View source for Wendelstein 7-X

{{Short description|Modern stellarator for plasma fusion experiments}}
{{Use dmy dates|date=May 2020}}
{{Infobox fusion devices
|name                 = Wendelstein 7-X
|fullname             =
|image                = Wendelstein7-X Torushall-2011.jpg
|imagetitle           = W7-X in 2011
|type                 = [[Stellarator]]
|city                 = [[Greifswald]]
|state                = 
|country              = [[Germany]]
|coordinates          =
|affiliation          = [[Max Planck Institute for Plasma Physics]]
|major_radius         = {{cvt|5.5|m}}
|minor_radius         = {{cvt|0.53|m}}
|volume               = {{val|30|ul=m3}}
|field                = {{cvt|3|T}}
|heating              = {{val|14|ul=MW}}
|temperature          = {{val|6|-|13|e=7|ul=K}}
|power                =
|time                 =
|current              =
|construction_date    =
|operation_start_year = 2015
|operation_end_year   =
|ongoing              = yes
|prev                 = [[Wendelstein 7-AS]]
|next                 =
|related              =
|website              =https://www.ipp.mpg.de/w7x
|other_links          =
}}
[[File:W7X-Spulen Plasma blau gelb.jpg|thumb|320x320px|Stellarator schema - coil system (blue), plasma (yellow), a magnetic field line (green) on the plasma surface.]]
[[File:W7x 038.jpg|thumb|Wendelstein 7-X research complex in Greifswald, experiment hall on the left.]]
[[File:Stellarator Wendelstein 7-X Planar-Spulen Vermessung.jpg|thumb|Superconducting feed lines being attached to the superconducting planar coils, 2008]]
[[File:W7-X Stellarator Experiment.jpg|thumb|Construction in May 2012. Visible are the torus, offset in the test cell, and the large overhead crane. Note the workers for scale.]]
[[File:Interior of W7-X stellarator.jpg|thumb|Wide-angle view inside the [[stellarator]], showing the stainless cover plates and the water-cooled copper backing plates which will eventually be covered by graphite tiles and function as armor to protect against plasma/wall interactions.]]
The '''Wendelstein 7-X''' (abbreviated '''W7-X''') reactor is an experimental [[stellarator]] built in [[Greifswald]], [[Germany]], by the [[Max Planck Institute for Plasma Physics]] (IPP), and completed in October 2015.<ref name=W7X>[https://www.ipp.mpg.de/16931/einfuehrung Introduction – the Wendelstein 7-X stellarator] Retrieved 5 November 2014.</ref><ref name=Clery2015>{{cite web|last1=Clery|first1=Daniel|title=The bizarre reactor that might save nuclear fusion|url=https://www.science.org/content/article/bizarre-reactor-might-save-nuclear-fusion|website=sciencemag.org|publisher=Science Magazine|access-date=25 October 2015|date=21 October 2015}}</ref> Its purpose is to advance stellarator technology: though this experimental reactor will not produce electricity, it is used to evaluate the main components of a future [[fusion power]] plant; it was developed based on the predecessor [[Wendelstein 7-AS]] experimental reactor.

{{As of|2023}}, the Wendelstein 7-X reactor is the world's largest stellarator device.<ref>{{cite web |title=Wendelstein 7-X achieves world record |url=https://www.ipp.mpg.de/4413312/04_18 |website=Max Planck Institute for Plasma Physics |access-date=27 December 2022}}</ref> After two successful operation phases ending in October 2018, the reactor was taken offline for upgrades.<ref>{{cite web |title=The second experimentation phase |url=https://www.ipp.mpg.de/4555488/op_1_2 |website=Max Planck Institute for Plasma Physics |access-date=26 September 2022}}</ref><ref>{{cite web |title=Wendelstein 7-X fusion device at Greifswald to be upgraded |url=https://www.ipp.mpg.de/4828222/01_20 |website=Max Planck Institute for Plasma Physics |access-date=26 September 2022|last1=Milch|first1=Isabella}}</ref> The upgrade completed in 2022. New fusion experiments in February 2023 demonstrated longer confinement and increased power.<ref name="Milestone2023Feb">{{cite web | url=https://www.ipp.mpg.de/5322229/01_23?c=5322195 | title=Wendelstein 7-X reaches milestone: Power plasma with gigajoule energy turnover generated for eight minutes | date=22 Feb 2023}}</ref> The goal of this phase is to gradually increase power and duration for up to 30 minutes of continuous plasma discharge, thus demonstrating an essential feature of a future fusion power plant: continuous operation.<ref>[https://idw-online.de/en/news799586 idw-online.de: Federal Research Minister Stark-Watzinger and Minister Martin visit IPP Greifswald], [https://web.archive.org/web/20220813070857/https://idw-online.de/en/news799586 backup]: Citat: "...After two successful initial operation phases, the Wendelstein 7-X fusion device has been further expanded. This final step, which upgrades the machine to demonstrate plasma pulses of up to 30 minutes with increased heating power, has now been completed and Wendelstein 7-X is finished. A water-cooled inner cladding and the new centrepiece, a water-cooled divertor, complete the device. In autumn 2022, Wendelstein 7-X will go back into operation..."</ref><ref>[https://www.ipp.mpg.de/5272648/03_22?c=4313165 ipp.mpg.de: Wendelstein 7-X on the verge of new peak performance]: Citat: "...From autumn 2022 onwards, an international team of scientists will once again drive W7-X to new heights of performance. "With the improved equipment, we want to be able to keep high-performance plasmas with up to 18 gigajoules of energy turnover stable for half an hour in a few years," [...] approaching this goal step-by-step and learning more about plasma operation at higher energies without putting too much stress on the machine too quickly,[...]"</ref>

