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99-399: FRCs are closely related to another self-stable magnetic confinement fusion device, the spheromak . Both are considered part of the compact toroid class of fusion devices. FRCs normally have a plasma that is more elongated than spheromaks, having the overall shape of a hollowed out sausage rather than the roughly spherical spheromak. FRCs were a major area of research in the 1960s and into

198-666: A gain factor of Q = 0.62 and 4 megawatts steady state fusion power with Q = 0.18 for 4 seconds. In 2021, JET sustained Q = 0.33 for 5 seconds and produced 59 megajoules of energy, beating the record 21.7 megajoules released in 1997 over around 4 seconds. One of the challenges of MCF research is the development and extrapolation of plasma scenarios to power plant conditions, where good fusion performance and energy confinement must be maintained. Potential solutions to other problems such as divertor power exhaust, mitigation of transients (disruptions, runaway electrons , edge-localized modes ), handling of neutron flux , tritium breeding and

297-459: A high beta . The high beta makes the FRC attractive as a fusion reactor and well-suited to aneutronic fuels because of the low required magnetic field. Spheromaks have β  ≈ 0.1 whereas a typical FRC has β  ≈ 1. In modern FRC experiments, the plasma current that reverses the magnetic field can be induced in a variety of ways. When a field-reversed configuration is formed using

396-413: A neutron , where the energy is released in the form of the kinetic energy of the reaction products. In order to overcome the electrostatic repulsion between the nuclei, the fuel must have a temperature of hundreds of millions of degrees, at which the fuel is fully ionized and becomes a plasma . In addition, the plasma must be at a sufficient density, and the energy must remain in the reacting region for

495-459: A "magnetic null," or circular line on which the magnetic field is zero. This is necessarily the case, as inside the null the magnetic field points one direction and outside the null the magnetic field points the opposite direction. Particles far from the null trace closed cyclotron orbits as in other magnetic fusion geometries. Particles which cross the null, however, trace not cyclotron or circular orbits but betatron or figure-eight-like orbits, as

594-431: A "patented high-efficiency closed-fuel cycle". Although the deuterium reactions (deuterium + He and deuterium + lithium) do not in themselves release neutrons, in a fusion reactor the plasma would also produce D–D side reactions that result in reaction product of He plus a neutron. Although neutron production can be minimized by running a plasma reaction hot and deuterium-lean, the fraction of energy released as neutrons

693-567: A $ 46 million grant for eight companies across seven states to advance fusion power plant designs and research, aiming to establish the U.S. as a leader in clean fusion energy. The funding from the Milestone-Based Fusion Development Program supports the goal to demonstrate pilot-scale fusion within ten years and achieve a net-zero economy by 2050. The grant recipients will tackle scientific and technological hurdles to create viable fusion pilot plant designs in

792-609: A 1.5 nanosecond laser pulse. In 2016, a team at the Shanghai Chinese Academy of Sciences produced a laser pulse of 5.3 petawatts with the Superintense Ultrafast Laser Facility (SULF) and expected to reach 10 petawatts with the same equipment. In 2021, TAE Technologies field-reversed configuration announced that its Norman device was regularly producing a stable plasma at temperatures over 50 million degrees. In 2021,

891-501: A 10-terawatt laser produced hydrogen–boron aneutronic fusions for a Russian team in 2005. However, the number of the resulting α particles (around 10 per laser pulse) was low. In 2006, the Z-machine at Sandia National Laboratory , a z-pinch device, reached 2 billion kelvins and 300 keV. In 2011, Lawrenceville Plasma Physics published initial results and outlined a theory and experimental program for aneutronic fusion with

990-470: A Russian team reported experimental results in a miniature device with electrodynamic (oscillatory) plasma confinement . It used a ~1–2 J nanosecond vacuum discharge with a virtual cathode. Its field accelerates boron ions and protons to ~ 100–300 keV under oscillating ions' collisions. α-particles of about 5 × 10 /4π (~ 10 α-particles/ns) were obtained during the 4 μs of applied voltage. Australian spin-off company HB11 Energy

1089-481: A US team stated they were not seeing this issue, the Soviets examined their experiment and noted this was due to a simple instrumentation error. The Soviet team also introduced a potential solution, in the form of "Ioffe bars". These bent the plasma into a new shape that was concave at all points, avoiding the problem Teller had pointed out. This demonstrated a clear improvement in confinement. A UK team then introduced

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1188-464: A background plasma. Neutral particles are then injected into the plasma. They ionize and the heavier, positively-charged particles form a current ring which reverses the magnetic field. Spheromaks are FRC-like configurations with finite toroidal magnetic field. FRCs have been formed through the merging of spheromaks of opposite and canceling toroidal field. Rotating magnetic fields have also been used to drive current. In such experiments, as above, gas

