Editing Fusion power (section)

== Methods ==
[[File:Chart of Fusion Approaches.png|thumb|upright=2|Approaches to fusion, in color coded families: Pinch Family (orange), Mirror Family (red), Cusp Systems (violet), Tokamaks & Stellarators (Green), Plasma Structures (gray), Inertial Electrostatic Confinement (dark yellow), Inertial Confinement Fusion (ICF, blue), Plasma Jet Magneto Inertial Fusion (PJMIF, dark pink).]]

=== Magnetic confinement ===
{{Main|Magnetic confinement fusion}}
* [[Tokamak]]: the most well-developed and well-funded approach. This method drives hot plasma around in a magnetically confined [[torus]], with an internal current. When completed, ITER will become the world's largest tokamak. As of September 2018 an estimated 226 experimental tokamaks were either planned, decommissioned or operating (50) worldwide.<ref>{{Cite web|title=All-the-Worlds-Tokamaks|url=http://www.tokamak.info/|access-date=October 11, 2020|website=www.tokamak.info}}</ref>
* [[Spherical tokamak]]: also known as spherical torus. A variation on the tokamak with a spherical shape.
* [[Stellarator]]: Twisted rings of hot plasma. The stellarator attempts to create a natural twisted plasma path, using external magnets. Stellarators were developed by [[Lyman Spitzer]] in 1950 and evolved into four designs: Torsatron, Heliotron, Heliac and Helias. One example is [[Wendelstein 7-X]], a German device. It is the world's largest stellarator.<ref>{{Cite web|title=The first plasma: the Wendelstein 7-X fusion device is now in operation|url=https://www.ipp.mpg.de/3984226/12_15|access-date=October 11, 2020|website=www.ipp.mpg.de|language=en}}</ref>
* Internal rings: Stellarators create a twisted plasma using external magnets, while tokamaks do so using a current induced in the plasma. Several classes of designs provide this twist using conductors inside the plasma. Early calculations showed that collisions between the plasma and the supports for the conductors would remove energy faster than fusion reactions could replace it. Modern variations, including the [[Levitated dipole|Levitated Dipole Experiment (LDX)]], use a solid superconducting torus that is magnetically levitated inside the reactor chamber.<ref>{{Cite web|last=Chandler|first=David|title=MIT tests unique approach to fusion power|url=https://news.mit.edu/2008/ldx-tt0319|access-date=October 11, 2020|website=MIT News {{!}} Massachusetts Institute of Technology|date=March 19, 2008 |language=en}}</ref>
* [[Magnetic mirror]]: Developed by [[Richard F. Post]] and teams at Lawrence Livermore National Laboratory ([[LLNL]]) in the 1960s.<ref name="Post 99–111">{{Citation|last=Post|first=R. F.|title=Mirror systems: fuel cycles, loss reduction and energy recovery|date=January 1, 1970|url=https://www.icevirtuallibrary.com/doi/abs/10.1680/nfr.44661.0007|work=Nuclear fusion reactors|pages=99–111|series=Conference Proceedings|publisher=Thomas Telford Publishing|doi=10.1680/nfr.44661|isbn=978-0727744661|access-date=October 11, 2020}}</ref> Magnetic mirrors reflect plasma back and forth in a line. Variations included the [[Tandem Mirror Experiment|Tandem Mirror]], magnetic bottle and the [[biconic cusp]].<ref>{{Cite book|last1=Berowitz|first1=J. L |title=Proceedings of the second United Nations International Conference on the Peaceful Uses of Atomic Energy |volume=31|last2=Grad|first2=H.|last3=Rubin|first3=H.|date=1958|publisher=United Nations|location=Geneva|language=en|oclc=840480538}}</ref> A series of mirror machines were built by the US government in the 1970s and 1980s, principally at LLNL.<ref>{{cite journal | last1=Bagryansky | first1=P. A. | last2=Shalashov | first2=A. G. | last3=Gospodchikov | first3=E. D. | last4=Lizunov | first4=A. A. | last5=Maximov | first5=V. V. | last6=Prikhodko | first6=V. V. | last7=Soldatkina | first7=E. I. | last8=Solomakhin | first8=A. L. | last9=Yakovlev | first9=D. V. | title=Threefold Increase of the Bulk Electron Temperature of Plasma Discharges in a Magnetic Mirror Device | journal=Physical Review Letters | volume=114 | issue=20 | date=May 18, 2015 | issn=0031-9007 | doi=10.1103/physrevlett.114.205001 | pmid=26047233 | page=205001| arxiv=1411.6288 | bibcode=2015PhRvL.114t5001B | s2cid=118484958 }}</ref> However, calculations in the 1970s estimated it was unlikely these would ever be commercially useful.
* [[Bumpy torus]]: A number of magnetic mirrors are arranged end-to-end in a toroidal ring. Any fuel ions that leak out of one are confined in a neighboring mirror, permitting the plasma pressure to be raised arbitrarily high without loss. An experimental facility, the ELMO Bumpy Torus or EBT was built and tested at [[Oak Ridge National Laboratory]] (ORNL) in the 1970s.
* [[Field-reversed configuration]]: This device traps plasma in a self-organized quasi-stable structure; where the particle motion makes an internal magnetic field which then traps itself.<ref name="Freidberg2007">{{cite book|first=Jeffrey P. |last=Freidberg|title=Plasma Physics and Fusion Energy|url={{google books |plainurl=y |id=ZGU-ngEACAAJ}}|date= 2007|publisher=Cambridge University Press|isbn=978-0521851077}}</ref>
* [[Spheromak]]: Similar to a field-reversed configuration, a semi-stable plasma structure made by using the plasmas' self-generated magnetic field. A spheromak has both toroidal and poloidal fields, while a field-reversed configuration has no toroidal field.<ref>{{cite book |title=Magnetic Fusion Technology |publisher=Springer London |year=2013 |isbn=978-1447155553 |editor-last=Dolan |editor-first=Thomas J. |series=Lecture Notes in Energy |volume=19 |location=London, England |pages=30–40 |language=en |doi=10.1007/978-1-4471-5556-0 |issn=2195-1284 }}</ref>
* [[Dynomak]] is a spheromak that is formed and sustained using continuous [[magnetic flux]] injection.<ref>D. A. Sutherland, T. R. Jarboe et al., "The dynomak: An advanced spheromak reactor concept with imposed-dynamo current drive and next-generation nuclear power technologies", Fusion Engineering and Design, Volume 89, Issue 4, April 2014, pp. 412–425.</ref><ref>Jarboe, T. R., et al. "Spheromak formation by steady inductive helicity injection." Physical Review Letters 97.11 (2006): 115003</ref><ref>Jarboe, T. R., et al. "Recent results from the HIT-SI experiment." Nuclear Fusion 51.6 (2011): 063029</ref> 
* [[Reversed field pinch]]: Here the plasma moves inside a ring. It has an internal magnetic field. Moving out from the center of this ring, the magnetic field reverses direction.

