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Fix Matter see-also invoke

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Fix Matter see-also invoke

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{{Quantum matter backlink|Plasma and fusion physics}}

'''Quantum magnetic confinement''' is the use of strong [[Physics:Magnetic field|magnetic fields]] to confine a hot [[Physics:Plasma|plasma]] long enough for [[Physics:Quantum Fusion|fusion]] reactions to occur. In fusion research, the fuel is usually a mixture of [[Physics:Quantum atoms/deuterium|deuterium]] and [[Physics:Quantum atoms/tritium|tritium]], whose nuclei can fuse to form helium, a neutron, and released kinetic energy.

At fusion temperatures the fuel is fully ionized, so its particles are electrically charged. This allows magnetic fields to influence their motion. Instead of trying to hold the plasma in an ordinary vessel, magnetic confinement uses the curved motion of charged particles around field lines to reduce contact with the wall.

The basic requirement is that the plasma remain hot, dense, and confined for a sufficient time. This is summarized by the [[Physics:Quantum Fusion reactions and Lawson criterion|Lawson criterion]], often expressed through the fusion triple product. Because the plasma temperature may reach hundreds of millions of kelvin, direct material containment is impossible.
<div style="float:right; border:1px solid #e0d890; background:#fff8cc; padding:6px; margin:0 0 1em 1em; width:420px;">
[[File:Magnetic Confinement.png|400px]]
<div style="font-size:90%;">Magnetic confinement keeps hot plasma away from material walls by guiding charged particles along magnetic field lines.</div>
</div>
== Fusion reaction ==

The most common reactor fuel cycle is the deuterium–tritium reaction:

:<math>{}^{2}_{1}\mathrm{H}+{}^{3}_{1}\mathrm{H}\rightarrow{}^{4}_{2}\mathrm{He}+{}^{1}_{0}\mathrm{n}+17.6\ \mathrm{MeV}</math>

The energy is carried mainly by the neutron and the helium nucleus. The neutron can escape the magnetic field because it is electrically neutral, while the charged helium nucleus remains magnetically confined and can help heat the plasma.

== Magnetic confinement principle ==

Charged particles in a magnetic field spiral around magnetic field lines. In a fusion device, the field geometry is arranged so that particles follow long paths inside the plasma rather than quickly striking the wall. In toroidal systems, such as [[Physics:Quantum Tokamak|tokamaks]] and [[Physics:Quantum Stellarator|stellarators]], the plasma is shaped into a closed ring.

A tokamak combines a strong toroidal magnetic field with a poloidal field generated partly by current in the plasma. A stellarator produces the required twisted magnetic geometry mainly with external coils, allowing steady-state operation without requiring a large plasma current.

== Tokamaks and stellarators ==

[[Physics:Quantum Tokamak|Tokamaks]] became the dominant magnetic-confinement concept after Soviet experiments reported high plasma temperatures and improved confinement. The T-3 tokamak results were confirmed by Thomson scattering measurements in 1969.<ref>{{Cite journal |last1=Peacock |first1=N. J. |last2=Robinson |first2=D. C. |last3=Forrest |first3=M. J. |last4=Wilcock |first4=P. D. |last5=Sannikov |first5=V. V. |date=1969 |title=Measurement of the Electron Temperature by Thomson Scattering in Tokamak T3 |journal=Nature |volume=224 |issue=5218 |pages=488–490 |doi=10.1038/224488a0 |bibcode=1969Natur.224..488P}}</ref>

Large tokamak experiments include [[Joint European Torus|JET]], TFTR, JT-60, EAST, DIII-D, and ITER. JET achieved 16 MW of fusion power in 1997 and later produced 59 MJ of fusion energy in a 5-second pulse in 2021.<ref>{{Cite journal |last=Gibney |first=Elizabeth |date=2022 |title=Nuclear-fusion reactor smashes energy record |journal=Nature |volume=602 |issue=7897 |page=371 |doi=10.1038/d41586-022-00391-1 |pmid=35140372}}</ref>

[[Physics:Quantum Stellarator|Stellarators]] use externally shaped magnetic coils to create twisted magnetic fields. Their main advantage is the possibility of steady-state operation with reduced risk of current-driven plasma disruptions. The Wendelstein 7-X stellarator in Germany is a major modern example of this approach.<ref>{{Cite journal |last1=Pedersen |first1=T. Sunn |last2=Otte |first2=M. |last3=Lazerson |first3=S. |last4=Helander |first4=P. |last5=Bozhenkov |first5=S. |date=2016 |title=Confirmation of the topology of the Wendelstein 7-X magnetic field to better than 1:100,000 |journal=Nature Communications |volume=7 |article-number=13493 |doi=10.1038/ncomms13493 |pmid=27901043 |pmc=5141350}}</ref>

== Challenges ==

Magnetic confinement fusion must solve several linked physics and engineering problems. The plasma must remain stable against turbulence, disruptions, edge-localized modes, and runaway electrons. The reactor wall and divertor must survive intense heat and neutron flux. A practical reactor also needs tritium breeding, efficient plasma heating, real-time control, and reliable superconducting magnets.

High-temperature superconducting magnets are important because stronger magnetic fields can improve confinement and allow more compact reactor designs. Modern projects such as SPARC explore this path using high-field magnet technology.<ref>{{Cite journal |last1=Sweeney |first1=R. |last2=Creely |first2=A. J. |last3=Doody |first3=J. |date=2020 |title=MHD stability and disruptions in the SPARC tokamak |journal=Journal of Plasma Physics |volume=86 |issue=5 |page=865860507 |doi=10.1017/S0022377820001129}}</ref>

== Importance ==

Magnetic confinement is one of the main routes toward controlled fusion power. It connects quantum nuclear reactions with large-scale plasma physics, superconducting magnet technology, and materials science. If successful, it could provide a high-energy-density power source with low greenhouse-gas emissions and relatively small long-lived radioactive waste compared with fission reactors.

=See also=
{{#invoke:PhysicsQC|tocHeadingAndList|Physics:Quantum basics/See also/Matter}}

=References=
{{reflist|3}}

{{Author|Harold Foppele}}

{{Sourceattribution|Physics:Quantum magnetic confinement|1}}

Physics:Quantum magnetic confinement - Revision history

imported>WikiHarold: Fix Matter see-also invoke

imported>WikiHarold: Fix Matter see-also invoke