The name of the project, referring to the mountain [[Wendelstein (mountain)|Wendelstein]] in Bavaria, was decided at the end of the 1950s, referencing the preceding project from [[Princeton University]] under the name [[Project Matterhorn]].<ref>WI-A, WI-B, WII-A, WII-B, W7-A: {{citation|surname1=G. Grieger|surname2=H. Renner|surname3=H. Wobig|periodical=Nuclear Fusion|title=Wendelstein stellarators |volume=25|issue=9|pages=1231|date=  1985|language=de|doi=10.1088/0029-5515/25/9/040|s2cid=250832456 }}</ref>

The research facility is an independent partner project of the ''Max-Planck Institute for Plasma Physics'' with the [[University of Greifswald]].

==Design and main components==
The Wendelstein 7-X device is based on a five-field-period [[Helias configuration]]. It is mainly a [[Torus|toroid]], consisting of 50 non-planar and 20 planar [[superconducting]] [[magnet]]ic [[electromagnet|coils]], 3.5&nbsp;m high, which induce a [[magnetic field]] that prevents the [[plasma (physics)|plasma]] from colliding with the reactor walls. The 50 non-planar coils are used for adjusting the magnetic field. It aims for a [[Plasma (physics)#Degree of ionization|plasma density]] of 3{{e|20}} particles per cubic metre, and a [[Plasma (physics)#Temperature|plasma temperature]] of 60–130&nbsp;[[Orders of magnitude (temperature)#SI multiples|megakelvins]] (MK).<ref name=W7X/>

The W7-X is optimised along the [[Quasi-isodynamic stellarators|quasi-isodynamic]] principle.<ref>{{cite web |url=https://inis.iaea.org/collection/NCLCollectionStore/_Public/36/080/36080625.pdf|title=Physics, Technologies, and Status of the Wendelstein 7-X Device}}</ref>

The main components are the magnetic coils, [[cryostat]], plasma vessel, [[divertor]] and heating systems.<ref name=Klinger2011/>

The coils ([[Niobium–titanium|NbTi]] in aluminium<ref name=Klinger2011/>) are arranged around a heat insulating cladding with a diameter of 16&nbsp;metres, called the cryostat. A cooling device produces enough liquid helium to cool down the magnets and their enclosure (about 425 metric tons of "cold mass") to [[superconductivity]] temperature (4&nbsp;K<ref name=rig2015/>). The coils will carry 12.8&nbsp;kA current and create a field of up to 3&nbsp;[[Tesla (unit)|teslas]].<ref name=rig2015/>

The plasma vessel, built of 20 parts, is on the inside adjusted to the complex shape of the magnetic field. It has 254 ports (holes) for plasma heating and observation diagnostics. The whole plant is built of five nearly identical modules, which were assembled in the experiment hall.<ref name=Klinger2011/>

The heating system<ref name=Heating>{{cite web |url=http://www.ipp.mpg.de/ippcms/eng/for/bereiche/e3/index | title=Stellarator Heating and Optimization | access-date=10 December 2015}}</ref> includes high power [[gyrotron|gyrotrons]] for [[electron cyclotron resonance]] heating (ECRH), which will deliver up to 15&nbsp;MW of heating to the plasma.<ref name=ECRH>{{cite web |url=http://www.ipp.mpg.de/3871954/ECRH | title=Microwave heating – ECRH | access-date=10 December 2015}}</ref> For operational phase 2 (OP-2), after completion of the full armor/water-cooling, up to 8&nbsp;megawatts of [[neutral beam injection]] will also be available for 10&nbsp;seconds.<ref name=NBI>{{cite web |url=http://www.ipp.mpg.de/3871988/NBI | title=Neutral Beam Injection Heating (NBI) | access-date=10 December 2015}}</ref> An [[ion cyclotron resonance]] heating (ICRH) system will become available for physics operation in OP1.2.<ref name=ICRH>{{cite web |url=http://www.ipp.mpg.de/3871973/ICRH | title=Ion Cyclotron Resonance Heating (ICRH) | access-date=10 December 2015}}</ref>

