1. LI et al. 1 G.Q. Li 1, X.Z. Gong 1, A.M. Garofalo 2, L.L. Lao 2, O. Meneghini 2, P.B. Snyder 2, Q.L. Ren 1, S.Y. Ding 1, W.F. Guo 1, J.P. Qian 1, B.N. Wan 1, G.S. Xu 1, C.T. Holcomb 3, W.M. Solomon 4 1 Institute of Plasma Physics, CAS, US 2 General Atomics, US 3 Lawrence Livermore National Laboratory, US 4 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

2. LI et al. 2 DIII-DEAST 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

3. 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)P ECH (MW) 154406 2.003.2 154407 2.002.3 154408 1.823.2/2.3/1.2 q95 NBI power ECH power Ip Density betap DαDα 154406 154407 154408 154407 has much lower ELM frequency parameter variations H98y2

4. 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

5. LI et al. 5 The three discharges have operating conditions Similar strong up-single null shape – Triangularity: δ up ~0.7, δ low ~0.4 Similar global plasma parameters – Ip ~ 600 kA – q 95 10~12 – β N > 3 – β p > 3 – ~ 5.0e19/m 3 – H98 ~ 1 – P NBI ~ 8.2 MW – P ECH 1.2~3.2 MW 154406 154407 154408

6. 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 (ρ ITB ~ [0.6, 0.7]) Density profile shows large density peaking rho Time (ms) DαDα ne Te Ti Impurity faction TS included ELM sync windows phase 0.70~ 0.99 ELM timing and time windows selected 154406@4820 ms Zeff Ti

7. 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 Time (ms) DαDα ELM timing and time windows selected 154407@5130 ms ne Te Ti Impurity faction Zeff Ti

8. 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 Time (ms) DαDα ELM timing and time windows selected 154408@5030 ms ne Te Ti Impurity faction Zeff Ti

9. 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 ne Te Ti 154406 154407 154408 Impurity faction

10. 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

11. 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`

12. LI et al. 12 Summary and discussion In high β p 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 β p 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

13. 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.