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Title: Impurity transport studies at Wendelstein 7-X by means of x-ray imaging spectrometer measurements

Abstract

This study reports on the effect of on- and off-axis heating power deposition on the impurity confinement in purely electron cyclotron resonance heated He plasmas on the stellarator Wendelstein 7-X. Therefore, impurity transport times τ I have been determined after Fe impurity injections by laser ablations and monitoring the temporal impurity emissivities by the x-ray imaging spectrometer HR-XIS. A significant increase of τ I has been observed when changing the power deposition from on- to off-axis heating with energy confinement times τ E being mainly unaffected. In addition, the scaling of impurity transport properties with respect to a variation of heating power P ECRH and electron density n e has been investigated by keeping the heating power deposition on-axis. The observed τ I scaling compares well to known τ I scaling laws observed in other machines. A comparison of τ I and τ E yields an averaged ratio of τ E /τ I = 1.3 and transport times in the range of τ I = 40–130 ms and τ E = 40–190 ms. Comparing those absolute values to neoclassical predictions supports the recently observed nature of anomalous transport in Wendelstein 7-X, given within the up to now investigated operational parameters.

Authors:
ORCiD logo [1]; ORCiD logo [1];  [1]; ORCiD logo [2];  [1]; ORCiD logo [1];  [3]; ORCiD logo [1];  [1];  [1]; ORCiD logo [1]; ORCiD logo [2];  [1];  [4];  [1];  [1];  [2]; ORCiD logo [1];  [1];  [2] more »;  [1];  [1];  [2];  [5];  [1];  [1];  [2];  [1];  [2];  [1];  [6]; ORCiD logo [1] « less
+ Show Author Affiliations
  1. Max-Planck-Institut fur Plasmaphysik, Greifswald (Germany)
  2. Forschungszentrum Julich GmbH, Julich (Germany)
  3. Lab. Nacional de Fusion, Madrid (Spain)
  4. Max-Planck-Institut fur Plasmaphysik, Greifswald (Germany); Technical Univ. of Denmark DTU, Lyngby (Denmark)
  5. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  6. Auburn Univ., Auburn, AL (United States)
Publication Date:
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org.:
USDOE
Contributing Org.:
the W7-X Team
OSTI Identifier:
1485104
Grant/Contract Number:  
No 633053
Resource Type:
Accepted Manuscript
Journal Name:
Plasma Physics and Controlled Fusion
Additional Journal Information:
Journal Volume: 61; Journal Issue: 1; Journal ID: ISSN 0741-3335
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; impurity transport; impurity confinement; energy confinement; imaging spectrometer; laser blow-off; plasma physics

