1 / 18

Long-distance correlation of fluctuations under strong ExB shear in TJ-K

Long-distance correlation of fluctuations under strong ExB shear in TJ-K. P. Manz, M. Ramisch, U. Stroth Institut für Plasmaforschung, Universität Stuttgart 5th Coordinated Working Group Meeting for Stellarator/Heliotron Studies, July 6-8 2009 Stuttgart, 07.07.09.

dasha
Download Presentation

Long-distance correlation of fluctuations under strong ExB shear in TJ-K

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Long-distance correlation of fluctuationsunder strong ExB shear in TJ-K P. Manz, M. Ramisch, U. Stroth Institut für Plasmaforschung, Universität Stuttgart 5th Coordinated Working Group Meeting for Stellarator/Heliotron Studies, July 6-8 2009 Stuttgart, 07.07.09

  2. Long-distance correlation of fluctuations in TJ-II Probes are 160° toroidally displaced A field line passing through one probe is approximately 150° poloidally apart when reaching the toroidal position of the other probe • Long-distance correlation occur during L-H transition Pedrosa et al, Phys. Rev. Lett. 100, 215003 (2008)

  3. Zonal flows are long-distance correlations Fujisawa et al, Phys. Rev. Lett. 93, 165002 (2004)

  4. Torsatron TJ-K • l=1, m=6 Torsatron • Large plasma radius: • R0 = 0.6 m • small plasma radius: • a = 0.1 m • Working gas: • He • Neutral gas pressure: • 7 mPa • Magnetic field strength: • 72 mT • Plasma heating: • ECRH (2.45 GHz, 1.8 kW) • Plasma parameter: • ne = 1∙1017 m-3 • Te = 10 eV • Ti < 1 eV Advantages of TJ-K: - Dimensionless plasma parameters are similar to those in fusion edge plasmas - The low temperature plasma has an excellent accessibility for probe arrays

  5. Diagnostics: global Reynolds stress array

  6. Biasing electrode

  7. Plasma biasing scenario Density profile Potential profile ExB-shear enhanced particle confinement • shear flow |s| >max Ramisch et al, Plasma Phys. & Control. Fusion 49, 777 (2007)

  8. Diagnostics: global Reynolds stress array

  9. Diagnostics: global Reynolds stress array

  10. Cross-correlation without biasing density potential

  11. Cross-correlation with biasing (+100V) density potential

  12. Cross-correlation with biasing (+100V) without biasing m=4 mode m=3 mode m=0 mode not zonal flow-like zonal flow-like Manz et al Phys. Plasmas 16, 042309 (2009)

  13. Spectra

  14. Cross-coherency Manz et al Phys. Plasmas 16, 042309 (2009)

  15. Zonal density (m=0) Hasegawa-Wakatani zonal average Manz et al, Plasma Phys. & Control. Fusion 50, 035008 (2008)

  16. Origin of the coherent mode (m=3) Similar observations in H1 heliac (Shats, PPCF 48, S17 (2006) CHS (Fujisawa, PPCF 48, S31 (2006)

  17. Summary • Shear flows causes a strong increase in the long-range correlation: • in the potential fluctuations, zonal flow-like modes are excited • density long-distance correlation is dominated by an m=3 mode • Coherency analysis reveals the existence of m=0 density fluctuations • due to • background profile fluctuations • zonal density

  18. Thank you for your attention

More Related