Wendelstein 7-X Explained

Wendelstein 7-X
Imagetitle:W7-X in 2011
Type:Stellarator
City:Greifswald
Country:Germany
Affiliation:Max Planck Institute for Plasma Physics
Operation Start Year:2015
Ongoing:yes
Prev:Wendelstein 7-AS
Website:https://www.ipp.mpg.de/w7x

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.[1] [2] 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.

, the Wendelstein 7-X reactor is the world's largest stellarator device.[3] After two successful operation phases ending in October 2018, the reactor was taken offline for upgrades.[4] [5] The upgrade completed in 2022. New fusion experiments in February 2023 demonstrated longer confinement and increased power.[6] 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.[7] [8]

The name of the project, referring to the mountain Wendelstein in Bavaria, was decided at the end of the 1950s, referencing the preceding project from Princeton University under the name Project Matterhorn.[9]

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 toroid, consisting of 50 non-planar and 20 planar superconducting magnetic coils, 3.5 m high, which induce a magnetic field that prevents the plasma from colliding with the reactor walls. The 50 non-planar coils are used for adjusting the magnetic field. It aims for a plasma density of 3 particles per cubic metre, and a plasma temperature of 60–130 megakelvins (MK).[1]

The W7-X is optimised along the quasi-isodynamic principle.[10]

The main components are the magnetic coils, cryostat, plasma vessel, divertor and heating systems.

The coils (NbTi in aluminium) are arranged around a heat insulating cladding with a diameter of 16 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 K). The coils will carry 12.8 kA current and create a field of up to 3 teslas.

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.

The heating system[11] includes high power gyrotrons for electron cyclotron resonance heating (ECRH), which will deliver up to 15 MW of heating to the plasma.[12] For operational phase 2 (OP-2), after completion of the full armor/water-cooling, up to 8 megawatts of neutral beam injection will also be available for 10 seconds.[13] An ion cyclotron resonance heating (ICRH) system will become available for physics operation in OP1.2.[14]

A system of sensors 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.[15]

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. The schedule slipped into late 2015.[16] [17] [18]

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.[19] In 2012, Princeton University and the Max Planck Society announced a new joint research center in plasma physics,[20] to include research on W7-X.

The end of the construction phase, which required more than 1 million assembly hours,[21] was officially marked by an inauguration ceremony on 20 May 2014.[22] After a period of vessel leak-checking, beginning in the summer of 2014, the cryostat was evacuated, and magnet testing was completed in July 2015.[23]

Operational phase 1 (OP1.1) began 10 December 2015.[24] On that day the reactor successfully produced helium plasma (with temperatures of about 1 MK) for about 0.1 s. For this initial test with about 1 mg of helium gas injected into the evacuated plasma vessel, microwave heating was applied for a short 1.3 MW pulse.[25]

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.[24] [26]

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 MK, while ion temperatures reached 10 MK. More than 2,000 pulses were conducted before shutdown.[27]

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.[28] [29]

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.[30] The special magnetic field topology was confirmed in 2016.[31] [32]

Operational phase 1 (OP1.1) concluded 10 March 2016[24] [33] and an upgrade phase began.

Operational phase 1 continued (OP1.2) in 2017[34] to test the (uncooled) divertor.[35] [24] [36]

In June 2018 a record ion temperature of about 40 million degrees, a density of 0.8 × 1020 particles/m3, and a confinement time of 0.2 second yielded a record fusion product of 6 × 1026 degree-seconds per cubic metre.[37]

During the last experiments of 2018, the density reached 2 × 1020 particles/m3 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.[38] [39] [40] [41]

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.[42] [43]

Timeline

DateEvent
1980 Planning initiated[44] [45]
1994 Project initiated
2005 Assembly began
2014 Inaugurated
December 2015Begin operational phase OP1.1
2015 Successful helium plasma test at 1 MK for ~0.1 s
2016 Hydrogen plasma at 80 MK for 0.25 s
March 2016End OP1.1, begin upgrade phase[46]
June 2017Begin operational phase OP1.2
June 2018Fusion triple product of 6 × 1026 degree-second/m3[47]
November 2018End OP1.2, begin upgrade phase
August 2022[48] Final assembly step with water-coolers finished
February 2023Start 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.[49]

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.[50]

