BACKGROUND OF THE INVENTION

The present invention pertains to generation of very high density lithium deuteride (LiD) plasma, and more specifically pertains to generation of field reversed configuration (FRC) plasma with a density close to solid material density, using a flux compression generator (FCG).

Flux compression generators are described, for example, in Grace et al., U.S. Patent No. 9,658,026, the entire disclosure of which is incorporated herein by reference, which discloses a flux compression generator in the form of a high-energy, explosively-driven electromagnetic pulse generator that can generate tens of mega-ampere and mega-gauss magnetic field to a small inductance and resistance load. Another flux compression generator is described in Kim et al., Patent Cooperation Treaty Published Application WO 2021/006938, the entire disclosure of which is incorporated herein by reference, which discloses a primary flux compression generator seeded by an auxiliary flux compression generator.

Kim et al., U.S. Patent No. 11,217,969, the entire disclosure of which is incorporated herein by reference, discloses a plasma generator that uses a high-intensity current pulse generated by a flux compression generator to generate an electrical explosion of a solid lithium load to convert the electrically conductive, ionizable lithium material into a plasma. The plasma is initially confined by a strong azimuthal magnetic field.

Examples of systems designed to generate fusion reaction conditions from FRC plasmas include Degnan et al., “Full Axial Coverage Radiography of Deformable Contact Finer Implosion Performed with 8 cm Diameter Electrode Apertures,” Pulsed Power Conference, IEEE, 2005, hereby incorporated herein by reference, which describes how an FRC plasma injected into a metal shell or liner is compressed through cylindrical liner implosion to raise the temperature to a possible fusion temperature for fusion reaction, and Intrator et al., “A High-

Density Field Reversed Configuration Plasma for Magnetized Target Fusion,” IEEE Transactions on Plasma Science, volume 32, number 1, February, 2004, hereby incorporated herein by reference, which describes use of a capacitor bank to implode a liner to compress an FRC plasma injected from a plasma injector.

SUMMARY OF THE INVENTION

The invention provides a system and method for generation of a high-density lithium deuteride plasma. The system includes a high-intensity current pulse generator, a lithium deuteride fuel load, an internal electrically conductive coil embedded within the lithium deuteride fuel load, and at least two auxiliary electrically conductive coils positioned around the lithium deuteride fuel load. The internal and auxiliary coils are connected to the high-intensity current pulse generator to receive currents from the high-intensity current pulse generator that flow through the internal coil in a direction opposite to a direction of flow through the auxiliary coils so as to generate a self-organized field reversed configuration plasma from the lithium deuteride fuel load.

FRC plasma generated according to the invention can be useful in very small amounts for various research purposes. For example, the FRC plasma can be used experimentally in implosion schemes for nuclear fusion for purposes such as reactors for energy production or engines for rocket propulsion, because the FRC plasma is relatively stable against magnetohydrodynamic instability even with a slow implosion mechanism. The implosion time can be orders of magnitude longer than the current inertial confinement fusion compression time scale of tens of nanoseconds. Furthermore, the high fuel density that can be generated according to the invention can enable a high energy yield.

In certain embodiments of the invention, the high-intensity current pulse generator can be a flux compression generator. The internal electrically conductive coil can be made of lithium, and can be thinner than and have a lower melting temperature than the auxiliary electrically conductive coils. The lithium deuteride fuel load can be a solid sphere at room temperature having a size of about one cubic centimeter, and can be encapsulated within a foam such as Styrofoam, polyurethane, or polystyrene (CH). The encapsulating foam is constructed of a material that does not melt, in microsecond time scale, while the fusion fuel load is at a thermonuclear temperature. The self-organized field reversed configuration plasma is generated by phase transition of the lithium deuteride fuel load as a solid at room temperature to an ionized plasma at low temperature. The internal electrically conductive coil undergoes an explosive phase transition to an electrically exploded plasma, while the auxiliary electrically conductive coils remain intact. Following phase transition of the internal electrically conductive coil from solid to an electrically exploded plasma, current applied to the electrically conductive plasma continues to heat and ionize the lithium deuteride fuel load to form the self-organized field reversed configuration plasma. The self-organized field reversed configuration plasma has a high density close to a density of the lithium deuteride fuel load from which it is formed.

Another aspect of the invention features a contained implosion system and method for imploding an expanding lithium deuteride plasma so as to initiate nuclear fusion. The contained implosion system includes a shell of hard material having low thermal conductivity, constructed so as to contain a fusion explosion therewithin. A plasma generation system according to the first aspect of the invention is positioned within the shell. An implosion mechanism, at least part of which is positioned around the lithium deuteride fuel load, is configured to implode an expanding lithium deuteride plasma produced by the plasma generation system so as to raise temperature of the plasma to thermonuclear burning temperature to initiate nuclear fusion.

