Stable heat and particle flux detachment with efficient particle exhaust in the island divertor of Wendelstein 7-X

Schmitz, Oliver; Feng, Yuhe; Jakubowski, Marcin; König, Ralf; Krychowiak, Maciej; Otte, Matthias; Reimold, Felix; Barbui, Tullio; Biedermann, Christoph; Bozhenkov, Sergey A.; Brezinsek, Sebastijan; Buttenschön, Birger; Brunner, Kai Jakob; Drewelow, Peter; Effenberg, Florian; Flom, Erik; Frerichs, Heinke; Ford, Oliver P.; Fuchert, Golo; Gao, Yu; Gradic, Dorothea; Grulke, Olaf; Hammond, Kenneth; Hergenhahn, Uwe; Höfel, Udo; Knauer, Jens P.; Kornejew, Petra; Kremeyer, Thierry; Niemann, Holger; Pasch, Ekkehard; Pavone, Andrea; Perseo, Valeria; Rudischhauser, Lukas; Schlisio, Georg; Sunn Pedersen, Thomas; Wenzel, U.; Winters, Victoria; Wurden, Glen Anthony; Zhang, Daihong

doi:10.1088/1741-4326/abb51e

Title: Stable heat and particle flux detachment with efficient particle exhaust in the island divertor of Wendelstein 7-X

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Abstract

The island divertor concept is an innovative and promising idea to handle heat and particle exhaust in stellarators. At the Wendelstein 7-X (W7-X) stellarator, this divertor concept plays a central role in the device mission to demonstrate reactor relevant plasma confinement for steady-state time scales of up to 30 minutes in the high-performance campaign (OP2) starting in 2022. During the recently concluded first campaign with the inertially cooled island divertor, a large step in the experimental qualification of this divertor concept has been made. In discharges heated with electron cylotron resonance heating of 5-6 MW, central densities in the range of 0.7-1.2 × 10²⁰ m^-3 have been reached in combination with full divertor heat flux detachment. Also, significant neutral gas pressures and neutral compression ratios were shown for the first time in combination with reduced divertor particle flux. The divertor heat loads drop by an order of magnitude from >5 MW m^-2 to below 0.5 MW m-2 with increasing density, and substantial compression of neutrals reaching neutral pressure in the sub-divertor volume of >6.0 × 10^-4 mbar was seen. These elevated neutral pressure levels can be obtained and maintained with an up to 80% reduction of the particle fluxes ontomore »« less

Authors:

; Feng, Yuhe; Jakubowski, Marcin; König, Ralf; Krychowiak, Maciej; Otte, Matthias; Reimold, Felix;

;

; Flom, Erik; Frerichs, Heinke; Ford, Oliver P.; Fuchert, Golo;

Publication Date:: Thu Sep 03 00:00:00 EDT 2020

Research Org.:: Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

Sponsoring Org.:: USDOE Office of Science (SC), Fusion Energy Sciences (FES); Euratom

Contributing Org.:: W7-X Team

OSTI Identifier:: 1814444

Alternate Identifier(s):: OSTI ID: 1821367

Report Number(s):: LA-UR-20-21706
Journal ID: ISSN 0029-5515; TRN: US2213434

Grant/Contract Number:: SC00013911; SC00014210; 633053; 89233218CNA000001

Resource Type:: Accepted Manuscript

Journal Name:: Nuclear Fusion

Additional Journal Information:: Journal Volume: 61; Journal Issue: 1; Journal ID: ISSN 0029-5515

Publisher:: IOP Science

Country of Publication:: United States

Language:: English

Subject:: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; stellarator; island divertor; plasma edge physics and material interaction; Magnetic Fusion Energy; Divertor; detachment; W7-X

Citation Formats


                    Schmitz, Oliver, Feng, Yuhe, Jakubowski, Marcin, König, Ralf, Krychowiak, Maciej, Otte, Matthias, Reimold, Felix, Barbui, Tullio, Biedermann, Christoph, Bozhenkov, Sergey A., Brezinsek, Sebastijan, Buttenschön, Birger, Brunner, Kai Jakob, Drewelow, Peter, Effenberg, Florian, Flom, Erik, Frerichs, Heinke, Ford, Oliver P., Fuchert, Golo, Gao, Yu, Gradic, Dorothea, Grulke, Olaf, Hammond, Kenneth, Hergenhahn, Uwe, Höfel, Udo, Knauer, Jens P., Kornejew, Petra, Kremeyer, Thierry, Niemann, Holger, Pasch, Ekkehard, Pavone, Andrea, Perseo, Valeria, Rudischhauser, Lukas, Schlisio, Georg, Sunn Pedersen, Thomas, Wenzel, U., Winters, Victoria, Wurden, Glen Anthony, and Zhang, Daihong. Stable heat and particle flux detachment with efficient particle exhaust in the island divertor of Wendelstein 7-X.  United States: N. p., 2020. 
Web.  doi:10.1088/1741-4326/abb51e.

