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113-465: Like other magnetic confinement fusion experiments, NSTX studies the physics principles of thermonuclear plasmas—ionized gases with sufficiently high temperatures and densities for nuclear fusion to occur—which are confined in a magnetic field. The spherical tokamak design implemented by NSTX is an offshoot of the conventional tokamak . Proponents claim that spherical tokamaks have dramatic practical advantages over conventional tokamaks. For this reason

226-567: 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

339-406: A 3rd party study demonstrated that the cost of electricity from PACER would be ten times the cost of conventional nuclear plants. Another outcome of Atoms For Peace was to prompt John Nuckolls to consider what happens on the fusion side of the bomb as fuel mass is reduced. This work suggested that at sizes on the order of milligrams, little energy would be needed to ignite the fuel, much less than

452-475: A D and T pair fuse is very small. Higher density and longer times allow more encounters among the atoms. This cross section is further dependent on individual ion energies. This combination, the fusion triple product , must reach the Lawson criterion , to reach ignition. The first ICF devices were the hydrogen bombs invented in the early 1950s. A hydrogen bomb consists of two bombs in a single case. The first,

565-481: 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

678-458: A beam diameter hitting a target which induces uneven compression on the target surface, thereby forming Rayleigh-Taylor instabilities in the fuel, prematurely mixing it and reducing heating efficacy at the instant of maximum compression. The Richtmyer-Meshkov instability is also formed during the process due to shock waves. These problems have been mitigated by beam smoothing techniques and beam energy diagnostics; however, RT instability remains

791-403: A bomb, they are instead used to either breed tritium through reactions in a lithium-deuteride fuel, or are used to split additional fissionable fuel surrounding the secondary stage, often part of the bomb casing. The requirement that the reaction has to be sparked by a fission bomb makes this method impractical for power generation. Not only would the fission triggers be expensive to produce, but

904-411: A burst by introducing a tiny seed signal. With this technique it appeared any limits to laser power were well into the region that would be useful for ICF. Starting in 1962, Livermore's director John S. Foster, Jr. and Edward Teller began a small ICF laser study. Even at this early stage the suitability of ICF for weapons research was well understood and was the primary reason for its funding. Over

1017-445: 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

1130-455: 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

1243-582: 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)

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1356-565: 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

1469-473: A few micrometres over its (inner and outer) surface. The lasers must be precisely targeted in space and time. Beam timing is relatively simple and is solved by using delay lines in the beams' optical path to achieve picosecond accuracy. The other major issue is so-called "beam-beam" imbalance and beam anisotropy . These problems are, respectively, where the energy delivered by one beam may be higher or lower than other beams impinging and of "hot spots" within

1582-402: 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

1695-449: 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

1808-457: A fission primary. He proposed building, in effect, tiny all-fusion explosives using a tiny drop of D-T fuel suspended in the center of a hohlraum. The shell provided the same effect as the bomb casing in an H-bomb, trapping x-rays inside to irradiate the fuel. The main difference is that the X-rays would be supplied by an external device that heated the shell from the outside until it was glowing in

1921-407: A high "bootstrap" electric current. This self-driven internal plasma current would reduce the power requirements of externally driven plasma currents required to heat and confine the plasma. The $ 94 million NSTX-U (Upgrade) was completed in 2015. It doubles the toroidal field (to 1 Tesla), plasma current (to 2 MA) and heating power. It increases the pulse duration by a factor of five. To achieve this

2034-433: A major issue. Modern cryogenic hydrogen ice targets tend to freeze a thin layer of deuterium on the inside of the shell while irradiating it with a low power infrared laser to smooth its inner surface and monitoring it with a microscope equipped camera , thereby allowing the layer to be closely monitored. Cryogenic targets filled with D-T are "self-smoothing" due to the small amount of heat created by tritium decay. This

