Ion temperature clamping in Wendelstein 7-X electron cyclotron heated plasmas
Abstract
The neoclassical transport optimization of the Wendelstein 7-X stellarator has not resulted in the predicted high energy confinement of gas fueled electron-cyclotron-resonance-heated (ECRH) plasmas as modelled in (Turkin et al 2011 Phys. Plasmas 18 022505) due to high levels of turbulent heat transport observed in the experiments. The electron-turbulent-heat transport appears non-stiff and is of the electron temperature gradient (ETG)/ion temperature gradient (ITG) type (Weir et al 2021 Nucl. Fusion 61 056001). As a result, the electron temperature Te can be varied freely from 1 keV–10 keV within the range of PECRH = 1–7 MW, with electron density ne values from 0.1–1.5 × 1020 m–3. By contrast, in combination with the broad electron-to-ion energy-exchange heating profile in ECRH plasmas, ion-turbulent-heat transport leads to clamping of the central ion temperature at Ti ~ 1.5 keV ± 0.2 keV. In a dedicated ECRH power scan at a constant density of $$\langle n_{e} \rangle$$ = 7 × 1019 m–3, an apparent 'negative ion temperature profile stiffness' was found in the central plasma for (r/a < 0.5), in which the normalized gradient ∇Ti/Ti decreases with increasing ion heat flux. The experiment was conducted in helium, which has a higher radiative density limit compared to hydrogen, allowing a broader power scan. This 'negative stiffness' is due to a strong exacerbation of turbulent transport with an increasing ratio of Te/Ti in this electron-heated plasma. This finding is consistent with electrostatic microinstabilities, such as ITG-driven turbulence. Theoretical calculations made by both linear and nonlinear gyro-kinetic simulations performed by the GENE code in the W7-X three-dimensional geometry show a strong enhancement of turbulence with an increasing ratio of Te/Ti. The exacerbation of turbulence with increasing Te/Ti is also found in tokamaks and inherently enhances ion heat transport in electron-heated plasmas. This finding strongly affects the prospects of future high-performance gas-fueled ECRH scenarios in W7-X and imposes a requirement for turbulence-suppression techniques.
- Authors:
-
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- Max Planck Institute for Plasma Physics, Greifswald (Germany)
- Research Centre for Energy, Environment and Technology (CIEMAT), Madrid (Spain). Laboratorio Nacional de Fusion
- Max Planck Institute for Plasma Physics, Greifswald (Germany); Technical Univ. of Denmark, Lyngby (Denmark)
- National Inst. of Natural Sciences (NINS), Toki (Japan)
- Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
- Publication Date:
- Research Org.:
- Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
- Sponsoring Org.:
- USDOE; Euratom Research and Training Program
- Contributing Org.:
- W7-X Team
- OSTI Identifier:
- 1878182
- Grant/Contract Number:
- AC02-09CH11466; 633053
- Resource Type:
- Accepted Manuscript
- Journal Name:
- Nuclear Fusion
- Additional Journal Information:
- Journal Volume: 61; Journal Issue: 11; Journal ID: ISSN 0029-5515
- Publisher:
- IOP Science
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; turbulent transport; electron heated plasmas; ion heat transport; neoclassically optimised stellarator; power balance; profile stiffness; ion temperature clamping; electron cyclotron heating
Citation Formats
Beurskens, Marc N.A., Bozhenkov, Sergey A., Ford, O., Xanthopoulos, Pavlos, Zocco, Alessandro, Turkin, Y., Alonso, Juan Arturo, Beidler, Craig, Calvo, I., Carralero, Daniel, Estrada, Teresa, Fuchert, G., Grulke, O., Hirsch, M., Ida, Katsumi, Jakubowski, Marcin, Killer, Carsten, Krychowiak, M., Kwak, Sehyun, Lazerson, Samuel, Langenberg, Andreas, Lunsford, Robert, Pablant, Novimir, Pasch, E., Pavone, Andrea, Reimold, F., Romba, Thilo, von Stechow, A., Smith, H. M., Windisch, T., Yoshinuma, M., Zhang, Diahong, and Wolf, Robert C. Ion temperature clamping in Wendelstein 7-X electron cyclotron heated plasmas. United States: N. p., 2021.
Web. doi:10.1088/1741-4326/ac1653.
