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{{Short description|Method of confining plasma for nuclear fusion using magnetic fields}}

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

'''Magnetic confinement fusion''' ('''MCF''') is an approach to controlled [[Physics:Quantum Fusion|thermonuclear fusion]] in which magnetic fields are used to confine fusion fuel in the form of a high-temperature [[Physics:Quantum matter/plasma|plasma]]. It is one of the two main branches of controlled fusion research, alongside inertial confinement fusion (ICF).<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 |s2cid=4290094}}</ref>

<div style="float:right; border:1px solid #ccc; padding:4px; background:#ffffe6; margin:0 0 1em 1em; width:400px;">
[[File:MASTA yellow.jpg|400px]]
<div style="font-size:90%;">Spherical tokamak plasma (MAST experiment) with modified color scheme for visualization.</div>
</div>

== Fusion conditions and magnetic confinement principles ==

The central problem of magnetic fusion is to satisfy the [[Physics:Quantum Fusion reactions and Lawson criterion|Lawson criterion]] while minimizing energy losses. In a deuterium–tritium plasma, fusion performance depends on plasma density, temperature, and energy confinement time, often summarized through the triple product.<ref>{{cite journal |author=ITER Physics Basis Editors |title=Chapter 6: Plasma auxiliary heating and current drive |journal=Nuclear Fusion |volume=39 |issue=12 |pages=2495–2539 |date=1999 |doi=10.1088/0029-5515/39/12/306 |bibcode=1999NucFu..39.2495I}}</ref>

Magnetic confinement generally operates at lower densities than inertial confinement, so it must compensate by maintaining the plasma for much longer times.<ref>{{Cite journal |last1=Keilhacker |first1=M. |last2=Gibson |first2=A. |last3=Gormezano |first3=C. |last4=Rebut |first4=P. H. |date=2001 |title=The scientific success of JET |journal=Nuclear Fusion |volume=41 |issue=12 |pages=1925–1966 |doi=10.1088/0029-5515/41/12/217 |s2cid=250759123}}</ref>

In a magnetic field, [[Physics:Quantum atoms/ion|ions]] and [[Physics:Quantum atoms/electron|electrons]] gyrate around field lines with characteristic Larmor radii. This does not by itself guarantee confinement, because particles can still drift, collide, and diffuse across the field. Practical MCF devices therefore use closed magnetic surfaces, rotational transform, magnetic shear, and auxiliary heating and control systems to reduce [[Physics:Quantum Transport theory|transport]] and maintain stability.<ref>{{Cite journal |last1=Pedersen |first1=T. Sunn |last2=Otte |first2=M. |last3=Lazerson |first3=S. |last4=Helander |first4=P. |last5=Bozhenkov |first5=S. |last6=Biedermann |first6=C. |last7=Klinger |first7=T. |last8=Wolf |first8=R. C. |last9=Bosch |first9=H.-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 |pages=13493 |doi=10.1038/ncomms13493 |pmid=27901043 |pmc=5141350 |bibcode=2016NatCo...713493P}}</ref>

One of the persistent difficulties of MCF is turbulent transport. Even when the magnetic geometry is nominally closed, small-scale turbulence can drive heat and particles outward, degrading energy confinement.<ref>{{Cite journal |last1=Fenstermacher |first1=M. E. |title=Recent progress in DIII-D research for next-step tokamaks |journal=Nuclear Fusion |volume=62 |issue=4 |pages=042024 |date=2022 |doi=10.1088/1741-4326/ac2ff2 |s2cid=244608556}}</ref>

This is one reason fusion research has required increasingly sophisticated diagnostics, real-time feedback control, and improved [[Physics:Quantum Plasma-wall interaction|plasma-facing components]].<ref>{{cite press release |title=DIII-D National Fusion Facility Begins Transformation to Prepare for Future Reactors |url=https://www.globenewswire.com/en/news-release/2018/05/18/1508976/0/en/DIII-D-National-Fusion-Facility-Begins-Transformation-to-Prepare-for-Future-Reactors.html |date=2018-05-18}}</ref>

== Historical development ==

Research into magnetic confinement began in the early 1950s, when several simple magnetic geometries were proposed as possible routes to fusion power. Early work focused on magnetic mirrors, pinch devices, stellarators, and toroidal systems.

The decisive breakthrough came in 1968, when the Soviet tokamak T3 demonstrated high plasma temperatures, later confirmed by Thomson scattering measurements.<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 |s2cid=4290094}}</ref>

This event established the tokamak as the dominant magnetic confinement configuration.

== Major magnetic confinement concepts ==

=== Tokamaks ===

The [[Physics:Quantum Tokamak|tokamak]] is the most widely developed magnetic confinement device. It uses combined magnetic fields to confine plasma in a toroidal geometry.

=== Stellarators ===

The stellarator provides magnetic confinement without relying on a strong plasma current, using complex external coil geometries.

=== Other configurations ===

Other concepts include reversed field pinch, spheromaks, and field-reversed configurations, which explore alternative confinement geometries.

== Key physics and engineering challenges ==

Magnetic confinement fusion faces several major challenges:

* Achieving sufficient confinement and stability
* Controlling turbulent transport
* Managing heat exhaust at the plasma edge
* Handling neutron damage to materials
* Sustaining long-duration or steady-state operation

== Outlook ==

Magnetic confinement fusion remains the most advanced route toward controlled thermonuclear power. While major challenges remain, continued advances in plasma physics, materials science, and engineering are steadily improving the feasibility of fusion energy.

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

== References ==
{{reflist|3}}

{{Author|Harold Foppele}}

{{Sourceattribution|Quantum Magnetic confinement fusion|1}}

Physics:Quantum Inertial confinement fusion - Revision history

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