Editing Fusion power (section)

== Common tools ==
Many approaches, equipment, and mechanisms are employed across multiple projects to address fusion heating, measurement, and power production.<ref>{{Cite journal|date=1972|title=Plasma Physics|journal=Government Reports Announcements|volume=72|pages=194}}</ref>

=== Machine learning ===
A [[deep reinforcement learning]] system has been used to control a [[tokamak]]-based reactor.<ref>{{cite journal |last1=Degrave |first1=J. |last2=Felici |first2=F. |date=2022 |title=Magnetic control of tokamak plasmas through deep reinforcement learning |journal=Nature |volume=602 |issue=7897 |pages=414–419 |doi=10.1038/s41586-021-04301-9 |pmid=35173339 |pmc=8850200 |bibcode=2022Natur.602..414D |url=https://doi.org/10.1038/s41586-021-04301-9 |access-date=February 5, 2025}}</ref> The system was able to manipulate the magnetic coils to manage the plasma. The system was able to continuously adjust to maintain appropriate behavior (more complex than step-based systems).{{cn|date=July 2024}} In 2014, Google began working with California-based fusion company [[TAE Technologies]] to control the [[Joint European Torus]] (JET) to predict plasma behavior.<ref>{{Cite magazine|last=Katwala|first=Amit|date=February 16, 2022|title=DeepMind Has Trained an AI to Control Nuclear Fusion|language=en-US|magazine=Wired|url=https://www.wired.com/story/deepmind-ai-nuclear-fusion/|access-date=February 17, 2022|issn=1059-1028}}</ref> [[DeepMind]] has also developed a control scheme with [[Tokamak à configuration variable|TCV]].<ref>{{cite magazine | url=https://www.wired.com/story/deepmind-ai-nuclear-fusion/ | title=DeepMind Has Trained an AI to Control Nuclear Fusion | magazine=Wired | last1=Katwala | first1=Amit }}</ref>

=== Heating ===
{{Main|Dielectric heating|Magnetic reconnection|Inertial electrostatic confinement|Neutral beam injection}}

