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H-mode
High-confinement mode, or H-mode, is an operating mode possible in toroidal magnetic confinement fusion devices mostly tokamaks, but also in stellarators.How Fritz Wagner "discovered" the H-Mode In this mode the plasma is more stable and better confined. It was discovered by in 1982 during neutral-beam heating of the plasma at ASDEX. It has since been reproduced in all major toroidal confinement devices and is planned in the operation of [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Friedrich Wagner
Friedrich E. Wagner (born November 16, 1943, sometimes abbreviated as Fritz Wagner) is a German physicist and emeritus professor who specializes in plasma physics. He was known to have discovered the high-confinement mode (i.e. H-mode) of magnetic confinement in fusion plasmas while working at the ASDEX tokamak in 1982. For this discovery and his subsequent contributions to fusion research, was awarded the John Dawson Award in 1987, the Hannes Alfvén Prize in 2007 and the Stern–Gerlach Medal in 2009. Life and career Wagner was born in Pfaffenhofen an der Roth in Bavaria, Germany. He studied at the Technical University of Munich and completed his doctorate in 1972. He then worked at Ohio State University from 1973 to 1974. At first, he worked on low-temperature physics, but switched to plasma fusion research during the energy crisis of the time. In 1975, he started working for the Max Planck Institute for Plasma Physics, and in 1986 he led the tokamak experiment ASDEX. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
COMPASS Tokamak
COMPASS, short for Compact Assembly, is a compact tokamak fusion energy device originally completed at the Culham Science Centre in 1989, upgraded in 1992, and operated until 2002. It was designed as a flexible research facility dedicated mostly to plasma physics studies in circular and D-shaped plasmas. When it was decommissioned at Culham, it was offered to the European Commission and found a new home at the Institute of Plasma Physics of the Czech Academy of Sciences in Prague where it began operations once again in 2006. It officially ended its experimental runs on 20 August 2021 and will be disassembled to leave room for a new device, COMPASS-U. History The first plasma in COMPASS was produced in 1989 in a C-shaped vacuum vessel, i.e., in a simpler vessel with a circular cross-section. Pioneering experiments followed, including for example the ITER-relevant tests of magnetic field correction with saddle coils for Resonant magnetic perturbations (RMP) experiments or exper ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tokamaks
A tokamak (; russian: токамáк; otk, 𐱃𐰸𐰢𐰴, Toḳamaḳ) is a device which uses a powerful magnetic field to confine plasma in the shape of a torus. The tokamak is one of several types of magnetic confinement devices being developed to produce controlled thermonuclear fusion power. , it was the leading candidate for a practical fusion reactor. Tokamaks were initially conceptualized in the 1950s by Soviet physicists Igor Tamm and Andrei Sakharov, inspired by a letter by Oleg Lavrentiev. The first working tokamak was attributed to the work of Natan Yavlinsky on the T-1 in 1958. It had been demonstrated that a stable plasma equilibrium requires magnetic field lines that wind around the torus in a helix. Devices like the z-pinch and stellarator had attempted this, but demonstrated serious instabilities. It was the development of the concept now known as the safety factor (labelled ''q'' in mathematical notation) that guided tokamak development; by arranging ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
KSTAR
The KSTAR (or Korea Superconducting Tokamak Advanced Research; ko, 초전도 핵융합연구장치, literally "superconducting nuclear fusion research device") is a magnetic fusion device at the Korea Institute of Fusion Energy in Daejeon, South Korea. It is intended to study aspects of magnetic fusion energy that will be pertinent to the ITER fusion project as part of that country's contribution to the ITER effort. The project was approved in 1995, but construction was delayed by the East Asian financial crisis, which weakened the South Korean economy considerably; however, the project's construction phase was completed on September 14, 2007. The first plasma was achieved in June 2008. Description KSTAR is one of the first research tokamaks in the world to feature fully superconducting magnets, which again will be of great relevance to ITER as this will also use superconducting magnets. The KSTAR magnet system consists of 16 niobium–tin direct current toroidal field magn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ASDEX Upgrade
ASDEX Upgrade (''Axially Symmetric Divertor Experiment'') is a divertor tokamak, that went into operation at the Max-Planck-Institut für Plasmaphysik, Garching in 1991. At present, it is Germany's second largest fusion experiment after stellarator Wendelstein 7-X. Overview To make experiments under reactor-like conditions possible, essential plasma properties, particularly the plasma density and pressure and the wall load, have been adapted in ASDEX Upgrade to the conditions that will be present in a future fusion power plant. ASDEX Upgrade is, compared to other international tokamaks, a midsize tokamak experiment. It began operation in 1991 and it succeeds the ASDEX experiment, which was in operation from 1980 until 1990. One innovative feature of the ASDEX Upgrade experiment is its all-tungsten first wall; tungsten is a good choice for the first wall of a tokamak because of its very high melting point (over 3000 degrees Celsius) which enables it to stand up to the very hig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Edge-localized Mode
An edge-localized mode (ELM) is a disruptive instability occurring in the edge region of a tokamak plasma due to the quasi-periodic relaxation of a transport barrier previously formed during a transition from low to high-confinement mode. This phenomenon was first observed in the ASDEX tokamak in 1981. Diamagnetic effects in the model equations expand the size of the parameter space in which solutions of repeated sawteeth can be recovered compared to a resistive MHD model. An ELM can expel up to 20 percent of the reactor's energy. Issues ELM is a major challenge in magnetic fusion research with tokamaks, as these instabilities can: * damage wall components (in particular divertor plates) by ablating them away due to their extremely high energy transfer rate (GW/m2); * potentially couple or trigger other instabilities, such as the resistive wall mode (RWM) or the neoclassical tearing mode (NTM). Prevention and control A variety of experiments/simulations have attempted to m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Confinement Fusion