1287-445: A clean, cost-competitive, and sustainable fuel cycle for fusion power. The results suggest that a hydrogen-boron fuel mix has the potential to be used in utility-scale fusion power. TAE Technologies is focused on developing a fusion power plant by the mid-2030s that will produce clean electricity. The private U.S. nuclear fusion company Helion Energy has signed a deal with Microsoft to provide electricity in about five years, marking

1386-455: A crucial role in regulating plasma purity and density. Wendelstein 7-X allows the investigation into plasma turbulence and the effectiveness of magnetic confinement and thermal insulation. The device's microwave heating system has also been improved to achieve higher energy throughput and plasma density. These advancements aim to demonstrate the suitability of stellarators for continuous fusion power generation. TAE Technologies achieved 2022

1485-582: A dead end. In the 1970s, a solution was developed. By placing a baseball coil at either end of a large solenoid, the entire assembly could hold a much larger volume of plasma, and thus produce more energy. Plans began to build a large device of this "tandem mirror" design, which became the Mirror Fusion Test Facility (MFTF). Having never tried this layout before, a smaller machine, the Tandem Mirror Experiment (TMX)

1584-565: A dead end. In addition to the fuel loss problems, it was also calculated that a power-producing machine based on this system would be enormous, the better part of a thousand feet (300 meters) long. When the tokamak was introduced in 1968, interest in the stellarator vanished, and the latest design at Princeton University , the Model C, was eventually converted to the Symmetrical Tokamak . Stellarators have seen renewed interest since

1683-402: A field that extended only part way into the plasma, which proved to have the significant advantage of adding "shear", which suppressed turbulence in the plasma. However, as larger devices were built on this model, it was seen that plasma was escaping from the system much more rapidly than expected, much more rapidly than could be replaced. By the mid-1960s it appeared the stellarator approach was

1782-449: A figure-8. This has the effect of propagating the nuclei from the inside to outside as it orbits the device, thereby cancelling out the drift across the axis, at least if the nuclei orbit fast enough. Not long after the construction of the earliest figure-8 machines, it was noticed the same effect could be achieved in a completely circular arrangement by adding a second set of helically wound magnets on either side. This arrangement generated

1881-557: A fusion reactor and convert this into voltage to drive current. Post helped develop the theoretical underpinnings of direct conversion, later demonstrated by Barr and Moir. They demonstrated a 48 percent energy capture efficiency on the Tandem Mirror Experiment in 1981. Polywell fusion was pioneered by the late Robert W. Bussard in 1995 and funded by the US Navy . Polywell uses inertial electrostatic confinement . He founded EMC2 to continue polywell research. A picosecond pulse of

1980-441: A measure of control over plasma turbulence and resultant energy leakage, long considered an unavoidable and intractable feature of plasmas. There is increased optimism that the plasma pressure above which the plasma disassembles can now be made large enough to sustain a fusion reaction rate acceptable for a power plant. Electromagnetic waves can be injected and steered to manipulate the paths of plasma particles and then to produce

2079-502: A more practical material. HTS will enable reactor magnets to produce greater magnetic field and proportionally increase the transport processes necessary to generate energy. One of the largest material considerations is ensuring the inner wall will be able to handle the intense amounts of heat that will be generated (expected to approach 10 GW per square meter in heat flux from the plasma). Not only does this material need to survive, but it needs to withstand damage enough to avoid contaminating

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2178-460: A nucleus, less true when addressing Coulomb energy, and does not speak to proton/neutron balance at all. Once reactants have gone past the Coulomb barrier, they're into a world dominated by a force that does not behave like electromagnetism. In most fusion concepts, the energy needed to overcome the Coulomb barrier is provided by collisions with other fuel ions. In a thermalized fluid like a plasma,

2277-432: A pair of reacting, charged particles depends both on total charge and on how equally those charges are distributed; the barrier is lowest when a low- Z particle reacts with a high- Z one and highest when the reactants are of roughly equal charge. Barrier energy is thus minimized for those ions with the fewest protons . Once the nuclear potential wells of the two reacting particles are within two proton radii of each other,

2376-428: A propellant to high levels of specific impulse (I sp ) for electrically powered spaceships and fusion rockets , with interest expressed by NASA . Producing fusion power by confining the plasma with magnetic fields is most effective if the field lines do not penetrate solid surfaces but close on themselves into circles or toroidal surfaces. The mainline confinement concepts of tokamak and stellarator do this in

