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ASIPP Characteristics of edge localized modes in the superconducting tokamak EAST M. Jiang Institute of Plasma Physics Chinese Academy of Sciences The.

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Presentation on theme: "ASIPP Characteristics of edge localized modes in the superconducting tokamak EAST M. Jiang Institute of Plasma Physics Chinese Academy of Sciences The."— Presentation transcript:

1 ASIPP Characteristics of edge localized modes in the superconducting tokamak EAST M. Jiang Institute of Plasma Physics Chinese Academy of Sciences The 1 st APTWG meeting, June 2011, NIFS, Japan

2 ASIPP Outline I.H-mode access on EAST II. ELMs behavior  ELMs crash  Classifications of ELMs  The effects in divertor plasmas  Statistical analysis of ELMs frequency  Control of ELMs by argon puffing III. Summary 2

3 ASIPP Outline I.H-mode access on EAST II. ELMs behavior  ELMs crash  Classifications of ELMs  The effects in divertor plasmas  Statistical analysis of ELMs frequency  Control of ELMs by argon puffing III. Summary 3

4 ASIPP H-mode access on EAST EAST parameters : Major radius : R 0 = 1.9 m Minor radius : a = 0.5 m Toroidal field : B t = 3.5 T Elongation :  = 2 Triangularity :  = H-mode shots so far Configurations: DN or unbalanced DN, LSN First L-H transition during Ip flat top, ramp-up and ramp- down 4

5 ASIPP Parameters at L-H : B t = 1.4~2 T I p = 0.4~0.8 MA n e = 1.9~3.4  m  3 P LHW = 0.5~1.1 MW P ICRF < 0.5 MW S A = 38~42 m 2  = 1.64~1.94  low = 0.45~0.58 q 95 = 2.7~5.0 H-mode access on EAST EAST shot

6 ASIPP Outline I.H-mode access on EAST II. ELMs behavior  ELMs crash  Classifications of ELMs  The effects in divertor plasmas  Statistical analysis of ELMs frequency  Control of ELMs by argon puffing III. Summary 6

7 ASIPP EAST shot The formation of pedestal was confirmed by a sharp rise in XUV at plasma edge. During ELMs, pressure gradient reduced. Between ELMs, it steepens, but is far from the steepness of the ELM- free period reaches MHD instability transport increase pedestal expels particles drops significantly and finally “avalanche model ” ELMs crash ELM and Pedestal structure 7

8 ASIPP Classifications of ELMs in EAST 1. Type III Most of ELMs on EAST are type III. They usually appeared at heating powers close to the threshold power. A coherent magnetic precursor oscillation was observed on magnetic and electrostatic probes. The frequency of ELMs precursor decreases from 130kHz to 60kHz within 0.4ms. 8 EAST shot D  [a.u.] Mirnov Time [s]

9 ASIPP Classifications of ELMs on EAST 2. Type I like  H mode was sustained by 0.3 MW as a result of the hysteresis effect.  Energy loss > 5%  deposited energy on divertor plates >3kJ  The heat load pulses on the outer target plates increase significantly and reach a peak heat load of 4MW/m 2. 9

10 ASIPP Classifications of ELMs on EAST 3. Compound ELM An initial MHD instability followed by a transient L-phase 10 EAST shot Time [s] D  [a.u.] Mirnov

11 ASIPP Inner target X-point Ionization region High density Not detached at the inner target Classifications of ELMs on EAST 4. Negative D  spikes near X-point 14

12 ASIPP Classifications of ELMs on EAST 5. quasi-periodic oscillations 6. No evident L-H transition Before L-H, quasi-periodic oscillation exists. It occurred in almost all H-mode discharge shots 12 EAST shot EAST shot Time [s] Time [s]

13 ASIPP 7. Strange ELM 8. Mossy ELM Classifications of ELMs on EAST Strange ELMs occurred at large current Small ELMs, so called “mossy ELM” 13 EAST shot EAST shot 33049

14 ASIPP ELM average heat load ~ 2MW/m 2 IR CCD camera, 20 ms time resolution Type III ELMs 14

15 ASIPP In-out asymmetry in target heat load LSN Type III ELMs LSN, dR sep =  1 cm Inner > Outer IR CCD data DN Type III ELMs DN, dR sep = 0 cm Outer > Inner 15

16 ASIPP Energy loss by ELM  W/W = 1~2% Target probes LSN & DN 16

17 ASIPP Statistical analysis for frequencies Shot no.Ip (kA)B T (T)q 95 f ELM (kHz) q 95 indicates the current profile, which dominates kink mode. Kink mode and ballooning mode drive ELM. q 95, the current density and pressure gradient will be in the peeling-ballooning mode stable region. 17

18 ASIPP ELM control by Argon seeding  Argon gas injected from lower outer target at a speed of 4  particles/s  ELM frequency rises  ELM amplitude decreases  P rad didn’t increase  P loss increased  W dia decreased  Effective for shielding impurity 18

19 ASIPP Outline I.H-mode access on EAST II. ELMs behavior  ELMs crash  Classifications of ELMs  The effects in divertor plasmas  Statistical analysis of ELMs frequency  Control of ELMs by argon puffing III. Summary 19

20 ASIPP Summary Type III ELMy H-mode has been obtained with low LHW power and lithium evaporation and real-time Li powder injection in EAST. Different kinds of ELMs have been observed in EAST with heating of LHW ELMs frequency is in the range of several hundred Hz, and decreases with q 95 ELMs behavior can be controlled by puffing gas 20


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