Gyro-fluid and two-fluid theory and simulations of edge-localized-modes

Journal Article · Wed May 15 00:00:00 EDT 2013 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4801746· OSTI ID:22228085

Xu, X. Q.; Dimits, A.; Joseph, I.; Umansky, M. V. ^[1]; Xi, P. W. ^[1]; Xia, T. Y.; Gui, B. ^[1]; Kim, S. S.; Park, G. Y.; Rhee, T.; Jhang, H. ^[2]; Diamond, P. H. ^[2]; Dudson, B. ^[3]; Snyder, P. B. ^[4]

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1. Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)
2. WCI Center for Fusion Theory, National Fusion Research Institute, Daejon 305-333 (Korea, Republic of)
3. University of York, Heslington, York YO10 5DD (United Kingdom)
4. General Atomics, San Diego, California 92186 (United States)

This paper reports on the theoretical and simulation results of a gyro-Landau-fluid extension of the BOUT++ code, which contributes to increasing the physics understanding of edge-localized-modes (ELMs). Large ELMs with low-to-intermediate-n peeling-ballooning (P-B) modes are significantly suppressed due to finite Larmor radius (FLR) effects when the ion temperature increases. For type-I ELMs, it is found from linear simulations that retaining complete first order FLR corrections as resulting from the incomplete “gyroviscous cancellation” in Braginskii's two-fluid model is necessary to obtain good agreement with gyro-fluid results for high ion temperature cases (T{sub i}≽3 keV) when the ion density has a strong radial variation, which goes beyond the simple local model of ion diamagnetic stabilization of ideal ballooning modes. The maximum growth rate is inversely proportional to T{sub i} because the FLR effect is proportional to T{sub i}. The FLR effect is also proportional to toroidal mode number n, so for high n cases, the P-B mode is stabilized by FLR effects. Nonlinear gyro-fluid simulations show results that are similar to those from the two-fluid model, namely that the P-B modes trigger magnetic reconnection, which drives the collapse of the pedestal pressure. Due to the additional FLR-corrected nonlinear E × B convection of the ion gyro-center density, for a ballooning-dominated equilibrium the gyro-fluid model further limits the radial spreading of ELMs. In six-field two fluid simulations, the parallel thermal diffusivity is found to prevent the ELM encroachment further into core plasmas and therefore leads to steady state L-mode profiles. The simulation results show that most energy is lost via ion channel during an ELM event, followed by particle loss and electron energy loss. Because edge plasmas have significant spatial inhomogeneities and complicated boundary conditions, we have developed a fast non-Fourier method for the computation of Landau-fluid closure terms based on an accurate and tunable approximation. The accuracy and the fast computational scaling of the method have been demonstrated.

• OSTI ID: 22228085
• Journal Information: Physics of Plasmas, Vol. 20, Issue 5; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
APPROXIMATIONS
BALLOONING INSTABILITY
BOUNDARY CONDITIONS
BOUNDARY LAYERS
CONVECTION
EDGE LOCALIZED MODES
ELECTRON TEMPERATURE
ELECTRONS
ENERGY LOSSES
ION TEMPERATURE
KEV RANGE
LARMOR RADIUS
L-MODE PLASMA CONFINEMENT
MAGNETIC RECONNECTION
PLASMA DENSITY
PLASMA SIMULATION
STEADY-STATE CONDITIONS
THERMAL DIFFUSIVITY
THERMODYNAMICS