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MAST-Upgrade
Mega Ampere Spherical Tokamak (MAST) was a nuclear fusion experiment, testing a spherical tokamak nuclear fusion reactor, and commissioned by EURATOM/UKAEA. The original MAST experiment took place at the Culham Centre for Fusion Energy, Oxfordshire, England from December 1999 to September 2013. A successor experiment called MAST Upgrade began operation in 2020. Design A spherical tokamak is shaped more like a cored apple than the conventional, doughnut-shaped toroidal design used by experiments such as ITER. Spherical tokamaks are more efficient in their use of the magnetic field. MAST included a neutral beam injector for plasma heating. It used a merging compression technique for plasma formation instead of the conventional direct induction. Merging compression saves central solenoid flux, which can then be used to increase the plasma current and/or maintain the required current flat-top. MAST's plasma volume was about 8 cubic meters. It confined plasmas with densities ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Fusion Experiments
Experiments directed toward developing fusion power are invariably done with dedicated machines which can be classified according to the principles they use to confine the plasma (physics), plasma fuel and keep it hot. The major division is between Magnetic confinement fusion, magnetic confinement and Inertial confinement fusion, inertial confinement. In magnetic confinement, the tendency of the hot plasma to expand is counteracted by the Lorentz force between currents in the plasma and magnetic fields produced by external coils. The particle densities tend to be in the range of to and the linear dimensions in the range of . The particle and energy confinement times may range from under a millisecond to over a second, but the configuration itself is often maintained through input of particles, energy, and current for times that are hundreds or thousands of times longer. Some concepts are capable of maintaining a plasma indefinitely. In contrast, with inertial confinement, ther ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spherical Tokamak
A spherical tokamak is a type of fusion power device based on the tokamak principle. It is notable for its very narrow profile, or ''aspect ratio''. A traditional tokamak has a toroidal confinement area that gives it an overall shape similar to a donut, complete with a large hole in the middle. The spherical tokamak reduces the size of the hole as much as possible, resulting in a plasma shape that is almost spherical, often compared to a cored apple. The spherical tokamak is sometimes referred to as a spherical torus and often shortened to ST. The spherical tokamak is an offshoot of the conventional tokamak design. Proponents claim that it has a number of substantial practical advantages over these devices. For this reason the ST has generated considerable interest since the late 1980s. However, development remains effectively one generation behind traditional tokamak efforts like JET. Major experiments in the ST field include the pioneering START and MAST at Culham in the UK ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Divertor
In magnetic confinement fusion, a divertor is a magnetic field configuration which diverts the heat and particles escaped from the magnetically confined plasma to dedicated plasma-facing components, thus spatially separating the region plasma-surface interactions from the confined core (in contrast to the limited configuration). This requires establishing a separatrix-bounded magnetic configuration, typically achieved by creating poloidal field nulls (X-points) using external coils. The divertor is a critical part of magnetic confinement fusion devices, first introduced by Lyman Spitzer in the 1950s for the stellarator concept. It extracts heat and ash produced by the fusion reaction while protecting the main chamber from thermal loads, and reduces the level of plasma contamination due to sputtered impurities. In tokamaks, high confinement modes are more readily achieved in diverted configurations. At present, it is expected that future fusion power plants will generate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Resonant Magnetic Perturbations
Resonance is a phenomenon that occurs when an object or system is subjected to an external force or vibration whose frequency matches a resonant frequency (or resonance frequency) of the system, defined as a frequency that generates a maximum amplitude response in the system. When this happens, the object or system absorbs energy from the external force and starts vibrating with a larger amplitude. Resonance can occur in various systems, such as mechanical, electrical, or acoustic systems, and it is often desirable in certain applications, such as musical instruments or radio receivers. However, resonance can also be detrimental, leading to excessive vibrations or even structural failure in some cases. All systems, including molecular systems and particles, tend to vibrate at a natural frequency depending upon their structure; when there is very little damping this frequency is approximately equal to, but slightly above, the resonant frequency. When an oscillating force, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thomson Scattering
Thomson scattering is the elastic scattering of electromagnetic radiation by a free charged particle, as described by classical electromagnetism. It is the low-energy limit of Compton scattering: the particle's kinetic energy and photon frequency do not change as a result of the scattering. This limit is valid as long as the photon energy is much smaller than the mass energy of the particle: , or equivalently, if the wavelength of the light is much greater than the Compton wavelength of the particle (e.g., for electrons, longer wavelengths than hard x-rays). Description of the phenomenon Thomson scattering describes the classical limit of electromagnetic radiation scattering from a free particle. An incident plane wave accelerates a charged particle which consequently emits radiation of the same frequency. The net effect is to scatter the incident radiation. Thomson scattering is an important phenomenon in plasma physics and was first explained by the physicist J. J. Thomson ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Langmuir Probe
