unit 120 is configured to control the inner velocity v, of the inner precursor plasma 126 to be substantially axial (e.g., parallel to the Z-pinch axis 114) upon entering the reaction chamber 108. Likewise, the outer precursor supply unit 122 is configured to control the outer velocity v₀ of the outer precursor plasma 130 to be substantially axial upon entering the reaction chamber 108. The outer velocity v₀ develops a radial component inside the reaction chamber 108 due to the compression force of the Z-pinch current. In some embodiments, however, the operation of the precursor supply device 104 may be controlled not only by adjusting a magnitude difference between the inner velocity v, of the inner precursor plasma 126 and the outer velocity v₀ of the outer precursor plasma 130, but also by adjusting a relative orientation between v, and v₀. For example, in some embodiments, the inner precursor supply unit 120 may be configured to control the inner velocity v, of the inner precursor plasma 126 to be substantially axial upon entering the reaction chamber 108, while the outer precursor supply unit 122 may be configured to control the outer velocity v₀ to have both an axial component and a radial component upon entering the reaction chamber 108. Such a configuration can be advantageous in that it can allow the outer precursor plasma 130 to be more naturally compressed to a sufficiently small radial extent for achieving fusion conditions in the Z-pinch plasma 132. It is appreciated that various plasma injection schemes and configurations are contemplated by the present techniques, in which the inner precursor plasma 126 and the outer precursor plasma 130 are injected into the reaction chamber 108 with different velocity directions.

[0088] Besides their different injection velocities and their different injection locations with respect to the Z-pinch axis 114, the inner precursor plasma 126 and the outer precursor plasma 130 may or may not have identical parameters. For example, in some embodiments, the inner precursor plasma 126 and the outer precursor plasma 130 may each have the following properties and parameters: an electron temperature ranging from about 1 eV to about 100 eV, an ion temperature ranging from about 1 eV to about 100 eV, an electron density ranging from about 10¹³ cm ³ to about 10¹⁶ cm ³. an ion density ranging from about 10¹³ cm ³ to about 10¹⁶ cm ⁵. velocities with magnitudes ranging from about 0 km/s to about 200 km/s, and a degree of ionization ranging from about 50% to about 100%. Depending on the application, the inner precursor plasma 126 and the outer precursor plasma 130 may be magnetized or unmagnetized. [0089] Referring still to Figs. 7 to 9, it is appreciated that many plasma formation and generation techniques exist, notably in fusion power applications, and may be used in the embodiments disclosed herein to form the inner precursor plasma 126 and the outer precursor plasma 130 with desired or required properties. In particular, the theory, instrumentation, implementation, and operation of plasma sources and generators are generally known in the art and need not be described in detail herein other than to facilitate an understanding of the present techniques.

[0090] In Figs. 7 to 9, the inner plasma generator 140 and the four outer plasma generators 142 are configured as coaxial plasma guns. It is appreciated, however, that other types of electromagnetic plasma generators can be used in other embodiments. It is also appreciated that the different inner and outer plasma generators 140, 142 of the inner and outer precursor supply units 120, 122 may or may not be identical to another one. Coaxial plasma guns and other electromagnetic plasma generators generally operate by using the electric field generated by a high-voltage power supply to energize a gas into a plasma, and by relying on the Lorentz force to propel the plasma toward an outlet of the plasma gun.

[0091] In the illustrated embodiment, the inner plasma generator 140 and the four outer plasma generators 142 each extend along a plasma formation axis 144 and include an inner electrode 146 and an outer electrode 148 disposed around the inner electrode 146 in a coaxial arrangement with respect to the plasma formation axis 144. The outer electrode 148 projects axially beyond the inner electrode 146 and terminates at the inner or outer injector 124, 128 formed through the first compression electrode 116. In other embodiments, however, the outer electrode 148 may not project axially beyond the inner electrode 146, so that both the inner electrode 146 and the outer electrode 148 terminate at inner or outer injector 124, 128. In some embodiments, the inner electrode 146 may have a length ranging from about 75 mm to about 250 mm and a radius ranging from about 2 mm to about 7.5 mm, while the outer electrode 148 may have a length ranging from about 75 mm to about 275 mm, a radius ranging from about 12 mm to about 25 mm, and a wall thickness ranging from about 2.5 mm to about 7.5 mm, although other electrode dimensions may be used in other embodiments. The annular volume extending between the inner electrode 146 and the outer electrode 148 defines a plasma formation region 150 configured to receive an inner or an outer process gas 152, 154 (e.g., a neutral gas or another plasma precursor gas) for the inner or outer process gas 152, 154 to be energized into the inner or outer precursor plasma 126, 130. The cylindrical volume surrounded by the outer electrode 148 and extending axially beyond the front end of the inner electrode 146 defines a plasma transport channel 156 of the inner or outer plasma generator 140, 142. The plasma transport channel 156 extends along the plasma formation axis 144 from the plasma formation region 150 to the inner or outer injector 124, 128. It is appreciated that the inner plasma generator 140 and the outer plasma generators 142 may be operated as plasma deflagration guns and will generally not form the inner precursor plasma 126 and the outer precursor plasma 130 as plasma pinches.

[0092] Referring still to Figs. 7 to 9, the inner process gas 152 can be any suitable gas or gas mixture capable of being energized into the inner precursor plasma 126 by the inner plasma generator 140. Likewise, the outer process gas 154 can be any suitable gas or gas mixture capable of being energized into the outer precursor plasma 130 by the outer plasma generators 142. Depending on the application, the inner and outer process gases 152, 154 can each be a neutral gas or gas mixture, or a weakly ionized gas or gas mixture. The inner and outer process gases 152, 154 may contain fusion reactants. For example, in some embodiments, the inner and outer process gases 152, 154 may be deuterium gas (D-D reaction), a gas mixture containing deuterium and tritium (D-T reaction), a gas mixture containing deuterium and helium- 3 (D-³He reaction), or a gas mixture containing protons and boron (p⁺-ⁿB reaction). Other process gas mixtures may include hydrogen or helium. The inner precursor plasma 126 may be formed by supplying the inner process gas 152 to the plasma formation region 150 of the inner plasma generator 140 and by applying a voltage between the inner and outer electrodes 146, 148 to ionize or otherwise energize the inner process gas 152 into the inner precursor plasma 126. Likewise, the outer precursor plasma 130 may be formed by supplying the outer process gas 154 to the plasma formation region 150 of each of the four outer plasma generators 142 and by applying a voltage between the inner and outer electrodes 146, 148 to ionize or otherwise energize the outer process gas 154 into four respective portions the outer precursor plasma 130.

[0093] Referring still to Figs. 7 to 9, the inner precursor supply unit 120 includes an inner process gas supply unit 158 configured to supply the inner process gas 152 in the plasma formation region 150 of the inner plasma generator 140. The inner precursor supply unit 120 also includes an inner plasma formation power supply 160 configured to apply a voltage between the inner electrode 146 and the outer electrode 148 of the inner plasma generator 140 to energize the inner process gas 152 into the inner precursor plasma 126 and cause the inner precursor plasma 126 to flow along the plasma formation region 150 and through the plasma transport channel 156 of the inner plasma generator 140 to reach the inner injector 124 for injection of the inner precursor plasma 126 into the reaction chamber 108. Depending on the application, the operation of introducing the inner process gas 152 into the plasma formation region 150 can be initiated before, at the same time as, or after initiating the operation of activating the inner plasma formation power supply 160 to apply the voltage between the inner electrode 140 and the outer electrode 142.