2475-506: A significant research milestone by conducting the first-ever hydrogen-boron fusion experiments in a magnetically confined fusion plasma. The experiments were conducted in collaboration with Japan's National Institute for Fusion Science using a boron powder injection system developed by scientists and engineers of the Princeton Plasma Physics Laboratory . TAE's pursuit of hydrogen-boron fusion aims to develop

2574-463: A simpler arrangement of these magnets they called the "tennis ball", which was taken up in the US as the "baseball". Several baseball series machines were tested and showed much-improved performance. However, theoretical calculations showed that the maximum amount of energy they could produce would be about the same as the energy needed to run the magnets. As a power-producing machine, the mirror appeared to be

2673-445: A solid boron target, "protected" by its electrons, which reduced the fusion rate. Experiments suggest that a petawatt-scale laser pulse could launch an 'avalanche' fusion reaction, although this remains controversial. The plasma lasts about one nanosecond , requiring the picosecond pulse of protons to be precisely synchronized. Unlike conventional methods, this approach does not require a magnetically confined plasma. The proton beam

2772-434: A spheromak has an extra toroidal field. This toroidal field can run along the same or opposite direction as the spinning plasma. In the spheromak the strength of the toroidal magnetic field is similar to that of the poloidal field . By contrast, the FRC has little to no toroidal field component and is confined solely by a poloidal field. The lack of a toroidal field means that the FRC has no magnetic helicity and that it has

2871-558: A sufficient time, as specified by the Lawson criterion (triple product). The high temperature of a fusion plasma precludes the use of material vessels for direct containment. Magnetic confinement fusion attempts to use the physics of charged particle motion to contain the plasma particles by applying strong magnetic fields. Tokamaks and stellarators are the two leading MCF device candidates as of today. Investigation of using various magnetic configurations to confine fusion plasma began in

2970-399: A target. The resulting nanosecond and picosecond two-pulse laser system provides next-generation input. The approach uses pulsed power (shots). Fuel pellets burn at a rate of about 1 per second. The energy released drives a conventional steam cycle generator. Laser power has been increasing at about 10 x/decade amid falling costs. Advancements include: Aneutronic fusion produces energy in

3069-424: A theoretical problem that suggested the plasma would also quickly escape sideways through the confinement fields. This would occur in any machine with convex magnetic fields, which existed in the centre of the mirror area. Existing machines were having other problems and it was not obvious whether this was occurring. In 1961, a Soviet team conclusively demonstrated this flute instability was indeed occurring, and when

Field-reversed configuration - Misplaced Pages Continue

3168-463: A toroidal chamber, which allows a great deal of control over the magnetic configuration, but requires a very complex construction. The field-reversed configuration offers an alternative in that the field lines are closed, providing good confinement, but the chamber is cylindrical, allowing simpler, easier construction and maintenance. Field-reversed configurations and spheromaks are together known as compact toroids . Spheromaks and FRC differ in that

3267-453: Is difficult to lower the neutron production by a significant fraction. A clever magnetic confinement scheme could in principle suppress the first reaction by extracting the alphas as they are created, but then their energy would not be available to keep the plasma hot. The second reaction could in principle be suppressed relative to the desired fusion by removing the high energy tail of the ion distribution, but this would probably be prohibited by

3366-406: Is ionized and an axial magnetic field is produced. A rotating magnetic field is produced by external magnetic coils perpendicular to the axis of the machine, and the direction of this field is rotated about the axis. When the rotation frequency is between the ion and electron gyro-frequencies, the electrons in the plasma co-rotate with the magnetic field (are "dragged"), producing current and reversing

3465-442: Is not described by classical magnetohydrodynamics , hence there are no Alfvén waves and almost no MHD instabilities despite their theoretical prediction, and it avoids the typical "anomalous transport", i.e. processes in which excess loss of particles or energy occurs. As of 2000, several remaining instabilities are being studied: Field-reversed configuration devices have been considered for spacecraft propulsion. By angling

3564-460: Is preceded by an electron beam, generated by the same laser, that strips electrons in the boron plasma, increasing the protons' chance to collide with the boron nuclei and fuse. Calculations show that at least 0.1% of the reactions in a thermal p– B plasma produce neutrons, although their energy accounts for less than 0.2% of the total energy released. These neutrons come primarily from the reaction: The reaction itself produces only 157 keV, but

3663-507: Is probably several percent, so that these fuel cycles, although neutron-poor, do not meet the 1% threshold. See He . The D– He reaction also suffers from the He fuel availability problem, as discussed above. Fusion reactions involving lithium are well studied due to the use of lithium for breeding tritium in thermonuclear weapons . They are intermediate in ignition difficulty between the reactions involving lower atomic-number species, H and He, and

