LI et al. 1

G.Q. Li1, X.Z. Gong1, A.M. Garofalo2, L.L. Lao2, O. Meneghini2, P.B. Snyder2, Q.L. Ren1, S.Y. Ding1, W.F. Guo1, J.P. Qian1, B.N. Wan1, G.S. Xu1, C.T. Holcomb3, W.M. Solomon4

1 Institute of Plasma Physics, CAS, US2 General Atomics, US

3 Lawrence Livermore National Laboratory, US4 Princeton Plasma Physics Laboratory, US

四室系列学术报告Dec. 8, 2015

ELM Behavior in High-βp EAST-Demonstration Plasmas on DIII-D

LI et al. 2

DIII-D EAST

Background/Motivation

• DIII-D/EAST joint experiments– Extend DIII-D Integrated High-Performance Results to Long-Pulse on

EAST– Accelerates progress toward common goal of fusion energy

• DIII-D uniqueness – Experience with many integrated scenarios– Well kinetic control and measurement

• EAST uniqueness– Long-pulse capacity with S.C. coils– W divertor and metal walls– RF dominant heating and low torque feature

• Since 2013, a number of experiments have been performed on DIII-D

• This study focuses on the ELM behavior in High-βp EAST-Demonstration Plasmas on DIII-D

LI et al. 3

ELM behavior is sensitive to details of operating conditions in high βp experiments

• In several similar high βp discharges, the input parameters vary slightly, but the ELM frequency changes significantly. why?

Bt0 (T) PECH(MW)

154406 2.00 3.2

154407 2.00 2.3

154408 1.82 3.2/2.3/1.2

q95

NBI powerECH power

Ip

Density

betap

Dα

154406 154407 154408

154407 has much lower ELM frequency

parameter variations H98y2

LI et al. 4

Outline

• Comparison of kinetic profiles before ELMs

• Stability analysis and comparison with the NEUPED model

• The relationship between ITB and pedestal structure

• Summary and discussion

LI et al. 5

The three discharges have operating conditions

• Similar strong up-single null shape

– Triangularity: δup~0.7, δlow~0.4

• Similar global plasma parameters

– Ip ~ 600 kA– q95 10~12– βN > 3 – βp > 3– <ne> ~ 5.0e19/m3

– H98 ~ 1– PNBI ~ 8.2 MW– PECH 1.2~3.2 MW

154406154407154408

LI et al. 6

Kinetic profiles are averaged by synchronization with the respect to ELM cycle• The profiles are averaged over 0.70-0.99 phase of ELM

cycle• Strong ITB for Te, at larger radius (ρITB~ [0.6, 0.7])• Density profile shows large density peaking

rho rhoTime (ms)

Dα

ne

Te

Ti

Impurity faction

TS included

ELM sync windowsphase 0.70~ 0.99

ELM timing and time windows selected

154406@4820 ms

Zeff

Ti

LI et al. 7

Profiles for low frequency ELM discharge are obtained similarly by averaging over ELM cycle• ECH power is a litter lower (3.2 MW -> 2.3 MW), NBI

power is kept same (~8.2 MW)• No ITBs, large pedestal height

rho rhoTime (ms)

Dα

ELM timing and time windows selected

154407@5130 ms ne

Te

Ti

Impurity faction

Zeff

Ti

LI et al. 8

Profiles for low Bt high frequency ELM discharge are obtained similarly by averaging over ELM cycle• Similar to 154407, lower the toroidal magnetic

field (2.00 T -> 1.82 T) • Strong ITB for Te at large radius, similar to 154406

rho rhoTime (ms)

Dα

ELM timing and time windows selected

154408@5030 ms ne

Te

Ti

Impurity faction

Zeff

Ti

LI et al. 9

Low frequency ELM discharge has higher pedestal height

• 154407 has higher pedestal height

• 154406 and 154408 have similar small pedestal height, but the ITB heights are different

rho rho

ne

Te

Ti

154406 154407 154408

Impurity faction

LI et al. 10

Kinetic equilibrium reconstruction shows large difference in pedestal and ITB structure

• Low frequency ELMs (154407) case has high pedestal height and large edge current

• High frequency ELMs (154408) case has the low pedestal height and small edge current with an ITB at large radius

• The edge current peak locations are similar

LI et al. 11

Pedestal structure is affected by the ITB?

• The ITB building-up appears accompanied with the pedestal height decreasing

• ITB affects pedestal by reducing the amount of heat flux flowing to the pedestal

Te history at different location

154406 (High Freq. ELM)

154407 (Low Freq. ELM) 154408 (High Freq. ELM)

rho=0.55

rho=0.70

rho=0.95

rho=0.90

rho=0.95

rho=0.55

strong ITB`

LI et al. 12

Summary and discussion

• In high βp experiments, ELM behaviours appear sensitive to details of operating conditions

• The low frequency ELM case has the high pedestal height and large edge current; whereas the high frequency ELM case has the low pedestal height and low edge current

• ITB appears affecting the pedestal structure by reducing the heat flux to the pedestal, thereby decrease the pedestal height

• For high βp plasma, without ITB the pedestal height and width appear larger than the NEUPED prediction; while with ITB the height and width can agree with the NEUPED prediction

LI et al. 13

Acknowledgment

• The experiment analysis was performed with the OMFIT integrated modelling framework and with the PyD3D toolbox, which are developed at GA

• Work supported by China MOST under 2014GB106001 and 2015GB102001 and US DOE under DE-FC02-04ER54698 and DE-FG03-95ER54309.