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136-712: Commonwealth Fusion Systems ( CFS ) is an American fusion power company founded in 2018 in Cambridge, Massachusetts after a spin-out from the Massachusetts Institute of Technology (MIT). Its stated goal is to build a small fusion power plant based on the ARC tokamak design. It has participated in the United States Department of Energy ’s INFUSE public-private knowledge innovation scheme, with several national labs and universities. CFS

272-568: A Ball mill . Solution chemistry processes such as coprecipitation , freeze-drying and sol–gel methods are alternative ways for preparing a homogeneous mixture. These powders are calcined in the temperature range from 1,070 to 1,220 K (800 to 950 °C) for several hours. The powders are cooled, reground and calcined again. This process is repeated several times to get homogeneous material. The powders are subsequently compacted to pellets and sintered. The sintering environment such as temperature, annealing time, atmosphere and cooling rate play

408-454: A fission-fusion hybrid . In these systems, the power output is enhanced by the fission events, and power is extracted using systems like those in conventional fission reactors. Designs that use other fuels, notably the proton-boron aneutronic fusion reaction, release much more of their energy in the form of charged particles. In these cases, power extraction systems based on the movement of these charges are possible. Direct energy conversion

544-479: A mixture of the two ), which react more easily than protium (the most common hydrogen isotope ) and produce a helium nucleus and an energized neutron , to allow them to reach the Lawson criterion requirements with less extreme conditions. Most designs aim to heat their fuel to around 100 million kelvins, which presents a major challenge in producing a successful design. Tritium is extremely rare on Earth, having

680-411: A probability distribution . If the plasma is thermalized , the distribution looks like a Gaussian curve , or Maxwell–Boltzmann distribution . In this case, it is useful to use the average particle cross section over the velocity distribution. This is entered into the volumetric fusion rate: where: The Lawson criterion considers the energy balance between the energy produced in fusion reactions to

816-479: A tokamak -based reactor. The system was able to manipulate the magnetic coils to manage the plasma. The system was able to continuously adjust to maintain appropriate behavior (more complex than step-based systems). In 2014, Google began working with California-based fusion company TAE Technologies to control the Joint European Torus (JET) to predict plasma behavior. DeepMind has also developed

952-473: A 1.5 nanosecond laser fire, 100 times greater than reported in previous experiments. Structural material stability is a critical issue. Materials that can survive the high temperatures and neutron bombardment experienced in a fusion reactor are considered key to success. The principal issues are the conditions generated by the plasma, neutron degradation of wall surfaces, and the related issue of plasma-wall surface conditions. Reducing hydrogen permeability

1088-526: A Russian and Japanese company, developed a new manufacturing process for making superconducting YBCO wire for fusion reactors. This new wire was shown to conduct between 700 and 2000 Amps per square millimeter. The company was able to produce 186 miles of wire in nine months. Even on smaller production scales, the containment apparatus is blasted with matter and energy. Designs for plasma containment must consider: High-temperature superconductivity The major advantage of high-temperature superconductors

1224-420: A bound pair. This is sometimes called the "water bed" effect. Each Cooper pair requires a certain minimum energy to be displaced, and if the thermal fluctuations in the crystal lattice are smaller than this energy the pair can flow without dissipating energy. This ability of the electrons to flow without resistance leads to superconductivity. In a high- T c superconductor, the mechanism is extremely similar to

1360-575: A confined environment with sufficient temperature , pressure , and confinement time to create a plasma in which fusion can occur. The combination of these figures that results in a power-producing system is known as the Lawson criterion . In stars the most common fuel is hydrogen , and gravity provides extremely long confinement times that reach the conditions needed for fusion energy production. Proposed fusion reactors generally use heavy hydrogen isotopes such as deuterium and tritium (and especially

1496-461: A control scheme with TCV . The diagnostics of a fusion scientific reactor are extremely complex and varied. The diagnostics required for a fusion power reactor will be various but less complicated than those of a scientific reactor as by the time of commercialization, many real-time feedback and control diagnostics will have been perfected. However, the operating environment of a commercial fusion reactor will be harsher for diagnostic systems than in

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1632-444: A conventional superconductor, except, in this case, phonons virtually play no role and their role is replaced by spin-density waves. Just as all known conventional superconductors are strong phonon systems, all known high- T c superconductors are strong spin-density wave systems, within close vicinity of a magnetic transition to, for example, an antiferromagnet. When an electron moves in a high- T c superconductor, its spin creates

1768-718: A directional dependence to the magnetic field response. All known high- T c superconductors are Type-II superconductors. In contrast to Type-I superconductors , which expel all magnetic fields due to the Meissner effect , Type-II superconductors allow magnetic fields to penetrate their interior in quantized units of flux, creating "holes" or "tubes" of normal metallic regions in the superconducting bulk called vortices . Consequently, high- T c superconductors can sustain much higher magnetic fields. Cuprates are layered materials, consisting of superconducting layers of copper oxide , separated by spacer layers. Cuprates generally have

1904-549: A half life of only ~12.3 years. Consequently, during the operation of envisioned fusion reactors, known as breeder reactors, helium cooled pebble beds (HCPBs) are subjected to neutron fluxes to generate tritium to complete the fuel cycle. As a source of power, nuclear fusion has a number of potential advantages compared to fission . These include reduced radioactivity in operation, little high-level nuclear waste , ample fuel supplies (assuming tritium breeding or some forms of aneutronic fuels ), and increased safety. However,

2040-663: A headquarters, manufacturing, and research campus (including the SPARC tokamak), in Devens, Massachusetts . Also in 2021, CEO Bob Mumgaard was appointed to the board of directors of the Fusion Industry Association , which was incorporated as a non profit association with a focus on combating climate change. In September 2021, the company announced the demonstration of a high temperature superconducting magnet, able to generate magnetic fields of 20 Tesla. According to

2176-797: A high critical magnetic field and critical current density (above which superconductivity is destroyed), would greatly benefit technological applications. In magnet applications, the high critical magnetic field may prove more valuable than the high T c itself. Some cuprates have an upper critical field of about 100 tesla. However, cuprate materials are brittle ceramics that are expensive to manufacture and not easily turned into wires or other useful shapes. Furthermore, high-temperature superconductors do not form large, continuous superconducting domains, rather clusters of microdomains within which superconductivity occurs. They are therefore unsuitable for applications requiring actual superconductive currents, such as magnets for magnetic resonance spectrometers. For

2312-407: A machine holding a thermalized and quasi- neutral plasma has to generate enough energy to overcome its energy losses. The amount of energy released in a given volume is a function of the temperature, and thus the reaction rate on a per-particle basis, the density of particles within that volume, and finally the confinement time, the length of time that energy stays within the volume. This is known as