Beurskens, Marc N.A., Bozhenkov, Sergey A., Ford, O., Xanthopoulos, Pavlos, Zocco, Alessandro, Turkin, Y., Alonso, Juan Arturo, Beidler, Craig, Calvo, I., Carralero, Daniel, Estrada, Teresa, Fuchert, G., Grulke, O., Hirsch, M., Ida, Katsumi, Jakubowski, Marcin, Killer, Carsten, Krychowiak, M., Kwak, Sehyun, Lazerson, Samuel, Langenberg, Andreas, Lunsford, Robert, Pablant, Novimir, Pasch, E., Pavone, Andrea, Reimold, F., Romba, Thilo, von Stechow, A., Smith, H. M., Windisch, T., Yoshinuma, M., Zhang, Diahong, & Wolf, Robert C. Ion temperature clamping in Wendelstein 7-X electron cyclotron heated plasmas. United States. https://doi.org/10.1088/1741-4326/ac1653
Beurskens, Marc N.A., Bozhenkov, Sergey A., Ford, O., Xanthopoulos, Pavlos, Zocco, Alessandro, Turkin, Y., Alonso, Juan Arturo, Beidler, Craig, Calvo, I., Carralero, Daniel, Estrada, Teresa, Fuchert, G., Grulke, O., Hirsch, M., Ida, Katsumi, Jakubowski, Marcin, Killer, Carsten, Krychowiak, M., Kwak, Sehyun, Lazerson, Samuel, Langenberg, Andreas, Lunsford, Robert, Pablant, Novimir, Pasch, E., Pavone, Andrea, Reimold, F., Romba, Thilo, von Stechow, A., Smith, H. M., Windisch, T., Yoshinuma, M., Zhang, Diahong, and Wolf, Robert C. Mon .
"Ion temperature clamping in Wendelstein 7-X electron cyclotron heated plasmas". United States. https://doi.org/10.1088/1741-4326/ac1653. https://www.osti.gov/servlets/purl/1878182.
@article{osti_1878182,
title = {Ion temperature clamping in Wendelstein 7-X electron cyclotron heated plasmas},
author = {Beurskens, Marc N.A. and Bozhenkov, Sergey A. and Ford, O. and Xanthopoulos, Pavlos and Zocco, Alessandro and Turkin, Y. and Alonso, Juan Arturo and Beidler, Craig and Calvo, I. and Carralero, Daniel and Estrada, Teresa and Fuchert, G. and Grulke, O. and Hirsch, M. and Ida, Katsumi and Jakubowski, Marcin and Killer, Carsten and Krychowiak, M. and Kwak, Sehyun and Lazerson, Samuel and Langenberg, Andreas and Lunsford, Robert and Pablant, Novimir and Pasch, E. and Pavone, Andrea and Reimold, F. and Romba, Thilo and von Stechow, A. and Smith, H. M. and Windisch, T. and Yoshinuma, M. and Zhang, Diahong and Wolf, Robert C.},
abstractNote = {The neoclassical transport optimization of the Wendelstein 7-X stellarator has not resulted in the predicted high energy confinement of gas fueled electron-cyclotron-resonance-heated (ECRH) plasmas as modelled in (Turkin et al 2011 Phys. Plasmas 18 022505) due to high levels of turbulent heat transport observed in the experiments. The electron-turbulent-heat transport appears non-stiff and is of the electron temperature gradient (ETG)/ion temperature gradient (ITG) type (Weir et al 2021 Nucl. Fusion 61 056001). As a result, the electron temperature Te can be varied freely from 1 keV–10 keV within the range of PECRH = 1–7 MW, with electron density ne values from 0.1–1.5 × 1020 m–3. By contrast, in combination with the broad electron-to-ion energy-exchange heating profile in ECRH plasmas, ion-turbulent-heat transport leads to clamping of the central ion temperature at Ti ~ 1.5 keV ± 0.2 keV. In a dedicated ECRH power scan at a constant density of $\langle n_{e} \rangle$ = 7 × 1019 m–3, an apparent 'negative ion temperature profile stiffness' was found in the central plasma for (r/a < 0.5), in which the normalized gradient ∇Ti/Ti decreases with increasing ion heat flux. The experiment was conducted in helium, which has a higher radiative density limit compared to hydrogen, allowing a broader power scan. This 'negative stiffness' is due to a strong exacerbation of turbulent transport with an increasing ratio of Te/Ti in this electron-heated plasma. This finding is consistent with electrostatic microinstabilities, such as ITG-driven turbulence. Theoretical calculations made by both linear and nonlinear gyro-kinetic simulations performed by the GENE code in the W7-X three-dimensional geometry show a strong enhancement of turbulence with an increasing ratio of Te/Ti. The exacerbation of turbulence with increasing Te/Ti is also found in tokamaks and inherently enhances ion heat transport in electron-heated plasmas. This finding strongly affects the prospects of future high-performance gas-fueled ECRH scenarios in W7-X and imposes a requirement for turbulence-suppression techniques.},
doi = {10.1088/1741-4326/ac1653},
journal = {Nuclear Fusion},
number = 11,
volume = 61,
place = {United States},
year = {Mon Oct 25 00:00:00 EDT 2021},
month = {Mon Oct 25 00:00:00 EDT 2021}
}
Works referenced in this record:
Heat pulse propagation and anomalous electron heat transport measurements on the optimized stellarator W7-X
journal, March 2021
- Weir, G. M.; Xanthopoulos, P.; Hirsch, M.
