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Experimental Progress on Zonal Flow Physics in Toroidal Plasmas

Experimental Progress on Zonal Flow Physics in Toroidal Plasmas. A. Fujisawa , T. Ido, A. Shimizu, S. Okamura, K. Matsuoka, Y. Hamada, 1 K. Hoshino, 2 Y. Nagashima, 1 K. Shinohara, H. Nakano, S. Ohshima, 1 Y. Miura, K. Itoh, S. –I. Itoh NIFS, 1 JAEA, 2 RIAM, Japan.

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Experimental Progress on Zonal Flow Physics in Toroidal Plasmas

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  1. Experimental Progress on Zonal Flow Physics in Toroidal Plasmas A. Fujisawa, T. Ido, A. Shimizu, S. Okamura, K. Matsuoka, Y. Hamada, 1K. Hoshino, 2Y. Nagashima, 1K. Shinohara, H. Nakano, S. Ohshima, 1Y. Miura, K. Itoh, S. –I. Itoh NIFS, 1JAEA,2RIAM, Japan M. Shats, H. Xia, ANU, Australia J. Q. Dong, L. W. Yan, K. J. Zhao, SWIP, China G. D. Conway, *U. Stroth, Max-Planck institute,*Universität Stuttgart, Germany A. Melnikov, L.G. Eliseev, S.E. Lysenko and S.V. Perfilov,Kurchatov Institute, Russia C. Hidalgo, CIEMAT, Spain G. R. Tynan, *G. R. Mckee, C. Holland, *R. J. Fonck, *D. K. Gupta, P. H. Diamond, UCSD, *Univ. Wisconsin U.S.A.

  2. ITER m=n=0, kr=finite 1. No linear instability Poloidal Crosssection 2. Turbulence driven ExB flows 3. No radial transport What is a ZONAL FLOW Is that really present in toroidal plasmas? Zonal flows are ubiquitous. Zonal flow in atmosphere in Jupiter Two braches of ZFs in a toroidal plasma i) stationary zonal flows (sZF) near-zero frequency ~0 kHz ii) geodesic acoustic modes (GAMs) an oscillatory branch ~ 10-50 kHz P. H. Diamond et al. PPCF 47 R35 (2005)

  3. sZF>GAM gradients shearing Drift waves turbulence Zonal flows no transport trapping damping transport Drift waves + Zonal flows Why are ZFs Important for Fusion? Because the zonal flows are deeply associated with anomalous transport. Plasma Transport the new paradigm Nonlinear interaction between zonal flows and turbulence controls transport. A question: the paradigm shift is experimentally supported?

  4. Devices Discoveries ASDEX-U (reflectometry) i) zonal structure CHS(HIBP) CASTOR (probes) symmetry (m=n=0) a finite radial wavelength CLD (probes) CSDX (probes) DIIID (BES) H1 (probes) ii) nonlinear coupling with turbulence HT-7 (probes) HL-2A (probes) JIPPT-IIU (HIBP) JFT-2M(HIBP&probes) LMD (probes) iii) effects on transport TEXT-U (HIBP) T-10 (HIBP) TJ-II(probes) TJ-K(probes) Zonal Flow Experiments A challenge to experimentalists - electric field or flow measurements in high temporal and spatial resolution More than a dozen papers have been published as a PPCF cluster (2006).

  5. Power (flow) time (ms) f (kHz) 1 100 DIII-D m=0 Power (flow) time (ms) 0 f (kHz) 50 Existence of Stationary Zonal Flow Proceeded by a pioneer work in HT-7, CHS has confirmed the existence of sZF G. S. Xu et al., PRL 91 125001 (2003). ASDEX-U sZF Showing Symmetry CHS f~0.5 kHz G. D. Conway, 31st EPS conf. London Showing a finite radial wavelength A. Fujisawa et al. PRL 93 165002 (2004). Zonal structure is found! This IAEA EX2-3: G. Mckee et al. New techniques for ZF detection are developed in CATOR and CLD.

  6. Pattern of Stationary Zonal Flow Using the cross-correlation functions between two electric fields at different radii, This is the discovery of stationary zonal flow.

