Review of Collaboration Activities

J.Q. Dong*

H.D. He, Y. Shen, and A.P. SunSouthwestern Institute of Physics, China

*Institute for Fusion Theory and Simulation, ZJU, China

Fourth US-PRC Magnetic Fusion Collaboration WorkshopMay 5-6, 2008 ， Austin, Texas, USA

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.

GATO fom GA code has been successfully transplanted and applied for the HL-2A experiment analysis at S

WIP

p

p

p

Unstable kink mode for HL-2A discharge #2895, with q0=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)

p

p

p

p

(a) Growth rate and (b) maximum edge

normal displacement of the n=1 mode. .

(a)

(b)

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

at SWIP

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 WorkshopMay 5-6, 2008 ， Austin, Texas, USA

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Related publications K.J. Zhao, T. Lan, J.Q. Dong et al., Toroidal Symmetry of the Geodesic Acoust

ic 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).

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Outline1. 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

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• 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.

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1. Introduction

2. Experiment Arrangements

Parameters of HL-2A•R 1.65 m

•a 0.4 m

•BT: 2.8 T 2.7 T

•IP: 480 kA 430 kA

•Duration 3.0 sec.•Plasma density 6.0 x 1019 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.

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• 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).

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Set up of the probe arrays

Toroidal direction

Po

loida

l dire

ction

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Discharge Parameters

•Toroidal magnetic field Bt=2.2-2.4T, discharge duration t~2s, ion-ion collisional frequency νii~1.5-3 104/s, safety factor q(r/a=0.93)=0.88qa

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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.

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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.

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• The general dispersion relations, straight lines without offsets , for the ATs and deviations from it in the GAM frequency region are clearly shown.

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)

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4. Effects of GAMZF on Ambient Turbulence

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• 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

5. Two regimes of turbulence?

Layout and structure of the Langmuir probe arrays

Representative auto-power spectrum of the floating potential fluctuation.

(a) Coherency spectra of and (the blue line, dθ=3mm), and of an

d (the pink line, dr=2mm ), (b) corresponding wave vector spectra.5f 6f

5f4f

Toroidal coherency spectra of dt=65mm (b) corresponding wave vector spectra.

(a) The auto-power spectra of the floating potential fluctuation, (b) the squared auto-bicoherence plotted in the plane. (weak GAM) 21 ff

6.Observation of low frequency zonal flow?

Toroidal structure

1 3 0.01 0.040.02 0.05

37.5

f en

d R

2 3 0.02 0.050.03 0.08

37.5

f en

d R

3 3 0.01 0.050.01 0.08

37.5

f en

d R

2008 年 1 月 20 日 · 第 24页

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 compone

nts of the ATs.

• 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.

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Proposals for experiment on Proposals for experiment on HL-2A are welcome!HL-2A are welcome!

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Thank you for your attentionThank you for your attention !