2147-441: 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

2260-502: 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

2373-497: A perfect driver mechanism. However, the maximum power produced by these devices appeared very limited, far below what would be needed. This was addressed with Gordon Gould 's introduction of the Q-switching which was applied to lasers in 1961 at Hughes Research Laboratories . Q-switching allows a laser amplifier to be pumped to very high energies without starting stimulated emission , and then triggered to release this energy in

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2486-432: A practical approach to power production and the field flourished. Experiments demonstrated that the efficiency of these devices was much lower than expected. Throughout the 1980s and '90s, experiments were conducted in order to understand the interaction of high-intensity laser light and plasma . These led to the design of much larger machines that achieved ignition-generating energies. The largest operational ICF experiment

2599-484: A pressure that would deliver the same rate of fusion. So, in theory, the ICF approach could offer dramatically more gain. This can be understood by considering the energy losses in a conventional scenario where the fuel is slowly heated, as in the case of magnetic fusion energy ; the rate of energy loss to the environment is based on the temperature difference between the fuel and its surroundings, which continues to increase as

2712-418: A separate laser to supply additional energy directly to the center of the fuel. This can be done mechanically, often using a small metal cone to puncture the outer fuel pellet wall to inject the energy into the center. In tests, this approach failed because the laser pulse had to reach the center at a precise moment, while the center is obscured by debris and free electrons from the compression pulse. It also has

2825-506: 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

2938-463: 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

3051-428: A spherical plasma with a hole through its center (a "cored apple" profile; see MAST ), different from the doughnut-shaped (toroidal) plasmas of conventional tokamaks . The low aspect ratio A (that is, an R / a of 1.31, with the major radius R of 0.85 m and the minor radius a of 0.65 m) experimental NSTX device had several advantages including plasma stability through improved confinement. Design challenges include

3164-424: 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

3277-521: A variety of mechanisms. For a one second confinement, the density needed to meet the Lawson criterion is about 10 particles per cubic centimetre (cc). For comparison, air at sea level has about 2.7 x 10 particles/cc, so the MFE approach has been described as "a good vacuum". Considering a 1 milligram drop of D-T fuel in liquid form, the size is about 1 mm and the density is about 4 x 10 /cc. Nothing holds

3390-418: A very short, very powerful pulse near the end of the compression cycle. The goal is to launch shock waves into the compressed fuel that travel inward to the center. When they reach the center they meet the waves coming in from other sides. This causes a brief period where the density in the center reaches much higher values, over 800 g/cm . The central hot spot ignition concept was the first to suggest ICF

3503-455: A water-filled cavern. The resulting steam could then be used to power conventional generators, and thereby provide electrical power. This meeting led to Operation Plowshare , formed in June 1957 and formally named in 1961. It included three primary concepts; energy generation under Project PACER, the use of nuclear explosions for excavation, and for fracking in the natural gas industry. PACER

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3616-439: A world-record 10.7 megawatts of fusion power from a plasma composed of equal parts of deuterium and tritium , a fuel mix likely to be used in commercial fusion power reactors. NSTX was a "proof of principle" experiment and therefore employed deuterium plasmas only. If successful it was to be followed by similar devices, eventually including a demonstration power reactor (e.g. ITER ), burning deuterium-tritium fuel. NSTX produced

3729-479: Is contained in a declassified report of the former East German Stasi (Staatsicherheitsdienst). In 1964 Winterberg proposed that ignition could be achieved by an intense beam of microparticles accelerated to a velocity of 1000 km/s. In 1968, he proposed to use intense electron and ion beams generated by Marx generators for the same purpose. The advantage of this proposal is that charged particle beams are not only less expensive than laser beams, but can entrap

3842-425: Is deposited in the target's outer layer, which explodes outward. This produces a reaction force in the form of shock waves that travel through the target. The waves compress and heat it. Sufficiently powerful shock waves will cause fusion of the fuel. ICF is one of two major branches of fusion energy research; the other is magnetic confinement fusion (MCF). When first proposed in the early 1970s, ICF appeared to be

