1. Review of Collaboration Activities J.Q. Dong* H.D. He, Y. Shen, and A.P. Sun Southwestern Institute of Physics, China *Institute for Fusion Theory and Simulation, ZJU, China Fourth US-PRC Magnetic Fusion Collaboration Workshop May 5-6, 2008 ， Austin, Texas, USA

2. EFIT code From GA has been successfully transplanted and applied for the HL-2A experiment analysis and HL-2M design at SWIP Reconstructed equilibrium configurations for shot #2895.

3. GATO fom GA code has been successfully transplanted and applied for the HL-2A experiment analysis at SWIP Unstable kink mode for HL-2A discharge #2895, with q 0 =0.95, mode displacement vectors projected onto the poloidal plane, (a) with =1.5 and (c) with =2.5; and Fourier decomposition of the unstable normal displacement, (b) with =1.5 and (d) with =2.5. (a) (b) (c) (d)

4. (a) Growth rate and (b) maximum edge normal displacement of the n=1 mode.. (a)(b)

5. ONETWO code from GA has been successfully transplanted and will be applied for the HL-2A experiment analysis at SWIP

6. Experimental Study of GAM and Turbulence at the Edge of the HL-2A Tokamak J.Q. Dong* K.J. Zhao, L.W. Yan, W.Y. Hong, T. Lan, A.D. Liu, C.X. Yu, J. Qian, J. Cheng, D.L. Yu, Q.W. Yang, X.T. Ding, X.R. Duan, Y. Liu Southwestern Institute of Physics, China *Institute for Fusion Theory and Simulation, ZJU, China University of Science and Technology of China Fourth US-PRC Magnetic Fusion Collaboration Workshop May 5-6, 2008 ， Austin, Texas, USA Southwestern Institute of Physics

7. Related publications K.J. Zhao, T. Lan, J.Q. Dong et al., Toroidal Symmetry of the Geodesic Acoustic Mode Zonal Flow in a Tokamak Plasma, Phys. Rev. Lett. 96 (25) 255004 (2006). L. W. Yan, W. Y. Hong, T. Lan, K. J. Zhao, J. Q. Dong et al., Three Dimensional Features of GAM Zonal Flows in the HL-2A Tokamak, Nucl. Fusion 47, 1673-1681(2007). J. K. Zhao, J. Q. Dong, L. W. Yan et al., Characteristics of geodesic acoustic mode zonal flow and ambient turbulence at the edge of the HL-2A tokamak plasmas, Physics of Plasmas 14, 122301 (2007). T. Lan, A. D. Liu, C. X. Yu, L.W. Yan, W.Y. Hong, K. J. Zhao, J. Q. Dong et al. ， Spectral features of the geodesic acoustic mode and its interaction with turbulence in the HL-2A tokamak plasma, Physics of Plasmas 15, 056105 (2008).. T. Lan, A. D. Liu, C. X. Yu, L.W. Yan, W.Y. Hong, K. J. Zhao, J. Q. Dong et al. ， Plasma, Phys. Control. Fusion 50, 045002 (2008). Southwestern Institute of Physics

8. Outline 1.Introduction 2.Experiment arrangements 3.Toroidal symmetry of GAMZF 4.Effects of GAMZF on turbulence 5.Two regimes of turbulence? 6.Observation of low frequency zonal flow? 7.Summary Southwestern Institute of Physics

9. Zonal flows of large scale structure are universal in turbulent systems and may reduce turbulence level and improve plasmas confinement. Theories and simulations predict two types of zonal flows : the near zero low frequency zonal flow (LFZF) and the geodesic acoustic mode zonal flow (GAMZF) The poloidal and radial structures of GAMZFs have been observed in experiment on a few fusion devices such as TEXT, DIII-D, ASDEX-U, JIPPT-IIU, JFT-2M, HT-7. Three dimensional (3D) features of GAMZFs were first observed on the HL-2A tokamak. 3D features LFZF and two regimes of the turbulence were observed on HL-2A for the first time, recently. Southwestern Institute of Physics 1. Introduction