3762-482: Is raised further, compressing and heating the plasma and providing a vacuum field between the plasma and the wall. Neutral beams are known to drive current in Tokamaks by directly injecting charged particles. FRCs can also be formed, sustained, and heated by application of neutral beams. In such experiments, as above, a cylindrical coil produces a uniform axial magnetic field and gas is introduced and ionized, creating

3861-404: Is simpler to convert the energy of charged particles into electrical power than it is to convert energy from uncharged particles, an aneutronic reaction would be attractive for power systems. Some proponents see a potential for dramatic cost reductions by converting energy directly to electricity, as well as in eliminating the radiation from neutrons, which are difficult to shield against. However,

3960-405: The B reaction. The p– Li reaction, although highly energetic, releases neutrons because of the high cross section for the alternate neutron-producing reaction p + Li → Be + n Many studies of aneutronic fusion concentrate on the p– B reaction, which uses easily available fuel. The fusion of the boron nucleus with a proton produces energetic alpha particles (helium nuclei). Since igniting

4059-600: The Larmor formula and comes in the X-ray, UV, visible, and IR spectra. Some of the energy radiated as X-rays may be converted directly to electricity. Because of the photoelectric effect , X-rays passing through an array of conducting foils transfer some of their energy to electrons, which can then be captured electrostatically. Since X-rays can go through far greater material thickness than electrons, hundreds or thousands of layers are needed to absorb them. Many challenges confront

Field-reversed configuration - Misplaced Pages Continue

4158-527: The MIT Plasma Science and Fusion Center in collaboration with Commonwealth Fusion Systems with the goal of producing a practical reactor design in the near future. In late 2020, a special issue of the Journal of Plasma Physics was published including seven studies speaking to a high level of confidence in the efficacy of the reactor design focusing on using simulations to validate predictions for

4257-560: The Max Planck Institute for Plasma Physics in Germany has finished its first plasma campaigns and underwent upgrades, including the installation of over 8,000 graphite wall tiles and ten divertor modules to protect the vessel walls and enable longer plasma discharges. The experiments will test the optimized concept of Wendelstein 7-X as a stellarator fusion device for potential use in a power plant. The island divertor plays

4356-499: The dense plasma focus (DPF). The effort was initially funded by NASA's Jet Propulsion Laboratory . Support for other DPF aneutronic fusion investigations came from the Air Force Research Laboratory . A French research team fused protons and boron-11 nuclei using a laser-accelerated proton beam and high-intensity laser pulse. In October 2013 they reported an estimated 80 million fusion reactions during

4455-535: The energy released is carried by neutrons . While the lowest-threshold nuclear fusion reactions release up to 80% of their energy in the form of neutrons , aneutronic reactions release energy in the form of charged particles , typically protons or alpha particles . Successful aneutronic fusion would greatly reduce problems associated with neutron radiation such as damaging ionizing radiation , neutron activation , reactor maintenance, and requirements for biological shielding, remote handling and safety. Since it

4554-480: The neutrons being seen were created by new instabilities in the plasma mass. Further studies showed any such design would be beset with similar problems, and research using the z-pinch approach largely ended. An early attempt to build a magnetic confinement system was the stellarator , introduced by Lyman Spitzer in 1951. Essentially the stellarator consists of a torus that has been cut in half and then attached back together with straight "crossover" sections to form

4653-451: The pinch effect in a toroidal container. A large transformer wrapping the container was used to induce a current in the plasma inside. This current creates a magnetic field that squeezes the plasma into a thin ring, thus "pinching" it. The combination of Joule heating by the current and adiabatic heating as it pinches raises the temperature of the plasma to the required range in the tens of millions of degrees Kelvin. First built in

4752-494: The temperature corresponds to an energy spectrum according to the Maxwell–Boltzmann distribution . Gases in this state have some particles with high energy even if the average energy is much lower. Fusion devices rely on this distribution; even at bulk temperatures far below the Coulomb barrier energy, the energy released by the reactions is great enough that capturing some of that can supply sufficient high-energy ions to keep

4851-409: The theta-pinch (or inductive electric field) method, a cylindrical coil first produces an axial magnetic field. Then the gas is pre-ionized, which "freezes in" the bias field from a magnetohydrodynamic standpoint, finally the axial field is reversed, hence "field-reversed configuration." At the ends, reconnection of the bias field and the main field occurs, producing closed field lines. The main field

