(2018) J. Bao -- APS DPP (Portland)

Effects of Rotation on Turbulent Transport in Field Reversed Configuration
Jian Bao1, Calvin Lau1, Daniel Fulton2, Zhihong Lin1, Toshiki Tajima1,2 and TAE team
1University of California, Irvine, CA 92697, 2TAE Technologies, Inc., 19631 Pauling, Foothill Ranch, CA 92610
Motivation
n A high performance FRC has been sustained for more than 5 ms, which is beyond the turbulent transport time scale [1,2].
n Local simulation of FRC finds that the drift wave instability is stable in the core region while is unstable in the SOL region [3,4,5]. Global particle in cell simulation cross the separatrix is required to study the turbulent transport.
n Parallel transport in the SOL region determines the plasma profile, and thus determines the turbulent transport.
n C-2W (Norman) constitutes an FRC inside a mirror machine with expander divertors. Electron parallel heat loss, self-consistent potential, pre-sheath and sheath must be resolved.
Global particle simulation of drift wave instability in FRC n Comparison of drift wave instability between FRC and tokamak
ü In FRC, the most unstable electrostatic drift mode is in the SOL region while the drift wave instability is stable in the core region.
ü FRC core: drift wave instability is linearly stable!!!(opposite direction between diamagnetic drift and grad-B drift, short electron transit distance, large ion FLR effect et al. [5])
n Preliminary results of Er effects
ü%&' < 0 : Positive Er shear suppress drift wave instability %(&
through breaking down the mode symmetry.
ü%&' > 0 : Negative Er shear increase growth rate through
enhancing the mode symmetry.
ü%&' = 0 (constant Er) : no effects on growth rate. %(&
%(&
Verification of ITG instability n Theoretical benchmark in slab geometry
ü Simulations of ITG instability in slab geometry agree well with theory. n Simulation of ITG in the SOL region of FRC geometry
ü GTC simulation shows that slab branch of ITG is unstable in the SOL region of field reversed configuration.
References
[1] M. W. Binderbauer et al, Phys. Plasmas 22, 056110 (2015). [2] L. Schmitz et al, Nature Communications 7, 13860 (2016). [3] D. P. Fulton et al, Phys. Plasmas 23, 012509 (2016).
[4] D. P. Fulton et al, Phys. Plasmas 23, 056111 (2016).
[5] C. K. Lau et al, Phys. Plasmas 24, 082512 (2017). [6] S. Parker et al, J. Comput. Phys. 104, 657 (1993). [7] http://www.trialphaenergy.com/research-library/
n This work is supported by the TAE subcontract to UCI. See posters by C. Lau and D. Fulton!
n Contact info: jianb@uci.edu
Gyrokinetic Toroidal Code (GTC) developments n Field aligned mesh
n Laplacian Poisson solver
n The simulation grids are aligned along the field line to suppress the high 𝑘|| noise.
n Core region and sol region share the grids on separatrix, which enables core and sol regions coupling.
n Greatly decrease computational costs by using much fewer grids along parallel direction since 𝑘|| ≪ 𝑘$ is generally true to drift-type instabilities.
n Particle trajectory
n Boris Push for 6D Vlasov particle, drift kinetic equation for guiding center particle.
Acknowledgements
Simulations were performed using resources at Oak Ridge Leadership Computing Facility, a DOE Office of Science User Facility supported under Contract No. DE-AC05-00OR22725, and the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported under Contract No. DEAC02-05CH11231.