2448-457: A metallic domain of an adjacent CuO 2 plane. The transition temperature maxima are reached when the host lattice has weak bond-bending forces, which produce strong electron–phonon interactions at the interlayer dopants. An experiment based on flux quantization of a three-grain ring of YBa 2 Cu 3 O 7 (YBCO) was proposed to test the symmetry of the order parameter in the HTS. The symmetry of

2584-556: A much higher conductivity parallel to the CuO 2 plane than in the perpendicular direction. Generally, critical temperatures depend on the chemical compositions, cations substitutions and oxygen content. They can be classified as superstripes ; i.e., particular realizations of superlattices at atomic limit made of superconducting atomic layers, wires, dots separated by spacer layers, that gives multiband and multigap superconductivity. An yttrium–barium cuprate, YBa 2 Cu 3 O 7−x (or Y123),

2720-545: A plasma oscillating device, a magnetically shielded-grid, a penning trap , the polywell , and the F1 cathode driver concept. The fuels considered for fusion power have all been light elements like the isotopes of hydrogen— protium , deuterium , and tritium . The deuterium and helium-3 reaction requires helium-3, an isotope of helium so scarce on Earth that it would have to be mined extraterrestrially or produced by other nuclear reactions. Ultimately, researchers hope to adopt

2856-477: A pyramidal arrangement. Cuprate of Tl–Ba–Ca: The first series of the Tl-based superconductor containing one Tl–O layer has the general formula TlBa 2 Ca n −1 Cu n O 2 n +3 , whereas the second series containing two Tl–O layers has a formula of Tl 2 Ba 2 Ca n −1 Cu n O 2 n +4 with n  =1, 2 and 3. In the structure of Tl 2 Ba 2 CuO 6 (Tl-2201), there is one CuO 2 layer with

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2992-509: A result of sanctions against Russia, CFS faced significant supply chain problems. By late 2022, CFS had grown to approximately 350 employees and was preparing to move into its Devens campus. A ceremonial opening for the Devens campus was held in February 2023. In March 2023, Eni and CFS signed a multi-year agreement to collaborate in obtaining the components and authorizations necessary for

3128-476: A scientific reactor because continuous operations may involve higher plasma temperatures and higher levels of neutron irradiation. In many proposed approaches, commercialization will require the additional ability to measure and separate diverter gases, for example helium and impurities, and to monitor fuel breeding, for instance the state of a tritium breeding liquid lithium liner. The following are some basic techniques. Neutron blankets absorb neutrons, which heats

3264-452: A series of D-T tests at JET , the vacuum vessel was sufficiently radioactive that it required remote handling for the year following the tests. In a production setting, the neutrons would react with lithium in the breeding blanket composed of lithium ceramic pebbles or liquid lithium, yielding tritium. The energy of the neutrons ends up in the lithium, which would then be transferred to drive electrical production. The lithium blanket protects

3400-413: A shell, driving the shell to radiate x-rays , which then implode the pellet. The beams are commonly laser beams, but ion and electron beams have been investigated. Electrostatic confinement fusion devices use electrostatic fields. The best known is the fusor . This device has a cathode inside an anode wire cage. Positive ions fly towards the negative inner cage, and are heated by the electric field in

3536-534: A single superconducting phase. For Bi–Sr–Ca–Cu–O, it is relatively simple to prepare the Bi-2212 ( T c  ≈ 85 K) phase, whereas it is very difficult to prepare a single phase of Bi-2223 ( T c  ≈ 110 K). The Bi-2212 phase appears only after few hours of sintering at 1,130–1,140 K (860–870 °C), but the larger fraction of the Bi-2223 phase is formed after a long reaction time of more than

3672-611: A solution to this (powders), see HTS wire . There has been considerable debate regarding high-temperature superconductivity coexisting with magnetic ordering in YBCO, iron-based superconductors , several ruthenocuprates and other exotic superconductors, and the search continues for other families of materials. HTS are Type-II superconductors , which allow magnetic fields to penetrate their interior in quantized units of flux, meaning that much higher magnetic fields are required to suppress superconductivity. The layered structure also gives

3808-430: A spin-density wave around it. This spin-density wave in turn causes a nearby electron to fall into the spin depression created by the first electron (water-bed effect again). Hence, again, a Cooper pair is formed. When the system temperature is lowered, more spin density waves and Cooper pairs are created, eventually leading to superconductivity. Note that in high- T c systems, as these systems are magnetic systems due to

3944-576: A structure close to that of a two-dimensional material. Their superconducting properties are determined by electrons moving within weakly coupled copper-oxide (CuO 2 ) layers. Neighbouring layers contain ions such as lanthanum , barium , strontium , or other atoms which act to stabilize the structures and dope electrons or holes onto the copper-oxide layers. The undoped "parent" or "mother" compounds are Mott insulators with long-range antiferromagnetic order at sufficiently low temperatures. Single band models are generally considered to be enough to describe

4080-422: A surface of the device, and transfer a portion of their kinetic energy to the other atoms. The rate of conduction is also based on the temperature and density. Radiation is energy that leaves the cloud as light. Radiation also increases with temperature as well as the mass of the ions. Fusion power systems must operate in a region where the rate of fusion is higher than the losses. The Lawson criterion argues that

4216-578: A tokamak via the SPARC tokamak , which will pave the way for a multi-hundred MW electric ARC plant. They plan to achieve this by incorporating a large-bore, high field (20 Tesla ) superconducting magnet made of VIPER, a yttrium barium copper oxide superconducting tape. As a high-temperature superconductor , VIPER can sustain higher electric currents and magnetic fields than were previously possible. Previous tokamaks used copper or low-temperature superconducting magnets that need to be large in size to create

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4352-422: A vacuum at temperature above 973 K (700 °C). The preparation of Bi-, Tl- and Hg-based high- T c superconductors is more difficult than the YBCO preparation. Problems in these superconductors arise because of the existence of three or more phases having a similar layered structure. Thus, syntactic intergrowth and defects such as stacking faults occur during synthesis and it becomes difficult to isolate

4488-423: A variety of heating methods that were developed in the early 1970s. In modern machines, as of 2019 , the major remaining issue was the confinement time. Plasmas in strong magnetic fields are subject to a number of inherent instabilities, which must be suppressed to reach useful durations. One way to do this is to simply make the reactor volume larger, which reduces the rate of leakage due to classical diffusion . This

4624-441: A very important role in getting good high- T c superconducting materials. The YBa 2 Cu 3 O 7− x compound is prepared by calcination and sintering of a homogeneous mixture of Y 2 O 3 , BaCO 3 and CuO in the appropriate atomic ratio. Calcination is done at 1,070 to 1,220 K (800 to 950 °C), whereas sintering is done at 1,220 K (950 °C) in an oxygen atmosphere. The oxygen stoichiometry in this material