In certain embodiments of the invention, the implosion mechanism raises the temperature of the lithium deuteride plasma to a thermonuclear fusion reaction temperature by adiabatic compressional heating or shock heating. Self-heating by high-energy particles created during an initial stage of the nuclear fusion can serve in turn as a heating mechanism of the lithium deuteride plasma. The shell of hard material can be made of graphite or carbon nanotube material, and it covers the inside of a burning chamber. The chamber can include a at least one loading door that can be opened for insertion of the plasma generation system into the shell and then closed, and at least one debris removal door that can be opened to permit removal of particles remaining after the nuclear fusion.

Another aspect of the invention features a nuclear fusion electrical power generation plant, and method of use thereof. The electrical power generation plant includes the contained implosion system, at least one turbine; and at least one passageway leading from the shell to the turbine, which can be turned by expelled energy from the nuclear fusion that passes through the at least one passageway to the at least one turbine, for the purpose of power generation.

These and other objects, features, and advantages of the invention will be apparent from the following detailed description taken in connection with the accompanying drawings.

DESCRIPTION THE DRAWINGS

Figs, la and lb are cross-sectional and perspective drawings, respectively, of an FRC plasma generation system according to the invention. Fig. 2 is a drawing of the FRC plasma generation system of Fig. 1, after phase transition of the lithium coil thereof to an electrically exploded plasma.

Fig. 3 is a drawing of the FRC plasma generation system of Fig. 2, after phase transition of the lithium deuteride fusion fuel thereof to a self-organized FRC plasma.

Fig. 4 is a schematic cross-sectional drawing of a nuclear fusion reactor chamber into which the FRC plasma generation system of Fig. 1 has been inserted.

DETAILED DESCRIPTION

Figs, la and lb illustrate a compact FRC plasma generation system 10 that produces plasma from a solid lithium deuteride ( ⁶ LiD) nuclear fusion fuel 12. Plasma generation system 10 includes a lithium coil 16 encapsulated within the solid lithium deuteride 12, and two external auxiliary coils 18 made of a conductive material other than lithium, internal coil 16 and external coils 18 being connectable to a high-intensity current pulse generator, such as a flux compression generator that injects very high current to the internal and external coils. Fig. 1 A shows the internal lithium coil 16 with reversed current to the current in the two external auxiliary coils 18, and Fig. IB shows the coil connections that are connectable to a flux compression generator that will inject high current to the coils.

Fuel load 12 can be one mole (about 9 grams) of lithium deuteride fuel, in a solid sphere at room temperature, having a size of about 1 cubic centimeter. In some embodiments fuel load 12 can have a diameter of about 1.7 centimeters.

Lithium coil 16 is embedded in lithium deuteride sphere 12, constructed by forming sphere 12 around lithium coil 16. Then, auxiliary coils 18 are added around sphere 12. Auxiliary coils 18 (Helmholtz coils) are external loop coils arranged in a way to generate a low- temperature FRC plasma from solid lithium deuteride fuel 12, when high currents from the flux compression generator are applied to internal lithium coil 16 through internal coil feeds 20 and to external loop coils 18 through external coil feeds 21, creating an intense magnetic field.

Two external auxiliary coils 18 are sufficient to position the FRC fuel in the center of the two coils. It is alternatively possible to have four, six, or eight external coils, to fine tune the magnetic field topology.

The direction of current in internal lithium coil 16 is opposite to that in external coils 18 (clockwise versus counterclockwise, or vice versa), such that internal coil 16 undergoes an explosive phase transition to an electrically exploded plasma, while external coils 18 remain intact at this stage, as illustrated in Fig. 2, due to internal lithium coil being thinner and having a lower melting temperature than external coils 18. Fig. 2 represents the state of the plasma generation system of Figs. 1A and IB at about 55 microseconds after current from the flux compression generator is applied to internal coil 16 and external coils 18, after phase transition of the internal lithium coil thereof to an electrically exploded plasma. Fig. 2 illustrates formation of LiD plasma after explosion of the internal lithium coil in the center. Note the magnetic field reversal illustrated in Fig. 2. Following phase transition of the lithium coil 16 from solid to electrically exploded plasma, current applied to the internal lithium plasma continues to heat and ionize the lithium deuteride fusion fuel 12 to form the self-organized FRC plasma 22, as illustrated in Fig. 3, with a low plasma temperature of a few electron volts and a high density close to the solid lithium deuteride density.

FRC plasma 22 can now be compressed by an implosion mechanism, such as pneumatic implosion with liquid compression, or electrical liner implosion through use of a capacitor bank to collapse a cylindrical or spherical liner, or laser implosion of the fuel through use of a laser beam impinging on the fuel, or magnetized liner inertial confinement fusion through use of a combination of laser heating and compression of a liner Such implosion mechanisms are designed to raise the temperature of the lithium deuteride plasma to a thermonuclear fusion reaction temperature by adiabatic compressional heating and shock heating depending on the implosion mechanism applied. Self-heating by the high energy particles created during the initial stage of fusion reaction is also a heating mechanism of the bulk fusion fuel. Energy output will be dependent on speed of implosion and amount of fuel.