[0094] Likewise, the outer precursor supply unit 122 includes four outer process gas supply units 162 and four outer plasma formation power supplies 164. Each process gas supply unit 162 is configured to supply the outer process gas 154 into the plasma formation region 150 of a respective one of the four outer plasma generators 142. Each outer plasma formation power supply 164 is configured to apply a voltage between the inner electrode 146 and the outer electrode 148 of a respective one of the four outer plasma generators 142 to energize the outer process gas 154 into a respective portion of the outer precursor plasma 130 and cause the respective portion of the outer precursor plasma 130 to flow along the plasma formation region 150 and through the plasma transport channel 156 of the respective outer plasma generator 142 to reach the respective outer injector 128 for injection of the respective portion of the outer precursor plasma 130 into the reaction chamber 108. Depending on the application, the operation of introducing the outer process gas 154 into the plasma formation region 150 of each outer plasma generator 142 can be initiated before, at the same time as, or after initiating the operation of activating each outer plasma formation power supply 164 to apply the voltage between the inner electrode 140 and the outer electrode 142.

[0095] Referring still to Figs. 7 to 9, each process gas supply unit 158, 162 can include or be coupled to a process gas source 166 configured to store the process gas 152, 154. The process gas source 166 may be embodied by a gas storage tank or any suitable pressurized gas dispensing container. Each process gas supply unit 158, 162 may also include a process gas supply line 168 (e.g., including gas conduits or channels) configured to transport the process gas 152, 154 from the process gas source 166 to the plasma formation region 150 of each plasma generator 140, 142. The process gas supply unit 158, 162 may further include a process gas supply valve 170 or other flow control devices configured to control a flow of the process gas 152, 154 along the process gas supply line 168, from the process gas source 166 to the plasma formation region 150 of each plasma generator 140, 142. The process gas supply valve 170 may be embodied by a variety of electrically actuated valves, such as solenoid valves. Other flow control devices (not shown), such as pumps, regulators, and restrictors, may be provided to control the process gas flow rate and pressure along the process gas supply line 168. Various process gas injection configurations may be used depending on the application. For example, in some embodiments, a single process gas source may be provided for supplying process gas 152, 154 to multiple or all of the plasma generators 140, 142, rather than each plasma generator 140, 142 being connected to its own dedicated process gas source 166, as in the embodiment of Figs. 7 to 9.

[0096] Referring still to Figs. 7 to 9, each plasma formation power supply 160, 164 is connected to the inner electrode 140 and the outer electrode 142 of its corresponding plasma generator 140, 142 via appropriate electrical connections. It is appreciated that the inner and outer plasma formation power supplies 160, 164 are distinct from the main power supply 106 coupled to the first compression electrode 116 and the second compression electrode 118 of the plasma confinement device 102. Suitable electrical insulators 136 may be provided to ensure electrical insulation between the inner and outer electrodes 146, 148 of the plasma generators 140, 142 and the first compression electrode 116. Depending on the application, the various plasma formation power supplies 160, 164 may or may not be identical to one another. In the illustrated embodiment, each plasma formation power supply 160, 164 includes a capacitor bank and a switch, although other suitable types of power supplies may be used in other embodiments (e.g., flywheel power supplies). Each plasma formation power supply 160, 164 is configured to apply a voltage between the inner and outer electrodes 140, 142 of its corresponding plasma generator 140, 142 to generate an ionizing electric field across the plasma formation region 150. The ionizing electric field is configured to ionize and break down the process gas 152, 154, thereby forming the inner precursor plasma 126 and the outer precursor plasma 130. In some embodiments, the voltage applied between the inner and outer electrodes 140, 142 may range from about 750 V to about 5 kV, although other voltage values may be used in other embodiments. [0097] It is appreciated that the configuration and the operation of the plasma formation power supplies 160, 164 may be adjusted to favor the breakdown of the process gas 152, 154 and control the parameters of the inner precursor plasma 126 and the outer precursor plasma 130. It is appreciated that in other embodiments, the precursor supply device 104 may use other types of plasma sources and plasma formation techniques to form the inner precursor plasma 126 and the outer precursor plasma 130. Nonlimiting examples of such possible plasma sources include, to name a few, gas injected washer plasma guns; plasma thrusters, for example, Hall effect thrusters and MHD thrusters; if the inner precursor plasma 126 or the outer precursor plasma 130 is magnetized, high-power helicon plasma sources; RF plasma sources; plasma torches; and laser-based plasma sources.

[0098] Referring still to Figs. 7 to 9, the inner precursor plasma 126 or the portions of the outer precursor plasma 130 formed by each plasma generator 140, 142 is flowed, directed, or otherwise moved along the plasma transport channel 156 from the plasma formation region 150 to the corresponding injector 124, 128 for injection into the reaction chamber 108 of the plasma confinement device 102. It is appreciated that the portions of the outer precursor plasma 130 formed by the four outer plasma generators 142 may have the same or different plasma compositions or parameters. Transport of the precursor plasma 126, 130 along the plasma transport channel 148 can be achieved by or as a result of the axial momentum imparted to the precursor plasma 126, 130 as it leaves the plasma formation region 144. In particular, the formation of the source precursor plasma 126, 130 can result in a radial electric current and an azimuthal magnetic field. The interaction between the radial electric current and the azimuthal magnetic field produces an axial Lorentz force that pushes and accelerates the precursor plasma 126, 130 forward along the plasma formation region 150 and into the plasma transport channel 156 toward the injector 124, 128.

[0099] In the illustrated embodiment, each one of the inner and outer injectors 124, 128 is provided as a plasma injection port or opening formed through the first compression electrode 116 and establishing a pathway between the plasma transport channel 156 of the corresponding plasma generator 140, 142 and the reaction chamber 108 of the plasma confinement device 102. The inner and outer injectors 124, 128 can be used to control the injection velocity v, and v₀ the inner and outer precursor plasmas 126, 130 into the reaction chamber 108, which in turn can provide better control over the lifetime and other properties of the Z-pinch plasma 132, including its embedded velocity shear. It is appreciated that the parameters of each injector 124, 128 may be individually adjusted in accordance with the application. Non-limiting examples of such parameters include the size and shape of the injector 124, 128; the axial, radial, and/or azimuthal position of the injector 124, 128 with respect to the Z-pinch axis 114; the plasma injection plane, which is defined as the plane encompassing the Z-pinch axis 114 and the plasma formation axis 144 of the plasma generator 140, 142 associated with the injector 124, 128; and the plasma injection angle, which defined as the angle between the Z-pinch axis 114 and the plasma formation axis 144 of the plasma generator 140, 142 associated with the injector 124, 128. [0100] It is appreciated that the injection of the inner precursor plasma 126 and the outer precursor plasma 130 in the reaction chamber 108 at the inner and outer velocities v, and v₀ can be a complex and delicate process, which involves creating a flowing plasma column with a radial differential axial velocity to embed a radially sheared axial flow in the Z-pinch plasma 132. As noted above, a velocity magnitude difference between the outer velocity v₀ of the outer precursor plasma 130 and the inner velocity v, of the inner precursor plasma 126 ranging from about 50 km/s to about 200 km/s may be involved to achieve a sufficiently large velocity shear in the Z-pinch plasma 132 provide stability and increase the pinch lifetime. In some embodiments, physical mechanisms such as mixing between the inner precursor plasma 126 and the outer precursor plasma 130 and viscosity may reduce the velocity magnitude difference between v₀ and v, injected velocity difference. In some embodiments, a required or desired velocity magnitude difference may be achieved by proper selection and adjustment of the various plasma generators 140, 142 and injectors 124, 128 of the precursor supply device 104 and/or by using more than one type of plasma generators 140, 142 and/or injectors 124, 128. In some embodiments, an electric potential difference may be applied between the plasma generators 140, 142 and the reaction chamber 108 to accelerate or decelerate the inner precursor plasma 126 and the outer precursor plasma 130 entering the reaction chamber 108. This can be achieved by floating the ground (e.g., by up to 1 kV) associated with the plasma generators 140, 142 and the ground associated with the plasma confinement device 102. In some embodiments, one or more of the plasma generators 140, 142 may be magnetized to reduce mixing and the impact of viscosity.