4760-499: A week at 1,140 K (870 °C). Although the substitution of Pb in the Bi–Sr–Ca–Cu–O compound has been found to promote the growth of the high- T c phase, a long sintering time is still required. The question of how superconductivity arises in high-temperature superconductors is one of the major unsolved problems of theoretical condensed matter physics . The mechanism that causes the electrons in these crystals to form pairs

4896-421: Is endothermic , requiring an input of energy. The heavy nuclei bigger than iron have many more protons resulting in a greater repulsive force. For nuclei lighter than iron-56, the reaction is exothermic , releasing energy when they fuse. Since hydrogen has a single proton in its nucleus, it requires the least effort to attain fusion, and yields the most net energy output. Also since it has one electron, hydrogen

5032-490: Is a proposed form of power generation that would generate electricity by using heat from nuclear fusion reactions . In a fusion process, two lighter atomic nuclei combine to form a heavier nucleus, while releasing energy. Devices designed to harness this energy are known as fusion reactors. Research into fusion reactors began in the 1940s, but as of 2024, no device has reached net power, although net positive reactions have been achieved. Fusion processes require fuel and

5168-471: Is also common in research. The optimum energy to initiate this reaction is 15 keV, only slightly higher than that for the D-T reaction. The first branch produces tritium, so that a D-D reactor is not tritium-free, even though it does not require an input of tritium or lithium. Unless the tritons are quickly removed, most of the tritium produced is burned in the reactor, which reduces the handling of tritium, with

5304-403: Is an alternating multi-layer of CuO 2 planes with superconductivity taking place between these layers. The more layers of CuO 2 , the higher T c . This structure causes a large anisotropy in normal conducting and superconducting properties, since electrical currents are carried by holes induced in the oxygen sites of the CuO 2 sheets. The electrical conduction is highly anisotropic, with

5440-497: Is called "tritium suppressed fusion". The removed tritium decays to He with a 12.5 year half life. By recycling the He decay into the reactor, the fusion reactor does not require materials resistant to fast neutrons. Assuming complete tritium burn-up, the reduction in the fraction of fusion energy carried by neutrons would be only about 18%, so that the primary advantage of the D-D fuel cycle

5576-521: Is copper oxides combined with other metals, especially the rare-earth barium copper oxides (REBCOs) such as yttrium barium copper oxide (YBCO). The second class of high-temperature superconductors in the practical classification is the iron-based compounds . Magnesium diboride is sometimes included in high-temperature superconductors: It is relatively simple to manufacture, but it superconducts only below 39 K (−234.2 °C), which makes it unsuitable for liquid nitrogen cooling. Superconductivity

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5712-453: Is currently BSCCO , a compound of Bi–Sr–Ca–Cu–O . The content of bismuth and strontium creates some chemical issues. It has three superconducting phases forming a homologous series as Bi 2 Sr 2 Ca n −1 Cu n O 4+2 n + x ( n =1, 2 and 3). These three phases are Bi-2201, Bi-2212 and Bi-2223, having transition temperatures of 20 K (−253.2 °C), 85 K (−188.2 °C) and 110 K (−163 °C), respectively, where

5848-483: Is currently the family with the second highest critical temperature, behind the cuprates. Interest in their superconducting properties began in 2006 with the discovery of superconductivity in LaFePO at 4 K (−269.15 °C) and gained much greater attention in 2008 after the analogous material LaFeAs(O,F) was found to superconduct at up to 43 K (−230.2 °C) under pressure. The highest critical temperatures in

5984-428: Is formed by oxidation alone. Alternative methods utilize specific gas environments with strong magnetic and electric fields. Assessment of barrier performance represents an additional challenge. Classical coated membranes gas permeation continues to be the most reliable method to determine hydrogen permeation barrier (HPB) efficiency. In 2021, in response to increasing numbers of designs for fusion power reactors for 2040,

6120-538: Is found to increase with the increase in CuO 2 layers. However, the value of T c decreases after four CuO 2 layers in TlBa 2 Ca n −1 Cu n O 2 n +3 , and in the Tl 2 Ba 2 Ca n −1 Cu n O 2 n +4 compound, it decreases after three CuO 2 layers. Cuprate of Hg–Ba–Ca The crystal structure of HgBa 2 CuO 4 (Hg-1201), HgBa 2 CaCu 2 O 6 (Hg-1212) and HgBa 2 Ca 2 Cu 3 O 8 (Hg-1223)

6256-442: Is further to extract access hydrogen from the reduction with CaH 2 , otherwise topotactic hydrogen may prevent superconductivity. The structure of cuprates which are superconductors are often closely related to perovskite structure, and the structure of these compounds has been described as a distorted, oxygen deficient multi-layered perovskite structure. One of the properties of the crystal structure of oxide superconductors

6392-405: Is increasing interest in magnetized target fusion and inertial electrostatic confinement , and new variations of the stellarator. Fusion reactions occur when two or more atomic nuclei come close enough for long enough that the nuclear force pulling them together exceeds the electrostatic force pushing them apart, fusing them into heavier nuclei. For nuclei heavier than iron-56 , the reaction

6528-596: Is intended to give "the world a clear path to fusion power," according to the CFS CEO Bob Mumgaard. As of January 2024, SPARC was targeted for completion by 2025. CFS also plans to build a power plant based on the ARC design at the beginning of the 2030s. Both SPARC and ARC plan to use deuterium - tritium fuel. SPARC is predicted to have a burning plasma. That means that the fusion process would be predominantly self-heating. Fusion power Fusion power

6664-402: Is more difficult than the YBCO preparation. They also have a different crystal structure: they are tetragonal where YBCO is orthorhombic . Problems in these superconductors arise because of the existence of three or more phases having a similar layered structure. Moreover, the crystal structure of other tested cuprate superconductors are very similar. Like YBCO, the perovskite-type feature and

6800-501: Is more generally regarded as the highest T c conventional superconductor, the increased T c resulting from two separate bands being present at the Fermi level . In 1991 Hebard et al. discovered Fulleride superconductors, where alkali-metal atoms are intercalated into C 60 molecules. In 2008 Ganin et al. demonstrated superconductivity at temperatures of up to 38 K (−235.2 °C) for Cs 3 C 60 . P-doped Graphane

6936-419: Is not known. Despite intensive research and many promising leads, an explanation has so far eluded scientists. One reason for this is that the materials in question are generally very complex, multi-layered crystals (for example, BSCCO ), making theoretical modelling difficult. Improving the quality and variety of samples also gives rise to considerable research, both with the aim of improved characterisation of