Collaborating institutes

European Union

United States

Japan

See also

External links

54.073°N 13.424°W

Notes and References

  1. https://www.ipp.mpg.de/16931/einfuehrung Introduction – the Wendelstein 7-X stellarator
  2. Web site: Clery. Daniel. The bizarre reactor that might save nuclear fusion. sciencemag.org. Science Magazine. 25 October 2015. 21 October 2015.
  3. Web site: Wendelstein 7-X achieves world record . Max Planck Institute for Plasma Physics . 27 December 2022.
  4. Web site: The second experimentation phase . Max Planck Institute for Plasma Physics . 26 September 2022.
  5. Web site: Wendelstein 7-X fusion device at Greifswald to be upgraded . Max Planck Institute for Plasma Physics . 26 September 2022. Milch. Isabella.
  6. Web site: Wendelstein 7-X reaches milestone: Power plasma with gigajoule energy turnover generated for eight minutes . 22 Feb 2023.
  7. https://idw-online.de/en/news799586 idw-online.de: Federal Research Minister Stark-Watzinger and Minister Martin visit IPP Greifswald
  8. https://www.ipp.mpg.de/5272648/03_22?c=4313165 ipp.mpg.de: Wendelstein 7-X on the verge of new peak performance
  9. WI-A, WI-B, WII-A, WII-B, W7-A:
  10. Web site: Physics, Technologies, and Status of the Wendelstein 7-X Device.
  11. Web site: Stellarator Heating and Optimization . 10 December 2015.
  12. Web site: Microwave heating – ECRH . 10 December 2015.
  13. Web site: Neutral Beam Injection Heating (NBI) . 10 December 2015.
  14. Web site: Ion Cyclotron Resonance Heating (ICRH) . 10 December 2015.
  15. Web site: Profile Diagnostics . 10 December 2015.
  16. Web site: Stellarators difficult to build? The construction of Wendelstein 7-X . Klinger, Thomas . 14 April 2011 . 13 June 2011. 53 slides - many photos
  17. Web site: The stellarator renaissance . Arnoux, Robert . 15 April 2011 . 13 June 2011.
  18. Web site: Wendelstein 7-x stellarator puts new twist on nuclear fusion power. www.gizmag.com. 27 October 2015. 25 October 2015. Colin. Jeffrey.
  19. Web site: US narrows fusion research focus, joins German stellarator. 1 September 2011.
  20. Web site: Princeton, Max Planck Society launch new research center plasma physics. 29 March 2012. 19 August 2013. 4 March 2016. 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. dead.
  21. News: Start of scientific experimentation at the Wendelstein 7-X fusion device. 7 June 2016. phys.org. 11 October 2016.
  22. Web site: Preparations for operation of Wendelstein 7-X starting . Milch, Isabella . 12 May 2014 . 16 May 2014.
  23. Web site: Magnet tests on Wendelstein 7-X successfully completed. 7 July 2015. dead. 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. 16 July 2015.
  24. Web site: Wendelstein 7-X Newsletter No. 13 / April 2017.
  25. Web site: The first plasma: the Wendelstein 7-X fusion device is now in operation. 10 December 2015. 10 December 2015. Max Planck Institute for Plasma Physics.
  26. Plans for the first plasma operation of Wendelstein 7-X. Nuclear Fusion . November 2015 . 55 . 12 . 126001 . 10.1088/0029-5515/55/12/126001 . Sunn Pedersen . T. . Andreeva . T. . Bosch . H. -S . Bozhenkov . S. . Effenberg . F. . Endler . M. . Feng . Y. . Gates . D. A. . Geiger . J. . Hartmann . D. . Hölbe . H. . Jakubowski . M. . König . R. . Laqua . H. P. . Lazerson . S. . Otte . M. . Preynas . M. . Schmitz . O. . Stange . T. . Turkin . Y. . 2015NucFu..55l6001P. 11858/00-001M-0000-0029-04EB-D . 67798335 . free .
  27. News: Wendelstein 7-X: Upgrading after successful first round of experiments. 11 July 2016. phys.org. 11 October 2016.
  28. F. Effenberg et al 2017 Nucl. Fusion 57 036021. 10.1088/1741-4326/aa4f83. 125707430 .
  29. G.A. Wurden et al 2017 Nucl. Fusion 57 056036. 10.1088/1741-4326/aa6609. 126252486 . 11584/213558. free.
