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

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

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) /2.3/1.2 q95 NBI power ECH power Ip Density betap DαDα 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: 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

LI et al. 6 Kinetic profiles are averaged by synchronization with the respect to ELM cycle The profiles are averaged over 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 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 Time (ms) DαDα ELM timing and time windows selected 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 , lower the toroidal magnetic field (2.00 T -> 1.82 T) Strong ITB for Te at large radius, similar to rho Time (ms) DαDα ELM timing and time windows selected ms ne Te Ti Impurity faction Zeff Ti

LI et al. 9 Low frequency ELM discharge has higher pedestal height has higher pedestal height and have similar small pedestal height, but the ITB heights are different rho ne Te Ti 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 (High Freq. ELM) (Low Freq. ELM) (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 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

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 2014GB and 2015GB and US DOE under DE-FC02-04ER54698 and DE-FG03- 95ER54309.