A Langmuir probe is a device used to determine the electron temperature, electron density, and electric potential of a plasma. It works by inserting one or more electrodes into a plasma, with a constant or time-varying electric potential between the various electrodes or between them and the surrounding vessel. The measured currents and potentials in this system allow the determination of the physical properties of the plasma. ''I-V'' characteristic of the Debye sheath The beginning of Langmuir probe theory is the ''I–V'' characteristic of the Debye sheath, that is, the current density flowing to a surface in a plasma as a function of the voltage drop across the sheath. The analysis presented here indicates how the electron temperature, electron density, and plasma potential can be derived from the ''I–V'' characteristic. In some situations a more detailed analysis can yield information on the ion density (n_i), the ion temperature T_i, or the electron energy distribution ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ball-pen Probe
A ball-pen probe is a modified Langmuir probe used to measure the plasma potential in magnetized plasmas. The ball-pen probe balances the electron and ion saturation currents, so that its floating potential is equal to the plasma potential. Because electrons have a much smaller gyroradius than ions, a moving ceramic shield can be used to screen off an adjustable part of the electron current from the probe collector. Ball-pen probes are used in plasma physics, notably in tokamaks such as CASTOR, (Czech Academy of Sciences Torus) ASDEX Upgrade, COMPASS, ISTTOK, MAST, TJ-K, RFX, H-1 Heliac, IR-T1, GOLEM as well as low temperature devices as DC cylindrical magnetron in Prague and linear magnetized plasma devices in Nancy and Ljubljana. Principle If a Langmuir probe (electrode) is inserted into a plasma, its potential is not equal to the plasma potential \Phi because a Debye sheath forms, but instead to a floating potential V_ . The difference with the plasma potential i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
National Spherical Torus Experiment
The National Spherical Torus Experiment (NSTX) is a magnetic fusion device based on the ''spherical tokamak'' concept. It was constructed by the Princeton Plasma Physics Laboratory (PPPL) in collaboration with the Oak Ridge National Laboratory, Columbia University, and the University of Washington at Seattle. It entered service in 1999. In 2012 it was shut down as part of an upgrade program and became NSTX-U, U for Upgrade. 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 the spherical tokamak has seen considerable interest since it was proposed in the late 1980s. However, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spherical Tokamak For Energy Production
Spherical Tokamak for Energy Production (STEP) is a spherical tokamak fusion plant concept proposed by the United Kingdom Atomic Energy Authority (UKAEA) and funded by the UK government. The project is a proposed DEMO-class successor device to the ITER tokamak proof-of-concept of a fusion plant, the most advanced tokamak fusion reactor to date, which is scheduled to achieve a ' burning plasma' in 2035. STEP aims to produce net electricity from fusion on a timescale of 2040. Jacob Rees-Mogg, then UK Secretary of State for Business, Energy and Industrial Strategy, announced West Burton A power station in Nottinghamshire as its site on 3 October 2022 during the Conservative Party Conference. A coal-fired power station at the site ceased production a few days earlier. The reactor is planned to have a 100 MW electrical output and be tritium self-sufficient via fuel breeding. Plans In September 2019, the United Kingdom announced a planned £200-million (US$248-million) investment to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
BBC News Online
BBC News Online is the website of BBC News, the division of the BBC responsible for newsgathering and production. It is one of the most popular news websites, with 1.2 billion website visits in April 2021, as well as being used by 60% of the UK's internet users for news. The website contains international news coverage, as well as British, entertainment, science, and political news. Many reports are accompanied by audio and video from the BBC's BBC Television, television and BBC Radio, radio news services, while the latest TV and radio bulletins are also available to view or listen to on the site together with other current affairs programmes. BBC News Online is closely linked to its sister department website, that of BBC Sport. Both sites follow similar layout and content options and respective journalists work alongside each other. Location information provided by users is also shared with the website of BBC Weather to provide local content. From 1998 to 2001 the site was n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Field
A magnetic field (sometimes called B-field) is a physical field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to the magnetic field. A permanent magnet's magnetic field pulls on ferromagnetic materials such as iron, and attracts or repels other magnets. In addition, a nonuniform magnetic field exerts minuscule forces on "nonmagnetic" materials by three other magnetic effects: paramagnetism, diamagnetism, and antiferromagnetism, although these forces are usually so small they can only be detected by laboratory equipment. Magnetic fields surround magnetized materials, electric currents, and electric fields varying in time. Since both strength and direction of a magnetic field may vary with location, it is described mathematically by a function (mathematics), function assigning a Euclidean vector, vector to each point of space, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
H-mode
In plasma physics and magnetic confinement fusion, the high-confinement mode (H-mode) is a phenomenon observed in toroidal fusion plasmas such as tokamaks. In general, plasma energy confinement degrades as the applied heating power is increased. Above a certain characteristic power threshold, the plasma transitions from L-(low-confinement) to H-mode regime, where the particle and energy confinement is significantly enhanced. The H-mode was discovered by Friedrich Wagner and team in 1982 on the ASDEX diverted tokamak.How Fritz Wagner "discovered" the H-Mode It has since been reproduced in all major toroidal confinement devices, and is foreseen to be the standard operational scenario of many future reactors, such as |