* Electrostatic heating: an electric field can do [[work (thermodynamics)|work]] on charged ions or electrons, heating them.<ref>{{Cite book|last=Miley, George H. |title=Inertial electrostatic confinement (IEC) fusion : fundamentals and applications|date=2013|publisher=Springer|others=Murali, S. Krupakar|isbn=978-1461493389|location=Dordrecht|oclc=878605320}}</ref>
* [[Neutral-beam injection|Neutral beam injection]]: hydrogen is ionized and accelerated by an electric field to form a charged beam that is shone through a source of neutral hydrogen gas towards the plasma which itself is ionized and contained by a magnetic field. Some of the intermediate hydrogen gas is accelerated towards the plasma by collisions with the charged beam while remaining neutral: this neutral beam is thus unaffected by the magnetic field and so reaches the plasma. Once inside the plasma the neutral beam transmits energy to the plasma by collisions which ionize it and allow it to be contained by the magnetic field, thereby both heating and refueling the reactor in one operation. The remainder of the charged beam is diverted by magnetic fields onto cooled beam dumps.<ref>{{Cite book |last=Kunkel |first=W. B. |title=Fusion |publisher=Lawrence Livermore National Laboratory |year=1981 |isbn=978-0126852417 |editor-last=Teller |editor-first=E. |chapter=Neutral-beam injection}}</ref>
* Radio frequency heating: a radio wave causes the plasma to oscillate (i.e., [[microwave oven]]). This is also known as [[electron cyclotron resonance heating]], using for example [[gyrotron]]s, or [[dielectric heating]].<ref>{{Cite journal|last1=Erckmann|first1=V|last2=Gasparino|first2=U|date=December 1, 1994|title=Electron cyclotron resonance heating and current drive in toroidal fusion plasmas|url=https://iopscience.iop.org/article/10.1088/0741-3335/36/12/001|journal=Plasma Physics and Controlled Fusion|volume=36|issue=12|pages=1869–1962|bibcode=1994PPCF...36.1869E|doi=10.1088/0741-3335/36/12/001|s2cid=250897078|issn=0741-3335}}</ref>
* [[Magnetic reconnection]]: when plasma gets dense, its electromagnetic properties can change, which can lead to [[magnetic reconnection]]. Reconnection helps fusion because it instantly dumps energy into a plasma, heating it quickly. Up to 45% of the magnetic field energy can heat the ions.<ref>{{Cite journal|last1=Ono|first1=Y.|last2=Tanabe|first2=H.|last3=Yamada|first3=T.|last4=Gi|first4=K.|last5=Watanabe|first5=T.|last6=Ii|first6=T.|last7=Gryaznevich|first7=M.|last8=Scannell|first8=R.|last9=Conway|first9=N.|last10=Crowley|first10=B.|last11=Michael|first11=C.|date=May 1, 2015|title=High power heating of magnetic reconnection in merging tokamak experiments|url=https://aip.scitation.org/doi/10.1063/1.4920944|journal=Physics of Plasmas|volume=22|issue=5|pages=055708|bibcode=2015PhPl...22e5708O|doi=10.1063/1.4920944|issn=1070-664X|hdl=1885/28549|hdl-access=free}}</ref><ref>{{Cite journal|last1=Yamada|first1=M.|last2=Chen|first2=L.-J.|last3=Yoo|first3=J.|last4=Wang|first4=S.|last5=Fox|first5=W.|last6=Jara-Almonte|first6=J.|last7=Ji|first7=H.|last8=Daughton|first8=W.|last9=Le|first9=A.|last10=Burch|first10=J.|last11=Giles|first11=B.|date=December 6, 2018|title=The two-fluid dynamics and energetics of the asymmetric magnetic reconnection in laboratory and space plasmas|url= |journal=Nature Communications|language=en|volume=9|issue=1|pages=5223|bibcode=2018NatCo...9.5223Y|doi=10.1038/s41467-018-07680-2|issn=2041-1723|pmc=6283883|pmid=30523290}}</ref>
* Magnetic oscillations: varying electric currents can be supplied to magnetic coils that heat plasma confined within a magnetic wall.<ref>McGuire, Thomas. Heating Plasma for Fusion Power Using Magnetic Field Oscillations. Baker Botts LLP, assignee. Issued: 4/2/14, Patent 14/243,447. N.d. Print.</ref>
* Antiproton annihilation: [[antiproton]]s injected into a mass of fusion fuel can induce thermonuclear reactions. This possibility as a method of spacecraft propulsion, known as [[antimatter-catalyzed nuclear pulse propulsion]], was investigated at [[Pennsylvania State University]] in connection with the proposed [[AIMStar]] project.{{Citation needed|date=June 2021}}

=== Measurement ===
{{Main|Flux loop|Langmuir probe|Neutron detection|Thomson scattering|X-ray detector}}