A system of [[sensor]]s and probes based on a variety of complementary technologies will measure key properties of the plasma, including the profiles of the electron density and of the electron and ion temperature, as well as the profiles of important plasma impurities and of the radial electric field resulting from electron and ion particle transport.<ref name=diagnostics>{{cite web |url=http://www.ipp.mpg.de/3872028/Profildiagnostik | title=Profile Diagnostics | access-date=10 December 2015}}</ref>

==History==
The German funding arrangement for the project was negotiated in 1994, establishing the Greifswald Branch Institute of the IPP in the north-eastern corner of the recently integrated [[East Germany]]. Its new building was completed in 2000. Construction of the stellarator was originally expected to reach completion in 2006. Assembly began in April 2005. Problems with the coils took about 3 years to fix.<ref name=Klinger2011/> The schedule slipped into late 2015.<ref name=Klinger2011>{{cite web |url=http://www.iter.org/doc/www/content/com/Lists/Stories/Attachments/680/ITER_W7X.pdf |author=Klinger, Thomas |title=Stellarators difficult to build? The construction of Wendelstein 7-X |date=14 April 2011 |access-date=13 June 2011}} 53 slides - many photos</ref><ref name=Arnoux2011>{{cite web |url=http://www.iter.org/newsline/172/680 |author=Arnoux, Robert |title=The stellarator renaissance |date=15 April 2011 |access-date=13 June 2011}}</ref><ref name=Jeffrey2015>{{Cite web|title = Wendelstein 7-x stellarator puts new twist on nuclear fusion power|url = http://www.gizmag.com/wendelstein7x-fusion-stellarator-plasma-tests/40014|website = www.gizmag.com|access-date = 27 October 2015|date = 25 October 2015|first = Colin|last = Jeffrey}}</ref>

A three-laboratory American consortium (Princeton, Oak Ridge, and Los Alamos) became a partner in the project, paying €6.8 million of the eventual total cost of €1.06 billion.<ref name=PT2011>{{cite web|url=http://www.physicstoday.org/resource/1/phtoad/v64/i9/p30_s1?view=print|title=US narrows fusion research focus, joins German stellarator|date=1 September 2011}}{{dead link|date=January 2018 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> In 2012, Princeton University and the Max Planck Society announced a new joint research center in plasma physics,<ref name=MPS2012>{{cite web|url=http://www.pppl.gov/news/press-releases/2012/03/princeton-max-planck-society-launch-new-research-center-plasma-physics|title=Princeton, Max Planck Society launch new research center plasma physics|date=29 March 2012|access-date=19 August 2013|archive-date=4 March 2016|archive-url=https://web.archive.org/web/20160304031725/http://www.pppl.gov/news/press-releases/2012/03/princeton-max-planck-society-launch-new-research-center-plasma-physics|url-status=dead}}</ref> to include research on W7-X.

The end of the construction phase, which required more than 1 million assembly hours,<ref>{{Cite news|url=http://phys.org/news/2016-06-scientific-experimentation-wendelstein-x-fusion.html|title=Start of scientific experimentation at the Wendelstein 7-X fusion device|date=7 June 2016|work=phys.org|access-date=11 October 2016}}</ref> was officially marked by an inauguration ceremony on 20 May 2014.<ref name=Milch2014>{{cite web |url=http://www.ipp.mpg.de/3397401/03_14 |author=Milch, Isabella |title=Preparations for operation of Wendelstein 7-X starting |date=12 May 2014 |access-date=16 May 2014}}</ref> After a period of vessel leak-checking, beginning in the summer of 2014, the cryostat was [[Vacuum|evacuated]], and magnet testing was completed in July 2015.<ref name=rig2015>{{cite web|url=http://research-in-germany.org/default/en/research-landscape/news/2015/07/2015-07-07-magnet-tests-on-wendelstein-7-x-successfully-completed.html|title=Magnet tests on Wendelstein 7-X successfully completed|date=7 July 2015|url-status=dead|archive-url=https://web.archive.org/web/20150716225905/http://research-in-germany.org/default/en/research-landscape/news/2015/07/2015-07-07-magnet-tests-on-wendelstein-7-x-successfully-completed.html|archive-date=16 July 2015}}</ref>

Operational phase 1 (OP1.1) began 10 December 2015.<ref name=":0">{{Cite web|url=https://www.ipp.mpg.de/4206699/013_April_2017_eng.pdf|title=Wendelstein 7-X Newsletter No. 13 / April 2017}}</ref> On that day the reactor successfully produced helium plasma (with temperatures of about 1&nbsp;MK) for about 0.1&nbsp;s. For this initial test with about 1&nbsp;mg of [[helium]] gas injected into the evacuated plasma vessel, microwave heating was applied for a short 1.3&nbsp;MW pulse.<ref name="plasma2015">{{cite web |url = http://www.ipp.mpg.de/3984226/12_15|title = The first plasma: the Wendelstein 7-X fusion device is now in operation|date = 10 December 2015|access-date = 10 December 2015|publisher = Max Planck Institute for Plasma Physics}}</ref>