4950-455: The 1950s were overshadowed by the initial success of tokamaks, interests in stellarators re-emerged attributing to their inherent capability for steady-state and disruption-free operation distinct from tokamaks. The world's largest stellarator experiment, Wendelstein 7-X , began operation in 2015. The current record of fusion power generated by MCF devices is held by JET . In 1997, JET set the record of 16 megawatts of transient fusion power with

5049-588: The 1950s. Early simple mirror and toroidal machines showed disappointing results of low confinement. After the declassification of fusion research by the United States , United Kingdom and Soviet Union in 1958, a breakthrough on toroidal devices was reported by the Kurchatov Institute in 1968, where its tokamak demonstrated a temperature of 1 kilo-electronvolts (around 11.6 million degree Kelvin) and some milliseconds of confinement time, and

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5148-535: The 1970s was Trisops . (Trisops fired two theta-pinch rings towards each other.) Some more novel configurations produced in toroidal machines are the reversed field pinch and the Levitated Dipole Experiment . The US Navy has also claimed a "Plasma Compression Fusion Device" capable of TW power levels in a 2018 US patent filing: "It is a feature of the present invention to provide a plasma compression fusion device that can produce power in

5247-403: The 1970s, but had problems scaling up into practical fusion triple products (target combinations of density, temperature and confinement time). Interest returned in the 1990s and as of 2019, FRCs were an active research area. The FRC was first observed in laboratories in the late 1950s during theta pinch experiments with a reversed background magnetic field. The original idea was attributed to

5346-636: The Greek scientist and engineer Nicholas C. Christofilos who developed the concept of E-layers for the Astron fusion reactor. The first studies were at the United States Naval Research Laboratory (NRL) in the 1960s. Considerable data were collected, with over 600 published papers. Almost all research was conducted during Project Sherwood at Los Alamos National Laboratory (LANL) from 1975 to 1990, and during 18 years at

5445-769: The Redmond Plasma Physics Laboratory of the University of Washington , with the large s experiment (LSX). Later research was at the Air Force Research Laboratory (AFRL), the Fusion Technology Institute (FTI) of the University of Wisconsin-Madison , Princeton Plasma Physics Laboratory , and the University of California, Irvine . Private companies now study FRCs for electricity generation, including General Fusion , TAE Technologies , and Helion Energy . The Electrodeless Lorentz Force Thruster (ELF) developed by MSNW

5544-461: The UK in 1948, and followed by a series of increasingly large and powerful machines in the UK and US, all early machines proved subject to powerful instabilities in the plasma. Notable among them was the kink instability , which caused the pinched ring to thrash about and hit the walls of the container long before it reached the required temperatures. The concept was so simple, however, that herculean effort

5643-521: The area is receiving considerable experimental attention. However, spherical tokamaks to date have been at low toroidal field and as such are impractical for fusion neutron devices. Compact toroids, e.g. the spheromak and the Field-Reversed Configuration , attempt to combine the good confinement of closed magnetic surfaces configurations with the simplicity of machines without a central core. An early experiment of this type in

5742-429: The chamber more rapidly than around the chamber's length. This would require the pinch current to be reduced and the external stabilizing magnets to be made much stronger. In 1968 Russian research on the toroidal tokamak was first presented in public, with results that far outstripped existing efforts from any competing design, magnetic or not. Since then the majority of effort in magnetic confinement has been based on

5841-428: The conditions required to harness aneutronic fusion are much more extreme than those required for deuterium–tritium (D–T) fusion such as at ITER . The first experiments in the field started in 1939, and serious efforts have been continual since the early 1950s. An early supporter was Richard F. Post at Lawrence Livermore . He proposed to capture the kinetic energy of charged particles as they were exhausted from

5940-558: The core plasma. Challenges such as this are being actively considered and accounted for in the models and predictive calculations used in the design process. Progress has been made in addressing the challenge of core-edge integration in future fusion reactors at the DIII-D National Fusion Facility. For a burning fusion plasma, it is crucial to maintain a plasma core hotter than the Sun's surface without damaging

6039-601: The energy demand of the United States, 15 to 20 tonnes per year given a more realistic end-to-end conversion efficiency. Extracting that amount of pure He would entail processing 2 billion tonnes of lunar material per year, even assuming a recovery rate of 100%. In 2022, Helion Energy claimed that their 7th fusion prototype (Polaris; fully funded and under construction as of September 2022) will demonstrate "net electricity from fusion", and will demonstrate "helium-3 production through deuterium–deuterium fusion" by means of

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6138-505: The first purpose-built spherical tokamak . This was essentially a spheromak with an inserted central rod. START produced impressive results, with β values at approximately 40% - three times that produced by standard tokamaks at the time. The concept has been scaled up to higher plasma currents and larger sizes, with the experiments NSTX (US), MAST (UK) and Globus-M (Russia) currently running. Spherical tokamaks have improved stability properties compared to conventional tokamaks and as such