=== Inertial confinement ===
{{Main|Inertial confinement fusion}}
[[File:NIF output over 11 years without legend.png|upright=1.7|thumb|alt=Plot of NIF results from 2012 to 2022|Plot of NIF results from 2012 to 2022]]

* Indirect drive: Lasers heat a structure known as a [[Hohlraum]] that becomes so hot it begins to radiate [[x-ray]] light. These x-rays heat a fuel pellet, causing it to collapse inward to compress the fuel. The largest system using this method is the [[National Ignition Facility]], followed closely by [[Laser Mégajoule]].<ref name="Nuckolls, John 1972">{{cite journal | last1 = Nuckolls | first1 = John | last2 = Wood | first2 = Lowell | last3 = Thiessen | first3 = Albert | last4 = Zimmerman | first4 = George | s2cid = 45684425 | year = 1972 | title = Laser Compression of Matter to Super-High Densities: Thermonuclear (CTR) Applications | journal = Nature | volume = 239 | issue = 5368| pages = 139–142 | doi = 10.1038/239139a0 |bibcode = 1972Natur.239..139N }}</ref>
* Direct drive: Lasers directly heat the fuel pellet. Notable direct drive experiments have been conducted at the [[Laboratory for Laser Energetics]] (LLE) and the [[GEKKO XII]] facilities. Good implosions require fuel pellets with close to a perfect shape in order to generate a symmetrical inward [[shock wave]] that produces the high-density plasma.{{citation needed|date=August 2023}}
* Fast ignition: This method uses two laser blasts. The first blast compresses the fusion fuel, while the second ignites it. {{as of|2019}} this technique had lost favor for energy production.<ref>{{Cite book|last=Turrell|first=Arthur |title=How to Build a Star: the science of nuclear fusion and the quest to harness its power|date=2021|publisher=Weidenfeld & Nicolson |isbn=978-1474611596|location=Place of publication not identified|language=en|oclc=1048447399}}</ref>
* [[Magneto-inertial fusion]] or [[Magnetized Liner Inertial Fusion]]: This combines a laser pulse with a magnetic pinch. The pinch community refers to it as magnetized liner inertial fusion while the ICF community refers to it as magneto-inertial fusion.<ref name="IFSA2007">{{cite journal |last=Thio |first=Y. C. F. |date=April 1, 2008 |title=Status of the US program in magneto-inertial fusion |journal=Journal of Physics: Conference Series |publisher=IOP Publishing |volume=112 |issue=4 |page=042084 |bibcode=2008JPhCS.112d2084T |doi=10.1088/1742-6596/112/4/042084 |issn=1742-6596 |doi-access=free}}</ref>
* Ion Beams: Ion beams replace laser beams to heat the fuel.<ref>{{cite conference |last1=Sharp |first1=W. M. |last2=Friedman |first2=A. |display-authors=1 |year=2011 |title=Inertial Fusion Driven by Intense Heavy-Ion Beams |url=https://accelconf.web.cern.ch/AccelConf/PAC2011/papers/weoas1.pdf |conference=Proceedings of 2011 Particle Accelerator Conference |location=New York, New York, USA |page=1386 |archive-url=https://web.archive.org/web/20171126054145/http://accelconf.web.cern.ch/AccelConf/PAC2011/papers/weoas1.pdf |archive-date=November 26, 2017 |access-date=August 3, 2019 |url-status=dead}}</ref> The main difference is that the beam has momentum due to mass, whereas lasers do not. As of 2019 it appears unlikely that ion beams can be sufficiently focused spatially and in time.
* [[Z Pulsed Power Facility|Z-machine]]: Sends an electric current through thin tungsten wires, heating them sufficiently to generate x-rays. Like the indirect drive approach, these x-rays then compress a fuel capsule.

=== Magnetic or electric pinches ===
{{Main|Pinch (plasma physics)}}