3955-478: Is difficult to achieve the energy densities required to implode a target efficiently, and most ion-beam systems require the use of a hohlraum surrounding the target to smooth out the irradiation. ICF history began as part of the " Atoms For Peace " conference in 1957. This was an international, UN-sponsored conference between the US and the Soviet Union . Some thought was given to using a hydrogen bomb to heat

4068-759: Is held by JET . In 1997, JET set the record of 16 megawatts of transient fusion power with 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

4181-414: 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 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

4294-407: Is referred to as " beta -layering". In the indirect drive approach, the absorption of thermal x-rays by the target is more efficient than the direct absorption of laser light. However, the hohlraums take up considerable energy to heat, significantly reducing energy transfer efficiency. Most often, indirect drive hohlraum targets are used to simulate thermonuclear weapons tests due to the fact that

4407-460: Is that the beams can be larger and less accurate. The disadvantage is that much of the delivered energy is used to heat the hohlraum until it is "X-ray hot", so the end-to-end energy efficiency is much lower than the direct drive method. The primary challenges with increasing ICF performance are: In order to focus the shock wave on the center of the target, the target must be made with great precision and sphericity with tolerances of no more than

4520-556: Is the National Ignition Facility (NIF) in the US. In 2022, the NIF produced fusion, delivering 2.05 megajoules (MJ) of energy to the target which produced 3.15 MJ, the first time that an ICF device produced more energy than was delivered to the target. Fusion reactions combine smaller atoms to form larger ones. This occurs when two atoms (or ions, atoms stripped of their electrons) come close enough to each other that

4633-527: 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

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4746-560: 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

4859-692: 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 was confirmed by a visiting team from the Culham Laboratory using the Thomson scattering technique. Since then, tokamaks became

4972-573: The University of Rochester , and krypton fluoride excimer lasers systems at Los Alamos and the Naval Research Laboratory . High-energy ICF experiments (multi-hundred joules per shot) began in the early 1970s, when better lasers appeared. Funding for fusion research was stimulated by energy crises produced rapid gains in performance, and inertial designs were soon reaching the same sort of "below break-even" conditions of

5085-480: 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

5198-452: The nuclear force dominates the electrostatic force that otherwise keeps them apart. Overcoming electrostatic repulsion requires kinetic energy sufficient to overcome the Coulomb barrier or fusion barrier . Less energy is needed to cause lighter nuclei to fuse, as they have less electrical charge and thus a lower barrier energy. Thus the barrier is lowest for hydrogen . Conversely,

5311-435: 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 the 1950s. Early simple mirror and toroidal machines showed disappointing results of low confinement. After the declassification of fusion research by

5424-451: 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

5537-415: The primary stage , is a fission-powered device normally using plutonium . When it explodes it gives off a burst of thermal X-rays that fill the interior of the specially designed bomb casing. These X-rays are absorbed by a special material surrounding the secondary stage , which consists mostly of the fusion fuel. The X-rays heat this material and cause it to explode. Due to Newton's Third Law , this causes

5650-535: 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

5763-474: The ICF concept. In early 1960, they performed a full simulation of the implosion of 1 mg of D-T fuel inside a dense shell. The simulation suggested that a 5 MJ power input to the hohlraum would produce 50 MJ of fusion output, a gain of 10x. This was before the laser and a variety of other possible drivers were considered, including pulsed power machines, charged particle accelerators, plasma guns, and hypervelocity pellet guns. Two theoretical advances advanced

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5876-461: 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

5989-731: The approach was valid. It was then believed that a much larger device of the Cyclops type could both compress and heat targets, leading to ignition. This misconception was based on extrapolation of the fusion yields seen from experiments utilizing the so-called "exploding pusher" fuel capsule. During the late 1970s and early 1980s the estimates for laser energy on target needed to achieve ignition doubled almost yearly as plasma instabilities and laser-plasma energy coupling loss modes were increasingly understood. The realization that exploding pusher target designs and single-digit kilojoule (kJ) laser irradiation intensities would never scale to high yields led to