[0101] In some embodiments, the Z-pinch plasma 132 may have the following properties and parameters: a plasma radius ranging from about 0.1 mm to about 5 mm; a magnetic field ranging from about 1 T to about 8 T; an electron temperature ranging from about 500 eV to about 10 keV, an ion temperature ranging from about 500 eV to about 10 keV, an electron density ranging from about 10¹⁶ cm ³ to about 10²° cm ⁵. an ion density ranging from about 10¹⁶ cm ³ to about IO²'¹ cm ³. and a stable lifetime exceeding 10 microseconds (e.g., up to 1 millisecond); and a radial velocity shear ranging from about 2* 10⁶ s ¹ to about 4* 10⁷ s '. These values are provided by way of example, so that other values may be used in other embodiments.

[0102] It is appreciated that the approach to forming and sustaining a sheared-flow-stabilized Z-pinch plasma implemented in the embodiment of Figs. 7 to 9 differs from conventional sheared-flow-stabilized Z-pinch plasma confinement approaches, such as that depicted in Figs. 1 to 5. In these conventional approaches, a plasma is formed inside an acceleration region of a reaction chamber, typically by injection and ionization of a neutral gas, and this internally formed plasma is flowed along the acceleration region and into an assembly region of the reaction chamber to be compressed into a Z-pinch plasma. In these approaches, the temperature, density, lifetime, and other parameters of the Z-pinch plasma are largely controlled by the neutral gas profile (e.g., spatial density profile) inside the plasma confinement device. However, plasma formation from a neutral gas is a complex, time-dependent process, which can make controlling the Z-pinch parameters challenging. Furthermore, in conventional approaches, the sheared axial flow imparted to the Z-pinch plasma is generated due to the velocity of the plasma as it exits the acceleration region and enters the assembly region where it is compressed into the Z-pinch plasma. This approach to establishing a sheared axial flow poses challenges because the velocity profile tends to be a constant across most of the Z-pinch plasma and the shear normally occurs only in a thin region at the outer edge. Efforts to change the velocity profile with different shapes at the end of the inner electrode have generally not shown large changes in velocity.

[0103] By contrast, in the embodiment of Figs. 7 to 9, the inner precursor plasma 126 and the outer precursor plasma 130 are formed outside the reaction chamber 108 of the plasma confinement device 102, and the externally formed inner and outer precursor plasmas 126, 130 are injected into the reaction chamber 108 with different velocities and different injection positions with respect the Z-pinch axis 114 so as to form and sustain a Z-pinch plasma 132 having an embedded radially sheared axial flow to provide pinch stabilization and increase pinch lifetime. In this approach, the present techniques can allow better control of the process of forming the inner and outer precursor plasmas 126, 130, the process of compressing the inner and outer precursor plasmas 126, 130 into the Z-pinch plasma 132, and the processing of imparting a radially sheared axial flow into the Z-pinch plasma 132. In particular, controlled plasma injection and flow shearing can allow for a stable Z-pinch plasma to provide higher fusion power gain sustained over longer periods of time, with reduced or better controlled power losses and other energy inefficiencies. In some embodiments, the present techniques can allow the formation and sustainment of sheared-flow Z-pinch plasma having a more predictable and controllable radially shear velocity profile. In some embodiments, the size of the inner and outer injectors 124, 128 can be adjusted to control the radial extent of the portion of the Z-pinch plasma 132 with a constant velocity. Furthermore, by having a reaction chamber 108 formed between two compression electrodes 116, 118, rather than a reaction chamber including an acceleration region followed by an assembly region as in Figs. 1 to 5, the compression of the inner and outer precursor plasmas 126, 130 into the Z-pinch plasma 132 may be made more gradual and controllable.

[0104] In some embodiments, the plasma processing system 100 may be configured to compress the Z- pinch plasma 132 sufficiently to reach fusion conditions, whereby particles inside the Z-pinch plasma 132 undergo nuclear fusion reactions. In some embodiments, the nuclear fusion reactions produced and sustained inside the Z-pinch plasma 132 can include neutronic fusion reactions, that is, nuclear reactions that produce neutrons. In some of these embodiments, the energy of the neutrons thus provided can be converted into electricity in fusion power applications. In such embodiments, the nuclear fusion reactions may occur mostly in the inner portion of the Z-pinch plasma 132 (which is formed from the inner precursor plasma 126) while the outer portion of the Z-pinch plasma 132 (which is formed from the outer precursor plasma 130) is configured to provide a sheared-flow stabilization effect to the Z-pinch plasma 132 due to the velocity difference between the inner velocity of the inner precursor plasma 126 and the outer velocity of the outer precursor plasma 130. [0105] Referring still Figs. 7 to 9, in some embodiments, the plasma processing system 100 may include a vacuum system 172. It is noted that the vacuum system 172 has been omitted in Figs. 7 and 8 for clarity and ease of illustration. The vacuum system 172 includes a vacuum chamber 174, for example, a stainless steel pressure vessel. The vacuum chamber 174 is configmed to house at least partially various components of the plasma processing system 100, including the plasma confinement device 102 and the precursor supply device 104. The vacuum chamber 174 may include vacuum ports (not shown) formed therethrough to allow access into the reaction chamber 108. The vacuum system 174 may also include a pressure control system 176 configured to control the operating pressure inside the vacuum chamber 174. In some embodiments, the pressure inside the vacuum chamber 174 may range from about 10 ⁹ Torr to about 20 Torr, for example, from about 10 ^x Torr to about 10 ⁴ Torr, although other ranges of pressure may be used in other embodiments.

[0106] Referring to Fig. 11, there is illustrated another possible embodiment of a plasma processing system 100. The embodiment of Fig. 11 shares several features with the embodiment of Figs. 7 to 9, which will not be described again other than to highlight differences between them. In the embodiment of Figs. 7 to 9, the inner injector 124 configured to inject the inner precursor plasma 126 and the outer four outer injectors 128 configured to inject the precursor plasma 130 are both formed through the first compression electrode 116, which located at the first end 110 of the reaction chamber 108 of the plasma confinement device 102. As a result, the axial component of the inner velocity v, of the inner precursor plasma 126 and the axial component of the outer velocity v₀ of the outer precursor plasma 130 point in the same direction (i.e., from left to right in Fig. 9). In contrast to the embodiment of Figs. 7 to 9, in Fig. 11, the inner precursor plasma 126 and the outer precursor plasma 130 are injected into the reaction chamber 108 from opposite ends 110, 112 of the reaction chamber 108. Specifically, the inner precursor supply unit 120 is configured to inject the inner precursor plasma 126 in the reaction chamber 108 via an inner injector 124 formed through the second compression electrode 118, which is located at the second end 112 of the reaction chamber 108. Meanwhile, the outer precursor supply unit 122 is configured to inject the outer precursor plasma 130 in the reaction chamber 108 via four outer injectors 128 (only two of which are depicted in the longitudinal cross-sectional view of Fig. 11) formed through the first compression electrode 116, at the first end 110 of the reaction chamber 108. As a result, the axial component of the inner velocity v, of the inner precursor plasma 126 and the axial component of the outer velocity v₀ of the outer precursor plasma 130 point in the same direction (i.e., from right to left for v, and from left to right for v₀). Such a configuration may be advantageous because inner and outer plasma generators 140, 142 with exit velocities of similar magnitudes (e.g., such that |v,j ~ |v₀|) could still be used to generate a meaningful velocity difference (e.g., of the order of twice |v,j or |v₀|) for stabilizing the Z-pinch plasma 132.