* ''[[Z-pinch]]:'' A current travels in the z-direction through the plasma. The current generates a magnetic field that compresses the plasma. Pinches were the first method for human-made controlled fusion.<ref name="Seife, Charles 2008">{{cite book |last=Seife |first=Charles |title=Sun in a bottle: the strange history of fusion and the science of wishful thinking |publisher=Viking |year=2008 |isbn=978-0670020331 |location=New York |language=en-us |oclc=213765956}}</ref><ref name="Phillips, James 2013">{{cite journal|last=Phillips|first=James|title=Magnetic Fusion|journal=Los Alamos Science|date=1983|pages=64–67|access-date=April 4, 2013|url=https://permalink.lanl.gov/object/tr?what=info:lanl-repo/lareport/LA-UR-83-5080|archive-url=https://web.archive.org/web/20161223163131/http://permalink.lanl.gov/object/tr?what=info%3Alanl-repo%2Flareport%2FLA-UR-83-5080|archive-date=December 23, 2016|url-status=dead}}</ref> The z-pinch has inherent instabilities that limit its compression and heating to values too low for practical fusion. The largest such machine, the UK's [[ZETA (fusion reactor)|ZETA]], was the last major experiment of the sort. The problems in z-pinch led to the tokamak design. The [[dense plasma focus]] is a possibly superior variation.
* ''[[Theta-pinch]]:'' A current circles around the outside of a plasma column, in the theta direction. This induces a magnetic field running down the center of the plasma, as opposed to around it. The early theta-pinch device Scylla was the first to conclusively demonstrate fusion, but later work demonstrated it had inherent limits that made it uninteresting for power production.
* ''Sheared Flow Stabilized Z-Pinch:'' Research at the [[University of Washington]] under Uri Shumlak investigated the use of sheared-flow stabilization to smooth out the instabilities of Z-pinch reactors. This involves accelerating neutral gas along the axis of the pinch. Experimental machines included the FuZE and Zap Flow Z-Pinch experimental reactors.<ref>{{Cite web|date=November 7, 2014|title=Flow Z-Pinch Experiments|url=https://www.aa.washington.edu/research/ZaP|access-date=October 11, 2020|website=Aeronautics and Astronautics|language=en}}</ref> In 2017, British technology investor and entrepreneur [[Benj Conway]], together with physicists Brian Nelson and Uri Shumlak, co-founded Zap Energy to attempt to commercialize the technology for power production.<ref>{{cite web |url=https://www.zapenergyinc.com/ |publisher=Zap Energy |title=Zap Energy |access-date=February 13, 2020 |archive-url=https://web.archive.org/web/20200213065735/https://www.zapenergyinc.com/ |archive-date=February 13, 2020 |url-status=dead }}</ref><ref>{{Cite web|title=Board of Directors|url=https://www.zapenergyinc.com/board|access-date=September 8, 2020|website=ZAP ENERGY|language=en-US}}</ref><ref>{{Cite web|date=August 13, 2020|title=Chevron announces investment in nuclear fusion start-up Zap Energy|url=https://www.power-technology.com/news/chevron-announces-investment-nuclear-fusion-start-up-company-zap-energy/|access-date=September 8, 2020|website=Power Technology {{!}} Energy News and Market Analysis|language=en-GB}}</ref>
* ''Screw Pinch:'' This method combines a theta and z-pinch for improved stabilization.<ref>{{cite journal | last1=Srivastava | first1=Krishna M. | last2=Vyas | first2=D. N. | title=Non-linear analysis of the stability of the Screw Pinch | journal=Astrophysics and Space Science | publisher=Springer Nature | volume=86 | issue=1 | year=1982 | issn=0004-640X | doi=10.1007/bf00651831 | pages=71–89| bibcode=1982Ap&SS..86...71S | s2cid=121575638 }}</ref>