- Nuclear Fusion, Vol. 61, Issue 5
(Expected difficulties with) density-profile control in W7-X high-performance plasmas
journal, August 2018
- Beidler, C. D.; Feng, Y.; Geiger, J.
- Plasma Physics and Controlled Fusion, Vol. 60, Issue 10
Atomic Data and Modelling for Fusion: the ADAS Project
conference, January 2011
- Summers, H. P.; O’Mullane, M. G.
- 7TH INTERNATIONAL CONFERENCE ON ATOMIC AND MOLECULAR DATA AND THEIR APPLICATIONS - ICAMDATA-2010, AIP Conference Proceedings
Current Control by ECCD for W7-X
journal, October 2006
- Turkin, Yu.; Maassberg, H.; Beidler, C. D.
- Fusion Science and Technology, Vol. 50, Issue 3
Electron temperature gradient driven turbulence
journal, May 2000
- Jenko, F.; Dorland, W.; Kotschenreuther, M.
- Physics of Plasmas, Vol. 7, Issue 5
Neoclassical transport simulations for stellarators
journal, February 2011
- Turkin, Y.; Beidler, C. D.; Maaßberg, H.
- Physics of Plasmas, Vol. 18, Issue 2
Performance of Wendelstein 7-X stellarator plasmas during the first divertor operation phase
journal, August 2019
- Wolf, R. C.; Alonso, A.; Äkäslompolo, S.
- Physics of Plasmas, Vol. 26, Issue 8
Stable stellarators with medium β and aspect ratio
journal, February 1986
- Nührenberg, J.; Zille, R.
- Physics Letters A, Vol. 114, Issue 3
ECE Diagnostic for the initial Operation of Wendelstein 7-X
journal, January 2019
- Hirsch, Matthias; Höfel, Udo; Oosterbeek, Johan Willem
- EPJ Web of Conferences, Vol. 203
Characterization of injection and confinement improvement through impurity induced profile modifications on the Wendelstein 7-X stellarator
journal, August 2021
- Lunsford, R.; Killer, C.; Nagy, A.
- Physics of Plasmas, Vol. 28, Issue 8
Plasma transport coefficients for nonsymmetric toroidal confinement systems
journal, September 1986
- Hirshman, S. P.; Shaing, K. C.; van Rij, W. I.
- Physics of Fluids, Vol. 29, Issue 9
Study of neutral hydrogen transport in LHD core plasmas based on high dynamic-range Balmer- α spectroscopy
journal, May 2015
- Fujii, K.; Goto, M.; Morita, S.
- Nuclear Fusion, Vol. 55, Issue 6
Charge-state independent anomalous transport for a wide range of different impurity species observed at Wendelstein 7-X
journal, May 2020
- Langenberg, A.; Wegner, Th.; Pablant, N. A.
- Physics of Plasmas, Vol. 27, Issue 5
Profile stiffness and global confinement
journal, July 2004
- Garbet, X.; Mantica, P.; Ryter, F.