6102-521: 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

6215-481: The best MCF systems. LLNL was, in particular, well funded and started a laser fusion development program. Their Janus laser started operation in 1974, and validated the approach of using Nd:glass lasers for high power devices. Focusing problems were explored in the Long path and Cyclops lasers , which led to the larger Argus laser . None of these were intended to be practical devices, but they increased confidence that

6328-399: The central stack (CS) solenoid was widened, and an OH coil, inner poloidal coils, and a 2nd neutral-ion beam line were added. This upgrade consisted of a copper coil installation, not a superconducting coil. The NSTX-U (Upgrade) was stopped in late 2016 just after its update, due to a failure of one its poloidal coils. The NSTX had been shut down since 2012 and only returned for 10 weeks at

6441-429: 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

6554-458: The charged fusion reaction products due to the strong self-magnetic beam field, drastically reducing the compression requirements for beam ignited cylindrical targets. In 1967, research fellow Gurgen Askaryan published an article proposing the use of focused laser beams in the fusion of lithium deuteride or deuterium. Through the late 1950s, and collaborators at Lawrence Livermore National Laboratory (LLNL) completed computer simulations of

6667-558: 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

6780-406: The disadvantage of requiring a second laser pulse, which generally involves a completely separate laser. Shock ignition is similar in concept to the hot-spot technique, but instead of achieving ignition via compression heating, a powerful shock wave is sent into the fuel at a later time through a combination of compression and shock heating. This increases the efficiency of the process while lowering

6893-674: 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 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

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7006-419: The drop is compressed from 1 mm to 0.1 mm in diameter, the confinement time drops by the same factor of 10, because the particles have less distance to travel before they escape. However, the density, which is the cube of the dimensions, increases by 1,000 times. This means the overall rate of fusion increases 1,000 times while the confinement drops by 10 times, a 100-fold improvement. In this case 10% of

7119-500: The effort to increase laser energies to the 100 kJ level in the ultraviolet band and to the production of advanced ablator and cryogenic DT ice target designs. One of the earliest large scale attempts at an ICF driver design was the Shiva laser , a 20-beam neodymium doped glass laser system at LLNL that started operation in 1978. Shiva was a "proof of concept" design intended to demonstrate compression of fusion fuel capsules to many times

7232-506: The end of 2016 just after it was updated. The origin of this failure is partly attributed to a non-compliance of the chilled copper winding, the manufacture of which had been sub-contracted. After a diagnostic phase requiring the complete dismantling of the device and coils, evaluation of the design, and a redesign of major components including the six inner poloidal coils, a restarting plan was adopted in March 2018, with reactivation scheduled for

7345-419: The end of 2020, though this was later pushed back to 2022. As of 2022, the restart was still delayed due to an insulation problem between the central solenoid and the coils around it. 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

7458-412: The energy needed to raise the mass as a whole to this temperature is 1.4  megajoules (MJ). In the more widely developed magnetic fusion energy (MFE) approach, confinement times are on the order of one second. However, plasmas can be sustained for minutes. In this case the confinement time represents the amount of time it takes for the energy from the reaction to be lost to the environment - through

7571-468: The engineering issues, but also demonstrated that it was not economically feasible. The cost of the bombs was far greater than the value of the resulting electricity. The energy needed to overcome the Coulomb barrier corresponds to the energy of the average particle in a gas heated to 100 million K . The specific heat of hydrogen is about 14 Joule per gram-K, so considering a 1 milligram fuel pellet,

7684-427: The field. One came from new simulations that considered the timing of the energy delivered in the pulse, known as "pulse shaping", leading to better implosion. The second was to make the shell much larger and thinner, forming a thin shell as opposed to an almost solid ball. These two changes dramatically increased implosion efficiency and thereby greatly lowered the required compression energy. Using these improvements, it

