Characterizing electron temperature gradient turbulence via numerical simulation
- Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)
Numerical simulations of electron temperature gradient (ETG) turbulence are presented that characterize the ETG fluctuation spectrum, establish limits to the validity of the adiabatic ion model often employed in studying ETG turbulence, and support the tentative conclusion that plasma-operating regimes exist in which ETG turbulence produces sufficient electron heat transport to be experimentally relevant. We resolve prior controversies regarding simulation techniques and convergence by benchmarking simulations of ETG turbulence from four microturbulence codes, demonstrating agreement on the electron heat flux, correlation functions, fluctuation intensity, and rms flow shear at fixed simulation cross section and resolution in the plane perpendicular to the magnetic field. Excellent convergence of both continuum and particle-in-cell codes with time step and velocity-space resolution is demonstrated, while numerical issues relating to perpendicular (to the magnetic field) simulation dimensions and resolution are discussed. A parameter scan in the magnetic shear, s, demonstrates that the adiabatic ion model is valid at small values of s (s<0.4 for the parameters used in this scan) but breaks down at higher magnetic shear. A proper treatment employing gyrokinetic ions reveals a steady increase in the electron heat transport with increasing magnetic shear, reaching electron heat transport rates consistent with analyses of experimental tokamak discharges.
- OSTI ID:
- 20860430
- Journal Information:
- Physics of Plasmas, Vol. 13, Issue 12; Other Information: DOI: 10.1063/1.2402510; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CONVERGENCE
CORRELATION FUNCTIONS
ELECTRON TEMPERATURE
ELECTRONS
FLUCTUATIONS
HEAT FLUX
HEAT TRANSFER
ION TEMPERATURE
IONS
MAGNETIC FIELDS
NUMERICAL ANALYSIS
PLASMA
PLASMA CONFINEMENT
PLASMA SIMULATION
RADIATION TRANSPORT
SHEAR
TEMPERATURE GRADIENTS
TOKAMAK DEVICES
TURBULENCE