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7072-651: Is pseudocubic, nearly orthorhombic . The other superconducting cuprates have another structure: they have a tetragonal cell. Each perovskite cell contains a Y or Ba atom at the center: Ba in the bottom unit cell, Y in the middle one, and Ba in the top unit cell. Thus, Y and Ba are stacked in the sequence [Ba–Y–Ba] along the c-axis. All corner sites of the unit cell are occupied by Cu, which has two different coordinations, Cu(1) and Cu(2), with respect to oxygen. There are four possible crystallographic sites for oxygen: O(1), O(2), O(3) and O(4). The coordination polyhedra of Y and Ba with respect to oxygen are different. The tripling of

7208-525: Is seen as crucial to hydrogen recycling and control of the tritium inventory. Materials with the lowest bulk hydrogen solubility and diffusivity provide the optimal candidates for stable barriers. A few pure metals, including tungsten and beryllium, and compounds such as carbides, dense oxides, and nitrides have been investigated. Research has highlighted that coating techniques for preparing well-adhered and perfect barriers are of equivalent importance. The most attractive techniques are those in which an ad-layer

7344-537: Is similar to that of Tl-1201, Tl-1212 and Tl-1223, with Hg in place of Tl. It is noteworthy that the T c of the Hg compound (Hg-1201) containing one CuO 2 layer is much larger as compared to the one-CuO 2 -layer compound of thallium (Tl-1201). In the Hg-based superconductor, T c is also found to increase as the CuO 2 layer increases. For Hg-1201, Hg-1212 and Hg-1223, the values of T c are 94, 128, and

7480-611: Is still considerably higher compared to fission reactors. Because the confinement properties of the tokamak and laser pellet fusion are marginal, most proposals for aneutronic fusion are based on radically different confinement concepts, such as the Polywell and the Dense Plasma Focus . In 2013, a research team led by Christine Labaune at École Polytechnique , reported a new fusion rate record for proton-boron fusion, with an estimated 80 million fusion reactions during

7616-433: Is still not clear, but it seems that instead of electron– phonon attraction mechanisms, as in conventional superconductivity, one is dealing with genuine electronic mechanisms (e.g. by antiferromagnetic correlations), and instead of conventional, purely s-wave pairing, more exotic pairing symmetries are thought to be involved ( d -wave in the case of the cuprates; primarily extended s -wave, but occasionally d -wave, in

7752-519: Is that they can be cooled using liquid nitrogen, in contrast to the previously known superconductors that require expensive and hard-to-handle coolants, primarily liquid helium . A second advantage of high- T c materials is they retain their superconductivity in higher magnetic fields than previous materials. This is important when constructing superconducting magnets , a primary application of high- T c materials. The majority of high-temperature superconductors are ceramic materials, rather than

7888-404: Is that tritium breeding is not required. Other advantages are independence from lithium resources and a somewhat softer neutron spectrum. The disadvantage of D-D compared to D-T is that the energy confinement time (at a given pressure) must be 30 times longer and the power produced (at a given pressure and volume) is 68 times less. Assuming complete removal of tritium and He recycling, only 6% of

8024-439: Is the easiest fuel to fully ionize. The repulsive electrostatic interaction between nuclei operates across larger distances than the strong force, which has a range of roughly one femtometer —the diameter of a proton or neutron. The fuel atoms must be supplied enough kinetic energy to approach one another closely enough for the strong force to overcome the electrostatic repulsion in order to initiate fusion. The " Coulomb barrier "

8160-527: Is the quantity of kinetic energy required to move the fuel atoms near enough. Atoms can be heated to extremely high temperatures or accelerated in a particle accelerator to produce this energy. An atom loses its electrons once it is heated past its ionization energy . An ion is the name for the resultant bare nucleus. The result of this ionization is plasma, which is a heated cloud of ions and free electrons that were formerly bound to them. Plasmas are electrically conducting and magnetically controlled because

8296-506: Is then reduced to Nd 0.8 Sr 0.2 NiO 2 via annealing the thin films at 533–553 K (260–280 °C) in the presence of CaH 2 . The superconducting phase is only observed in the oxygen reduced film and is not seen in oxygen reduced bulk material of the same stoichiometry, suggesting that the strain induced by the oxygen reduction of the Nd 0.8 Sr 0.2 NiO 2 thin film changes the phase space to allow for superconductivity. Of important

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8432-404: Is unaffected by the confinement scheme. In most designs, it is captured in a thick "blanket" of lithium surrounding the reactor core. When struck by a high-energy neutron, the blanket heats up. It is then actively cooled with a working fluid that drives a turbine to produce power. Another design proposed to use the neutrons to breed fission fuel in a blanket of nuclear waste , a concept known as

8568-540: Is very crucial for obtaining a superconducting YBa 2 Cu 3 O 7− x compound. At the time of sintering, the semiconducting tetragonal YBa 2 Cu 3 O 6 compound is formed, which, on slow cooling in oxygen atmosphere, turns into superconducting YBa 2 Cu 3 O 7− x . The uptake and loss of oxygen are reversible in YBa 2 Cu 3 O 7 −x . A fully oxygenated orthorhombic YBa 2 Cu 3 O 7− x sample can be transformed into tetragonal YBa 2 Cu 3 O 6 by heating in

8704-404: Is why ITER is so large. In contrast, inertial confinement systems approach useful triple product values via higher density, and have short confinement intervals. In NIF , the initial frozen hydrogen fuel load has a density less than water that is increased to about 100 times the density of lead. In these conditions, the rate of fusion is so high that the fuel fuses in the microseconds it takes for

8840-593: The IBM research lab near Zürich in Switzerland, Bednorz and Müller were looking for superconductivity in a new class of ceramics : the copper oxides , or cuprates . Bednorz encountered a particular copper oxide whose resistance dropped to zero at a temperature around 35.1 K (−238 °C). Their results were soon confirmed by many groups, notably Paul Chu at the University of Houston and Shoji Tanaka at

8976-676: The United Kingdom Atomic Energy Authority published the UK Fusion Materials Roadmap 2021–2040 , focusing on five priority areas, with a focus on tokamak family reactors: In a plasma that is embedded in a magnetic field (known as a magnetized plasma) the fusion rate scales as the magnetic field strength to the 4th power. For this reason, many fusion companies that rely on magnetic fields to control their plasma are trying to develop high temperature superconducting devices. In 2021, SuperOx,

9112-410: The University of Tokyo . In 1987, Philip W. Anderson gave the first theoretical description of these materials, based on the resonating valence bond (RVB) theory , but a full understanding of these materials is still developing today. These superconductors are now known to possess a d -wave pair symmetry. The first proposal that high-temperature cuprate superconductivity involves d -wave pairing

