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Impact of density on the ion diamagnetic stabilizations of edge Peeling–Ballooning modes

Author: Tengfei Tang
Requested Type: Consider for Invited
Submitted: 2015-01-16 18:40:07

Co-authors: X.Q.Xu, T Y Xia,C. Holland

Contact Info:
Lawrence Livermore National Laboratory
5863 Fruitwood CMN.
Livermore, CA   94550
USA

Abstract Text:
The recent DIII-D experiments [1] show that at high density an assumption of reduced diamagnetic stabilization of edge Peeling–Ballooning modes in EPED [2] is required for reasonable agreement with measurements. In this work, we present a systematic study of ion diamagnetic stabilization of edge Peeling–Ballooning modes using BOUT++ different physics models and different assumption of density profiles.

Some 3-field BOUT++ code simulations under the X-point geometry show that the large density gradient may drive instability and the ion diamagnetic stabilizations may be reduced, which is different from the 3-field results using circular equilibrium [3]. Since the 3-field model only has a limited finite Larmor radius (FLR) effect, the difference above may mean that the instability comes from the missing terms of the FLR effects or other kinetic effects. Here, the gyro-Landau-fluid (GLF) 3+1 module in BOUT++ [4], containing full FLR effects, Landau damping and toroidal resonance, is employed to study this problem. First, a series of self-consistent ITER-FEAT equilibrium models with a fixed temperature profile and different β is used to benchmark the GLF code with the local and global runs of GYRO code for ballooning modes. The large density gradient effects are then investigated in both GLF code and GYRO code for the circular case. The results show the consistent ion diamagnetic stabilization under the circular geometry. The β scan of both codes will be presented. Finally, the GLF results will be presented in X-point geometry with different assumption of density profiles.

[1] A.W. Leonard, et al., J. Nucl. Mater. (2014)
[2] P.B. Snyder et al., Nucl. Fusion 51, 103016 (2011)
[3] P.W. Xi, et.al, Nucl. Fusion 53,113020 (2013)
[4] C. H. Ma, et.al, Phys. Plasmas 22, 010702 (2015)

ACKNOWLEDGMENTS

This work was performed under the auspices of the U.S. DoE by LLNL under Contract No. DE-AC52-7NA27344 and is supported by the China Scholarship Council (No. 201406060053).

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