Citation Formats

Langenberg, Andreas, Warmer, F., Fuchert, G., Marchuk, O., Dinklage, A., Wegner, Th, Alonso, J. A., Bozhenkov, S., Brunner, K. J., Burhenn, R., Buttenschön, B., Drews, P., Geiger, B., Grulke, O., Hirsch, M., Höfel, U., Hollfeld, K. P., Killer, C., Knauer, J., Krings, T., Kunkel, F., Neuner, U., Offermanns, G., Pablant, N. A., Pasch, E., Rahbarnia, K., Satheeswaran, G., Schilling, J., Schweer, B., Thomsen, H., Traverso, P., and Wolf, R. C. Impurity transport studies at Wendelstein 7-X by means of x-ray imaging spectrometer measurements. United States: N. p., 2018. Web. doi:10.1088/1361-6587/aaeb74.
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Langenberg, Andreas, Warmer, F., Fuchert, G., Marchuk, O., Dinklage, A., Wegner, Th, Alonso, J. A., Bozhenkov, S., Brunner, K. J., Burhenn, R., Buttenschön, B., Drews, P., Geiger, B., Grulke, O., Hirsch, M., Höfel, U., Hollfeld, K. P., Killer, C., Knauer, J., Krings, T., Kunkel, F., Neuner, U., Offermanns, G., Pablant, N. A., Pasch, E., Rahbarnia, K., Satheeswaran, G., Schilling, J., Schweer, B., Thomsen, H., Traverso, P., & Wolf, R. C. Impurity transport studies at Wendelstein 7-X by means of x-ray imaging spectrometer measurements. United States. https://doi.org/10.1088/1361-6587/aaeb74
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Langenberg, Andreas, Warmer, F., Fuchert, G., Marchuk, O., Dinklage, A., Wegner, Th, Alonso, J. A., Bozhenkov, S., Brunner, K. J., Burhenn, R., Buttenschön, B., Drews, P., Geiger, B., Grulke, O., Hirsch, M., Höfel, U., Hollfeld, K. P., Killer, C., Knauer, J., Krings, T., Kunkel, F., Neuner, U., Offermanns, G., Pablant, N. A., Pasch, E., Rahbarnia, K., Satheeswaran, G., Schilling, J., Schweer, B., Thomsen, H., Traverso, P., and Wolf, R. C. Fri . "Impurity transport studies at Wendelstein 7-X by means of x-ray imaging spectrometer measurements". United States. https://doi.org/10.1088/1361-6587/aaeb74. https://www.osti.gov/servlets/purl/1485104.
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@article{osti_1485104,
title = {Impurity transport studies at Wendelstein 7-X by means of x-ray imaging spectrometer measurements},
author = {Langenberg, Andreas and Warmer, F. and Fuchert, G. and Marchuk, O. and Dinklage, A. and Wegner, Th and Alonso, J. A. and Bozhenkov, S. and Brunner, K. J. and Burhenn, R. and Buttenschön, B. and Drews, P. and Geiger, B. and Grulke, O. and Hirsch, M. and Höfel, U. and Hollfeld, K. P. and Killer, C. and Knauer, J. and Krings, T. and Kunkel, F. and Neuner, U. and Offermanns, G. and Pablant, N. A. and Pasch, E. and Rahbarnia, K. and Satheeswaran, G. and Schilling, J. and Schweer, B. and Thomsen, H. and Traverso, P. and Wolf, R. C.},
abstractNote = {This study reports on the effect of on- and off-axis heating power deposition on the impurity confinement in purely electron cyclotron resonance heated He plasmas on the stellarator Wendelstein 7-X. Therefore, impurity transport times τ I have been determined after Fe impurity injections by laser ablations and monitoring the temporal impurity emissivities by the x-ray imaging spectrometer HR-XIS. A significant increase of τ I has been observed when changing the power deposition from on- to off-axis heating with energy confinement times τ E being mainly unaffected. In addition, the scaling of impurity transport properties with respect to a variation of heating power P ECRH and electron density n e has been investigated by keeping the heating power deposition on-axis. The observed τ I scaling compares well to known τ I scaling laws observed in other machines. A comparison of τ I and τ E yields an averaged ratio of τ E /τ I = 1.3 and transport times in the range of τ I = 40–130 ms and τ E = 40–190 ms. Comparing those absolute values to neoclassical predictions supports the recently observed nature of anomalous transport in Wendelstein 7-X, given within the up to now investigated operational parameters.},
doi = {10.1088/1361-6587/aaeb74},
journal = {Plasma Physics and Controlled Fusion},
number = 1,
volume = 61,
place = {United States},
year = {Fri Nov 23 00:00:00 EST 2018},
month = {Fri Nov 23 00:00:00 EST 2018}
}
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Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
https://doi.org/10.1088/1361-6587/aaeb74
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Cited by: 7 works
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Figures / Tables:

Figure 1 Figure 1: Time traces of a centrally ECR heated experimental program in the magnetic standard configuration of W7-X showing the total ECR heating power PECRH, line of sight integrated density ne, central, mid, and outer radius electron temperatures, central ion temperature, and the brightness of He-like iron emission lines.
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Works referenced in this record:

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
  • DOI: 10.1063/1.4999842

Diamagnetic energy measurement during the first operational phase at the Wendelstein 7-X stellarator
journal, July 2018