The diagnostics of a fusion scientific reactor are extremely complex and varied.<ref>{{Citation|title=Towards a fusion reactor|work=Nuclear Fusion|year=2002|publisher=IOP Publishing Ltd|doi=10.1887/0750307056/b888c9|isbn=0750307056|doi-access=free}}</ref> The diagnostics required for a fusion power reactor will be various but less complicated than those of a scientific reactor as by the time of commercialization, many real-time feedback and control diagnostics will have been perfected. However, the operating environment of a commercial fusion reactor will be harsher for diagnostic systems than in a scientific reactor because continuous operations may involve higher plasma temperatures and higher levels of neutron irradiation. In many proposed approaches, commercialization will require the additional ability to measure and separate diverter gases, for example helium and impurities, and to monitor fuel breeding, for instance the state of a tritium breeding liquid lithium liner.<ref>{{Citation|last1=Pearson|first1=Richard J|title=Review of approaches to fusion energy|date=2020|url=http://dx.doi.org/10.1088/978-0-7503-2719-0ch2|work=Commercialising Fusion Energy|publisher=IOP Publishing|access-date=December 12, 2021|last2=Takeda|first2=Shutaro|doi=10.1088/978-0-7503-2719-0ch2|isbn=978-0750327190|s2cid=234561187}}</ref> The following are some basic techniques.
* [[Flux loop]]: a loop of wire is inserted into the magnetic field. As the field passes through the loop, a current is made. The current measures the total magnetic flux through that loop. This has been used on the [[National Compact Stellarator Experiment]],<ref>{{Cite book|last1=Labik|first1=George|last2=Brown|first2=Tom|last3=Johnson|first3=Dave|last4=Pomphrey|first4=Neil|last5=Stratton|first5=Brentley|last6=Viola|first6=Michael|last7=Zarnstorff|first7=Michael|last8=Duco|first8=Mike|last9=Edwards|first9=John|last10=Cole|first10=Mike|last11=Lazarus|first11=Ed|title=2007 IEEE 22nd Symposium on Fusion Engineering |chapter=National Compact Stellarator Experiment Vacuum Vessel External Flux Loops Design and Installation |date=2007|chapter-url=https://ieeexplore.ieee.org/document/4337935|pages=1–3|doi=10.1109/FUSION.2007.4337935|isbn=978-1424411931|s2cid=9298179}}</ref> the [[polywell]],<ref>{{Cite journal|last1=Park|first1=Jaeyoung|last2=Krall|first2=Nicholas A.|last3=Sieck|first3=Paul E.|last4=Offermann|first4=Dustin T.|last5=Skillicorn|first5=Michael|last6=Sanchez|first6=Andrew|last7=Davis|first7=Kevin|last8=Alderson|first8=Eric|last9=Lapenta|first9=Giovanni|date=June 1, 2014|title=High Energy Electron Confinement in a Magnetic Cusp Configuration|journal=Physical Review X|volume=5|issue=2|pages=021024|arxiv=1406.0133|bibcode=2015PhRvX...5b1024P|doi=10.1103/PhysRevX.5.021024|s2cid=118478508}}</ref> and the [[Levitated dipole|LDX]] machines. A [[Langmuir probe]], a metal object placed in a plasma, can be employed. A potential is applied to it, giving it a [[voltage]] against the surrounding plasma. The metal collects charged particles, drawing a current. As the voltage changes, the current changes. This makes an [[Current–voltage characteristic|IV Curve]]. The IV-curve can be used to determine the local plasma density, potential and temperature.<ref>{{cite journal|last1=Mott-Smith|first1=H. M.|last2=Langmuir|first2=Irving|date=September 1, 1926|title=The Theory of Collectors in Gaseous Discharges|journal=Physical Review|publisher=American Physical Society (APS)|volume=28|issue=4|pages=727–763|bibcode=1926PhRv...28..727M|doi=10.1103/physrev.28.727|issn=0031-899X}}</ref>
* [[Thomson scattering]]: "Light scatters" from plasma can be used to reconstruct plasma behavior, including density and temperature. It is common in [[Inertial confinement fusion]],<ref>{{cite journal | last1=Esarey | first1=Eric | last2=Ride | first2=Sally K. | last3=Sprangle | first3=Phillip | title=Nonlinear Thomson scattering of intense laser pulses from beams and plasmas | journal=Physical Review E | publisher=American Physical Society (APS) | volume=48 | issue=4 | date=September 1, 1993 | issn=1063-651X | doi=10.1103/physreve.48.3003 | pmid=9960936 | pages=3003–3021| bibcode=1993PhRvE..48.3003E }}</ref> [[Tokamak]]s,<ref>{{Cite journal |last1=Kantor |first1=M. Yu |last2=Donné |first2=A. J. H. |last3=Jaspers |first3=R. |last4=van der Meiden |first4=H. J. |date=February 26, 2009 |title=Thomson scattering system on the TEXTOR tokamak using a multi-pass laser beam configuration |url=https://iopscience.iop.org/article/10.1088/0741-3335/51/5/055002 |journal=Plasma Physics and Controlled Fusion |language=en |volume=51 |issue=5 |pages=055002 |bibcode=2009PPCF...51e5002K |doi=10.1088/0741-3335/51/5/055002 |issn=0741-3335 |s2cid=123495440}}</ref> and [[fusor]]s. In ICF systems, firing a second beam into a gold foil adjacent to the target makes x-rays that traverse the plasma. In tokamaks, this can be done using mirrors and detectors to reflect light.
* [[Neutron detection|Neutron detectors]]: [[Neutron detection#Types of neutron detectors|Several types of neutron detectors]] can record the rate at which neutrons are produced.<ref>{{Cite book|last=Tsoulfanidis|first=Nicholas|url=http://archive.org/details/measurementdetec00tsou|title=Measurement and detection of radiation|date=1995|publisher=Washington, DC : Taylor & Francis|others=Library Genesis|isbn=978-1560323174}}</ref><ref>{{Cite book|last=Knoll, Glenn F. |title=Radiation detection and measurement|date=2010|publisher=John Wiley|isbn=978-0470131480|edition=4th|location=Hoboken, NJ|oclc=612350364}}</ref>
* [[X-ray detectors]] Visible, IR, UV, and X-rays are emitted anytime a particle changes velocity.<ref>{{Cite journal|last=Larmor|first=Joseph|date=January 1, 1897|title=IX. A dynamical theory of the electric and luminiferous medium. Part III. relations with material media|journal=Philosophical Transactions of the Royal Society of London. Series A, Containing Papers of a Mathematical or Physical Character|volume=190|pages=205–300|doi=10.1098/rsta.1897.0020|bibcode=1897RSPTA.190..205L|doi-access=free}}</ref> If the reason is deflection by a magnetic field, the radiation is [[cyclotron]] radiation at low speeds and [[synchrotron]] radiation at high speeds. If the reason is deflection by another particle, plasma radiates X-rays, known as [[Bremsstrahlung]] radiation.<ref>{{Cite book |title=Diagnostics for experimental thermonuclear fusion reactors 2|date=1998|publisher=Springer |veditors=Stott PE, Gorini G, Prandoni P, Sindoni E |isbn=978-1461553533|location=New York|oclc=828735433}}</ref>