7797-426: The first fusion experiment to achieve scientific breakeven on December 5, 2022, with an experiment producing 3.15 megajoules of energy from a 2.05 megajoule input of laser light (somewhat less than the energy needed to boil 1 kg of water) for an energy gain of about 1.5. Fast ignition may offer a way to directly heat fuel after compression, thus decoupling the heating and compression phases. In this approach,

7910-505: 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

8023-500: 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

8136-420: The first time fusion energy generated was greater than the energy absorbed into deuterium–tritium fuel. In June, 2018 NIF announced record production of 54kJ of fusion energy output. On August 8, 2021 the NIF produced 1.3MJ of output, 25x higher than the 2018 result, generating 70% of the break-even definition of ignition - when energy out equals energy in. As of December 2022, the NIF claims to have become

8249-421: 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

8362-488: The fuel inside to be driven inward, compressing and heating it. This causes the fusion fuel to reach the temperature and density where fusion reactions begin. In the case of D-T fuel, most of the energy is released in the form of alpha particles and neutrons. Under normal conditions, an alpha can travel about 10 mm through the fuel, but in the ultra-dense conditions in the compressed fuel, they can travel about 0.01 mm before their electrical charge, interacting with

8475-441: The fuel is deposited as a layer on the inside by injecting and freezing the gaseous fuel into the shell. Shining the driver beams directly onto the fuel capsule is known as "direct drive". The implosion process must be extremely uniform in order to avoid asymmetry due to Rayleigh–Taylor instability and similar effects. For a beam energy of 1 MJ, the fuel capsule cannot be larger than about 2 mm before these effects disrupt

8588-511: The fuel temperature increases. In the ICF case, the entire hohlraum is filled with high-temperature radiation, limiting losses. In 1956 a meeting was organized at the Max Planck Institute in Germany by fusion pioneer Carl Friedrich von Weizsäcker . At this meeting Friedwardt Winterberg proposed the non-fission ignition of a thermonuclear micro-explosion by a convergent shock wave driven with high explosives. Further reference to Winterberg's work in Germany on nuclear micro explosions (mininukes)

8701-411: The fuel together. Heat created by fusion events causes it to expand at the speed of sound , which leads to a confinement time around 2 x 10 seconds. At liquid density the required confinement time is about 2 x 10 s. In this case only about 0.1 percent of the fuel fuses before the drop blows apart. The rate of fusion reactions is a function of density, and density can be improved through compression. If

8814-454: The fuel undergoes fusion; 10% of 1 mg of fuel produces about 30 MJ of energy, 30 times the amount needed to compress it to that density. The other key concept in ICF is that the entire fuel mass does not have to be raised to 100 million K. In a fusion bomb the reaction continues because the alpha particles released in the interior heat the fuel around it. At liquid density the alphas travel about 10 mm and thus their energy escapes

8927-402: The fuel. In the 0.1 mm compressed fuel, the alphas have a range of about 0.016 mm, meaning that they will stop within the fuel and heat it. In this case a "propagating burn" can be caused by heating only the center of the fuel to the needed temperature. This requires far less energy; calculations suggested 1 kJ is enough to reach the compression goal. Some method is needed to heat

9040-417: The fusion fuel in weapons is also imploded mainly by X-ray radiation. ICF drivers are evolving. Lasers have scaled up from a few joules and kilowatts to megajoules and hundreds of terawatts, using mostly frequency doubled or tripled light from neodymium glass amplifiers. Heavy ion beams are particularly interesting for commercial generation, as they are easy to create, control, and focus. However, it

9153-465: 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

9266-418: The implosion symmetry. This limits the size of the laser beams to a diameter so narrow that it is difficult to achieve in practice. Alternatively "indirect drive" illuminates a small cylinder of heavy metal, often gold or lead , known as a hohlraum . The beam energy heats the hohlraum until it emits X-rays . These X-rays fill the interior of the hohlraum and heat the capsule. The advantage of indirect drive