6237-500: The first such agreement for fusion power. Helion's plant, expected to be online by 2028, aims to generate 50 megawatts or more of power. The company plans to use helium-3 , a rare gas as a fuel source. Kronos Fusion Energy has announced the development of an aneutronic fusion energy generator for clean and limitless power in national defense. In May 2023, the United States Department of Energy (DOE) announced

6336-421: The focus of a non-planar magnetic field generated in a solenoid with the field strength increased at either end of the tube. In order to escape the confinement area, nuclei had to enter a small annular area near each magnet. It was known that nuclei would escape through this area, but by adding and heating fuel continually it was felt this could be overcome. In 1954, Edward Teller gave a talk in which he outlined

6435-445: The form of charged particles instead of neutrons . This means that energy from aneutronic fusion could be captured directly instead of blasting neutrons at a target to boil something. Direct conversion can be either inductive, based on changes in magnetic fields, electrostatic, based on pitting charged particles against an electric field, or photoelectric, in which light energy is captured in a pulsed mode. Electrostatic conversion uses

6534-459: The fuel with the lowest total Coulomb barrier. All other potential fuels have higher Coulomb barriers, and thus require higher operational temperatures. Additionally, D–T fuels have the highest nuclear cross-sections, which means the reaction rates are higher than any other fuel. This makes D–T fusion the easiest to achieve. Comparing the potential of other fuels to the D–T reaction: The table below shows

6633-465: The gigawatt to terawatt range (and higher), with input power in the kilowatt to megawatt range." However, the patent has since been abandoned. All of these devices have faced considerable problems being scaled up and in their approach toward the Lawson criterion . One researcher has described the magnetic confinement problem in simple terms, likening it to squeezing a balloon – the air will always attempt to "pop out" somewhere else. Turbulence in

6732-481: The ignition temperature and cross-section for three of the candidate aneutronic reactions, compared to D–T: T [keV] σv / T [m /s/keV ] The easiest to ignite of the aneutronic reactions, D– He, has an ignition temperature over four times as high as that of the D–T reaction, and correspondingly lower cross-sections, while the p– B reaction is nearly ten times more difficult to ignite. Several fusion reactions produce no neutrons on any of their branches. Those with

6831-462: The large electrical currents necessary to produce the magnetic fields to confine the plasma. These and other control capabilities have come from advances in basic understanding of plasma science in such areas as plasma turbulence, plasma macroscopic stability, and plasma wave propagation. Much of this progress has been achieved with a particular emphasis on the tokamak . SPARC is a tokamak using deuterium–tritium (DT) fuel, currently being designed at

6930-425: The largest cross sections are: The He–D reaction has been studied as an alternative fusion plasma because it has the lowest energy threshold. The p– Li, He– Li, and He– He reaction rates are not particularly high in a thermal plasma. When treated as a chain, however, they offer the possibility of enhanced reactivity due to a non-thermal distribution . The product He from the p– Li reaction could participate in

7029-412: The magnetic field. More recently, so-called odd parity rotating magnetic fields have been used to preserve the closed topology of the FRC. It was analytically shown that at a very high critical threshold magnitude of 'odd parity' rotating magnetic field, the axisymmetric equilibrium magnetic field lines loses closure and fundamentally changes field topology. FRCs contain an important and uncommon feature:

7128-556: The motion of charged particles to create voltage that produces current–electrical power. It is the reverse of phenomena that use a voltage to put a particle in motion. It has been described as a linear accelerator running backwards. Aneutronic fusion loses much of its energy as light. This energy results from the acceleration and deceleration of charged particles. These speed changes can be caused by bremsstrahlung radiation , cyclotron radiation , synchrotron radiation , or electric field interactions. The radiation can be estimated using

7227-423: The neutron carries a large fraction of the alpha energy, close to E fusion /3 = 2.9  MeV . Another significant source of neutrons is: These neutrons are less energetic, with an energy comparable to the fuel temperature. In addition, C itself is radioactive, but quickly decays to B with a half life of only 20 minutes. Since these reactions involve the reactants and products of the primary reaction, it

7326-400: The next 5–10 years. The awardees include Commonwealth Fusion Systems , Focused Energy Inc., Princeton Stellarators Inc., Realta Fusion Inc., Tokamak Energy Inc., Type One Energy Group, Xcimer Energy Inc., and Zap Energy Inc. The world's major magnetic confinement fusion laboratories are: Aneutronic fusion Aneutronic fusion is any form of fusion power in which very little of