[0107] Referring to Fig. 12, there is illustrated another possible embodiment of a plasma processing system 100. The embodiment of Fig. 12 shares several features with the embodiment of Figs. 7 to 9, which will not be described again other than to highlight differences between them. The plasma processing system 100 of Fig. 12 generally includes a plasma confinement device 102, a precursor supply device 104, and a main power supply 106. The precursor supply device 104 includes, in addition to an inner precursor supply unit 120 and an outer precursor supply unit 122 as in Figs. 7 to 9, an intermediate precursor supply unit 178. The intermediate precursor supply unit 178 includes an intermediate plasma generator 180 configured to generate an intermediate precursor plasma 182, an intermediate injector 184 disposed radially between the inner injector 124 and the outer injector 128 with respect to the Z-pinch axis 114. In some embodiments, the inner plasma generator 180 includes an inner electrode 146 and an outer electrode 148 surrounding the inner electrode 146 to define a plasma formation region 150 therebetween for forming the intermediate precursor plasma 182. The outer electrode 148 can extend beyond the inner electrode 146 along a plasma formation axis 144 to enclose a plasma transport channel 156 extending from the plasma formation 150 region to the intermediate injector 184 along the plasma formation axis 144. In some embodiments, the intermediate precursor supply unit 178 includes an intermediate process gas supply unit 208 configured to supply an intermediate process gas 210 to the plasma formation region 150 of the intermediate plasma generator 180, and an intermediate plasma formation power supply 212 configured to apply a voltage between the inner electrode 146 and the outer electrode 148 of the intermediate plasma generator 180 to energize the intermediate process gas 210 into the intermediate precursor plasma 182 and cause the intermediate precursor plasma 182 to flow along the plasma formation region 150 and through the plasma transport channel 156 of the intermediate plasma generator 180 to reach the intermediate injector 184 for injection of the intermediate precursor plasma 182 into the reaction chamber 108. The intermediate process gas supply unit 208 and the intermediate plasma formation power supply 212 may be similar to the inner and outer process gas supply units 158, 162 and the inner and outer plasma formation power supplies 160, 164 described above. In some embodiments, the intermediate process gas 210 includes deuterium, tritium, hydrogen, or helium, or any combination thereof. The intermediate injector 184 is configured to inject the intermediate precursor plasma 182 into the reaction chamber 108 at an intermediate velocity Vinter different from both the inner velocity v, of the inner precursor plasma 126 and the outer velocity v₀ of the outer precursor plasma 130. In some embodiments, the magnitude of the intermediate velocity v_mter may be larger that the magnitude of the inner velocity v, but smaller than the magnitude of the outer velocity v₀. The injection of an intermediate precursor plasma 182 whose velocity and injection location are different from those of both the inner precursor plasma 126 and the outer precursor plasma 130 can be advantageous in that it can provide an additional degree of freedom to control and adjust the velocity shear imparted to the Z-pinch plasma 132. Other possible advantages include better control of the plasma density and/or temperature profdes. It is appreciated that, in some embodiments, the precursor supply device 104 may include multiple intermediate precursor supply units to provide intermediate injectors at multiple corresponding intermediate radial positions between the radial position of the inner injector 124 and the radial position of the outer injector 128.

[0108] Referring to Fig. 10, there is illustrated another possible embodiment of a plasma processing system 100. The embodiment of Fig. 10 shares several features with the embodiment of Figs. 7 to 9, which will not be described again other than to highlight differences between them. In the embodiment of Fig. 10, the inner precursor medium 126 injected into the reaction chamber 108 via the inner injector 124 of the inner precursor supply unit 120 is an inner precursor gas, rather than an inner precursor plasma as in Figs. 7 to 9. In some embodiments, the inner precursor gas 126 may contain fusion reactants. For example, in some embodiments, the inner precursor gas 126 may be deuterium gas (D-D reaction), a gas mixture containing deuterium and tritium (D-T reaction), a gas mixture containing deuterium and helium-3 (D-³He reaction), or a gas mixture containing protons and boron (p⁺-ⁿB reaction). Other process gas mixtures may include hydrogen or helium. The inner precursor supply unit 120 in Fig. 10 includes an inner precursor gas source 186 configured to store the inner precursor gas 126, and an inner precursor gas supply line 188 configured to transport the inner precursor gas 126 from the inner precursor gas source 186 to the inner injector 124 for injection of the inner precursor gas 126 into the reaction chamber 108. The inner precursor gas source 186 may be embodied by a gas storage tank or any suitable pressurized gas dispensing container. The inner precursor supply unit 120 may further include a gas supply valve or other flow control devices (e.g., pumps, regulators, and restrictors) configured to control a flow of the inner precursor gas 126 along the inner precursor gas supply line 188, from the inner precursor gas source 186 to the inner injector 124. Various inner precursor gas injection configurations may be used depending on the application.

[0109] In the embodiment of Fig. 10, the formation of the sheared-flow Z-pinch plasma 132 can involve steps of supplying, through the inner injector 124, the inner precursor gas 126 into the reaction chamber 108, and supplying, through the outer injector 128, the outer precursor plasma 130 into the reaction chamber 108. Depending on the application, the inner precursor supply unit 120 may be configured to start supplying the inner precursor gas 126 into the reaction chamber 108 before, at the same time as, or after the outer precursor supply 122 is configured to supply the outer precursor plasma 130 into the reaction chamber 108. The formation of the sheared-flow Z-pinch plasma 132 can also involve a step of using the main power supply 106 to supply power to the plasma confinement device 102 to apply a compression voltage between the first compression electrode 116 and the second compression electrode 116 that is configured to energize and compress the inner precursor gas 126 and the outer precursor plasma 130 into the sheared-flow Z-pinch plasma 132. Depending on the application, the precursor supply device 104 may be configured to start supplying the inner precursor gas 126 and the outer precursor plasma 130 into the reaction chamber 108 before, at the same time as, or after the main power supply 106 is configured to start supplying power to the plasma confinement device 102. The energization and compression process involves the ionization the inner precursor gas 126 into an inner plasma 190, and the energization and compression of the inner plasma 190 together with the outer precursor plasma 130 to form the Z-pinch plasma 132. In this configuration, the inner plasma 190 and the outer precursor plasma 130 respectively provide the inner portion and the outer portion of the Z-pinch plasma 132. In order to impart a sufficient large velocity shear to the Z-pinch plasma 132 to provide stability, the outer precursor plasma 130 may be injected into the reaction chamber 108 at an outer velocity v₀ having a magnitude ranging from about 70 km/s to about 200 km/s. In some embodiments, using a gas rather than an already formed plasma as the inner precursor medium can be advantageous in that it can increase the density of the inner portion of the Z-pinch plasma 132, enable a null or nearly velocity in the inner portion of the Z-pinch plasma 132, and/or ensure better protection of the first compression electrode 116.