9379-785: The infrared light from the laser into the ultraviolet at 351 nm. Schemes to efficiently triple the frequency of laser light discovered at the Laboratory for Laser Energetics in 1980 was experimented with in the 24 beam OMEGA laser and the NOVETTE laser , which was followed by the Nova laser design with 10 times Shiva's energy, the first design with the specific goal of reaching ignition. Nova also failed, this time due to severe variation in laser intensity in its beams (and differences in intensity between beams) caused by filamentation that resulted in large non-uniformity in irradiation smoothness at

9492-416: The interior to fusion temperatures, and do so while when the fuel is compressed and the density is high enough. In modern ICF devices, the density of the compressed fuel mixture is as much as one-thousand times the density of water, or one-hundred times that of lead, around 1000 g/cm . Much of the work since the 1970s has been on ways to create the central hot-spot that starts off the burning, and dealing with

9605-414: The kJ range, and high-gain systems with MJ drivers. In spite of limited resources and business problems, KMS Fusion successfully demonstrated IFC fusion on 1 May 1974. This success was soon followed by Siegel's death and the end of KMS Fusion a year later. By this point several weapons labs and universities had started their own programs, notably the solid-state lasers ( Nd:glass lasers ) at LLNL and

9718-462: 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

9831-399: The liquid density of hydrogen. In this, Shiva succeeded, reaching 100 times the liquid density of deuterium. However, due to the laser's coupling with hot electrons, premature heating of the dense plasma was problematic and fusion yields were low. This failure to efficiently heat the compressed plasma pointed to the use of optical frequency multipliers as a solution that would frequency triple

9944-412: The many practical problems in reaching the desired density. Early calculations suggested that the amount of energy needed to ignite the fuel was very small, but this does not match subsequent experience. The initial solution to the heating problem involved deliberate "shaping" of the energy delivery. The idea was to use an initial lower-energy pulse to vaporize the capsule and cause compression, and then

10057-407: The minimum size of such a bomb is large, defined roughly by the critical mass of the plutonium fuel used. Generally, it seems difficult to build efficient nuclear fusion devices much smaller than about 1 kiloton in yield, and the fusion secondary would add to this yield. This makes it a difficult engineering problem to extract power from the resulting explosions. Project PACER studied solutions to

10170-596: 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: Inertial confinement fusion Inertial confinement fusion ( ICF ) is a fusion energy process that initiates nuclear fusion reactions by compressing and heating targets filled with fuel. The targets are small pellets, typically containing deuterium ( H) and tritium ( H). Energy

10283-432: The next decade, LLNL made small experimental devices for basic laser-plasma interaction studies. In 1967 Kip Siegel started KMS Industries. In the early 1970s he formed KMS Fusion to begin development of a laser-based ICF system. This development led to considerable opposition from the weapons labs, including LLNL, who put forth a variety of reasons that KMS should not be allowed to develop ICF in public. This opposition

10396-406: The nuclear force increases with the number of nucleons , so isotopes of hydrogen that contain additional neutrons reduce the required energy. The easiest fuel is a mixture of H, and H, known as D-T. The odds of fusion occurring are a function of the fuel density and temperature and the length of time that the density and temperature are maintained. Even under ideal conditions, the chance that

10509-474: 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 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

10622-496: 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

10735-402: The overall amount of power required. In the simplest method of inertial confinement, the fuel is arranged as a sphere. This allows it to be compressed uniformly from all sides. To produce the inward force, the fuel is placed within a thin capsule that absorbs energy from the driver beams, causing the capsule shell to explode outward. The capsule shell is usually made of a lightweight plastic, and

