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Science Action: How does a magnetic field confine a plasma?
Science Action: How does a magnetic field confine a plasma?
Published: 2014/06/10
Channel: Science Action
Magnetic Confinement of Nuclear Fusion
Magnetic Confinement of Nuclear Fusion
Published: 2014/04/24
Channel: AK LECTURES
Magnetic Confinement Concepts
Magnetic Confinement Concepts
Published: 2013/11/17
Channel: Animations for Physics and Astronomy
Magnetic confinement fusion - Video Learning - WizScience.com
Magnetic confinement fusion - Video Learning - WizScience.com
Published: 2015/09/10
Channel: Wiz Science™
Magnetic Confinement Fusion
Magnetic Confinement Fusion
Published: 2013/04/26
Channel: Mike F
"#MCF: The physics of magnetic confinement in 180 minutes I" - Michael Barnes
"#MCF: The physics of magnetic confinement in 180 minutes I" - Michael Barnes
Published: 2016/07/20
Channel: Institute for Advanced Study
Lesson 14 - Magnetic Confinement And The Earth
Lesson 14 - Magnetic Confinement And The Earth's Aurora (Physics Tutor)
Published: 2016/08/19
Channel: mathtutordvd
Fusion Power Explained – Future or Failure
Fusion Power Explained – Future or Failure
Published: 2016/11/10
Channel: Kurzgesagt – In a Nutshell
Magnetic Confinement (360 VR)
Magnetic Confinement (360 VR)
Published: 2017/06/23
Channel: Animations for Physics and Astronomy
Plasma Magnetic Confinement In Glass
Plasma Magnetic Confinement In Glass
Published: 2015/01/31
Channel: Physics Is Wonderful
Fusion Power On The Horizon
Fusion Power On The Horizon
Published: 2015/11/16
Channel: 10 Reasons Why Show
KStar Ufo Power Plant  Magnetic Plasma Fusion Reactor
KStar Ufo Power Plant Magnetic Plasma Fusion Reactor
Published: 2010/05/25
Channel: freeenergy4everyone
Fusion Energy Production by Deuterium Particle Injection
Fusion Energy Production by Deuterium Particle Injection
Published: 2012/09/28
Channel: Jamison Daniel
Building a homemade magnetic confinement fusion reactor
Building a homemade magnetic confinement fusion reactor
Published: 2012/01/13
Channel: Lloyd Share
Magnetic confinement fusion
Magnetic confinement fusion
Published: 2015/11/12
Channel: Hiren Shah
Magnetic Confinement Fusion Driven Thermonuclear Energy
Magnetic Confinement Fusion Driven Thermonuclear Energy
Published: 2017/06/16
Channel: ikka tigris
Energy Of The Future: Nuclear Fusion Research
Energy Of The Future: Nuclear Fusion Research
Published: 2009/01/10
Channel: FFreeThinker
How Fusion Reactors Control Plasma - 2016 CHRISTMAS LECTURES
How Fusion Reactors Control Plasma - 2016 CHRISTMAS LECTURES
Published: 2017/03/02
Channel: The Royal Institution
Inertial Confinement Fusion
Inertial Confinement Fusion
Published: 2015/01/16
Channel: OaklandLYM
ITER Fusion Reactor
ITER Fusion Reactor
Published: 2012/10/08
Channel: Jamison Daniel
Pression magnétique- magnetic confinement
Pression magnétique- magnetic confinement
Published: 2016/01/03
Channel: gilbondfac
The World
The World's Largest Fusion Experiment
Published: 2017/09/13
Channel: Fast, Furious & Funny
Fusion Plasma and Tokamak
Fusion Plasma and Tokamak
Published: 2015/01/12
Channel: Rhythm
Fusion   Magnetic Confinement   Home Energy Reactor
Fusion Magnetic Confinement Home Energy Reactor
Published: 2017/04/20
Channel: Nicholas T
Fusion Plasma Physics and ITER - An Introduction (1/4)
Fusion Plasma Physics and ITER - An Introduction (1/4)
Published: 2012/05/16
Channel: Teknociencia
Plasma confinement on disk shaped
Plasma confinement on disk shaped
Published: 2014/08/20
Channel: gilbondfac
Minute Physics- Inertial Confinement Fusion
Minute Physics- Inertial Confinement Fusion
Published: 2012/05/20
Channel: thevolkmann
#MCF: The Physics of Magnetic Confinement in 180 Minutes (Part 2) - Michael Barnes
#MCF: The Physics of Magnetic Confinement in 180 Minutes (Part 2) - Michael Barnes