=== Inertial electrostatic confinement ===
{{Main|Inertial electrostatic confinement}}

*''[[Polywell]]:'' Attempts to combine magnetic confinement with electrostatic fields, to avoid the [[Electrical conductor|conduction]] losses generated by the cage.<ref>US patent 5,160,695, Robert W. Bussard, "Method and apparatus for creating and controlling nuclear fusion reactions", issued November 3, 1992</ref>

=== Other thermonuclear ===
* ''[[Magnetized target fusion]]:'' Confines hot plasma using a magnetic field and squeezes it using inertia. Examples include [[LANL]] FRX-L machine,<ref>{{Cite journal|last1=Taccetti|first1=J. M.|last2=Intrator|first2=T. P.|last3=Wurden|first3=G. A.|last4=Zhang|first4=S. Y.|last5=Aragonez|first5=R.|last6=Assmus|first6=P. N.|last7=Bass|first7=C. M.|last8=Carey|first8=C.|last9=deVries|first9=S. A.|last10=Fienup|first10=W. J.|last11=Furno|first11=I.|date=September 25, 2003|title=FRX-L: A field-reversed configuration plasma injector for magnetized target fusion|url=https://aip.scitation.org/doi/10.1063/1.1606534|journal=Review of Scientific Instruments|volume=74|issue=10|pages=4314–4323|doi=10.1063/1.1606534|bibcode=2003RScI...74.4314T|issn=0034-6748}}</ref> [[General Fusion]] (piston compression with liquid metal liner), HyperJet Fusion (plasma jet compression with plasma liner).<ref>{{Cite journal|last1=Hsu|first1=S. C.|last2=Awe|first2=T. J.|last3=Brockington|first3=S.|last4=Case|first4=A.|last5=Cassibry|first5=J. T.|last6=Kagan|first6=G.|last7=Messer|first7=S. J.|last8=Stanic|first8=M.|last9=Tang|first9=X.|last10=Welch|first10=D. R.|last11=Witherspoon|first11=F. D.|date=2012|title=Spherically Imploding Plasma Liners as a Standoff Driver for Magnetoinertial Fusion|url=https://ieeexplore.ieee.org/document/6168279/?denied=|journal=IEEE Transactions on Plasma Science|volume=40|issue=5|pages=1287–1298|doi=10.1109/TPS.2012.2186829|bibcode=2012ITPS...40.1287H|s2cid=32998378|issn=1939-9375}}</ref><ref name=5big/>
* ''Uncontrolled:'' Fusion has been initiated by man, using uncontrolled fission explosions to stimulate fusion. Early proposals for fusion power included using bombs to initiate reactions. See [[Project PACER]].