7425-524: The null and this effect is negligible. At low-s, ~2, this effect dominates and the FRC is said to be "kinetic" rather than "MHD." At low s-parameter, most ions inside an FRC follow large betatron orbits (their average gyroradius is about half the size of the plasma) which are typical in accelerator physics rather than plasma physics . These FRCs are very stable because the plasma is not dominated by usual small gyroradius particles like other thermodynamic equilibrium or nonthermal plasmas . Its behavior

7524-435: The occupational dose of both neutron and gamma radiation to a negligible level. The primary components are water (to moderate the fast neutrons), boron (to absorb the moderated neutrons) and metal (to absorb X-rays). The total thickness is estimated to be about one meter, mostly water. HB11 Energy uses thousands of merged diode-pumped lasers. This allows mass-produced and less expensive kilojoule lasers to deliver megajoules to

7623-496: The operation and capacity of the reactor. One study focused on modeling the magnetohydrodynamic (MHD) conditions in the reactor. The stability of this condition will define the limits of plasma pressure that can be achieved under varying magnetic field pressures. The progress made with SPARC has built off previously mentioned work on the ITER project and is aiming to utilize new technology in high-temperature superconductors (HTS) as

7722-447: The orbit's curvature changes direction when it crosses the magnetic null. Because the particle's orbits are not cyclotron, models of plasma behavior based on cyclotron motion like magnetohydrodynamics (MHD) are inapplicable in the region around the null. The size of this region is related to the s-parameter, or the ratio of the distance between the null and separatrix, and the thermal ion gyroradius. At high-s, most particles do not cross

7821-500: The physics of burning plasmas are being actively studied. Development of new technologies in plasma diagnostics , real-time control , plasma-facing materials , high-power microwave sources , vacuum engineering , cryogenics and superconducting magnets are essential in MCF research. A major area of research in the early years of fusion energy research was the magnetic mirror . Most early mirror devices attempted to confine plasma near

7920-617: The plasma boundary with minimal impact on the performance of high-confinement mode plasmas. This approach could be applied to larger fusion devices like ITER and contribute to core-edge integration in future fusion power plants. Recent experiments have also made progress in disruption prediction, ELM control, and material migration. The program is installing additional tools to optimize tokamak operation and exploring edge plasma and materials interactions. Major upgrades are being considered to enhance performance and flexibility for future fusion reactors. The Wendelstein 7-X stellarator at

8019-543: The plasma has proven to be a major problem, causing the plasma to escape the confinement area, and potentially touch the walls of the container. If this happens, a process known as " sputtering ", high-mass particles from the container (often steel and other metals) are mixed into the fusion fuel, lowering its temperature. In 1997, scientists at the Joint European Torus (JET) facilities in the UK produced 16 megawatts of fusion power. Scientists can now exercise

8118-575: The potential advantage of aneutronic fusion) or mined from extraterrestrial sources. The amount of He needed for large-scale applications can also be described in terms of total consumption: according to the US Energy Information Administration , "Electricity consumption by 107 million U.S. households in 2001 totalled 1,140 billion kW·h" ( 1.14 × 10  W·h ). Again assuming 100% conversion efficiency, 6.7 tonnes per year of He would be required for that segment of

8217-508: The power required to prevent the distribution from thermalizing. In addition to neutrons, large quantities of hard X-rays are produced by bremsstrahlung , and 4, 12, and 16 MeV gamma rays are produced by the fusion reaction with a branching probability relative to the primary fusion reaction of about 10 . The hydrogen must be isotopically pure and the influx of impurities into the plasma must be controlled to prevent neutron-producing side reactions such as: The shielding design reduces

8316-425: The p– B reaction is much more difficult than D–T, alternatives to the usual tokamak fusion reactors are usually proposed, such as inertial confinement fusion . One proposed method uses one laser to create a boron-11 plasma and another to create a stream of protons that smash into the plasma. The proton beam produces a tenfold increase of fusion because protons and boron nuclei collide directly. Earlier methods used

8415-454: The reaction going. Thus, steady operation of the reactor is based on a balance between the rate that energy is added to the fuel by fusion reactions and the rate energy is lost to the surroundings. This concept is best expressed as the fusion triple product , the product of the temperature, density and "confinement time", the amount of time energy remains in the fuel before escaping to the environment. The product of temperature and density gives

8514-409: The reaction rate for any given fuel. The rate of reaction is proportional to the nuclear cross section ( σ ). Any given device can sustain some maximum plasma pressure. An efficient device would continuously operate near this maximum. Given this pressure, the largest fusion output is obtained when the temperature is such that σv / T is a maximum. This is also the temperature at which the value of