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                    Schmitz, Oliver, Feng, Yuhe, Jakubowski, Marcin, König, Ralf, Krychowiak, Maciej, Otte, Matthias, Reimold, Felix, Barbui, Tullio, Biedermann, Christoph, Bozhenkov, Sergey A., Brezinsek, Sebastijan, Buttenschön, Birger, Brunner, Kai Jakob, Drewelow, Peter, Effenberg, Florian, Flom, Erik, Frerichs, Heinke, Ford, Oliver P., Fuchert, Golo, Gao, Yu, Gradic, Dorothea, Grulke, Olaf, Hammond, Kenneth, Hergenhahn, Uwe, Höfel, Udo, Knauer, Jens P., Kornejew, Petra, Kremeyer, Thierry, Niemann, Holger, Pasch, Ekkehard, Pavone, Andrea, Perseo, Valeria, Rudischhauser, Lukas, Schlisio, Georg, Sunn Pedersen, Thomas, Wenzel, U., Winters, Victoria, Wurden, Glen Anthony, & Zhang, Daihong. Stable heat and particle flux detachment with efficient particle exhaust in the island divertor of Wendelstein 7-X.  United States.  https://doi.org/10.1088/1741-4326/abb51e

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                    Schmitz, Oliver, Feng, Yuhe, Jakubowski, Marcin, König, Ralf, Krychowiak, Maciej, Otte, Matthias, Reimold, Felix, Barbui, Tullio, Biedermann, Christoph, Bozhenkov, Sergey A., Brezinsek, Sebastijan, Buttenschön, Birger, Brunner, Kai Jakob, Drewelow, Peter, Effenberg, Florian, Flom, Erik, Frerichs, Heinke, Ford, Oliver P., Fuchert, Golo, Gao, Yu, Gradic, Dorothea, Grulke, Olaf, Hammond, Kenneth, Hergenhahn, Uwe, Höfel, Udo, Knauer, Jens P., Kornejew, Petra, Kremeyer, Thierry, Niemann, Holger, Pasch, Ekkehard, Pavone, Andrea, Perseo, Valeria, Rudischhauser, Lukas, Schlisio, Georg, Sunn Pedersen, Thomas, Wenzel, U., Winters, Victoria, Wurden, Glen Anthony, and Zhang, Daihong. Thu .  
"Stable heat and particle flux detachment with efficient particle exhaust in the island divertor of Wendelstein 7-X".  United States.  https://doi.org/10.1088/1741-4326/abb51e.  https://www.osti.gov/servlets/purl/1814444.

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@article{osti_1814444,

  title        = {Stable heat and particle flux detachment with efficient particle exhaust in the island divertor of Wendelstein 7-X},

  author       = {Schmitz, Oliver and Feng, Yuhe and Jakubowski, Marcin and König, Ralf and Krychowiak, Maciej and Otte, Matthias and Reimold, Felix and Barbui, Tullio and Biedermann, Christoph and Bozhenkov, Sergey A. and Brezinsek, Sebastijan and Buttenschön, Birger and Brunner, Kai Jakob and Drewelow, Peter and Effenberg, Florian and Flom, Erik and Frerichs, Heinke and Ford, Oliver P. and Fuchert, Golo and Gao, Yu and Gradic, Dorothea and Grulke, Olaf and Hammond, Kenneth and Hergenhahn, Uwe and Höfel, Udo and Knauer, Jens P. and Kornejew, Petra and Kremeyer, Thierry and Niemann, Holger and Pasch, Ekkehard and Pavone, Andrea and Perseo, Valeria and Rudischhauser, Lukas and Schlisio, Georg and Sunn Pedersen, Thomas and Wenzel, U. and Winters, Victoria and Wurden, Glen Anthony and Zhang, Daihong},

  abstractNote = {The island divertor concept is an innovative and promising idea to handle heat and particle exhaust in stellarators. At the Wendelstein 7-X (W7-X) stellarator, this divertor concept plays a central role in the device mission to demonstrate reactor relevant plasma confinement for steady-state time scales of up to 30 minutes in the high-performance campaign (OP2) starting in 2022. During the recently concluded first campaign with the inertially cooled island divertor, a large step in the experimental qualification of this divertor concept has been made. In discharges heated with electron cylotron resonance heating of 5-6 MW, central densities in the range of 0.7-1.2 × 1020 m-3 have been reached in combination with full divertor heat flux detachment. Also, significant neutral gas pressures and neutral compression ratios were shown for the first time in combination with reduced divertor particle flux. The divertor heat loads drop by an order of magnitude from >5 MW m-2 to below 0.5 MW m-2 with increasing density, and substantial compression of neutrals reaching neutral pressure in the sub-divertor volume of >6.0 × 10-4 mbar was seen. These elevated neutral pressure levels can be obtained and maintained with an up to 80% reduction of the particle fluxes onto the divertor target tiles. This discharge scenario was held stably detached for up to 28 seconds, which is equivalent to several hundred energy confinement times τE and longer than the time scales for current relaxation. No impurity accumulation was seen at constant Zeff ≈ 1.5 and the stored energy stayed constant at levels of Wdia >600 kJ. The level of neutral pressure and compression reached in this scenario extrapolates well to the steady-state particle exhaust requirements for high-performance steady-state operation in OP2, in which the fully actively cooled high-heat-flux divertor will be available. Finally, an overview of this recently discovered divertor regime is given and the status of the physics understanding based on modeling of these regimes with the EMC3-EIRENE code is presented.},

  doi          = {10.1088/1741-4326/abb51e},

  journal      = {Nuclear Fusion},

  number       = 1,

  volume       = 61,

  place        = {United States},

  year         = {Thu Sep 03 00:00:00 EDT 2020},

  month        = {Thu Sep 03 00:00:00 EDT 2020}

}

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