9248-415: The uranium enrichment process. Tritium is a natural isotope of hydrogen, but because it has a short half-life of 12.32 years, it is hard to find, store, produce, and is expensive. Consequently, the deuterium-tritium fuel cycle requires the breeding of tritium from lithium using one of the following reactions: The reactant neutron is supplied by the D-T fusion reaction shown above, and the one that has

9384-460: The "triple product": the plasma density, temperature, and confinement time. In magnetic confinement, the density is low, on the order of a "good vacuum". For instance, in the ITER device the fuel density is about 1.0 × 10 m , which is about one-millionth atmospheric density. This means that the temperature and/or confinement time must increase. Fusion-relevant temperatures have been achieved using

9520-539: The Coulomb interaction, there is a strong Coulomb repulsion between electrons. This Coulomb repulsion prevents pairing of the Cooper pairs on the same lattice site. The pairing of the electrons occur at near-neighbor lattice sites as a result. This is the so-called d -wave pairing, where the pairing state has a node (zero) at the origin. Examples of high- T c cuprate superconductors include YBCO and BSCCO , which are

9656-537: The CuO 2 lattice. The typical Fermi surface within the first CuO 2 Brillouin zone is sketched in Fig. 1 (left). It can be derived from the band structure calculations or measured by angle resolved photoemission spectroscopy ( ARPES ). Fig. 1 (right) shows the Fermi surface of BSCCO measured by ARPES. In a wide range of charge carrier concentration (doping level), in which the hole-doped HTSC are superconducting,

9792-516: The CuO 2 layers in both Bi-2212 and Bi-2223; there is no Ca layer in the Bi-2201 phase. The three phases differ with each other in the number of cuprate planes; Bi-2201, Bi-2212 and Bi-2223 phases have one, two and three CuO 2 planes, respectively. The c axis lattice constants of these phases increases with the number of cuprate planes (see table below). The coordination of the Cu atom is different in

9928-509: The CuO 2 planes which is also caused by phonons. The gap decreases with increasing charge carriers, and as it nears the superconductive gap, the latter reaches its maximum. The reason for the high transition temperature is then argued to be due to the percolating behaviour of the carriers – the carriers follow zig-zag percolative paths, largely in metallic domains in the CuO 2 planes, until blocked by charge density wave domain walls , where they use dopant bridges to cross over to

10064-415: The Fermi surface is hole-like ( i.e. open, as shown in Fig. 1). This results in an inherent in-plane anisotropy of the electronic properties of HTSC. In 2018, the full three dimensional Fermi surface structure was derived from soft x-ray ARPES. Iron-based superconductors contain layers of iron and a pnictogen  – such as arsenic or phosphorus  – or a chalcogen . This

10200-571: The New York Times, this was a successful test of "the world's most powerful version of the type of magnet crucial to many fusion efforts" In November 2021, the company raised an additional $ 1.8 billion in Series B funding to construct and operate the SPARC tokamak, funded by Temasek Holdings , Google , Bill Gates and Eni . In December the company began construction on SPARC in Devens, Massachusetts . In March 2022, Axios reported that as

10336-509: The RVB theory. The confirmation of the d -wave nature of the cuprate superconductors was made by a variety of experiments, including the direct observation of the d -wave nodes in the excitation spectrum through angle resolved photoemission spectroscopy (ARPES), the observation of a half-integer flux in tunneling experiments, and indirectly from the temperature dependence of the penetration depth, specific heat and thermal conductivity. As of 2021,

10472-472: The Y plane is to serve as a spacer between two CuO 2 planes. In YBCO, the Cu–O chains are known to play an important role for superconductivity. T c is maximal near 92 K (−181.2 °C) when x  ≈ 0.15 and the structure is orthorhombic. Superconductivity disappears at x  ≈ 0.6, where the structural transformation of YBCO occurs from orthorhombic to tetragonal. The preparation of other cuprates

10608-491: The ambiguous results came from the defects inside the HTS, so that they designed an experiment where both clean limit (no defects) and dirty limit (maximal defects) were considered simultaneously. In the experiment, the spontaneous magnetization was clearly observed in YBCO, which supported the d symmetry of the order parameter in YBCO. But, since YBCO is orthorhombic, it might inherently have an admixture of s symmetry. So, by tuning their technique further, they found that there

10744-410: The blanket. Power can be extracted from the blanket in various ways: Confinement refers to all the conditions necessary to keep a plasma dense and hot long enough to undergo fusion. General principles: To produce self-sustaining fusion, part of the energy released by the reaction must be used to heat new reactants and maintain the conditions for fusion. Magnetic mirror effect. If a particle follows

10880-429: The boiling point of liquid nitrogen . However, a number of materials – including the original discovery and recently discovered pnictide superconductors – have critical temperatures below 77 K (−196.2 °C) but nonetheless are commonly referred to in publications as high- T c class. A substance with a critical temperature above the boiling point of liquid nitrogen, together with

11016-478: The case of the iron-based superconductors). In 2014, evidence showing that fractional particles can happen in quasi two-dimensional magnetic materials, was found by École Polytechnique Fédérale de Lausanne (EPFL) scientists lending support for Anderson's theory of high-temperature superconductivity. The "high-temperature" superconductor class has had many definitions. The label high- T c should be reserved for materials with critical temperatures greater than

11152-448: The charges are separated. This is used by several fusion devices to confine the hot particles. A reaction's cross section , denoted σ, measures the probability that a fusion reaction will happen. This depends on the relative velocity of the two nuclei. Higher relative velocities generally increase the probability, but the probability begins to decrease again at very high energies. In a plasma, particle velocity can be characterized using

11288-503: The company reported significant progress in the physics and engineering design of the SPARC tokamak , and in October 2020, the development of a new high temperature superconducting cable, called VIPER. Over the 9-month period from 2019 to 2020, the company purchased over 186 miles of the wire in 400-600 meter lengths from vendors, more than was produced by some vendors over the preceding 6 years. In March 2021, CFS announced plans to build

11424-519: The construction of the first SPARC experimental plant, as well as the construction of the first Arc power plant and the identification of countries that may be interested in hosting it. In May 2023, United States Department of Energy granted the company additional funding along with seven other US companies via the Milestone-Based Fusion Development Program . CFS intends to demonstrate net-positive energy in

11560-475: The cuprate superconductors. However, they are poor metals rather than Mott insulators and have five bands at the Fermi surface rather than one. The phase diagram emerging as the iron-arsenide layers are doped is remarkably similar, with the superconducting phase close to or overlapping the magnetic phase. Strong evidence that the T c value varies with the As–Fe–As bond angles has already emerged and shows that