10848-500: 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

10961-617: 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

11074-543: 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

11187-455: 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

11300-590: The spherical tokamak has seen considerable interest since it was proposed in the late 1980s. However, development remains effectively one generation behind mainline tokamak efforts such as JET . Other major spherical tokamak experiments include the START and MAST at Culham in the UK. First plasma was obtained on NSTX on Friday, February 12, 1999 at 7:06 p.m. Magnetic fusion experiments use plasmas composed of one or more hydrogen isotopes . For example, in 1994, PPPL's Tokamak Fusion Test Reactor ( TFTR ) produced

11413-451: The surrounding plasma, causes them to lose velocity. This means the majority of the energy released by the alphas is redeposited in the fuel. This transfer of kinetic energy heats the surrounding particles to the energies they need to undergo fusion. This process causes the fusion fuel to burn outward from the center. The electrically neutral neutrons travel longer distances in the fuel mass and do not contribute to this self-heating process. In

11526-462: The target and asymmetric implosion. The techniques pioneered earlier could not address these new issues. This failure led to a much greater understanding of the process of implosion, and the way forward again seemed clear, namely to increase the uniformity of irradiation, reduce hot-spots in the laser beams through beam smoothing techniques to reduce Rayleigh–Taylor instabilities and increase laser energy on target by at least an order of magnitude. Funding

11639-401: 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

11752-535: The toroidal and poloidal field coils, vacuum vessels and plasma-facing components . This plasma configuration can confine a higher pressure plasma than a doughnut tokamak of high aspect ratio for a given, confinement magnetic field strength. Since the amount of fusion power produced is proportional to the square of the plasma pressure, the use of spherically shaped plasmas could allow the development of smaller, more economical and more stable fusion reactors. NSTX's attractiveness may be further enhanced by its ability to trap

11865-412: 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

11978-476: The x-ray region. The power would be delivered by a then-unidentified pulsed power source he referred to, using bomb terminology, as the "primary". The main advantage to this scheme is the fusion efficiency at high densities. According to the Lawson criterion, the amount of energy needed to heat the D-T fuel to break-even conditions at ambient pressure is perhaps 100 times greater than the energy needed to compress it to

12091-402: 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

12204-533: Was calculated that a driver of about 1 MJ would be needed, a five-fold reduction. Over the next two years, other theoretical advancements were proposed, notably Ray Kidder 's development of an implosion system without a hohlraum, the so-called "direct drive" approach, and Stirling Colgate and Ron Zabawski's work on systems with as little as 1 μg of D-T fuel. The introduction of the laser in 1960 at Hughes Research Laboratories in California appeared to present

12317-428: Was constrained in the 1980s. The resulting 192-beam design, dubbed the National Ignition Facility , started construction at LLNL in 1997. NIF's main objective is to operate as the flagship experimental device of the so-called nuclear stewardship program , supporting LLNLs traditional bomb-making role. Completed in March 2009, NIF experiments set new records for power delivery by a laser. As of September 27, 2013, for

12430-601: Was directly tested in December 1961 when the 3 kt Project Gnome device was detonated in bedded salt in New Mexico. While the press looked on, radioactive steam was released from the drill shaft, at some distance from the test site. Further studies designed engineered cavities to replace natural ones, but Plowshare turned from bad to worse, especially after the failure of 1962's Sedan which produced significant fallout . PACER continued to receive funding until 1975, when

12543-461: 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

12656-526: Was funnelled through the Atomic Energy Commission , which controlled funding. Adding to the background noise were rumours of an aggressive Soviet ICF program, new higher-powered CO 2 and glass lasers, the electron beam driver concept, and the energy crisis which added impetus to many energy projects. In 1972 John Nuckolls wrote a paper introducing ICF and suggesting that testbed systems could be made to generate fusion with drivers in

12769-445: Was not only a practical route to fusion, but relatively simple. This led to numerous efforts to build working systems in the early 1970s. These experiments revealed unexpected loss mechanisms. Early calculations suggested about 4.5x10  J/g would be needed, but modern calculations place it closer to 10  J/g. Greater understanding led to complex shaping of the pulse into multiple time intervals. The fast ignition approach employs

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