[0110] Referring to Figs. 13A and 13B, there is illustrated another possible embodiment of a plasma processing system 100. The embodiment of Figs. 13A and 13B shares several features with the embodiment of Figs. 7 to 9, which will not be described again other than to highlight differences between them. As in the embodiment of Figs. 7 to 9, the plasma processing system 100 of Figs. 13 A and 13B generally includes a plasma confinement device 102, a precursor supply device 104, and a main power supply 106. The operation of the plasma processing system 100 of Figs. 13A and 13B generally involves two main process phases, namely a first process phase, depicted in Fig. 13A and during which the inner precursor medium 126 is an inner precursor gas, and a second process phase, depicted in Fig. 13B and during which the inner precursor medium 126 is an inner precursor plasma. In the illustrated embodiment, the inner precursor supply unit 120 is configured to start by supplying the inner precursor medium 126 into the reaction chamber as an inner precursor gas, and to switch, after a certain time duration, to supplying the inner precursor medium 126 as an inner precursor plasma. In some embodiments, the time duration between the step of starting to supply the inner precursor medium 126 as an inner precursor gas and the step of switching to supplying the inner precursor medium 126 as an inner precursor plasma ranges from about 0.5 millisecond to about 5 milliseconds.

[oni] In the first process phase depicted in Fig. 13A, the inner precursor medium 126 may be injected into the reaction chamber 108 as an inner precursor gas by passing the inner process gas 152 supplied by the inner process gas supply unit 158 along the plasma formation region 150 and the plasma transport channel 156 of the inner plasma generator 140 without applying a voltage between the inner electrode 146 and the outer electrode 148 to ionize the inner process gas 152 into an inner precursor plasma prior. In this configuration, the inner injector 124 is configured to inject the unionized process gas 152 into the reaction chamber 108 as an inner precursor gas 126. Turning to Fig. 13B, in the second process phase, the inner plasma formation power supply 160 is activated to apply a voltage between the inner electrode 146 and the outer electrode 148 of the inner plasma generator 140. As described above with respect to the embodiment of Figs. 7 to 9, the application of a voltage across the plasma formation region 150 of the inner plasma generator 140 energizes the inner process gas 152 into an inner precursor plasma 126 cause the inner precursor plasma 126 to flow along the plasma formation region 150 and through the plasma transport channel 156 of the inner plasma generator 140 to reach the inner injector 124 for injection of the inner precursor plasma 126 into the reaction chamber 108. In some embodiments, starting the Z-pinch formation process using an inner precursor gas and then switching to an inner precursor plasma can be advantageous in that it can provide the benefits listed above with respect to the embodiment of Fig. 10, while taking advantage of the fact that replenishing the Z -plasma 132 with plasma rather than with neutral gas tends to be more effective. In some implementations, the second process phase may be initiated at the same time or slightly before (rather than after as in Figs. 13A and 13B) the application of the voltage by the main power supply 106, in which case the Z-pinch plasma 132 would be formed in the second process phase. [0112] Returning to Figs. 7 to 9, the plasma processing system 100 can further include a control and processing device 190, which is configmed to control, monitor, and coordinate the functions and operation of various components of the plasma processing system 100, as well as various temperature, pressure, and power conditions. Non-limiting examples of components that can be controlled by the control and processing device 192 include the main power supply 106; various components of the inner and outer precursor supply units 120, 122, including the inner and outer process gas supply units 158, 162, the inner and outer plasma formation power supplies 160, 164; and the vacuum system 172. For example, the control and processing device 192 may be configmed to control the operation of the inner and outer process gas supply units 158, 162 to supply the inner and outer process gases 152, 154 to the plasma formation region 150 of the inner and outer plasma generators 140, 142; to control the operation of the inner and outer plasma formation power supplies 160, 164 to supply power to the inner and outer plasma generators 140, 142 to energize the inner and outer process gases 152, 154 into the inner and outer precursor plasmas 126, 130; and to control the operation of the main power supply 106 to apply a voltage between the first and second compression electrodes 116, 118 of the plasma confinement device 102 to energize and compress the flowing inner and outer precmsor plasmas 126, 130 injecting into the reaction chamber 108 into the sheared-flow Z-pinch plasma 132. In particular, the control and processing device 192 may be configured to synchronize or otherwise time-coordinate the functions and operation of various components of the plasma processing system 100. The control and processing device 192 may be implemented in hardware, software, firmware, or any combination thereof, and be connected to various components of the plasma processing system 100 via wired and/or wireless communication links configured to send and/or receive various types of signals, such as timing and control signals, measurement signals, and data signals. The control and processing device 192 may be controlled by direct user input and/or by programmed instructions, and may include an operating system for controlling and managing various functions of the plasma processing system 100. Depending on the application, the control and processing device 192 may be fully or partly integrated with, or physically separate from, the other hardware components of the plasma processing system 100. The control and processing device 192 can include a processor 194 and a memory 196.

[0113] The processor 194 may be able to execute computer programs, also generally known as commands, instructions, functions, processes, software codes, executables, applications, and the like. It should be noted that although the processor 194 in Figs. 7 to 9 is depicted as a single entity for illustrative purposes, the term “processor” should not be construed as being limited to a single processor, and accordingly, any known processor architecture may be used. In some implementations, the processor 194 may include a plurality of processing units. Such processing units may be physically located within the same device, or the processor 194 may represent processing functionality of a plurality of devices operating in coordination. For example, the processor 194 may include or be part of a computer; a microprocessor; a microcontroller; a coprocessor; a central processing unit (CPU); an image signal processor (ISP); a digital signal processor (DSP) running on a system on a chip (SoC); a single-board computer (SBC); a dedicated graphics processing unit (GPU); a special-purpose programmable logic device embodied in hardware device, such as, for example, a field-programmable gate array (FPGA) or an application-specific integrated circuit (ASIC); a digital processor; an analog processor; a digital circuit designed to process information; an analog circuit designed to process information; a state machine; and/or other mechanisms configured to electronically process information and to operate collectively as a processor.

[0114] The memory 196, which may also be referred to as a “computer readable storage medium” is capable of storing computer programs and other data to be retrieved by the processor 196. In the present description, the terms “computer readable storage medium” and “computer readable memory” are intended to refer to a non-transitory and tangible computer product that can store and communicate executable instructions for the implementation of various steps of the methods disclosed herein. The computer readable memory may be any computer data storage device or assembly of such devices, including a random-access memory (RAM); a dynamic RAM; a read-only memory (ROM); a magnetic storage device, such as a hard disk drive, a solid state drive, a floppy disk, and a magnetic tape; an optical storage device, such as a compact disc (CD or CDROM), a digital video disc (DVD), and a Blu-Ray™ disc; a flash drive memory; and/or any other non-transitory memory technologies. A plurality of such storage devices may be provided. The computer readable memory may be associated with, coupled to, or included in a computer or processor configured to execute instructions contained in a computer program stored in the computer readable memory and relating to various functions associated with the computer.