Published: 2016/07/22
Channel: Institute for Advanced Study
Books of Nuclear Fusion Half a Century of Magnetic Confinement Fusion Research Plasma Physics
Books of Nuclear Fusion Half a Century of Magnetic Confinement Fusion Research Plasma Physics
Published: 2015/10/21
Channel: Evelyn McKinney
6c Fusion: inertial and magnetic approaches
6c Fusion: inertial and magnetic approaches
Published: 2015/09/15
Channel: Plasma Physics and Applications
Superconductors - super-magnetic confinement!
Superconductors - super-magnetic confinement!
Published: 2013/09/27
Channel: EFDAJET
CPEP PHYSICS Magnetic Confinement
CPEP PHYSICS Magnetic Confinement
Published: 2012/07/30
Channel: Cheryl Harper
Can We Harness The Star Power | Fusion
Can We Harness The Star Power | Fusion
Published: 2017/11/15
Channel: Trillion Thoughts
Polywell Fusion: Electrostatic Fusion in a Magnetic Cusp
Polywell Fusion: Electrostatic Fusion in a Magnetic Cusp
Published: 2016/08/04
Channel: Microsoft Research
Nuclear Fusion: Clean Power for the Next Hundred Centuries
Nuclear Fusion: Clean Power for the Next Hundred Centuries
Published: 2009/09/10
Channel: GoogleTechTalks
Magnetic Confinement Simulation with JavaScript & D3.js
Magnetic Confinement Simulation with JavaScript & D3.js
Published: 2015/10/13
Channel: Matthew Loftus
Fusion An Introduction to the Physics and Technology of Magnetic Confinement Fusion Pdf Book
Fusion An Introduction to the Physics and Technology of Magnetic Confinement Fusion Pdf Book
Published: 2016/06/03
Channel: Linda. A
6d Simple design of a magnetic fusion reactor
6d Simple design of a magnetic fusion reactor
Published: 2015/09/15
Channel: Plasma Physics and Applications
Download Fusion Volume 1 Magnetic Confinement Part B Book
Download Fusion Volume 1 Magnetic Confinement Part B Book
Published: 2016/09/19
Channel: F. Bingham
28A Inertial Magnetic Fusion | Introduction to Plasma Physics by J D Callen
28A Inertial Magnetic Fusion | Introduction to Plasma Physics by J D Callen
Published: 2015/12/24
Channel: Lucius Fox
Fusion An Introduction to the Physics and Technology of Magnetic Confinement Fusion
Fusion An Introduction to the Physics and Technology of Magnetic Confinement Fusion
Published: 2017/02/07
Channel: Josefina
Fusion An Introduction to the Physics and Technology of Magnetic Confinement Fusion
Fusion An Introduction to the Physics and Technology of Magnetic Confinement Fusion
Published: 2017/03/07
Channel: Paul B
Mellotron + Magnetic Confinement Plasma Beam Generator
Mellotron + Magnetic Confinement Plasma Beam Generator
Published: 2010/01/10
Channel: TheTesteccles
Understanding turbulence to use magnetically confined fusion
Understanding turbulence to use magnetically confined fusion
Published: 2008/11/17
Channel: KyleBGustafson
Fusion and magnetic confinement of high temperature plasmas | Фридрих Вагнер | Лекториум
Fusion and magnetic confinement of high temperature plasmas | Фридрих Вагнер | Лекториум
Published: 2014/01/21
Channel: Лекториум
4a The Sun: a gravitationally confined fusion reactor
4a The Sun: a gravitationally confined fusion reactor
Published: 2016/02/01
Channel: Plasma Physics and Applications
Download Fusion An Introduction to the Physics and Technology of Magnetic Confinement Fusion
Download Fusion An Introduction to the Physics and Technology of Magnetic Confinement Fusion
Published: 2017/02/22
Channel: Jamie S
Inertial Confinement Fusion Simulation
Inertial Confinement Fusion Simulation
Published: 2014/03/04
Channel: Michael Knox
Inertial confinement fusion Top # 20 Facts
Inertial confinement fusion Top # 20 Facts
Published: 2015/10/26
Channel: Harshal Pandya
discovering physics magnetic confinement
discovering physics magnetic confinement
Published: 2013/01/01
Channel: mrcotton333
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WIKIPEDIA ARTICLE