11696-411: The cuprate superconductors. Superconductivity in an infinite-layer nickelate, Nd 0.8 Sr 0.2 NiO 2 , was reported at the end of 2019 with a superconducting transition temperature between 9 and 15 K (−264.15 and −258.15 °C). This superconducting phase is observed in oxygen-reduced thin films created by the pulsed laser deposition of Nd 0.8 Sr 0.2 NiO 3 onto SrTiO 3 substrates that

11832-487: The cuprates continue to be the subject of considerable debate and further research. Certain aspects common to all materials have been identified. Similarities between the antiferromagnetic the low-temperature state of undoped materials and the superconducting state that emerges upon doping, primarily the d x −y orbital state of the Cu ions, suggest that electron–electron interactions are more significant than electron–phonon interactions in cuprates – making

11968-401: The different material properties allow a different pairing symmetry.) Secondly, there was the interlayer coupling model , according to which a layered structure consisting of BCS-type ( s -wave symmetry) superconductors can enhance the superconductivity by itself. By introducing an additional tunnelling interaction between each layer, this model successfully explained the anisotropic symmetry of

12104-405: The disadvantage of producing more, and higher-energy, neutrons. The neutron from the second branch of the D-D reaction has an energy of only 2.45 MeV (0.393 pJ), while the neutron from the D-T reaction has an energy of 14.1 MeV (2.26 pJ), resulting in greater isotope production and material damage. When the tritons are removed quickly while allowing the He to react, the fuel cycle

12240-487: The electronic properties. The cuprate superconductors adopt a perovskite structure. The copper-oxide planes are checkerboard lattices with squares of O ions with a Cu ion at the centre of each square. The unit cell is rotated by 45° from these squares. Chemical formulae of superconducting materials generally contain fractional numbers to describe the doping required for superconductivity. There are several families of cuprate superconductors and they can be categorized by

12376-501: The elements they contain and the number of adjacent copper-oxide layers in each superconducting block. For example, YBCO and BSCCO can alternatively be referred to as "Y123" and Bi2201/Bi2212/Bi2223 depending on the number of layers in each superconducting block ( n ). The superconducting transition temperature has been found to peak at an optimal doping value ( p =0.16) and an optimal number of layers in each superconducting block, typically n =3. Possible mechanisms for superconductivity in

12512-448: The energy being lost to the environment. In order to generate usable energy, a system would have to produce more energy than it loses. Lawson assumed an energy balance , shown below. where: The rate of fusion, and thus P fusion , depends on the temperature and density of the plasma. The plasma loses energy through conduction and radiation . Conduction occurs when ions , electrons , or neutrals impact other substances, typically

12648-485: The field line and enters a region of higher field strength, the particles can be reflected. Several devices apply this effect. The most famous was the magnetic mirror machines, a series of devices built at LLNL from the 1960s to the 1980s. Other examples include magnetic bottles and Biconic cusp . Because the mirror machines were straight, they had some advantages over ring-shaped designs. The mirrors were easier to construct and maintain and direct conversion energy capture

12784-410: The fusion energy is carried by neutrons. The tritium-suppressed D-D fusion requires an energy confinement that is 10 times longer compared to D-T and double the plasma temperature. A second-generation approach to controlled fusion power involves combining helium-3 ( He) and deuterium ( H): This reaction produces He and a high-energy proton. As with the p- B aneutronic fusion fuel cycle, most of

12920-455: The greatest energy yield. The reaction with Li is exothermic , providing a small energy gain for the reactor. The reaction with Li is endothermic , but does not consume the neutron. Neutron multiplication reactions are required to replace the neutrons lost to absorption by other elements. Leading candidate neutron multiplication materials are beryllium and lead , but the Li reaction helps to keep

13056-406: The heat generated by the reactions to blow the fuel apart. Although NIF is also large, this is a function of its "driver" design, not inherent to the fusion process. Multiple approaches have been proposed to capture the energy that fusion produces. The simplest is to heat a fluid. The commonly targeted D-T reaction releases much of its energy as fast-moving neutrons. Electrically neutral, the neutron

13192-402: The indirect nature of the experimental evidence, as well as experimental issues such as sample quality, impurity scattering, twinning, etc. This summary makes an implicit assumption : superconductive properties can be treated by mean-field theory . It also fails to mention that in addition to the superconductive gap, there is a second gap, the pseudogap . The cuprate layers are insulating, and

13328-419: The iron-based superconductor family exist in thin films of FeSe, where a critical temperature in excess of 100 K (−173 °C) was reported in 2014. Since the original discoveries several families of iron-based superconductors have emerged: Most undoped iron-based superconductors show a tetragonal-orthorhombic structural phase transition followed at lower temperature by magnetic ordering, similar to

13464-479: The magnetic field that is necessary to achieve net energy. The CFS high-temperature superconductor magnet is intended to create much stronger magnetic fields, allowing the tokamaks to be much smaller. The first magnet of this type was built and tested in 2021. The D-shaped magnet consisted of 16 layers, each containing HTS tape. It weighed 10 tons and stood 8 feet tall, including 165 miles of tape. SPARC will include 18 similar magnets. The magnet technology used in SPARC

13600-597: The most reactive aneutronic fuel is He. However, obtaining reasonable quantities of He implies large scale extraterrestrial mining on the Moon or in the atmosphere of Uranus or Saturn. Therefore, the most promising candidate fuel for such fusion is fusing the readily available protium (i.e. a proton ) and boron . Their fusion releases no neutrons, but produces energetic charged alpha (helium) particles whose energy can directly be converted to electrical power: Side reactions are likely to yield neutrons that carry only about 0.1% of

13736-417: The necessary combination of temperature, pressure, and duration has proven to be difficult to produce in a practical and economical manner. A second issue that affects common reactions is managing neutrons that are released during the reaction, which over time degrade many common materials used within the reaction chamber. Fusion researchers have investigated various confinement concepts. The early emphasis

13872-415: The neutron population high. Natural lithium is mainly Li, which has a low tritium production cross section compared to Li so most reactor designs use breeding blankets with enriched Li. Drawbacks commonly attributed to D-T fusion power include: The neutron flux expected in a commercial D-T fusion reactor is about 100 times that of fission power reactors, posing problems for material design . After

14008-449: The numbering system represent number of atoms for Bi Sr, Ca and Cu respectively. The two phases have a tetragonal structure which consists of two sheared crystallographic unit cells. The unit cell of these phases has double Bi–O planes which are stacked in a way that the Bi atom of one plane sits below the oxygen atom of the next consecutive plane. The Ca atom forms a layer within the interior of