=== Power production ===
Neutron blankets absorb neutrons, which heats the blanket. Power can be extracted from the blanket in various ways:

* [[Steam turbine]]s can be driven by heat transferred into a [[working fluid]] that turns into steam, driving electric generators.<ref>{{Cite journal|last1=Ishiyama|first1=Shintaro|last2=Muto|first2=Yasushi|last3=Kato|first3=Yasuyoshi|last4=Nishio|first4=Satoshi|last5=Hayashi|first5=Takumi|last6=Nomoto|first6=Yasunobu|date=March 1, 2008|title=Study of steam, helium and supercritical CO2 turbine power generations in prototype fusion power reactor|url=http://www.sciencedirect.com/science/article/pii/S0149197007001552|journal=Progress in Nuclear Energy |language=en|volume=50|issue=2|pages=325–332|doi=10.1016/j.pnucene.2007.11.078|issn=0149-1970}}</ref>
* Neutron blankets: These neutrons can regenerate spent fission fuel.<ref>{{cite web |last1=Anklam |first1=T. |last2=Simon |first2=A. J. |last3=Powers |first3=S. |last4=Meier |first4=W. R. |date=December 2, 2010 |title=LIFE: The Case for Early Commercialization of Fusion Energy |url=https://e-reports-ext.llnl.gov/pdf/459730.pdf |url-status=dead |archive-url=https://web.archive.org/web/20150904055903/https://e-reports-ext.llnl.gov/pdf/459730.pdf |archive-date=September 4, 2015 |access-date=October 30, 2014 |publisher=Lawrence Livermore National Laboratory, LLNL-JRNL-463536}}</ref> Tritium can be produced using a breeder blanket of liquid lithium or a helium cooled pebble bed made of lithium-bearing ceramic pebbles.<ref name="l2s">{{cite journal |last1=Hanaor |first1=D. A. H. |last2=Kolb |first2=M. H. H. |last3=Gan |first3=Y. |last4=Kamlah |first4=M. |last5=Knitter |first5=R. |year=2014 |title=Solution based synthesis of mixed-phase materials in the Li<sub>2</sub>TiO<sub>3</sub>-Li<sub>4</sub>SiO<sub>4</sub> system |journal=Journal of Nuclear Materials |volume=456 |pages=151–161 |arxiv=1410.7128 |bibcode=2015JNuM..456..151H |doi=10.1016/j.jnucmat.2014.09.028 |s2cid=94426898}}</ref>
* [[Direct energy conversion|Direct conversion]]: The [[kinetic energy]] of a particle can be converted into [[voltage]].<ref name="Post 99–111" /> It was first suggested by [[Richard F. Post]] in conjunction with [[magnetic mirror]]s, in the late 1960s. It has been proposed for [[Field-Reversed Configuration]]s as well as [[Dense Plasma Focus]] devices. The process converts a large fraction of the random energy of the fusion products into directed motion. The particles are then collected on electrodes at various large electrical potentials. This method has demonstrated an experimental efficiency of 48 percent.<ref>{{Cite journal|last1=Barr|first1=William L.|last2=Moir|first2=Ralph W.|date=January 1, 1983|title=Test Results on Plasma Direct Converters|url=https://doi.org/10.13182/FST83-A20820|journal=Nuclear Technology – Fusion|volume=3|issue=1|pages=98–111|doi=10.13182/FST83-A20820|bibcode=1983NucTF...3...98B |issn=0272-3921}}</ref>
* [[Traveling-wave tube]]s pass charged helium atoms at several megavolts and just coming off the fusion reaction through a tube with a coil of wire around the outside. This passing charge at high voltage pulls electricity through the wire.