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The reaction chamber of the TCV, an experimental tokamak fusion reactor at École polytechnique fédérale de Lausanne, Lausanne, Switzerland which has been used in research since it was built in 1992. The characteristic torus-shaped chamber is clad with graphite to help withstand the extreme heat (the shape is distorted by the camera's fisheye lens).

Magnetic confinement fusion is an approach to generating thermonuclear fusion power that uses magnetic fields to confine the hot fusion fuel in the form of a plasma. Magnetic confinement is one of two major branches of fusion energy research, the other being inertial confinement fusion. The magnetic approach dates into the 1940s and has seen the majority of development since then. It is usually considered more promising for practical power production.

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 several tens of millions of degrees, under which conditions they no longer form neutral atoms but exist in the plasma state. In addition, sufficient density and energy confinement are required, as specified by the Lawson criterion.

At these temperatures, no material container could withstand the extreme heat of the plasma. Magnetic confinement fusion attempts to create these conditions by using the electrical conductivity of the plasma to contain it with magnetic fields. The basic concept can be thought of in a fluid picture as a balance between magnetic pressure and plasma pressure, or in terms of individual particles spiralling along magnetic field lines. Developing a suitable arrangement of fields that contain the fuel ions without introducing turbulence or leaking the fuel at a profuse rate has proven to be a difficult problem.

The development of MFE has gone through three distinct phases. In the 1950s it was believed MFE would be relatively easy to achieve, and this developed into a race to build a suitable machine. By the late 1950s, it was clear that turbulence and instabilities in the plasma were a serious problem, and during the 1960s, "the doldrums", effort turned to a better understanding of the physics of plasmas. In 1968, a Soviet team invented the tokamak magnetic confinement device, which demonstrated performance ten times better than the best alternatives. Since then the MFE field has been dominated by the tokamak approach. Construction of a 500-MW power generating fusion plant using this design, the ITER, began in France in 2007 and is scheduled to begin operation 2035.

Magnetic mirrors[edit]

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 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 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 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 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 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) was built to test this layout. TMX demonstrated a new series of problems that suggested MFTF would not reach its performance goals, and one day after the construction of MFTF was completed it was mothballed. Mirrors have seen little development since that time.

Toroidal machines[edit]

Stellarators[edit]

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 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 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 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 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 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.

Tokamaks[edit]

Tokamak magnetic fields.

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 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 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 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.

Other[edit]

Some more novel configurations produced in toroidal machines are the reversed field pinch and the Levitated Dipole Experiment.

Compact toroids[edit]

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[dubious ] in the 1970s was Trisops. (Trisops fired two theta-pinch rings towards each other.)

Magnetic fusion energy[edit]

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 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 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.[1] Electromagnetic waves can be injected and steered to manipulate the paths of plasma particles and then to produce the large electrical currents necessary to produce the magnetic fields to confine the plasma.[citation needed] 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.

See also[edit]

References[edit]

  1. ^ ITER Physics Basis Editors (1999). "Chapter 6: Plasma auxiliary heating and current drive". Nucl. Fusion. ITER Physics Expert Group on Energetic Particles, Heating and Current drive. 39: 2495. 

External links[edit]

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