Fig. 4 illustrates a nuclear fusion reactor chamber 24 of an electrical power plant, which chamber includes a thick spherical shell 26 of very hard material having low thermal conductivity, such as graphite or carbon nanotube material, the thick spherical shell being constructed with good blast tolerance so as to contain a fusion explosion therewithin, and with radiation absorbing material if any radiative output is involved in the process. Shell 26 may include lead blanket, or recirculating liquid lithium blanket if there is radiative neutron output.

The solid lithium deuteride (LiD) 12 of the plasma generation system is encapsulated within a foam 28, such as Styrofoam, polyurethane, or polystyrene (CH) as is described for example in Hu, Suxing et al., “A Review on Ab Initio Studies of Static, Transport, and Optical Properties of Polystyrene Under Extreme Conditions for Inertial Confinement Fusion Applications,” Physics of Plasmas, May 2018, hereby incorporated herein by reference. Alternatively, the solid lithium deuteride can be encapsulated within a multi-layer structure having a conductive outer surface, which conductive outer surface assists in confining the plasma formed from the solid lithium deuteride. Foam ball 28 forms a spherical shell shape surrounding fuel load 12 and inside coils 16. A foam block 46 fills up the remainder of the space within cylindrical liner 32. Foam ball 28 and foam block 46 can be made of a material of the type presently used in connection with inertial confinement fusion fuel, or a multilayered structure of conducting and insulating layers to take advantage of magnetic compression during implosion. Foam ball 28 and foam block 46 should not melt, in microsecond time scale, during implosion while the fuel center temperature reaches thermonuclear temperature (100 - 1000 million degrees Celsius). After fusion is initialed, foam ball 28 and foam block 46 will be destroyed or vaporized.

Flux compression generator 14 can be, for example, a high-energy, explosively- driven electromagnetic pulse generator of the type described in Grace et al., U.S. Patent No. 9,658,026, or a primary flux compression generator seeded by an auxiliary flux compression generator of the type described in Kim et al., Patent Cooperation Treaty Published Application WO 2021/006938. Flux compression generator 14 is connected both to internal coil 16 and external coils 18 of plasma generation system 10.

An implosion system is provided such as a liner implosion system 30, having a cylindrical liner 32 and annular magnets 34. Liner implosion system 30 causes a cylindrical liner 32 to compress the plasma, as is described, for example, in Siemon, RE., et al., “Measurements of Solid Liner Implosion for Magnetized Target Fusion,” International Atomic Energy Agency, 2001, hereby incorporated herein by reference, and in Intrator, T.P. et al., “A High-Density Field Reversed Configuration Plasma for Magnetized Target Fusion,” IEEE Transactions on Plasma Science, volume 32, number 1, February, 2004, hereby incorporated herein by reference. Liner implosion system 30 is connected to capacitor banks 36, located outside of spherical shell 26, which capacitor banks feed high current to liner implosion system 30 to cause liner 32 to implode to compress the FRC plasma. Liner 32 can be a conductive material such as copper or copper-tungsten. In operation of nuclear fusion reactor chamber 24, an assembly that includes flux compression generator 14, internal coil 16, external coils 18, solid lithium deuteride 12, foam 28, and liner implosion system 30 including liner 32, is inserted into chamber 24, as often as every two minutes through loading doors 42 that can be opened for insertion of the assembly into chamber 24 and then closed. Flux compression generator 14 is activated to cause generation of lithium deuteride plasma, and current from capacitor banks 36 is applied to liner implosion system 30 to cause implosion of liner 32 onto the plasma to compress the plasma, thereby creating a fusion explosion within chamber 24 that consumes the contents of chamber 24 and that expels energy that passes through lengthy passageways 38 leading to turbines 40 that are turned by the expelled energy for the purpose of power generation. Debris removal doors 44 at the bottom of chamber 24 can be opened to permit removal of any remaining particles that collect on the floor of chamber 24 after each explosion to avoid redistribution of the remaining particles during subsequent operations and potential injection of the particles into turbines 40.

In certain embodiments, a star configuration of capacitor banks (Shiva star) can be employed outside of chamber 24 to create a current as high as 10 mega amps to be applied to liner implosion system 30. Examples of Shiva star configurations of capacitor banks are described in Reinovsky, R.E. et al., “Shiva Star Inductive Pulse Compression System,” Proc. Of 4 ^th IEEE Pulsed Power Conf, June 1, 1983, hereby incorporated herein by reference, and Degnan, J.H. et al., “Experimental and Computational Progress on Liner Implosions for Compression of FRC’s,” IEEE Transactions on Plasma Science 36(1 ): 80-91 , March 2008, hereby incorporated herein by reference.

Due to the stability of the FRC during relatively slow implosion (microsecond time scale), implosion mechanisms such as the above-described mechanical implosion or Shiva-star electrical implosion can be employed, and it is not necessary to employ nanosecond-timescale implosion schemes used in connection with inertial confinement fusion.

It is evident that those skilled in the art may now make numerous other uses and modifications of and departures from the specific embodiments described herein without departing from the inventive concepts. Consequently, the invention is to be construed as embracing each and every novel feature and novel combination of features present in, or possessed by, the apparatus and techniques herein disclosed and limited solely by the scope and spirit of the appended claims.