8613-455: The reactor walls. Injecting impurities heavier than the plasma particles into the plasma and power exhaust region (the Divertor ) is crucial for cooling the plasma boundary without affecting the fusion performance. Conventional experiments used gaseous impurities, but the injection of boron, boron nitride, and lithium in powder form has also been tested. Experiments showed effective cooling of

8712-425: The second reaction before thermalizing, and the product p from He– Li could participate in the former before thermalizing. Detailed analyses, however, do not show sufficient reactivity enhancement to overcome the inherently low cross section. The He reaction suffers from a He availability problem. He occurs in only minuscule amounts on Earth, so it would either have to be bred from neutron reactions (counteracting

8811-404: The subject include reactions that do not meet this criterion. The Coulomb barrier is the minimum energy required for the nuclei in a fusion reaction to overcome their mutual electrostatic repulsion . Repulsive force between a particle with charge Z 1 and one with Z 2 is proportional to ( Z 1 × Z 2 ) / r , where r is the distance between them. The Coulomb barrier facing

8910-401: The tokamak principle. In the tokamak a current is periodically driven through the plasma itself, creating a field "around" the torus that combines with the toroidal field to produce a winding field in some ways similar to that in a modern stellarator, at least in that nuclei move from the inside to the outside of the device as they flow around it. In 1991, START was built at Culham , UK , as

9009-436: The triple product nTτ required for ignition is a minimum, since that required value is inversely proportional to σv / T . A plasma is "ignited" if the fusion reactions produce enough power to maintain the temperature without external heating. Because the Coulomb barrier is proportional to the product of proton counts ( Z 1 × Z 2 ) of the two reactants, varieties of heavy hydrogen, deuterium and tritium (D–T), give

9108-412: The turn of the millennium as they avoid several problems subsequently found in the tokamak. Newer models have been built, but these remain about two generations behind the latest tokamak designs. In the late 1950s, Soviet researchers noticed that the kink instability would be strongly suppressed if the twists in the path were strong enough that a particle travelled around the circumference of the inside of

9207-450: The two can begin attracting one another via nuclear force . Because this interaction is much stronger than electromagnetic interaction, the particles will be drawn together despite the ongoing electrical repulsion, releasing nuclear energy. Nuclear force is a very short-range force, though, so it is a little oversimplified to say it increases with the number of nucleons . The statement is true when describing volume energy or surface energy of

9306-618: The walls of the device outward, the plasmoid can be accelerated in the axial direction and out of the device, generating thrust. Magnetic confinement fusion Magnetic confinement fusion ( MCF ) is an approach to generate thermonuclear fusion power that uses magnetic fields to confine fusion fuel in the form of a plasma . Magnetic confinement is one of two major branches of controlled fusion research, along with inertial confinement fusion . Fusion reactions for reactors usually combine light atomic nuclei of deuterium and tritium to form an alpha particle (Helium-4 nucleus) and

9405-467: Was created in September 2019. In 2022, they claimed to be the first commercial company to demonstrate fusion. Fusion reactions can be categorized according to their neutronicity: the fraction of the fusion energy released as energetic neutrons. The State of New Jersey defined an aneutronic reaction as one in which neutrons carry no more than 1% of the total released energy, although many papers on

9504-544: Was an attempt to design a space propulsion device. ELF was a candidate in NASA 's NextSTEP advanced electric propulsion program, along with the X-3 Nested-Channel Hall Thruster and VASIMR before MSNW dissolved. The primary application is for fusion power generation. The FRC is also considered for deep space exploration , not only as a possible nuclear energy source, but as means of accelerating

9603-402: Was built to test this layout. TMX demonstrated a new series of problems that suggested MFTF would not reach its performance goals, and during construction MFTF was modified to MFTF-B. However, due to budget cuts, one day after the construction of MFTF was completed it was mothballed. Mirrors have seen little development since that time. The first real effort to build a control fusion reactor used

9702-566: Was confirmed by a visiting team from the Culham Laboratory using the Thomson scattering technique. Since then, tokamaks became the dominant line of research globally with large tokamaks such as JET , TFTR and JT-60 being constructed and operated. The ITER tokamak experiment under construction, which aims to demonstrate scientific breakeven , will be the world's largest MCF device. While early stellarators of low confinement in

9801-461: Was expended to address these issues. This led to the "stabilized pinch" concept, which added external magnets to "give the plasma a backbone" while it compressed. The largest such machine was the UK's ZETA reactor, completed in 1957, which appeared to successfully produce fusion. Only a few months after its public announcement in January 1958, these claims had to be retracted when it was discovered

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