10. 2. Experiment Arrangements Parameters of HL-2A R 1.65 m a 0.4 m B T :2.8 T2.7 T I P :480 kA430 kA Duration3.0 sec. Plasma density 6.0 x 10 19 m -3 Electron temp. ~5 keV Ion temperature >1 keV Fuelling sys. GP, SMBI, PI Heating sys.ECRH, LHCD, NBI HL-2A is a middle sized tokamak device built at the Southwestern Institute of Physics, China, in 2002. Southwestern Institute of Physics

11. Structure (a) and layout (b) of the three step langmuir probes (TSLPs) TSLPs are distributed toroidally and polodially. Two of them form poloidal ZF probe set (W1). The third array of electromotive 6 probes is located 800mm away in toroidal direction (W2). There is a fourth array of fast reciprocating 6 probes (W3). Southwestern Institute of Physics

12. Set up of the probe arrays Toroidal direction Poloidal direction Southwestern Institute of Physics

13. Discharge Parameters Toroidal magnetic field Bt=2.2-2.4T, discharge duration t~2s, ion-ion collisional frequency ν ii ~1.5-3 10 4 /s, safety factor q(r/a=0.93)=0.88q a Southwestern Institute of Physics

14. 3. Toroidal Symmetry of GAMZFs The frequencies at the centers of the peaks in the spectra are f~6.8kHz and 9.3kHz for Te=17eV and 38eV, respectively. The lifetime of the GAMZF is estimated as 200-300µs from the widths of 3-5kHz of the peaks. Southwestern Institute of Physics

15. Poloidal mode number (m<1) The poloidal coherencies (a), the phase differences (b) and the poloidal wave vector spectra (c). The poloidal mode numbers are less than 1. The ambient turbulences (ATs) propagate in electron diamagnetic drift direction. Southwestern Institute of Physics The general dispersion relations, straight lines without offsets, for the ATs and deviations from it in the GAM frequency region are clearly shown.

16.  The toroidal mode numbers are n~0. GAM is uniform at a flux surface but the AT is localized to and aligned along a magnetic filed line. (a)(b) along magnetic field line, (c )(d) deviating from a magnetic filed line Toroidal mode number (n~0) Southwestern Institute of Physics

17. 4. Effects of GAMZF on Ambient Turbulence Southwestern Institute of Physics The coherencies of the ATs in the presence of GAMZF are lower than that in the absence of GAMZF. The reduction occurs in frequency range of 10 kHz < f < 60 kHz

18. 5. Two regimes of turbulence?  Layout and structure of the Langmuir probe arrays

19.  Representative auto-power spectrum of the floating potential fluctuation.

20. (a) Coherency spectra of and (the blue line, d θ =3mm), and of and (the pink line, d r =2mm ), (b) corresponding wave vector spectra.

21. Toroidal coherency spectra of d t =65mm (b) corresponding wave vector spectra.

22. (a) The auto-power spectra of the floating potential fluctuation, (b) the squared auto-bicoherence plotted in the plane. (weak GAM)

23. 6. Observation of low frequency zonal flow?

24. Toroidal structure 2008 年 1 月 20 日 · 第 24 页

25. 7. Summary Toroidal symmetry of GAMZFs was observed at the edge of HL-2A tokamak plasmas for the first time. Symmetric (m<1,n=0) potential fluctuation with the radial scale length (2.4-4.2cm) was measured in GAM frequency region (7-9kHz). Three wave coupling between high frequency fluctuations and the flows is a plausible creation mechanism of the GAMZFs. Regulation effects of the GAM on the ATs are analyzed. GAMZFs are probably generated by small scale components of the ATs.

26. Preliminary evidences for two regimes of the AT are observed. Preliminary evidences for LFZF are observed. Preliminary evidences for fluctuations of multi-spatial and -temporal scales are observed. Detailed investigations are in progress. Southwestern Institute of Physics

27. Proposals for experiment on HL-2A are welcome! Southwestern Institute of Physics Thank you for your attention Thank you for your attention !