Editing Stellarator (section)

== Configurations ==
[[Image:Magnetic field stellarator.png|thumb|Sketch of a classical stellarator with helical coils (white) and toroidal field coils (green)]]
Several different configurations of stellarator exist, including:
; Spatial stellarator : The Princeton Model A stellarator is based on the 1953's figure-eight design. It achieved a rotational transform using torsion of the magnetic axis. This is a helix configuration.<ref name="auto">{{cite arXiv |title=An Introduction to Stellarators |eprint=1908.05360 |last1=Imbert-Gerard |first1=Lise-Marie |last2=Paul |first2=Elizabeth J. |last3=Wright |first3=Adelle M. |date=2019 |class=physics.plasm-ph }}</ref>
; Classical stellarator : Also known as Princeton Model C, this stellarator generates a magnetic field by connecting the plasma poloidally and toroidally through helical coils. Stellarators with this helitron configuration were only operational until the late 1960s due to issues with particle confinement.<ref name="auto"/>
[[Image:Advanced Toroidal Facility, 1986 (49743086486).png|thumb|Construction of the torsatron ATF (1986)]]
; Torsatron : A torsatron is a type of stellarator that uses external, continuously wound [[helix|helical]] coils to generate the [[magnetic field]]. The helical coils that wrap around the torus simplifies the coils structure, which can potentially improve the stability of the plasma. An example of a torsatron is the [[Compact Toroidal Hybrid]] (CTH).
; Heliotron : The heliotron is a stellarator designed in Japan that uses a helical coil is used to confine the plasma and a pair of poloidal field coils to generate a vertical field. Helical and toroidal coils work together to generate the magnetic field. Its simplified coil structure makes manufacturing easier, while its modular coil system offers more flexibility in manipulating the magnetic field. The [[Large Helical Device]] in Japan is an example of this configuration.
; Modular stellarator : A stellarator with a set of modular (separated) coils and a twisted toroidal coil.<ref>{{cite book |last=Wakatani |first=M. |year=1998 |title=Stellarator and Heliotron Devices |url=https://books.google.com/books?id=MxttViyhaaEC |publisher=Oxford University Press |isbn=978-0-19-507831-2}}</ref> e.g. [[Helically Symmetric Experiment]] (HSX) (and Helias (below))
[[Image:TJ-II model including plasma, coils and vacuum vessel.jpg|thumb|TJ-II Heliac]]
; Heliac : A ''helical axis stellarator'', in which the magnetic axis (and plasma) follows a helical path to form a toroidal helix rather than a simple ring shape. The twisted plasma induces twist in the magnetic field lines to effect drift cancellation, and typically can provide more twist than the Torsatron or Heliotron, especially near the centre of the plasma (magnetic axis). The original Heliac consists only of circular coils, and the '''flexible heliac'''<ref>{{cite journal |last1=Harris |first1=J.H. |last2=Cantrell |first2=J.L. |last3=Hender |first3=T.C. |last4=Carreras |first4=B.A. |last5=Morris |first5=R.N. |year=1985 |title=A flexible heliac configuration |journal=Nuclear Fusion |volume=25 |issue=5 |page=623 |doi=10.1088/0029-5515/25/5/005|osti=5800899 |s2cid=123277092 |url=https://zenodo.org/record/1235714 }}</ref> ([[H-1NF]], [[TJ-II]], [[TU-Heliac]]) adds a small helical coil to allow the twist to be varied by a factor of up to 2.
; Helias : A ''helical advanced stellarator'', using an optimized modular coil set designed to simultaneously achieve high plasma, low Pfirsch–Schluter currents and good confinement of energetic particles; i.e., alpha particles for reactor scenarios.<ref>{{cite web |url=http://www.ipp.mpg.de/ippcms/eng/for/bereiche/e3/projekte/sss/sss_basics.html |title=Basics of Helias-type Stellarators |access-date=13 June 2010 |url-status=dead |archive-url=https://web.archive.org/web/20130621170651/http://www.ipp.mpg.de/ippcms/eng/for/bereiche/e3/projekte/sss/sss_basics.html |archive-date=21 June 2013 }}</ref> The Helias has been proposed to be the most promising stellarator concept for a power plant, with a modular engineering design and optimised plasma, MHD and magnetic field properties.{{citation needed|date=December 2015}} The [[Wendelstein 7-X]] device is based on a five field-period Helias configuration.