=== Confinement ===
[[File:IFE and MFE parameter space.svg|thumb|upright=1.75|Parameter space occupied by [[inertial fusion energy]] and [[magnetic fusion energy]] devices as of the mid-1990s. The regime allowing thermonuclear ignition with high gain lies near the upper right corner of the plot.]]

Confinement refers to all the conditions necessary to keep a plasma dense and hot long enough to undergo fusion. General principles:

* [[Mechanical equilibrium|Equilibrium]]: The forces acting on the plasma must be balanced. One exception is [[inertial confinement fusion|inertial confinement]], where the fusion must occur faster than the dispersal time.
* [[Plasma stability|Stability]]: The plasma must be constructed so that disturbances will not lead to the plasma dispersing.
* Transport or [[conduction (heat)|conduction]]: The loss of material must be sufficiently slow.<ref name="Lawson"/> The plasma carries energy off with it, so rapid loss of material will disrupt fusion. Material can be lost by transport into different regions or [[conduction (heat)|conduction]] through a solid or liquid.

To produce self-sustaining fusion, part of the energy released by the reaction must be used to heat new reactants and maintain the conditions for fusion.

==== Magnetic confinement ====
===== Magnetic Mirror =====
[[Magnetic mirror]] effect. If a particle follows the field line and enters a region of higher field strength, the particles can be reflected. Several devices apply this effect. The most famous was the magnetic mirror machines, a series of devices built at LLNL from the 1960s to the 1980s.<ref name=Booth>{{cite journal|last=Booth|first=William|title=Fusion's $372-Million Mothball|journal=Science|date=October 9, 1987|volume=238|issue=4824|pages=152–155|doi= 10.1126/science.238.4824.152|pmid=17800453|bibcode=1987Sci...238..152B}}</ref> Other examples include magnetic bottles and [[Biconic cusp]].<ref>{{Cite book|last=Grad|first=Harold |title=Containment in cusped plasma systems (classic reprint).|date=2016|publisher=Forgotten Books |isbn=978-1333477035|location=<!-- Place of publication not identified -->|language=en|oclc=980257709}}</ref> Because the mirror machines were straight, they had some advantages over ring-shaped designs. The mirrors were easier to construct and maintain and [[Direct energy conversion|direct conversion]] energy capture was easier to implement.<ref name="ReferenceA"/> Poor confinement has led this approach to be abandoned, except in the polywell design.<ref>{{Cite web|last=Lee|first=Chris|date=June 22, 2015|title=Magnetic mirror holds promise for fusion|url=https://arstechnica.com/science/2015/06/magnetic-mirror-holds-promise-for-fusion/|access-date=October 11, 2020|website=Ars Technica|language=en-us}}</ref>

===== Magnetic loops =====
Magnetic loops bend the field lines back on themselves, either in circles or more commonly in nested [[torus|toroidal]] surfaces. The most highly developed systems of this type are the [[tokamak]], the stellarator, and the reversed field pinch. [[Compact toroid]]s, especially the field-reversed configuration and the spheromak, attempt to combine the advantages of toroidal magnetic surfaces with those of a [[simply connected space|simply connected]] (non-toroidal) machine, resulting in a mechanically simpler and smaller confinement area.