14144-405: The occurrence of the Meissner effect . LK-99 , copper - doped lead-apatite, has also been proposed as a room-temperature superconductor. There have been two representative theories for high-temperature or unconventional superconductivity . Firstly, weak coupling theory suggests superconductivity emerges from antiferromagnetic spin fluctuations in a doped system. According to this theory,

14280-422: The optimal T c value is obtained with undistorted FeAs 4 tetrahedra. The symmetry of the pairing wavefunction is still widely debated, but an extended s -wave scenario is currently favoured. Magnesium diboride is occasionally referred to as a high-temperature superconductor because its T c value of 39 K (−234.2 °C) is above that historically expected for BCS superconductors. However, it

14416-401: The order parameter as well as the emergence of the HTS. Thus, in order to solve this unsettled problem, there have been numerous experiments such as photoemission spectroscopy , NMR , specific heat measurements, etc. Up to date the results were ambiguous, some reports supported the d symmetry for the HTS whereas others supported the s symmetry. This muddy situation possibly originated from

14552-478: The order parameter could best be probed at the junction interface as the Cooper pairs tunnel across a Josephson junction or weak link. It was expected that a half-integer flux, that is, a spontaneous magnetization could only occur for a junction of d symmetry superconductors. But, even if the junction experiment is the strongest method to determine the symmetry of the HTS order parameter, the results have been ambiguous. John R. Kirtley and C. C. Tsuei thought that

14688-574: The outer portions of the reactor from the neutron flux. Newer designs, the advanced tokamak in particular, use lithium inside the reactor core as a design element. The plasma interacts directly with the lithium, preventing a problem known as "recycling". The advantage of this design was demonstrated in the Lithium Tokamak Experiment . Fusing two deuterium nuclei is the second easiest fusion reaction. The reaction has two branches that occur with nearly equal probability: This reaction

14824-443: The pairing mechanism for these systems. The qualitative explanation is as follows: In a superconductor, the flow of electrons cannot be resolved into individual electrons, but instead consists of many pairs of bound electrons, called Cooper pairs. In conventional superconductors, these pairs are formed when an electron moving through the material distorts the surrounding crystal lattice, which in turn attracts another electron and forms

14960-533: The pairing wave function of the cuprate HTS should have a d x -y symmetry. Thus, determining whether the pairing wave function has d -wave symmetry is essential to test the spin fluctuation mechanism. That is, if the HTS order parameter (a pairing wave function like in Ginzburg–Landau theory ) does not have d -wave symmetry, then a pairing mechanism related to spin fluctuations can be ruled out. (Similar arguments can be made for iron-based superconductors but

15096-405: The perovskite unit cell leads to nine oxygen atoms, whereas YBa 2 Cu 3 O 7 has seven oxygen atoms and, therefore, is referred to as an oxygen-deficient perovskite structure. The structure has a stacking of different layers: (CuO)(BaO)(CuO 2 )(Y)(CuO 2 )(BaO)(CuO). One of the key feature of the unit cell of YBa 2 Cu 3 O 7−x (YBCO) is the presence of two layers of CuO 2 . The role of

15232-437: The physical properties of existing compounds, and synthesizing new materials, often with the hope of increasing T c . Technological research focuses on making HTS materials in sufficient quantities to make their use economically viable as well as in optimizing their properties in relation to applications . Metallic hydrogen has been proposed as a room-temperature superconductor, some experimental observations have detected

15368-453: The power, which means that neutron scattering is not used for energy transfer and material activation is reduced several thousand-fold. The optimum temperature for this reaction of 123 keV is nearly ten times higher than that for pure hydrogen reactions, and energy confinement must be 500 times better than that required for the D-T reaction. In addition, the power density is 2500 times lower than for D-T, although per unit mass of fuel, this

15504-454: The presence of simple copper oxide (CuO 2 ) layers also exist in these superconductors. However, unlike YBCO, Cu–O chains are not present in these superconductors. The YBCO superconductor has an orthorhombic structure, whereas the other high- T c superconductors have a tetragonal structure. There are three main classes of superconducting cuprates: bismuth-based, thallium-based and mercury-based. The second cuprate by practical importance

15640-416: The previously known metallic materials. Ceramic superconductors are suitable for some practical uses but they still have many manufacturing issues. For example, most ceramics are brittle , which makes the fabrication of wires from them very problematic. However, overcoming these drawbacks is the subject of considerable research, and progress is ongoing. The main class of high-temperature superconductors

15776-420: The process. If they miss the inner cage they can collide and fuse. Ions typically hit the cathode, however, creating prohibitory high conduction losses. Fusion rates in fusors are low because of competing physical effects, such as energy loss in the form of light radiation. Designs have been proposed to avoid the problems associated with the cage, by generating the field using a non-neutral cloud. These include

15912-409: The properties of hole-doped and electron doped cuprates: The electronic structure of superconducting cuprates is highly anisotropic (see the crystal structure of YBCO or BSCCO ). Therefore, the Fermi surface of HTSC is very close to the Fermi surface of the doped CuO 2 plane (or multi-planes, in case of multi-layer cuprates) and can be presented on the 2‑D reciprocal space (or momentum space) of

16048-447: The protium–boron-11 reaction, because it does not directly produce neutrons, although side reactions can. The easiest nuclear reaction, at the lowest energy, is D+T: This reaction is common in research, industrial and military applications, usually as a neutron source. Deuterium is a naturally occurring isotope of hydrogen and is commonly available. The large mass ratio of the hydrogen isotopes makes their separation easy compared to

16184-448: The reaction energy is released as charged particles, reducing activation of the reactor housing and potentially allowing more efficient energy harvesting (via any of several pathways). In practice, D-D side reactions produce a significant number of neutrons, leaving p- B as the preferred cycle for aneutronic fusion. Both material science problems and non-proliferation concerns are greatly diminished by aneutronic fusion . Theoretically,

16320-560: The record value at ambient pressure 134 K (−139 °C), respectively, as shown in table below. The observation that the T c of Hg-1223 increases to 153 K (−120 °C) under high pressure indicates that the T c of this compound is very sensitive to the structure of the compound. The simplest method for preparing ceramic superconductors is a solid-state thermochemical reaction involving mixing, calcination and sintering . The appropriate amounts of precursor powders, usually oxides and carbonates, are mixed thoroughly using

16456-405: The sample metallic. The Sr impurities also act as electronic bridges, enabling interlayer coupling. Proceeding from this picture, some theories argue that the basic pairing interaction is still interaction with phonons , as in the conventional superconductors with Cooper pairs . While the undoped materials are antiferromagnetic, even a few percent of impurity dopants introduce a smaller pseudogap in