=== Other non-thermonuclear ===
* ''[[Muon-catalyzed fusion]]:'' This approach replaces [[electron]]s in [[diatomic molecule]]s of [[isotope]]s of [[hydrogen]] with [[muon]]s—more massive particles with the same [[electric charge]]. Their greater mass compresses the nuclei enough such that the [[strong interaction]] can cause fusion.{{sfn|Nagamine|2003}} As of 2007 producing muons required more energy than can be obtained from muon-catalyzed fusion.<ref>{{Cite book |last=Nagamine |first=K. |title=Introductory muon science |date=2007 |publisher=Cambridge University Press |isbn=978-0521038201 |location=Cambridge, England |language=en |oclc=124025585}}</ref>
* ''[[Lattice confinement fusion]]:'' Lattice confinement fusion ('''LCF''') is a type of [[nuclear fusion]] in which [[deuteron]]-saturated metals are exposed to [[gamma radiation]] or ion beams, such as in an [[Inertial electrostatic confinement|IEC fusor]], avoiding the confined high-temperature plasmas used in other methods of fusion.<ref>{{Cite web|url=https://spectrum.ieee.org/lattice-confinement-fusion|title=NASA's New Shortcut to Fusion Power|last1=Baramsai |first1=Bayardadrakh |last2=Benyo |first2=Theresa |last3=Forsley |first3=Lawrence |last4=Steinetz |first4=Bruce |date=February 27, 2022|website=IEEE Spectrum}}</ref><ref name="erbium">{{Cite journal|url=http://dx.doi.org/10.1103/PhysRevC.101.044610|title=Novel nuclear reactions observed in bremsstrahlung-irradiated deuterated metals|first1=Bruce M.|last1=Steinetz|first2=Theresa L.|last2=Benyo|first3=Arnon|last3=Chait|first4=Robert C.|last4=Hendricks|first5=Lawrence P.|last5=Forsley|first6=Bayarbadrakh|last6=Baramsai|first7=Philip B.|last7=Ugorowski|first8=Michael D.|last8=Becks|first9=Vladimir|last9=Pines|first10=Marianna|last10=Pines|first11=Richard E.|last11=Martin|first12=Nicholas|last12=Penney|first13=Gustave C.|last13=Fralick|first14=Carl E.|last14=Sandifer|date=April 20, 2020|journal=Physical Review C|volume=101|issue=4|pages=044610|via=APS|doi=10.1103/physrevc.101.044610|bibcode=2020PhRvC.101d4610S|s2cid=219083603}}</ref>

=== Negative power methods ===
These methods inherently consume more power than they can provide via fusion.

* ''[[Fusor]]:'' An electric field heats ions to fusion conditions. The machine typically uses two spherical cages, a cathode inside the anode, inside a vacuum. These machines are not considered a viable approach to net power because of their high [[Electrical conductor|conduction]] and [[radiation]] losses.<ref>{{cite journal |last=Rider |first=Todd H. |year=1995 |title=A general critique of inertial-electrostatic confinement fusion systems |journal=Physics of Plasmas |publisher=AIP Publishing |volume=2 |issue=6 |pages=1853–1872 |bibcode=1995PhPl....2.1853R |doi=10.1063/1.871273 |issn=1070-664X |s2cid=12336904 |hdl-access=free |hdl=1721.1/29869}}</ref> They are simple enough to build that amateurs have fused atoms using them.<ref>{{cite web |last=Clynes |first=Tom |date=February 14, 2012 |title=The Boy Who Played With Fusion |url=https://www.popsci.com/science/article/2012-02/boy-who-played-fusion/ |access-date=August 3, 2019 |website=Popular Science}}</ref>
* ''[[Colliding beam fusion]]:'' A beam of high energy particles fired at another beam or target can initiate fusion. This was used in the 1970s and 1980s to study the cross sections of fusion reactions.<ref name="osti.gov" /> However beam systems cannot be used for power because keeping a beam coherent takes more energy than comes from fusion.