==== Inertial confinement ====
[[File:Electra Laser Generates 90K Shots.webm|thumb|alt=The Electra Laser at Naval Research Laboratory demonstrates 90,000 shots in 10 hours, repetition needed for IFE power plant.|The Electra Laser at Naval Research Laboratory demonstrates 90,000 shots in 10 hours, repetition needed for IFE power plant.]]

Inertial confinement is the use of rapid implosion to heat and confine plasma. A shell surrounding the fuel is imploded using a direct laser blast (direct drive), a secondary x-ray blast (indirect drive), or heavy beams. The fuel must be compressed to about 30 times solid density with energetic beams. Direct drive can in principle be efficient, but insufficient uniformity has prevented success.<ref name="confinement">{{Cite book|last=Pfalzner, Susanne |title=An introduction to inertial confinement fusion|date=2006|publisher=Taylor & Francis/CRC Press|isbn=1420011847|location=New York|oclc=72564680}}</ref><sup>:19–20</sup> Indirect drive uses beams to heat a shell, driving the shell to radiate [[x-rays]], which then implode the pellet. The beams are commonly laser beams, but ion and electron beams have been investigated.<ref name="confinement" /><sup>:182–193</sup>

===== Electrostatic confinement =====
[[Inertial electrostatic confinement|Electrostatic confinement fusion]] devices use electrostatic fields. The best known is the [[fusor]]. This device has a cathode inside an anode wire cage. Positive ions fly towards the negative inner cage, and are heated by the electric field in the process. If they miss the inner cage they can collide and fuse. Ions typically hit the cathode, however, creating prohibitory high [[conduction (heat)|conduction]] losses. Fusion rates in [[fusor]]s are low because of competing physical effects, such as energy loss in the form of light radiation.<ref name="Thorson1996">{{cite book|first=Timothy A. |last=Thorson|title=Ion flow and fusion reactivity characterization of a spherically convergent ion focus|url={{google books |plainurl=y |id=k6zVAAAAMAAJ}}|year=1996|publisher=University of Wisconsin, Madison}}</ref> Designs have been proposed to avoid the problems associated with the cage, by generating the field using a non-neutral cloud. These include a plasma oscillating device,<ref>{{Cite journal|last1=Barnes|first1=D. C.|last2=Nebel|first2=R. A.|date=July 1998|title=Stable, thermal equilibrium, large-amplitude, spherical plasma oscillations in electrostatic confinement devices|url=http://dx.doi.org/10.1063/1.872933|journal=Physics of Plasmas|volume=5|issue=7|pages=2498–2503|doi=10.1063/1.872933|bibcode=1998PhPl....5.2498B|issn=1070-664X}}</ref> a magnetically shielded-grid,<ref>{{Cite journal|last1=Hedditch|first1=John|last2=Bowden-Reid|first2=Richard|last3=Khachan|first3=Joe|date=October 2015|title=Fusion in a magnetically-shielded-grid inertial electrostatic confinement device|journal=Physics of Plasmas|volume=22|issue=10|pages=102705|doi=10.1063/1.4933213|issn=1070-664X|arxiv=1510.01788|bibcode=2015PhPl...22j2705H }}</ref> a [[penning trap]], the [[polywell]],<ref>{{cite journal | last1 = Carr | first1 = M. | last2 = Khachan | first2 = J. | year = 2013 | title = A biased probe analysis of potential well formation in an electron only, low beta Polywell magnetic field | url = https://zenodo.org/record/1244056| journal = Physics of Plasmas | volume = 20 | issue = 5| page = 052504 | doi = 10.1063/1.4804279 | bibcode = 2013PhPl...20e2504C }}</ref> and the F1 cathode driver concept.<ref>{{Cite book|last1=Sieckand|first1=Paul|url=https://arpa-e.energy.gov/sites/default/files/3_VOLBERG.pdf|title=Fusion One Corporation|last2=Volberg|first2=Randall|publisher=Fusion One Corporation|year=2017}}</ref>