[0115] The plasma processing system 100 may also include one or more user interface devices (not shown) operatively connected to the control and processing device 192 to allow the input of commands and queries to the plasma processing system 100, as well as present the outcomes of the commands and queries. The user interface devices may include input devices (e.g., a touch screen, a keypad, a keyboard, a mouse, a switch, and the like) and output devices (e.g., a display screen, a printer, visual and audible indicators and alerts, and the like).

[0116] Referring to Figs. 14A to 14D, a method of operating a plasma processing system 100 to generate a sheared-flow Z-pinch plasma 132 will be described in greater detail. The plasma processing system 100 illustrated in Figs. 14A to 14D corresponds to that illustrated in the embodiment of Figs. 7 to 9, depicted at different stages of its operation. The plasma processing system 100 of Figs. 14A to 14D generally includes a plasma confinement device 102, a precursor supply device 104, a main power supply 106, and a control and processing device 192, as described above with respect to the embodiment of Figs. 7 to 9. The plasma confinement device 102 includes a reaction chamber 108 having a first end 110, a second end 112, and a Z-pinch axis 114 extending longitudinally between the first end 110 and the second end 112. The plasma confinement device 102 also includes a first compression electrode 116 provided at the first end 110 of the reaction chamber 108, and a second compression electrode 118 provided at the second end 112 of the reaction chamber 108. The precursor supply device 104 includes an inner precursor supply unit 120 and an outer precursor supply unit 122. The inner precursor supply unit 120 includes an inner injector 124 and is configured to supply, through the inner injector 124, an inner precursor plasma 126 into the reaction chamber 108. The outer precursor supply unit 122 includes four outer injectors 128 disposed radially outwardly of the inner injector 124 with respect to the Z-pinch axis 114. The outer precursor supply unit 122 is configured to supply, through the four outer injectors 128, an outer precursor plasma 130 into the reaction chamber 108. The main power supply 106 is configured to supply power to the plasma confinement device 102 to apply a compression voltage between the first compression electrode 116 and the second compression electrode 118 configured to energize and compress the inner precursor medium 126 and the outer precursor plasma 130 into a Z-pinch plasma 132 having a radially sheared axial flow along the Z-pinch axis 114. The control and processing device 192 is configured to control and time-coordinate the functions and operation of the other components of the plasma processing system 100.

[0117] The method can include a step of forming the inner precursor plasma 126 and the outer precursor plasma 130 outside the reaction chamber 108 of the plasma confinement device 102. The formation of the inner precursor plasma 126 can include a step of using an inner process gas supply unit 158 to supply an inner process gas 152 into the plasma formation region 150 of the inner plasma generator 140 of the inner precursor supply unit 120, as depicted in Fig. 14A. The formation of the inner precursor plasma 126 can also include a step of using an inner plasma formation power supply 160 to apply a voltage between the inner electrode 146 and the outer electrode 148 of the inner plasma generator 140 to energize the inner process gas 152 into the inner precursor plasma 126, as depicted in Fig. 14B. Once formed, the inner precursor plasma 126 is flowed along the plasma formation region 150 and the plasma transport 156 toward the inner injector 124. The formation of the outer precursor plasma 130 can include a step of using an outer process gas supply unit 162 to supply an outer process gas 154 into the plasma formation region 150 of each of four outer plasma generators 142 of the outer precursor supply unit 122, as depicted in Fig. 14A. The formation of the outer precursor plasma 130 can also include a step of using an outer plasma formation power supply 164 to apply a voltage between the inner electrode 146 and the outer electrode 148 of each outer plasma generator 142 to energize the outer process gas 154 into a respective portion of the outer precursor plasma 130, as depicted in Fig. 14B. Once formed, each portion of the outer precursor plasma 130 is flowed along the plasma formation region 150 and the plasma transport 156 toward its corresponding outer injector 128. In the steps of the method illustrated in Figs. 14A and 14B, the operation of introducing the process gases 152, 154 into the plasma generators 140, 142 are initiated before initiating the operation of activating the plasma formation power supplies 160, 164 to supply power to the plasma generators 140, 142. For example, in some embodiments, the time delay between initiating the introduction of the process gases 152, 154 and initiating the activation of the plasma formation power supplies 158, 160 can range from about 500 microseconds to about 3 milliseconds. However, in other embodiments, the operation of introducing the process gases 152, 154 into the plasma generators 140, 142 can be initiated at the same time as or after initiating the operation of activating the plasma formation power supplies 160, 164. [0118] Referring to Fig. 14C, the method of operating the plasma processing system 100 can include a step of injecting, via the inner injector 124 and the outer injectors 128, the inner precursor plasma 126 and the outer precursor plasma 130 into the reaction chamber 108 at different velocities v, v₀. In some embodiments, the injection of the inner precursor plasma 126 and the outer precursor plasma 130 into the reaction chamber 108 can include a step of controlling the magnitude of the outer plasma velocity v₀ to be larger than the magnitude of the inner plasma velocity by a velocity magnitude difference ranging from about 50 km/s to about 200 km/s. Depending on the application, the step of supplying the inner precursor plasma 126 into the reaction chamber 108 can be initiated before, at the same as, or after the step of supplying the outer precursor plasma 130 into the reaction chamber 108 is initiated. It is appreciated that, in general, the inner precursor plasma 126 and the outer precursor plasma 130 can also be injected in the reaction chamber 108 with different injection velocities, start times, end times, durations, and/or temporal profdes.

[0119] Referring to Fig. 14D, the method of operating the plasma processing system 100 can include a step of using the main power supply 106 to supply power to the plasma confinement device 102 to apply a voltage between the first compression electrode 116 and the second compression electrode 118. The voltage is configured to energize and compress the inner precursor plasma 126 and the outer precursor plasma 130 into a Z-pinch plasma 132 having a radially sheared axial flow along the Z-pinch axis 114. In the steps of the method illustrated in Figs. 14C and 14D, the operation of introducing the inner and outer precursor plasmas 126, 130 into the reaction chamber 108 is initiated before initiating the operation of activating the main power supply 106 to apply the voltage between the first and second compression electrodes 116, 118. For example, in some embodiments, the time delay between initiating the introduction of the inner and outer precursor plasmas 126, 130 into the reaction chamber 108 and initiating the activation of the main power supply 106 can range from about 0 ps and about 200 ps. However, in other embodiments, the operation of introducing the inner and outer precursor plasmas 126, 130 into the reaction chamber 108 can be initiated at the same time as or after initiating the operation of activating the main power supply 106. In some embodiments, the operation of the plasma processing system 100 can include continuing to supply the inner and outer precursor plasmas 126, 130 into the reaction chamber 108 during a sustainment phase after the formation of the Z-pinch plasma 132. In some embodiments, the sustainment phase can have a duration ranging from about 5 microseconds to about 10 milliseconds, although duration values outside this range are possible in other embodiments.

[0120] Numerous modifications could be made to the embodiments described above without departing from the scope of the appended claims.

Claims

1. A plasma processing system including: a plasma confinement device comprising: a reaction chamber having a first end, a second end, and a Z-pinch axis extending longitudinally between the first end and the second end; a first compression electrode provided at the first end of the reaction chamber, and a second compression electrode provided at the second end of the reaction chamber; a precursor supply device coupled to the plasma confinement device and comprising: an inner precursor supply unit comprising an inner injector, the inner precursor supply unit being configured to supply, through the inner injector, an inner precursor medium into the reaction chamber; and an outer precursor supply unit comprising an outer injector disposed radially outwardly of the inner injector with respect to the Z-pinch axis, the outer precursor supply unit being configured to supply, through the outer injector, an outer precursor plasma into the reaction chamber at an outer velocity; and a main power supply configured to supply power to the plasma confinement device to apply a compression voltage between the first compression electrode and the second compression electrode configured to energize and compress the inner precursor medium and the outer precursor plasma into a Z-pinch plasma having a radially sheared axial flow along the Z-pinch axis.