The aim for the OP 1.1 was to conduct integrated testing of the most important systems as quickly as possible and to gain first experience with the physics of the machine.<ref name=":0"/><ref name="tsp2015">{{Cite journal|url=https://iopscience.iop.org/article/10.1088/0029-5515/55/12/126001|title= Plans for the first plasma operation of Wendelstein 7-X|journal=Nuclear Fusion |date=November 2015 |volume=55 |issue=12 |page=126001 |doi=10.1088/0029-5515/55/12/126001 |last1=Sunn Pedersen |first1=T. |last2=Andreeva |first2=T. |last3=Bosch |first3=H. -S |last4=Bozhenkov |first4=S. |last5=Effenberg |first5=F. |last6=Endler |first6=M. |last7=Feng |first7=Y. |last8=Gates |first8=D. A. |last9=Geiger |first9=J. |last10=Hartmann |first10=D. |last11=Hölbe |first11=H. |last12=Jakubowski |first12=M. |last13=König |first13=R. |last14=Laqua |first14=H. P. |last15=Lazerson |first15=S. |last16=Otte |first16=M. |last17=Preynas |first17=M. |last18=Schmitz |first18=O. |last19=Stange |first19=T. |last20=Turkin |first20=Y. |bibcode= 2015NucFu..55l6001P|hdl=11858/00-001M-0000-0029-04EB-D |s2cid=67798335 |hdl-access=free }}</ref>

More than 300 discharges with helium were done in December and January with gradually increasing temperatures finally reaching six million degrees Celsius, to clean the vacuum vessel walls and test the plasma diagnostic systems. Then, on 3 February 2016, production of the first hydrogen plasma initiated the science program. The highest temperature plasmas were produced by four-megawatt microwave heater pulses lasting one second; plasma electron temperatures reached 100&nbsp;MK, while ion temperatures reached 10&nbsp;MK. More than 2,000 pulses were conducted before shutdown.<ref>{{Cite news|url=http://phys.org/news/2016-07-wendelstein-x-successful.html|title=Wendelstein 7-X: Upgrading after successful first round of experiments|date=11 July 2016|work=phys.org|access-date=11 October 2016}}</ref>

Five poloidal graphite limiters served as the main plasma-facing components during this first campaign (instead of the divertor modules). Experimental observations confirmed 3D modeling predictions that showed heat and particle flux deposition patterns on the limiters in clear correlation with the lengths of the open magnetic field lines in the plasma boundary.<ref name="fe2017">{{cite journal |last1=Effenberg |first1=F. |last2=Feng |first2=Y. |last3=Schmitz |first3=O. |last4=Frerichs |first4=H. |last5=Bozhenkov |first5=S.A. |last6=Hölbe |first6=H. |last7=König |first7=R. |last8=Krychowiak |first8=M. |last9=Pedersen |first9=T. Sunn |last10=Reiter |first10=D. |last11=Stephey |first11=L. |title=Numerical investigation of plasma edge transport and limiter heat fluxes in Wendelstein 7-X startup plasmas with EMC3-EIRENE |journal=Nuclear Fusion |volume=57 |issue=3 |year=2017 |doi=10.1088/1741-4326/aa4f83 |hdl=11584/213558|hdl-access=free| url=https://hal.archives-ouvertes.fr/hal-03741000/file/numerical-investigation-w7x-limiter-emc3-eirene-florian-effenberg.pdf}}</ref><ref name="gw2017">{{Cite journal|url=https://doi.org/10.1088/1741-4326/aa6609|title=G.A. Wurden et al 2017 Nucl. Fusion 57 056036|journal=Nuclear Fusion |doi=10.1088/1741-4326/aa6609|s2cid=126252486 |hdl=11584/213558|hdl-access=free}}</ref>

Such tests were planned to continue for about a month, followed by a scheduled shut-down to open the vacuum vessel and line it with protective carbon tiles and install a "divertor" for removing impurities and heat from the plasma. The science program continued while gradually increasing discharge power and duration.<ref name="Hyd2016">{{cite web |url = http://www.ipp.mpg.de/4010154/02_16 | title = Wendelstein 7-X fusion device produces its first hydrogen plasma |date = 3 February 2016|access-date = 4 February 2016 |publisher = Max Planck Institute for Plasma Physics}}</ref> The special magnetic field topology was confirmed in 2016.<ref>{{cite journal |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 |year=2016 |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. |last10=Abramovic |first10=Ivana |last11=Äkäslompolo |first11=Simppa |last12=Aleynikov |first12=Pavel |last13=Aleynikova |first13=Ksenia |last14=Ali |first14=Adnan |last15=Alonso |first15=Arturo |last16=Anda |first16=Gabor |last17=Andreeva |first17=Tamara |last18=Ascasibar |first18=Enrique |last19=Baldzuhn |first19=Jürgen |last20=Banduch |first20=Martin |last21=Barbui |first21=Tullio |last22=Beidler |first22=Craig |last23=Benndorf |first23=Andree |last24=Beurskens |first24=Marc |last25=Biel |first25=Wolfgang |last26=Birus |first26=Dietrich |last27=Blackwell |first27=Boyd |last28=Blanco |first28=Emilio |last29=Blatzheim |first29=Marko |last30=Bluhm |first30=Torsten |display-authors=29 |bibcode=2016NatCo...713493P }}</ref><ref>{{cite web|url= http://www.sciencealert.com/tests-confirm-that-germany-s-massive-nuclear-fusion-machine-really-works |title=Tests confirm that Germany's massive nuclear fusion machine really works|work=ScienceAlert |date=6 December 2016 |access-date= 7 December 2016 }}</ref>

Operational phase 1 (OP1.1) concluded 10 March 2016<ref name=":0"/><ref name="rcw2017">{{Cite journal|title=R.C. Wolf et al 2017 Nucl. Fusion 57 102020|journal=Nuclear Fusion |date=27 July 2017 |volume=57 |issue=10 |page=102020 |doi=10.1088/1741-4326/aa770d |last1=Wolf |first1=R. C. |last2=Ali |first2=A. |last3=Alonso |first3=A. |last4=Baldzuhn |first4=J. |last5=Beidler |first5=C. |last6=Beurskens |first6=M. |last7=Biedermann |first7=C. |last8=Bosch |first8=H. -S |last9=Bozhenkov |first9=S. |last10=Brakel |first10=R. |last11=Dinklage |first11=A. |last12=Feng |first12=Y. |last13=Fuchert |first13=G. |last14=Geiger |first14=J. |last15=Grulke |first15=O. |last16=Helander |first16=P. |last17=Hirsch |first17=M. |last18=Höfel |first18=U. |last19=Jakubowski |first19=M. |last20=Knauer |first20=J. |last21=Kocsis |first21=G. |last22=König |first22=R. |last23=Kornejew |first23=P. |last24=Krämer-Flecken |first24=A. |last25=Krychowiak |first25=M. |last26=Landreman |first26=M. |last27=Langenberg |first27=A. |last28=Laqua |first28=H. P. |last29=Lazerson |first29=S. |last30=Maaßberg |first30=H. |s2cid=1986901 |display-authors=1 |doi-access=free |hdl=2434/616000 |hdl-access=free }}</ref> and an upgrade phase began.

Operational phase 1 continued (OP1.2) in 2017<ref>{{Cite web|url=https://www.ipp.mpg.de/de/aktuelles/presse/pi/2017/08_17|title=Wendelstein 7-X: Zweite Experimentierrunde hat begonnen|website=www.ipp.mpg.de}}</ref> to test the (uncooled) divertor.<ref>{{Cite journal|title=Performance of Wendelstein 7-X stellarator plasmas during the first divertor operation phase|first1=R. C.|last1=Wolf|first2=A.|last2=Alonso|first3=S.|last3=Äkäslompolo|first4=J.|last4=Baldzuhn|first5=M.|last5=Beurskens|first6=C. D.|last6=Beidler|first7=C.|last7=Biedermann|first8=H.-S.|last8=Bosch|first9=S.|last9=Bozhenkov|first10=R.|last10=Brakel|first11=H.|last11=Braune|first12=S.|last12=Brezinsek|first13=K.-J.|last13=Brunner|first14=H.|last14=Damm|first15=A.|last15=Dinklage|first16=P.|last16=Drewelow|first17=F.|last17=Effenberg|first18=Y.|last18=Feng|first19=O.|last19=Ford|first20=G.|last20=Fuchert|first21=Y.|last21=Gao|first22=J.|last22=Geiger|first23=O.|last23=Grulke|first24=N.|last24=Harder|first25=D.|last25=Hartmann|first26=P.|last26=Helander|first27=B.|last27=Heinemann|first28=M.|last28=Hirsch|first29=U.|last29=Höfel|first30=C.|last30=Hopf|first31=K.|last31=Ida|first32=M.|last32=Isobe|first33=M. W.|last33=Jakubowski|first34=Y. O.|last34=Kazakov|first35=C.|last35=Killer|first36=T.|last36=Klinger|first37=J.|last37=Knauer|first38=R.|last38=König|first39=M.|last39=Krychowiak|first40=A.|last40=Langenberg|first41=H. P.|last41=Laqua|first42=S.|last42=Lazerson|first43=P.|last43=McNeely|first44=S.|last44=Marsen|first45=N.|last45=Marushchenko|first46=R.|last46=Nocentini|first47=K.|last47=Ogawa|first48=G.|last48=Orozco|first49=M.|last49=Osakabe|first50=M.|last50=Otte|first51=N.|last51=Pablant|first52=E.|last52=Pasch|first53=A.|last53=Pavone|first54=M.|last54=Porkolab|first55=A.|last55=Puig Sitjes|first56=K.|last56=Rahbarnia|first57=R.|last57=Riedl|first58=N.|last58=Rust|first59=E.|last59=Scott|first60=J.|last60=Schilling|first61=R.|last61=Schroeder|first62=T.|last62=Stange|first63=A.|last63=von Stechow|first64=E.|last64=Strumberger|first65=T.|last65=Sunn Pedersen|first66=J.|last66=Svensson|first67=H.|last67=Thomson|first68=Y.|last68=Turkin|first69=L.|last69=Vano|first70=T.|last70=Wauters|first71=G.|last71=Wurden|first72=M.|last72=Yoshinuma|first73=M.|last73=Zanini|first74=D.|last74=Zhang|date=1 August 2019|journal=Physics of Plasmas|volume=26|issue=8|pages=082504|doi=10.1063/1.5098761|bibcode=2019PhPl...26h2504W |s2cid=202127809 |doi-access=free|hdl=1721.1/130063|hdl-access=free}}</ref><ref name=":0"/><ref name="sb2022">{{Cite journal|title=S. BrezƖnsek et al 2022 Nucl. Fusion 62 016006| journal=Nuclear Fusion|doi=10.1088/1741-4326/ac3508 |s2cid=240484560 |doi-access=free|url=https://publikationen.bibliothek.kit.edu/1000142438/142588326}}</ref>

[[File:Wendelstein-7X-June-26-2018.jpg|thumb|Wendelstein 7-X during OP1.2b]]

In June 2018 a record ion temperature of about 40 million degrees, a density of 0.8 × 10<sup>20</sup> particles/m<sup>3</sup>, and a confinement time of 0.2 second yielded a record fusion product of 6 × 10<sup>26</sup> degree-seconds per cubic metre.<ref>[https://phys.org/news/2018-06-wendelstein-x-world.html "Wendelstein 7-X achieves world record for fusion product"] Phys.org, 25 June 2018</ref>

During the last experiments of 2018, the density reached 2 × 10<sup>20</sup> particles/m<sup>3</sup> at a temperature of 20 million degrees. With good plasma values, long-lasting plasmas with long discharge times of 100 seconds were obtained. Energy content exceeded 1 megajoule.<ref>{{Cite web|url=https://www.ipp.mpg.de/4550215/11_18|title=Successful second round of experiments with Wendelstein 7-X|website=www.ipp.mpg.de|language=en|access-date=22 March 2019}}</ref><ref>{{Cite web|url=https://newatlas.com/wendelstein-7-x-nuclear-fusion-records/57394|title=Wendelstein 7-X fusion reactor keeps its cool en route to record-breaking results|last=Lavars|first=Nick|date=26 November 2018|website=newatlas.com|language=en|access-date=1 December 2018}}</ref><ref>{{Cite journal|title=T. Klinger et al 2019 Nucl. Fusion 59 112004|journal=Nuclear Fusion|doi=10.1088/1741-4326/ab03a7 |s2cid=128140454 |doi-access=free|hdl=2434/653115|hdl-access=free}}</ref><ref>{{Cite journal|title=Thomas Sunn Pedersen et al 2022 Nucl. Fusion 62 042022|journal=Nuclear Fusion |date=April 2022 |volume=62 |issue=4 |page=042022 |doi=10.1088/1741-4326/ac2cf5 |last1=Sunn Pedersen |first1=Thomas |last2=Abramovic |first2=I. |last3=Agostinetti |first3=P. |last4=Agredano Torres |first4=M. |last5=Äkäslompolo |first5=S. |last6=Alcuson Belloso |first6=J. |last7=Aleynikov |first7=P. |last8=Aleynikova |first8=K. |last9=Alhashimi |first9=M. |last10=Ali |first10=A. |last11=Allen |first11=N. |last12=Alonso |first12=A. |last13=Anda |first13=G. |last14=Andreeva |first14=T. |last15=Angioni |first15=C. |last16=Arkhipov |first16=A. |last17=Arnold |first17=A. |last18=Asad |first18=W. |last19=Ascasibar |first19=E. |last20=Aumeunier |first20=M. -H |last21=Avramidis |first21=K. |last22=Aymerich |first22=E. |last23=Baek |first23=S. -G |last24=Bähner |first24=J. |last25=Baillod |first25=A. |last26=Balden |first26=M. |last27=Balden |first27=M. |last28=Baldzuhn |first28=J. |last29=Ballinger |first29=S. |last30=Banduch |first30=M. |s2cid=234338848 |display-authors=1 |doi-access=free |hdl=1721.1/147631 |hdl-access=free }}</ref>

In 2021 an analysis of X-ray imaging crystal spectrometer data collected in the 2018 experiment substantially reduced troubling [[neoclassical transport]] heat loss. Collisions between heated particles cause some to escape the magnetic field. This was due to magnetic field cage optimization that was essential in achieving the record results.<ref>{{Cite journal|last1=Beidler|first1=C. D.|last2=Smith|first2=H. M.|last3=Alonso|first3=A.|last4=Andreeva|first4=T.|last5=Baldzuhn|first5=J.|last6=Beurskens|first6=M. N. A.|last7=Borchardt|first7=M.|last8=Bozhenkov|first8=S. A.|last9=Brunner|first9=K. J.|last10=Damm|first10=H.|last11=Drevlak|first11=M.|date=11 August 2021|title=Demonstration of reduced neoclassical energy transport in Wendelstein 7-X|journal=Nature|language=en|volume=596|issue=7871|pages=221–226|pmid=34381232|doi=10.1038/s41586-021-03687-w|issn=1476-4687|pmc=8357633|bibcode=2021Natur.596..221B}}</ref><ref>{{Cite web|last=Lavars|first=Nick|date=2021-09-01|title=Wendelstein 7-X fusion reactor on path to plasma twice as hot as the Sun|url=https://newatlas.com/energy/wendelstein-7-x-fusion-reactor-double-temperature-sun/|access-date=2021-09-02|website=New Atlas|language=en-US}}</ref>

=== Timeline ===
{| class="wikitable"
!Date!! Event
|-
| 1980 || Planning initiated<ref>{{Cite web|url=https://www.ipp.mpg.de/17019/meilensteine|title=Milestones|website=www.ipp.mpg.de}}</ref><ref name="GriegerRenner1985">{{cite journal|last1=Grieger|first1=G.|last2=Renner|first2=H.|last3=Wobig|first3=H.|title=Wendelstein stellarators|journal=Nuclear Fusion|volume=25|issue=9|year=1985|pages=1231–1242|issn=0029-5515|doi=10.1088/0029-5515/25/9/040|s2cid=250832456 }}</ref>
|-
| 1994 || Project initiated
|-
| 2005 || Assembly began
|-
| 2014 || Inaugurated
|-
|December 2015
|Begin operational phase OP1.1
|-
| 2015 || Successful helium plasma test at 1&nbsp;MK for ~0.1&nbsp;s
|-
| 2016 || Hydrogen plasma at 80&nbsp;MK for 0.25&nbsp;s
|-
|March 2016
|End OP1.1, begin upgrade phase<ref name=":0"/><ref name="dh2018">{{Cite journal|title= Upgrades of edge, divertor and scrape-off layer diagnostics of W7-X for OP1.2| journal= [[Fusion Engineering and Design]] | date= 2018 |doi=10.1016/j.fusengdes.2018.02.013 |doi-access=free|url=https://juser.fz-juelich.de/record/858024/files/Paper_Hathiramani_ISFNT-13_reviesed.pdf | last1= Hathiramani | first1= D. | last2= Ali | first2= A. | last3= Anda | first3= G. | last4= Barbui | first4= T. | last5= Biedermann | first5= C. | last6= Charl | first6= A. | last7= Chauvin | first7= D. | last8= Czymek | first8= G. | last9= Dhard | first9= C.P. | last10= Drewelow | first10= P. | last11= Dudek | first11= A. | last12= Effenberg | first12= F. | last13= Ehrke | first13= G. | last14= Endler | first14= M. | last15= Ennis | first15= D.A. | last16= Fellinger | first16= J. | last17= Ford | first17= O. | last18= Freundt | first18= S. | last19= Gradic | first19= D. | last20= Grosser | first20= K. | last21= Harris | first21= J. | last22= Hölbe | first22= H. | last23= Jakubowski | first23= M.W. | last24= Knaup | first24= M. | last25= Kocsis | first25= G. | last26= König | first26= R. | last27= Krause | first27= M. | last28= Kremeyer | first28= T. | last29= Kornejew | first29= P. | last30= Krychowiak | first30= M. | volume= 136 | pages= 304–308 | bibcode= 2018FusED.136..304H | display-authors= 1 }}</ref>
|-
|June 2017
|Begin operational phase OP1.2
|-
|June 2018
|Fusion [[Lawson criterion#Extension into the "triple product"|triple product]] of 6 × 10<sup>26</sup> degree-second/m<sup>3</sup><ref>{{Cite web|url=https://www.ipp.mpg.de/4413312/04_18|title=Wendelstein 7-X achieves world record|website=www.ipp.mpg.de|access-date=30 June 2018}}</ref>
|-
|November 2018
|End OP1.2, begin upgrade phase
|-
|August 2022<ref>{{cite web | url=https://www.ipp.mpg.de/5265532/02_22?c=14226 | title=Expansion of the Wendelstein 7-X fusion device completed / Experiments to start in autumn | date=9 August 2022 | author=Julia Sieber}}</ref>
|Final assembly step with water-coolers finished
|-
|February 2023<ref name="Milestone2023Feb" />
|Start of OP2, demonstrated steady-state operation at higher power levels
|}

==Financing ==
Financial support for the project is about 80% from Germany and about 20% from the European Union. 90% of German funding comes from the federal government and 10% from the state government of [[Mecklenburg-Vorpommern]]. The total investment for the stellarator itself over 1997–2014 amounted to €370 million, while the total cost for the IPP site in [[Greifswald]] including investment plus operating costs (personnel and material resources) amounted to €1.06 billion for that 18-year period. This exceeded the original budget estimate, mainly because the initial development phase was longer than expected, doubling the personnel costs.<ref>[https://www.faz.net/aktuell/wissen/physik-chemie/wendelstein-7-x-start-frei-fuer-deutschen-sonnenofen-12948367.html FAZ: Start frei für deutschen Sonnenofen] {{Webarchive|url=https://web.archive.org/web/20151107052325/https://www.faz.net/aktuell/wissen/physik-chemie/wendelstein-7-x-start-frei-fuer-deutschen-sonnenofen-12948367.html |date=7 November 2015 }} vom 20. Mai 2014</ref>

In July 2011, the President of the [[Max Planck Society]], [[Peter Gruss]], announced that the United States would contribute $7.5 million under the program "Innovative Approaches to Fusion" of the [[United States Department of Energy]].<ref>{{cite web|author=Isabella Milch|url= http://www.ipp.mpg.de/ippcms/eng/presse/pi/08_11_pi|title=USA joining the Wendelstein 7-X fusion project|publisher=Max Planck Institute of Plasma Physics|date=7 July 2011|access-date=4 February 2016}}</ref>

== Collaborating institutes ==
=== European Union ===
* FJFI at [[Czech Technical University in Prague]] (Czech Republic)
* [[Charles University]] (Czech Republic)
* [[Technische Universität Berlin]] (Germany)
* [[University of Greifswald]] (Germany)
* [[Forschungszentrum Jülich]] (Germany)
* [[Karlsruhe Institute of Technology]] (Germany)
* Institute of Interfacial Process Engineering and Plasma Technology (IGVP) at the [[University of Stuttgart]] (Germany)
* [[Physikalisch-Technische Bundesanstalt]] (Germany)
* [[Commissariat à l'énergie atomique et aux énergies alternatives]] (CEA; France)
* [[Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas]] (CIEMAT; Spain)
* Institute of Nuclear Physics Kraków and National Centre for Nuclear Research (Poland)
* Institute of Plasma Physics and Laser Microfusion, Warsaw (Poland)
* KFKI Research Institute for Particle and Nuclear Physics of the Hungarian Academy of Sciences (Hungary)
* Trilateral Euregio Cluster (Germany/Belgium/Netherlands)
* [[Technical University of Denmark]] (DTU) (Denmark)
* [[Eindhoven University of Technology]] (The Netherlands)

=== United States ===
* [[Los Alamos National Laboratory]]
* [[Oak Ridge National Laboratory]]
* [[Princeton Plasma Physics Laboratory]]
* [[University of Wisconsin–Madison]]
* [[Massachusetts Institute of Technology]]
* [[Auburn University]]
* Xantho Technologies, LLC

=== Japan ===
* [[National Institutes of Natural Sciences, Japan#National Institute for Fusion Science|National Institute for Fusion Science]]

== See also ==
{{Portal|Germany|Nuclear technology|Energy|Science}}
* [[Fusion power]]
* Similar stellarators:
**[[Large Helical Device]], Japan, Heliotron, superconducting (1998– )
** [[Helically Symmetric Experiment]], USA, Quasi-Helically Symmetric
** [[National Compact Stellarator Experiment]], three field-period Helias configuration – had similar coil problems – construction halted in 2008

==References==
{{Reflist|30em}}

==External links==
{{Commons category|Wendelstein 7-X}}
* {{official website|https://www.ipp.mpg.de/w7x}}
* {{YouTube|title = The First Helium Plasma|id = R_kPM1J-F0Q}}

{{fusion experiments}}
{{University of Greifswald}}
{{Nuclear power in Germany}}

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[[Category:Stellarators]]
[[Category:University of Greifswald]]
[[Category:Nuclear technology in Germany]]
[[Category:2015 in science]]