Molybdenum transport in high density FTU plasmas with strong radio frequency electron heating
journal, October 2007

Electrostatic potential variation on the flux surface and its impact on impurity transport
journal, March 2017

A possible mechanism for confinement power degradation in the TJ-II stellarator
journal, June 2018

  • van Milligen, B. Ph.; Carreras, B. A.; Hidalgo, C.
  • Physics of Plasmas, Vol. 25, Issue 6
  • DOI: 10.1063/1.5029881

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
  • DOI: 10.1088/1361-6587/aaeab2

Influence of the heating profile on impurity transport in ASDEX Upgrade
journal, August 2003

Stellarator and tokamak plasmas: a comparison
journal, November 2012

On impurity handling in high performance stellarator/heliotron plasmas
journal, April 2009

Prospects of X-ray imaging spectrometers for impurity transport: Recent results from the stellarator Wendelstein 7-X (invited)
journal, October 2018

  • Langenberg, A.; Pablant, N. A.; Wegner, Th.
  • Review of Scientific Instruments, Vol. 89, Issue 10
  • DOI: 10.1063/1.5036536

Impurity shielding criteria for steady state hydrogen plasmas in the LHD, a heliotron-type device
journal, May 2014

Design, capabilities, and first results of the new laser blow-off system on Wendelstein 7-X
journal, July 2018

  • Wegner, Th.; Geiger, B.; Kunkel, F.
  • Review of Scientific Instruments, Vol. 89, Issue 7
  • DOI: 10.1063/1.5037543

Plasma performance and impurity behaviour in long pulse discharges on LHD
journal, March 2003

Impurity Transport Studies in the Wendelstein 7-AS Stellarator
journal, July 2004

  • Burhenn, Rainer; Baldzuhn, Jürgen; Brakel, Rudolf
  • Fusion Science and Technology, Vol. 46, Issue 1
  • DOI: 10.13182/fst04-a547

Effects of ECRH power and safety factor on laser blow-off injected impurity confinement in TCV
journal, April 2004

First results from protective ECRH diagnostics for Wendelstein 7-X
journal, June 2017

Incompressibility of impurity flows in low density TJ-II plasmas and comparison with neoclassical theory
journal, January 2013

Comparison of impurity transport model with measurements of He-like spectra of argon at the tokamak TEXTOR
journal, October 2006

The Thomson scattering diagnostic at Wendelstein 7-X and its performance in the first operation phase
journal, October 2017

Magnetic configuration effects on the Wendelstein 7-X stellarator
journal, May 2018

Laser blow-off injected impurity particle confinement times in JET and Tore Supra
journal, September 1995

Observation of the ECH effect on the impurity accumulation in the LHD
journal, May 2017

  • Tamura, N.; Suzuki, C.; Satake, S.
  • Physics of Plasmas, Vol. 24, Issue 5
  • DOI: 10.1063/1.4983626

Impact of heat deposition profile on global confinement of NBI heated plasmas in the LHD
journal, August 2003

Impurity transport studies in RFX-mod multiple helicity and enhanced confinement QSH regimes
journal, July 2010

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
  • DOI: 10.13182/fst15-181

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
  • DOI: 10.1063/1.4962248

Impurity Transport in a Mixed-Collisionality Stellarator Plasma
journal, April 2017

Confinement of Injected Silicon in the Alcator- A Tokamak
journal, December 1980

Evidence for Convective Inward Particle Transport in a Stellarator
journal, February 1999

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    Works referencing / citing this record:

    Inference of temperature and density profiles via forward modeling of an x-ray imaging crystal spectrometer within the Minerva Bayesian analysis framework
    journal, June 2019

    • Langenberg, A.; Svensson, J.; Marchuk, O.
    • Review of Scientific Instruments, Vol. 90, Issue 6
    • DOI: 10.1063/1.5086283
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      Table 1 (p. 5)table
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      Figure 4 (p. 6)figure
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