  7. JFT2M 0 100 f (kHz) 1 1000 f (kHz) 0 40 f (kHz) (Log) T10 HL-2A f (kHz) 0 40 TEXT-U (Log) 100 1 f (kHz) 0 60 f (kHz) GAMs in Spectra After H1-heliac reported the existence of GAM, M. G. Shats et al., PRL 88 45001 (2002) flow(BES) flow(reflectometry) Potential (HIBP) DIII-D ASDEX-U potential (probe) Coherent modes have been detected in many toroidal devices The HL-2A tokamak confirms the complete symmetry (n=m=0) of GAM This IAEA EX/P4-35 L.W. Yan et al.

  8. 25 k=1.27 k=1.12 k=1.40 k=1.62 fGAM (kHZ) k=1.73 0 cs/R DIII-D Landau damping? GAM amplitude fGAM (kHz)- theory q95 4.0 7.0 GAM Frequency Dependence ASDEX This IAEA EX2-1 G. Conway et al. DIII-D The frequency of the coherent modes satisfies the expected dependence. The studies of GAM have an impact on understanding of plasma turbulence G. R. McKee et al., PPCF 48 S123 (2006).

  9. JFT2M 100 f1+f2=f3 ~±10kHz f2 (kHz) 0 strong coupling • Direct evaluation of perpendicular term • has been widely performed (CSDX, HT-6M, LMD, TJ-K, etc.) -100 - Direct measurement of energy transfer term from turbulence to flow is performed in TJ-II, showing importance of parallel component . 0 120 f1 (kHz) This IAEA EX2-2 K. Hoshino et al. How to Prove Nonlinear Couplings Bicoherence analysis can quantify the strength of three wave coupling. (k1+k2= k3 ) f1+f2= f3 (bicoherence=0, if f1+f2≠0) Other techniques (energy transfer, autocorrelation, etc. ) are developed M. Shats et al., PPCF 48 S17 (2006). Reynolds stress to drive mean flow G. R. Tynan et al.PPCF 48 S51 (2006). This IAEA EX/P7-2 C. Hidalgo et al.

  10. turbulence power ‘sZF’ turbulence normalized power coherence GAM GAM 40 70 Time (ms) ‘sZF’ Energy Transfer between ZF and Turbulence Turbulence power changes intermittently with ‘zonal flow’ CHS sZF turb. GAM Anti-phase behavior suggests direct energy transfer between ‘zonal flow’ and turbulence A. Fujisawa et al. PPCF 48 A365 (2006).

  11. Effects on Transports

  12. 5ms potential fluctuation maximum Stationary zonal flow 0.5 Conditional averages ZF 200 power minimum particle flux density f (kHz) 0 0 40 70 30 80 f (kHz) Time (ms) ZF Effects on Transport HIBP has an advantage in simultaneous measurements of ZF and particle flux CHS A. Fujisawa et al., PPCF 48 S205 (2006). Particle flux is really modulated with stationary zonal flow. Similar result is obtained for GAMs in JFT-2M. T. Ido et al., PPCF 48 S41(2006)

  13. ~ Power ( E/∇T) confinement is improved without shear Potential (or Temperature) 10-3 0 radius 1 Common ITB in helical plasmas Better Confinement in Enhanced ZF CHS Why is the confinement improved in shearless regime inside the barrier? At a radius without mean Er-shear inside the barrier No ITB Clear difference in energy partition ITB A larger fraction of zonal flows contributes to confinement improvement inside the barrier! Importance ofzonal flows on confinement is demonstrated.

  14. m=0 confirmed n=m=0 in a case kr=finite proven What Experiments Achieved effects on transport structure nonlinear coupling n=0 confirmed Importance of flow energy partition is demonstrated confirmed (temporal correlation) S-ZF m=0 confirmed Turbulence modulation is observed. kr=finite confirmed confirmed (bicoherence) Turbulence modulation is observed GAM fGAM~cs/R Eigenmode property The experiments on zonal flowshave made a large progress. The obtained knowledge are still fragmental, butsupport the fundamental expectations of the theories.

  15. Drift waves - Zonal flows really do exist in toroidal plasmas. - The experiments support the paradigm shift! Common physics Zonal flow in CHS Drift waves + Zonal flows - The prospect of ITER is enhanced. ITER will be more analogous to the Sun than the Jupiter. Summary The world-wide experiments on zonal flows show, ASDEX-U, CASTOR, CHS, CLD, CSDX , DIII-D, H1, HL-2A, HT-6M, HT-7, JFT-2M, JIPPT-IIU,LMD, T-10, TEXT-U, TJ-II, TJ-K and so on

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