Investigation of the plasma shaping effects on the H-mode pedestal structure using coupled kinetic neoclassical/MHD stability simulations

Journal Article · Thu Jun 08 00:00:00 EDT 2017 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4984256· OSTI ID:1367977

Pankin, A. Y. ^[1]; Rafiq, T. ^[2]; Kritz, A. H. ^[2]; Park, G. Y. ^[3]; Snyder, P. B. ^[4]; Chang, C. S.  ^[5]

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1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2. Lehigh Univ., Bethlehem, PA (United States). Dept. of Physics
3. National Fusion Research Inst., Daejeon (South Korea)
4. General Atomics, San Diego, CA (United States)
5. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

The effects of plasma shaping on the H-mode pedestal structure are investigated. High fidelity kinetic simulations of the neoclassical pedestal dynamics are combined with the magnetohydrodynamic (MHD) stability conditions for triggering edge localized mode (ELM) instabilities that limit the pedestal width and height in H-mode plasmas. We use the neoclassical kinetic XGC0 code [Chang et al., Phys. Plasmas 11, 2649 (2004)] to carry out a scan over plasma elongation and triangularity. As plasma profiles evolve, the MHD stability limits of these profiles are analyzed with the ideal MHD ELITE code [Snyder et al., Phys. Plasmas 9, 2037 (2002)]. In simulations with the XGC0 code, which includes coupled ion-electron dynamics, yield predictions for both ion and electron pedestal profiles. The differences in the predicted H-mode pedestal width and height for the DIII-D discharges with different elongation and triangularities are discussed. For the discharges with higher elongation, it is found that the gradients of the plasma profiles in the H-mode pedestal reach semi-steady states. In these simulations, the pedestal slowly continues to evolve to higher pedestal pressures and bootstrap currents until the peeling-ballooning stability conditions are satisfied. The discharges with lower elongation do not reach the semi-steady state, and ELM crashes are triggered at earlier times. The plasma elongation is found to have a stronger stabilizing effect than the plasma triangularity. For the discharges with lower elongation and lower triangularity, the ELM frequency is large, and the H-mode pedestal evolves rapidly. It is found that the temperature of neutrals in the scrape-off-layer (SOL) region can affect the dynamics of the H-mode pedestal buildup. But the final pedestal profiles are nearly independent of the neutral temperature. The elongation and triangularity affect the pedestal widths of plasma density and electron temperature profiles differently. This provides a new mechanism of controlling the pedestal bootstrap current and the pedestal stability.

• Research Organization: Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Fusion Energy Sciences (FES)
• Grant/Contract Number: AC52-07NA27344; SC0012174; SC0008605; FG02-92ER54141; SC0013977; AC02-05CH1131; AC02-05CH11231
• OSTI ID: 1367977
• Alternate ID(s): OSTI ID: 1361916
• Report Number(s): LLNL-JRNL-718637; PHPAEN
• Journal Information: Physics of Plasmas, Vol. 24, Issue 6; ISSN 1070-664X
• Publisher: American Institute of Physics (AIP)
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION