Editing Stellarator (section)

=== Proof of divertor concepts ===

At Wendelstein 7-X, the island [[divertor]] has been successful in stabilizing detached plasma scenarios and reducing the [[Heat flux|heat fluxes]] on divertor targets.<ref>{{cite journal |title=O. Schmitz et al Nucl. Fusion 61, 016026 (2021) |journal=Nuclear Fusion |date=3 September 2020 |volume=61 |issue=1 |doi=10.1088/1741-4326/abb51e |osti=1814444 |s2cid=225288529 |url=https://www.osti.gov/biblio/1814444 |last1=Schmitz |first1=Oliver |last2=Feng |first2=Yuhe |last3=Jakubowski |first3=Marcin |last4=König |first4=Ralf |last5=Krychowiak |first5=Maciej |last6=Otte |first6=Matthias |last7=Reimold |first7=Felix |last8=Barbui |first8=Tullio |last9=Biedermann |first9=Christoph |last10=Bozhenkov |first10=Sergey A. |last11=Brezinsek |first11=Sebastijan |last12=Buttenschön |first12=Birger |last13=Brunner |first13=Kai Jakob |last14=Drewelow |first14=Peter |last15=Effenberg |first15=Florian |last16=Flom |first16=Erik |last17=Frerichs |first17=Heinke |last18=Ford |first18=Oliver P. |last19=Fuchert |first19=Golo |last20=Gao |first20=Yu |last21=Gradic |first21=Dorothea |last22=Grulke |first22=Olaf |last23=Hammond |first23=Kenneth |last24=Hergenhahn |first24=Uwe |last25=Höfel |first25=Udo |last26=Knauer |first26=Jens P. |last27=Kornejew |first27=Petra |last28=Kremeyer |first28=Thierry |last29=Niemann |first29=Holger |last30=Pasch |first30=Ekkehard |hdl=21.11116/0000-0007-A4DC-8 |display-authors=1 |hdl-access=free }}</ref><ref>{{cite journal |last1=Jakubowski |first1=M. |display-authors=etal |date=2021 |title=Overview of the results from divertor experiments with attached and detached plasmas at Wendelstein 7-X and their implications for steady-state operation |journal=Nuclear Fusion |volume=61 |issue=10 |doi=10.1088/1741-4326/ac1b68 |s2cid=237408135 |url=https://publikationen.bibliothek.kit.edu/1000140073/133022842 |doi-access=free }}</ref> This topology has multiple adjacent counter-streaming flow regions that can reduce the flow speed parallel to magnetic field lines, leading to substantial heat flux mitigation.<ref>{{cite journal |author1-last=Perseo |author1-first=V. |author2-first=F. |author2-last=Effenberg |author3-first=D. |author3-last=Gradic |author4-first=R. |author4-last=König |author5-first=O.P. |author5-last=Ford |author6-first=F. |author6-last=Reimold |author7-first=D.A. |author7-last=Ennis| author8-first=O. |author8-last=Schmitz |author9-first=T. Sunn |author9-last=Pedersen |display-authors=1 |title=Direct measurements of counter-streaming flows in a low-shear stellarator magnetic island topology |journal=Nuclear Fusion |volume=59 |number=12 |date=2019 |doi=10.1088/1741-4326/ab4320|osti=1572710 |s2cid=203087561 |doi-access=free }}</ref> Radiative power exhaust by impurity seeding has been demonstrated in island divertor configurations, resulting in stable plasma operation and reduced divertor heat loads.<ref>{{cite journal |title=First demonstration of radiative power exhaust with impurity seeding in the island divertor at Wendelstein 7-X |author=F. Effenberg |display-authors=etal |journal=Nucl. Fusion |volume=59 |number=10 |page=106020 |year=2019 |doi=10.1088/1741-4326/ab32c4 |s2cid=199132000 |url=https://hal.archives-ouvertes.fr/hal-03740994/file/w7x-impurity-seeding-power-exhaust-florian-effenberg.pdf }}</ref> This makes the island divertor a promising solution for future detachment control in high-performance scenarios and upgrades towards a metal divertor.<ref>{{cite journal|title=First feedback-controlled divertor detachment in W7-X: Experience from TDU operation and prospects for operation with actively cooled divertor |author=M. Krychowiak |display-authors=etal |journal=Nucl. Mater. Energy |volume=34 |page=101363 |year=2023 |doi=10.1016/j.nme.2023.101363|osti=1957530 |s2cid=255694619 |doi-access=free}}</ref> The edge magnetic structure in quasi-omnigenous and helically symmetric stellarators, like W7-X and HSX, has a significant impact on particle fueling and exhaust. It has been shown that the magnetic island chain can be used to control plasma fueling from the recycling source and active gas injection.<ref>{{cite journal |author1-first=L. |author1-last=Stephey |author2-first=A. |author2-last=Bader |author3-first=F. |author3-last=Effenberg |author4-first=O. |author4-last=Schmitz |author5-first=G. |author5-last=Wurden |author6-first=D. |author6-last=Anderson |author7-first=F. |author7-last=Anderson |author8-first=C. |author8-last=Biedermann |author9-first=A. |author9-last=Dinklage |author10-first=Y. |author10-last=Feng |author11-first=H. |author11-last=Frerichs |author12-first=G. |author12-last=Fuchert |author13-first=J. |author13-last=Geiger |author14-first=J. |author14-last=Harris |author15-first=R. |author15-last=König |author16-first=P. |author16-last=Kornejew |author17-first=M. |author17-last=Krychowiak |author18-first=J. |author18-last=Lore |author19-first=E. |author19-last=Unterberg |author20-first=I. |author20-last=Waters |display-authors=1 |title=Impact of magnetic islands in the plasma edge on particle fueling and exhaust in the HSX and W7-X stellarators |journal=Physics of Plasmas |volume=25 |issue=6 |year=2018 |doi=10.1063/1.5026324 |hdl=21.11116/0000-0001-6AE2-9 |osti=1439332 |s2cid=125652747 |hdl-access=free }}</ref>