2. The plasma processing system of claim 1, wherein the outer precursor supply unit comprises an outer plasma generator configured to generate the outer precursor plasma.

3. The plasma processing system of claim 2, wherein the outer plasma generator comprises: an inner electrode; and an outer electrode surrounding the inner electrode to define a plasma formation region for forming the outer precursor plasma and a plasma transport channel extending from the plasma formation region to the outer injector.

4. The plasma processing system of claim 3, wherein the outer precursor supply unit comprises: an outer process gas supply unit configured to supply an outer process gas to the plasma formation region of the outer plasma generator; and an outer plasma formation power supply configured to apply a voltage between the inner electrode and the outer electrode of the outer plasma generator to energize the outer process gas into the outer precursor plasma and cause the outer precursor plasma to flow along the plasma formation region and through the plasma transport channel of the outer plasma generator to reach the outer injector for injection of the outer precursor plasma into the reaction chamber.

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5. The plasma processing system of claim 4, wherein the outer process gas comprises deuterium, tritium, hydrogen, or helium, or any combination thereof.

6. The plasma processing system of any one of claims 1 to 5, wherein the outer velocity of the outer precursor plasma has a magnitude ranging from about 70 km/s to about 200 km/s.

7. The plasma processing system of any one of claims 1 to 6, wherein the outer velocity of the outer precursor plasma is substantially axial upon entering the reaction chamber.

8. The plasma processing system of any one of claims 1 to 7, wherein: the inner precursor medium is an inner precursor plasma; and the inner precursor supply unit is configured to supply the inner precursor plasma into the reaction chamber at an inner velocity different from the outer velocity of the outer precursor plasma.

9. The plasma processing system of claim 8, wherein the inner precursor supply unit comprises an inner plasma generator configured to generate the inner precursor plasma.

10. The plasma processing system of claim 9, wherein the inner plasma generator comprises: an inner electrode; and an outer electrode surrounding the inner electrode to define a plasma formation region for forming the inner precursor plasma and a plasma transport channel extending from the plasma formation region to the inner injector.

11. The plasma processing system of claim 10, wherein the inner precursor supply unit comprises: an inner process gas supply unit configured to supply an inner process gas to the plasma formation region of the inner plasma generator; and an inner plasma formation power supply configured to apply a voltage between the inner electrode and the outer electrode of the inner plasma generator to energize the inner process gas into the inner precursor plasma and cause the inner precursor plasma to flow along the plasma formation region and through the plasma transport channel of the inner plasma generator to reach the inner injector for injection of the inner precursor plasma into the reaction chamber.

12. The plasma processing system of claim 11, wherein the inner process gas comprises deuterium, tritium, hydrogen, or helium, or any combination thereof.

13. The plasma processing system of any one of claims 8 to 12, wherein the inner velocity of the inner precursor plasma has a magnitude ranging from about 0 km/s to about 60 km/s.

14. The plasma processing system of any one of claims 8 to 13, wherein the inner velocity of the inner precursor plasma is substantially axial upon entering the reaction chamber.

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15. The plasma processing system of any one of claims 8 to 14, wherein a velocity magnitude difference between the outer velocity of the outer precursor plasma and the inner velocity of the inner precursor plasma ranges from about 50 km/s to about 200 km/s.

16. The plasma processing system of any one of claims 8 to 15, wherein, upon entering the reaction chamber: the inner precursor plasma has a cylindrical geometry centered about the Z-pinch axis; and the outer precursor plasma is coaxially arranged around the inner precursor plasma.

17. The plasma processing system of any one of claims 1 to 7, wherein: the inner precursor medium is an inner precursor gas; and the inner precursor supply unit comprises: an inner precursor gas source configured to store the inner precursor gas; and an inner precursor gas supply line configured to transport the inner precursor gas from the inner precursor gas source to the inner injector for injection of the inner precursor gas into the reaction chamber.

18. The plasma processing system of claim 17, wherein the inner precursor gas comprises deuterium, tritium, hydrogen, or helium, or any combination thereof.

19. The plasma processing system of any one of claims 1 to 7, wherein the inner precursor supply unit is configured to: start by supplying the inner precursor medium as an inner precursor gas; and switch to supplying the inner precursor medium as an inner precursor plasma.

20. The plasma processing system of claim 19, wherein a time duration between starting to supply the inner precursor medium as the inner precursor gas and switching to supplying the inner precursor medium as the inner precursor plasma ranges from about 0.5 millisecond to about 5 milliseconds.

21. The plasma processing system of any one of claims 1 to 20, wherein the inner precursor supply unit is configured to start supplying the inner precursor medium into the reaction chamber at the same time as the outer precursor supply is configured to supply the outer precursor plasma into the reaction chamber.

22. The plasma processing system of any one of claims 1 to 20, wherein the inner precursor supply unit is configured to start supplying the inner precursor medium into the reaction chamber before or after the outer precursor supply is configured to supply the outer precursor plasma into the reaction chamber.

23. The plasma processing system of any one of claims 1 to 22, wherein the precursor supply device is configured to start supplying the inner precursor medium and the outer precursor plasma into the reaction chamber before the main power supply is configured to start supplying power to the plasma confinement device.

24. The plasma processing system of any one of claims 1 to 22, wherein the precursor supply device is configured to start supplying the inner precursor medium and the outer precursor plasma into the reaction chamber at the same time as or after the main power supply is configured to start supplying power to the plasma confinement device.

25. The plasma processing system of any one of claims 1 to 24, wherein the precursor supply device is configured to continue supplying the inner precursor medium and the outer precursor plasma into the reaction chamber during a sustainment phase after formation of the Z-pinch plasma, the sustainment phase having a duration ranging from about 5 microseconds to about 10 milliseconds.

26. The plasma processing system of any one of claims 1 to 25, wherein the inner injector is disposed at one of the first end and the second end of the plasma confinement device, and wherein the outer injector is disposed at the same one of the first end and the second end of the plasma confinement device.

27. The plasma processing system of any one of claims 1 to 25, wherein the inner injector is disposed at one of the first end and the second end of the plasma confinement device, and wherein the outer injector is disposed at the other one of the first end and the second end of the plasma confinement device.

28. The plasma processing system of any one of claims 1 to 27, wherein the inner injector is a single inner injector.

29. The plasma processing system of any one of claims 1 to 28, wherein the outer injector comprises a plurality of outer injectors azimuthally distributed about the Z-pinch axis and around the inner injector.

30. The plasma processing system of claim 29, wherein a number of the outer injectors ranges from about two to about fifty.

31. The plasma processing system of any one of claims 1 to 30, wherein the precursor supply device further comprises an intermediate precursor supply unit comprising: an intermediate plasma generator configured to generate an intermediate precursor plasma; and an intermediate injector disposed radially between the inner injector and the outer injector with respect to the Z-pinch axis, the intermediate injector being configured to inject the intermediate precursor plasma into the reaction chamber at an intermediate velocity different from the outer velocity of the outer precursor plasma.

32. The plasma processing system of any one of claims 1 to 31, wherein the main power supply is a pulsed- DC power supply comprising a capacitor bank and a switch.