  30. Web site: Wendelstein 7-X fusion device produces its first hydrogen plasma . 3 February 2016. 4 February 2016 . Max Planck Institute for Plasma Physics.
  31. Confirmation of the topology of the Wendelstein 7-X magnetic field to better than 1:100,000 . Nature Communications . 7 . 13493 . 10.1038/ncomms13493. 27901043 . 5141350 . 2016 . Pedersen . T. Sunn . Otte . M. . Lazerson . S. . Helander . P. . Bozhenkov . S. . Biedermann . C. . Klinger . T. . Wolf . R. C. . Bosch . H. -S. . Abramovic . Ivana . Äkäslompolo . Simppa . Aleynikov . Pavel . Aleynikova . Ksenia . Ali . Adnan . Alonso . Arturo . Anda . Gabor . Andreeva . Tamara . Ascasibar . Enrique . Baldzuhn . Jürgen . Banduch . Martin . Barbui . Tullio . Beidler . Craig . Benndorf . Andree . Beurskens . Marc . Biel . Wolfgang . Birus . Dietrich . Blackwell . Boyd . Blanco . Emilio . Blatzheim . Marko . Bluhm . Torsten . 29 . 2016NatCo...713493P .
  32. Web site: Tests confirm that Germany's massive nuclear fusion machine really works. ScienceAlert . 6 December 2016 . 7 December 2016 .
  33. R.C. Wolf et al 2017 Nucl. Fusion 57 102020. Nuclear Fusion . 27 July 2017 . 57 . 10 . 102020 . 10.1088/1741-4326/aa770d . Wolf . R. C. . Ali . A. . Alonso . A. . Baldzuhn . J. . Beidler . C. . Beurskens . M. . Biedermann . C. . Bosch . H. -S . Bozhenkov . S. . Brakel . R. . Dinklage . A. . Feng . Y. . Fuchert . G. . Geiger . J. . Grulke . O. . Helander . P. . Hirsch . M. . Höfel . U. . Jakubowski . M. . Knauer . J. . Kocsis . G. . König . R. . Kornejew . P. . Krämer-Flecken . A. . Krychowiak . M. . Landreman . M. . Langenberg . A. . Laqua . H. P. . Lazerson . S. . Maaßberg . H. . 1986901 . 1 . free . 2434/616000 . free .
  34. Web site: Wendelstein 7-X: Zweite Experimentierrunde hat begonnen. www.ipp.mpg.de.
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  37. https://phys.org/news/2018-06-wendelstein-x-world.html "Wendelstein 7-X achieves world record for fusion product"
  38. Web site: Successful second round of experiments with Wendelstein 7-X. www.ipp.mpg.de. en. 22 March 2019.
  39. Web site: Wendelstein 7-X fusion reactor keeps its cool en route to record-breaking results. Lavars. Nick. 26 November 2018. newatlas.com. en. 1 December 2018.
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  43. Web site: Lavars. Nick. 2021-09-01. Wendelstein 7-X fusion reactor on path to plasma twice as hot as the Sun. 2021-09-02. New Atlas. en-US.
  44. Web site: Milestones. www.ipp.mpg.de.
  45. Grieger. G.. Renner. H.. Wobig. H.. Wendelstein stellarators. Nuclear Fusion. 25. 9. 1985. 1231–1242. 0029-5515. 10.1088/0029-5515/25/9/040. 250832456 .
  46. Upgrades of edge, divertor and scrape-off layer diagnostics of W7-X for OP1.2. . 2018 . 10.1016/j.fusengdes.2018.02.013 . free. Hathiramani . D. . Ali . A. . Anda . G. . Barbui . T. . Biedermann . C. . Charl . A. . Chauvin . D. . Czymek . G. . Dhard . C.P. . Drewelow . P. . Dudek . A. . Effenberg . F. . Ehrke . G. . Endler . M. . Ennis . D.A. . Fellinger . J. . Ford . O. . Freundt . S. . Gradic . D. . Grosser . K. . Harris . J. . Hölbe . H. . Jakubowski . M.W. . Knaup . M. . Kocsis . G. . König . R. . Krause . M. . Kremeyer . T. . Kornejew . P. . Krychowiak . M. . 136 . 304–308 . 2018FusED.136..304H . 1 .
  47. Web site: Wendelstein 7-X achieves world record. www.ipp.mpg.de. 30 June 2018.
  48. Web site: Expansion of the Wendelstein 7-X fusion device completed / Experiments to start in autumn . 9 August 2022 . Julia Sieber.
  49. https://www.faz.net/aktuell/wissen/physik-chemie/wendelstein-7-x-start-frei-fuer-deutschen-sonnenofen-12948367.html FAZ: Start frei für deutschen Sonnenofen
  50. Web site: Isabella Milch. USA joining the Wendelstein 7-X fusion project. Max Planck Institute of Plasma Physics. 7 July 2011. 4 February 2016.

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