16592-639: The spheromak, attempt to combine the advantages of toroidal magnetic surfaces with those of a simply connected (non-toroidal) machine, resulting in a mechanically simpler and smaller confinement area. Inertial confinement is the use of rapid implosion to heat and confine plasma. A shell surrounding the fuel is imploded using a direct laser blast (direct drive), a secondary x-ray blast (indirect drive), or heavy beams. The fuel must be compressed to about 30 times solid density with energetic beams. Direct drive can in principle be efficient, but insufficient uniformity has prevented success. Indirect drive uses beams to heat

16728-476: The stacking sequence (Tl–O) (Tl–O) (Ba–O) (Cu–O) (Ba–O) (Tl–O) (Tl–O). In Tl 2 Ba 2 CaCu 2 O 8 (Tl-2212), there are two Cu–O layers with a Ca layer in between. Similar to the Tl 2 Ba 2 CuO 6 structure, Tl–O layers are present outside the Ba–O layers. In Tl 2 Ba 2 Ca 2 Cu 3 O 10 (Tl-2223), there are three CuO 2 layers enclosing Ca layers between each of these. In Tl-based superconductors, T c

16864-417: The superconductivity unconventional. Recent work on the Fermi surface has shown that nesting occurs at four points in the antiferromagnetic Brillouin zone where spin waves exist and that the superconducting energy gap is larger at these points. The weak isotope effects observed for most cuprates contrast with conventional superconductors that are well described by BCS theory. Similarities and differences in

17000-419: The superconductor with the highest transition temperature at ambient pressure is the cuprate of mercury, barium, and calcium, at around 133 K (−140 °C). There are other superconductors with higher recorded transition temperatures – for example lanthanum superhydride at 250 K (−23 °C), but these only occur at very high pressures. The origin of high-temperature superconductivity

17136-470: The superconductors are doped with interlayer impurities to make them metallic. The superconductive transition temperature can be maximized by varying the dopant concentration. The simplest example is La 2 CuO 4 , which consist of alternating CuO 2 and LaO layers which are insulating when pure. When 8% of the La is replaced by Sr, the latter act as dopants, contributing holes to the CuO 2 layers, and making

17272-411: The three phases. The Cu atom forms an octahedral coordination with respect to oxygen atoms in the 2201 phase, whereas in 2212, the Cu atom is surrounded by five oxygen atoms in a pyramidal arrangement. In the 2223 structure, Cu has two coordinations with respect to oxygen: one Cu atom is bonded with four oxygen atoms in square planar configuration and another Cu atom is coordinated with five oxygen atoms in

17408-531: Was an admixture of s symmetry in YBCO within about 3%. Also, they found that there was a pure d x −y order parameter symmetry in the tetragonal Tl 2 Ba 2 CuO 6 . Despite all these years, the mechanism of high- T c superconductivity is still highly controversial, mostly due to the lack of exact theoretical computations on such strongly interacting electron systems. However, most rigorous theoretical calculations, including phenomenological and diagrammatic approaches, converge on magnetic fluctuations as

17544-800: Was developed at Lawrence Livermore National Laboratory (LLNL) in the 1980s as a method to maintain a voltage directly using fusion reaction products. This has demonstrated energy capture efficiency of 48 percent. Plasma is an ionized gas that conducts electricity. In bulk, it is modeled using magnetohydrodynamics , which is a combination of the Navier–Stokes equations governing fluids and Maxwell's equations governing how magnetic and electric fields behave. Fusion exploits several plasma properties, including: Many approaches, equipment, and mechanisms are employed across multiple projects to address fusion heating, measurement, and power production. A deep reinforcement learning system has been used to control

17680-515: Was discovered by Kamerlingh Onnes in 1911, in a metal solid. Ever since, researchers have attempted to observe superconductivity at increasing temperatures with the goal of finding a room-temperature superconductor . By the late 1970s, superconductivity was observed in several metallic compounds (in particular Nb -based, such as NbTi , Nb 3 Sn , and Nb 3 Ge ) at temperatures that were much higher than those for elemental metals and which could even exceed 20 K (−253.2 °C). In 1986, at

17816-417: Was easier to implement. Poor confinement has led this approach to be abandoned, except in the polywell design. Magnetic loops bend the field lines back on themselves, either in circles or more commonly in nested toroidal surfaces. The most highly developed systems of this type are the tokamak , the stellarator, and the reversed field pinch. Compact toroids , especially the field-reversed configuration and

17952-760: Was founded in 2018 as a spin-off from the MIT Plasma Science and Fusion Center . After initial funding of $ 50 million in 2018 from the Italian multinational Eni , CFS closed its series A round of venture capital funding in 2019 with a total of US$ 115 million in funding from Eni , Bill Gates 's Breakthrough Energy Ventures , Vinod Khosla 's Khosla Ventures , and others. CFS raised an additional US$ 84 million in series A2 funding from Singapore 's Temasek , Norway 's Equinor , and Devonshire Investors, as well as from previous investors. As of October 2020, CFS had approximately 100 employees. In September 2020,

18088-464: Was made in 1987 by N. E. Bickers, Douglas James Scalapino and R. T. Scalettar, followed by three subsequent theories in 1988 by Masahiko Inui, Sebastian Doniach, Peter J. Hirschfeld and Andrei E. Ruckenstein, using spin-fluctuation theory, and by Claudius Gros , Didier Poilblanc, Maurice T. Rice and FC. Zhang, and by Gabriel Kotliar and Jialin Liu identifying d -wave pairing as a natural consequence of

18224-646: Was on three main systems: z-pinch , stellarator , and magnetic mirror . The current leading designs are the tokamak and inertial confinement (ICF) by laser . Both designs are under research at very large scales, most notably the ITER tokamak in France and the National Ignition Facility (NIF) laser in the United States. Researchers are also studying other designs that may offer less expensive approaches. Among these alternatives, there

18360-629: Was proposed in 2010 to be capable of sustaining high-temperature superconductivity. On 31st of December 2023 "Global Room-Temperature Superconductivity in Graphite" was published in the journal "Advanced Quantum Technologies" claiming to demonstrate superconductivity at room temperature and ambient pressure in Highly oriented pyrolytic graphite with dense arrays of nearly parallel line defects. In 1999, Anisimov et al. conjectured superconductivity in nickelates, proposing nickel oxides as direct analogs to

18496-481: Was the first superconductor found above liquid nitrogen boiling point. There are two atoms of Barium for each atom of Yttrium. The proportions of the three different metals in the YBa 2 Cu 3 O 7 superconductor are in the mole ratio of 1 to 2 to 3 for yttrium to barium to copper, respectively: this particular superconductor has also often been referred to as the 123 superconductor. The unit cell of YBa 2 Cu 3 O 7 consists of three perovskite unit cells, which

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