33. The plasma processing system of any one of claims 1 to 32, wherein the Z-pinch plasma is configured to undergo nuclear fusion reactions in response to compression of the Z-pinch plasma.

34. The plasma processing system of claim 33, wherein the nuclear fusion reactions comprise neutronic fusion reactions.

35. The plasma processing system of any one of claims 1 to 34, wherein the radially sheared axial flow is uniform.

36. The plasma processing system of any one of claims 1 to 34, wherein the radially sheared axial flow is nonuniform.

37. A plasma processing method comprising: providing a plasma confinement device comprising: a reaction chamber having a Z-pinch axis; a first compression electrode; and a second compression electrode longitudinally spaced apart from the first compression electrode along the Z-pinch axis; supplying, through an inner injector, an inner precursor medium into the reaction chamber; supplying, through an outer injector disposed radially outwardly of the inner injector with respect to the Z-pinch axis, an outer precursor plasma into the reaction chamber at an outer velocity; and supplying power to the plasma confinement device to apply a compression voltage between the first compression electrode and the second compression electrode configured to energize and compress the inner precursor medium and the outer precursor plasma into a Z-pinch plasma having a radially sheared axial flow along the Z-pinch axis.

38. The plasma processing method of claim 37, wherein supplying the outer precursor plasma into the reaction chamber comprises: generating the outer precursor plasma, comprising: supplying an outer process gas into a plasma formation region of an outer plasma generator; and supplying power to the outer plasma generator to apply a voltage across the plasma formation region of the outer plasma generator configured to energize the outer process gas into the outer precursor plasma; and flowing the outer precursor plasma from the plasma formation region to the outer injector for injection of the outer precursor plasma into the reaction chamber.

39. The plasma processing method of claim 38, wherein the outer plasma generator comprises: an inner electrode; and an outer electrode surrounding the inner electrode to define therebetween the plasma formation region.

40. The plasma processing method of claim 38 or 39, wherein the outer process gas comprises deuterium, tritium, hydrogen, or helium, or any combination thereof.

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41. The plasma processing method of any one of claims 37 to 40, wherein supplying the outer precursor plasma into the reaction chamber comprises controlling a magnitude of the outer velocity of the outer precursor plasma in a range from about 70 km/s to about 200 km/s.

42. The plasma processing method of any one of claims 37 to 41, wherein supplying the outer precursor plasma into the reaction chamber comprises controlling the outer velocity of the outer precursor plasma to be substantially axial upon entering the reaction chamber.

43. The plasma processing method of any one of claims 37 to 42, wherein supplying the inner precursor medium into the reaction chamber comprises supplying, as the inner precursor medium, an inner precursor plasma into the reaction chamber at an inner velocity different from the outer velocity of the outer precursor plasma.

44. The plasma processing method of claim 43, wherein supplying the inner precursor plasma into the reaction chamber comprises: generating the inner precursor plasma, comprising: supplying an inner process gas into a plasma formation region of an inner plasma generator; and supplying power to the inner plasma generator to apply a voltage across the plasma formation region of the inner plasma generator configured to energize the inner process gas into the inner precursor plasma; and flowing the inner precursor plasma from the plasma formation region to the inner injector for injection of the inner precursor plasma into the reaction chamber.

45. The plasma processing method of claim 44, wherein the inner plasma generator comprises: an inner electrode; and an outer electrode surrounding the inner electrode to define therebetween the plasma formation region.

46. The plasma processing method of claim 44 or 45, wherein the inner process gas comprises deuterium, tritium, hydrogen, or helium, or any combination thereof.

47. The plasma processing method of any one of claims 43 to 46, wherein supplying the inner precursor plasma into the reaction chamber comprises controlling a magnitude of the inner velocity of the inner precursor plasma in a range from about 0 km/s to about 60 km/s.

48. The plasma processing method of any one of claims 43 to 47, wherein supplying the inner precursor plasma into the reaction chamber comprises controlling the inner velocity of the inner precursor plasma to be substantially axial upon entering the reaction chamber.

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49. The plasma processing method of any one of claims 43 to 48, further comprising controlling a velocity magnitude difference between the outer velocity of the outer precursor plasma and the inner velocity of the inner precursor plasma in a range from about 50 km/s to about 200 km/s.

50. The plasma processing method of any one of claims 37 to 42, wherein supplying the inner precursor medium into the reaction chamber comprises supplying, as the inner precursor medium, an inner precursor gas into the reaction chamber.

51. The plasma processing method of claim 50, wherein the inner precursor gas comprises deuterium, tritium, hydrogen, or helium, or any combination thereof.

52. The plasma processing method of any one of claims 37 to 42, wherein supplying the inner precursor medium into the reaction chamber comprises: starting by supplying the inner precursor medium as an inner precursor gas during a first phase of operation; and switching to supplying the inner precursor medium as an inner precursor plasma during a second phase of operation of the plasma processing system.

53. The plasma processing method of claim 52, wherein a duration between starting to supply the inner precursor medium as the inner precursor gas and switching to supplying the inner precursor medium as the inner precursor plasma ranges from about 0.5 millisecond to about 5 milliseconds.

54. The plasma processing method of any one of claims 37 to 53, wherein the step of supplying the inner precursor medium into the reaction chamber and the step of supplying the outer precursor plasma into the reaction chamber are initiated at the same time.

55. The plasma processing method of any one of claims 37 to 53, wherein the step of supplying the inner precursor medium into the reaction chamber is initiated before or after the step of supplying the outer precursor plasma into the reaction chamber is initiated.

56. The plasma processing method of any one of claims 37 to 55, wherein the step of supplying the inner precursor medium and the outer precursor plasma into the reaction chamber is initiated before the step of supplying power to the plasma confinement device is initiated.

57. The plasma processing method of any one of claims 37 to 55, wherein the step of supplying the inner precursor medium and the outer precursor plasma into the reaction chamber is initiated at the same time as or after the step of supplying power to the plasma confinement device is initiated.

58. The plasma processing method of any one of claims 37 to 57, further comprising continuing to supply the inner precursor medium and the outer precursor plasma into the reaction chamber during a sustainment phase after formation of the Z-pinch plasma, the sustainment phase having a duration ranging from about 5 microseconds to about 10 milliseconds.

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59. The plasma processing method of any one of claims 37 to 58, wherein the inner injector is formed through one of the first compression electrode and the second compression electrode, and wherein the outer injector is formed through the same one of the first compression electrode and the second compression electrode.

60. The plasma processing method of any one of claims 37 to 58, wherein the inner injector is formed through one of the first compression electrode and the second compression electrode, and wherein the outer injector is formed through the other one of the first compression electrode and the second compression electrode.

61. The plasma processing method of any one of claims 37 to 60, wherein the inner injector is a single inner injector, and wherein the outer injector comprises a plurality of outer injectors azimuthally distributed about the Z-pinch axis and around the inner injector.

62. The plasma processing method of any one of claims 37 to 61, further comprising supplying, through an intermediate injector disposed radially between the inner injector and the outer injector with respect to the Z-pinch axis, an intermediate precursor plasma into the reaction chamber at an intermediate velocity different from the outer velocity of the outer precursor plasma.

63. The plasma processing method of any one of claims 37 to 62, further comprising generating nuclear fusion reactions inside the Z-pinch plasma in response to compression of the Z-pinch plasma.

64. The plasma processing method of claim 63, wherein the nuclear fusion reactions comprise neutronic fusion reactions.

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