Magnetic confinement fusion is an approach to generate thermonuclear fusion power that uses magnetic fields to confine fusion fuel in the form of a plasma. Magnetic confinement is one of two major branches of fusion energy research, along with inertial confinement fusion. The magnetic approach began in the 1940s and absorbed the majority of subsequent development. Fusion reactions combine light atomic nuclei such as hydrogen to form heavier ones such as helium, producing energy. In order to overcome the electrostatic repulsion between the nuclei, they must have a temperature of tens of millions of degrees, creating a plasma. In addition, the plasma must be contained at a sufficient density for a sufficient time, as specified by the Lawson criterion (triple product). Magnetic confinement fusion attempts to use the electrical conductivity of the plasma to contain it through interaction with magnetic fields. The magnetic pressure offsets the plasma pressure. Developing a suitable ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stellarator
A stellarator is a plasma device that relies primarily on external magnets to confine a plasma. Scientists researching magnetic confinement fusion aim to use stellarator devices as a vessel for nuclear fusion reactions. The name refers to the possibility of harnessing the power source of the stars, such as the Sun. It is one of the earliest fusion power devices, along with the z-pinch and magnetic mirror. The stellarator was invented by American scientist Lyman Spitzer of Princeton University in 1951, and much of its early development was carried out by his team at what became the Princeton Plasma Physics Laboratory (PPPL). Lyman's Model A began operation in 1953 and demonstrated plasma confinement. Larger models followed, but these demonstrated poor performance, losing plasma at rates far worse than theoretical predictions. By the early 1960s, any hope of quickly producing a commercial machine faded, and attention turned to studying the fundamental theory of high-energy plasma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neutral-beam Injection
Neutral-beam injection (NBI) is one method used to heat plasma inside a fusion device consisting in a beam of high-energy neutral particles that can enter the magnetic confinement field. When these neutral particles are ionized by collision with the plasma particles, they are kept in the plasma by the confining magnetic field and can transfer most of their energy by further collisions with the plasma. By tangential injection in the torus, neutral beams also provide momentum to the plasma and current drive, one essential feature for long pulses of burning plasmas. Neutral-beam injection is a flexible and reliable technique, which has been the main heating system on a large variety of fusion devices. To date, all NBI systems were based on positive precursor ion beams. In the 1990s there has been impressive progress in negative ion sources and accelerators with the construction of multi-megawatt negative-ion-based NBI systems at LHD (H0, 180 keV) and JT-60U (D0, 500 keV). Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ITER
ITER (initially the International Thermonuclear Experimental Reactor, ''iter'' meaning "the way" or "the path" in Latin) is an international nuclear fusion research and engineering megaproject aimed at creating energy by replicating, on Earth, the fusion processes of the Sun. Upon completion of construction of the main reactor and first plasma, planned for late 2025, it will be the world's largest magnetic confinement plasma physics experiment and the largest experimental tokamak nuclear fusion reactor. It is being built next to the Cadarache facility in southern France. ITER will be the largest of more than 100 fusion reactors built since the 1950s, with ten times the plasma volume of any other tokamak operating today. The long-term goal of fusion research is to generate electricity. ITER's stated purpose is scientific research, and technological demonstration of a large fusion reactor, without electricity generation. ITER's goals are to achieve enough fusion to produce 10 ti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lotka–Volterra Equations
The Lotka–Volterra equations, also known as the predator–prey equations, are a pair of first-order nonlinear differential equations, frequently used to describe the dynamics of biological systems in which two species interact, one as a predator and the other as prey. The populations change through time according to the pair of equations: \begin \frac &= \alpha x - \beta x y, \\ \frac &= \delta x y - \gamma y, \end where * is the number of prey (for example, rabbits); * is the number of some predator (for example, foxes); *\tfrac and \tfrac represent the instantaneous growth rates of the two populations; * represents time; *, , , are positive real parameters describing the interaction of the two species. The Lotka–Volterra system of equations is an example of a Kolmogorov model, which is a more general framework that can model the dynamics of ecological systems with predator–prey interactions, competition, disease, and mutualism. History The Lotka–Volterra predat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Design Envelope
A specification often refers to a set of documented requirements to be satisfied by a material, design, product, or service. A specification is often a type of technical standard. There are different types of technical or engineering specifications (specs), and the term is used differently in different technical contexts. They often refer to particular documents, and/or particular information within them. The word ''specification'' is broadly defined as "to state explicitly or in detail" or "to be specific". A requirement specification is a documented requirement, or set of documented requirements, to be satisfied by a given material, design, product, service, etc. It is a common early part of engineering design and product development processes in many fields. A functional specification is a kind of requirement specification, and may show functional block diagrams. A design or product specification describes the features of the ''solutions'' for the Requirement Specification, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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