- Plasma Physics and Controlled Fusion, Vol. 46, Issue 9
Steepest-descent moment method for three-dimensional magnetohydrodynamic equilibria
journal, January 1983
- Hirshman, S. P.
- Physics of Fluids, Vol. 26, Issue 12
Density control problems in large stellarators with neoclassical transport
journal, August 1999
- Maaßberg, H.; Beidler, C. D.; Simmet, E. E.
- Plasma Physics and Controlled Fusion, Vol. 41, Issue 9
In situ wavelength calibration system for the X-ray Imaging Crystal Spectrometer (XICS) on W7-X
journal, October 2018
- Kring, J.; Pablant, N.; Langenberg, A.
- Review of Scientific Instruments, Vol. 89, Issue 10
Radial electric field and density fluctuations measured by Doppler reflectometry during the post-pellet enhanced confinement phase in W7-X
journal, March 2021
- Estrada, T.; Carralero, D.; Windisch, T.
- Nuclear Fusion, Vol. 61, Issue 4
Physical model assessment of the energy confinement time scaling in stellarators
journal, August 2007
- Dinklage, A.; Maaßberg, H.; Preuss, R.
- Nuclear Fusion, Vol. 47, Issue 9
Magnetic configuration effects on the Wendelstein 7-X stellarator
journal, May 2018
- Dinklage, A.; Beidler, C. D.; Helander, P.
- Nature Physics, Vol. 14, Issue 8
Comparisons and physics basis of tokamak transport models and turbulence simulations
journal, March 2000
- Dimits, A. M.; Bateman, G.; Beer, M. A.
- Physics of Plasmas, Vol. 7, Issue 3
Comparison of hybrid and baseline ELMy H-mode confinement in JET with the carbon wall
journal, December 2012
- Beurskens, M. N. A.; Frassinetti, L.; Challis, C.
- Nuclear Fusion, Vol. 53, Issue 1
Forward Modeling of X-Ray Imaging Crystal Spectrometers Within the Minerva Bayesian Analysis Framework
journal, April 2016
- Langenberg, A.; Svensson, J.; Thomsen, H.
- Fusion Science and Technology, Vol. 69, Issue 2
Suppression of electrostatic micro-instabilities in maximum- J stellarators
journal, January 2020
- Alcusón, J. A.; Xanthopoulos, P.; Plunk, G. G.
- Plasma Physics and Controlled Fusion, Vol. 62, Issue 3
Experimental studies of electron transport
journal, November 2001
- Ryter, F.; Angioni, C.; Beurskens, M.
- Plasma Physics and Controlled Fusion, Vol. 43, Issue 12A
Ray-tracing code TRAVIS for ECR heating, EC current drive and ECE diagnostic
journal, January 2014
- Marushchenko, N. B.; Turkin, Y.; Maassberg, H.
- Computer Physics Communications, Vol. 185, Issue 1
Core radial electric field and transport in Wendelstein 7-X plasmas
journal, February 2018
- Pablant, N. A.; Langenberg, A.; Alonso, A.
- Physics of Plasmas, Vol. 25, Issue 2
Real-time dispersion interferometry for density feedback in fusion devices
journal, September 2018
- Brunner, K. J.; Akiyama, T.; Hirsch, M.
- Journal of Instrumentation, Vol. 13, Issue 09
Profile stiffness and global confinement
journal, May 2005
- Garbet, X.; Mantica, P.; Ryter, F.
- Plasma Physics and Controlled Fusion, Vol. 47, Issue 6
Variational bounds for transport coefficients in three‐dimensional toroidal plasmas
journal, March 1989
- van Rij, W. I.; Hirshman, S. P.
- Physics of Fluids B: Plasma Physics, Vol. 1, Issue 3
Electron-cyclotron-resonance heating in Wendelstein 7-X: A versatile heating and current-drive method and a tool for in-depth physics studies
journal, November 2018
- Wolf, R. C.; Bozhenkov, S.; Dinklage, A.
- Plasma Physics and Controlled Fusion, Vol. 61, Issue 1
The first transport code simulations using the trapped gyro-Landau-fluid model
journal, May 2008
- Kinsey, J. E.; Staebler, G. M.; Waltz, R. E.
- Physics of Plasmas, Vol. 15, Issue 5
Infrared imaging systems for wall protection in the W7-X stellarator (invited)
journal, October 2018
- Jakubowski, Marcin; Drewelow, Peter; Fellinger, Joris
- Review of Scientific Instruments, Vol. 89, Issue 10
Turbulence Mechanisms of Enhanced Performance Stellarator Plasmas
journal, August 2020
- Xanthopoulos, P.; Bozhenkov, S. A.; Beurskens, M. N.
- Physical Review Letters, Vol. 125, Issue 7
Wall conditioning throughout the first carbon divertor campaign on Wendelstein 7-X
journal, December 2018
- Wauters, Tom; Goriaev, Andrei; Alonso, Arturo
- Nuclear Materials and Energy, Vol. 17
Overview of the results from divertor experiments with attached and detached plasmas at Wendelstein 7-X and their implications for steady-state operation
journal, August 2021
- Jakubowski, M.; Endler, M.; Feng, Y.
- Nuclear Fusion, Vol. 61, Issue 10
First results from divertor operation in Wendelstein 7-X
journal, November 2018
- Pedersen, Thomas Sunn; König, Ralf; Krychowiak, Maciej
- Plasma Physics and Controlled Fusion, Vol. 61, Issue 1
Characterization of energy confinement in net-current free plasmas using the extended International Stellarator Database
journal, November 2005
- Yamada, H.; Harris, J. H.; Dinklage, A.
- Nuclear Fusion, Vol. 45, Issue 12
Impact of the temperature ratio on turbulent impurity transport in Wendelstein 7-X
journal, September 2020
- Wegner, Thomas; Alcuson, Jorge Alberto; Geiger, Benedikt
- Nuclear Fusion
Strongly driven surface-global kinetic ballooning modes in general toroidal geometry
journal, June 2018
- Zocco, A.; Aleynikova, K.; Xanthopoulos, P.
- Journal of Plasma Physics, Vol. 84, Issue 3
Transformation-Invariant Metamaterials
journal, August 2019
- Zhang, Youming; Luo, Yu; Pendry, J. B.
- Physical Review Letters, Vol. 123, Issue 6
Heat transport driven by the ion temperature gradient and electron temperature gradient instabilities in ASDEX Upgrade H-modes
journal, August 2019
- Ryter, F.; Angioni, C.; Dunne, M.
- Nuclear Fusion, Vol. 59, Issue 9
Bayesian modeling of microwave radiometer calibration on the example of the Wendelstein 7-X electron cyclotron emission diagnostic
journal, April 2019
- Hoefel, Udo; Hirsch, Matthias; Kwak, Sehyun
- Review of Scientific Instruments, Vol. 90, Issue 4
First steps towards modeling of ion-driven turbulence in Wendelstein 7-X
journal, November 2017
- Warmer, F.; Xanthopoulos, P.; Proll, J. H. E.
- Nuclear Fusion, Vol. 58, Issue 1
The Thomson scattering diagnostic at Wendelstein 7-X and its performance in the first operation phase
journal, October 2017
- Bozhenkov, S. A.; Beurskens, M.; Molin, A. Dal
- Journal of Instrumentation, Vol. 12, Issue 10
Demonstration of reduced neoclassical energy transport in Wendelstein 7-X
journal, August 2021
- Beidler, C. D.; Smith, H. M.; Alonso, A.
- Nature, Vol. 596, Issue 7871
Enhanced energy confinement after series of pellets in Wendelstein 7-X
journal, April 2020
- Baldzuhn, J.; Damm, H.; Beidler, C. D.
- Plasma Physics and Controlled Fusion, Vol. 62, Issue 5
Simultaneous analysis of ion and electron heat transport by power modulation in JET
journal, October 2011
- Ryter, F.; Angioni, C.; Giroud, C.
- Nuclear Fusion, Vol. 51, Issue 11
Charge exchange recombination spectroscopy at Wendelstein 7-X
journal, February 2020
- Ford, O. P.; Vanó, L.; Alonso, J. A.
- Review of Scientific Instruments, Vol. 91, Issue 2
The Thomson scattering system at Wendelstein 7-X
journal, September 2016
- Pasch, E.; Beurskens, M. N. A.; Bozhenkov, S. A.
- Review of Scientific Instruments, Vol. 87, Issue 11