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GTC Status: Physics Capabilities & Recent Applications Y. Xiao for GTC team UC Irvine. Global Gyrokinetic Toroidal Code (GTC). Non-perturbative (full-f) & perturbative ( d f) simulation General geometry using EFIT & TRANSP data Kinetic electrons & electromagnetic simulation - PowerPoint PPT Presentation
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GTC Status: Physics Capabilities & Recent Applications
Y. Xiao for GTC team
UC Irvine
• Non-perturbative (full-f) & perturbative (f) simulation
• General geometry using EFIT & TRANSP data
• Kinetic electrons & electromagnetic simulation
• Neoclassical effects using Fokker-Planck collision operators conserving energy & momentum
• Equilibrium radial electric field, toroidal & poloidal rotations; Multiple ion species
• Parallelization >100,000 cores
• Global field-aligned mesh
• Parallel solver PETSc
• Advanced I/O ADIOS
• Applications: microturbulence & MHD modes
Global Gyrokinetic Toroidal Code (GTC)
[Lin et al, Science, 1998]Lin, Holod, Zhang, Xiao, UCIKlasky, ORNL; Ethier, PPPL;Decyk, UCLA; et al
General geometry and profiles• General global toroidal magnetic geometry from Grad-
Shafranov equilibrium• Realistic density and temperature profiles using spline fits
of EFIT and TRANSP data• No additional equilibrium model
is needed• Experimental validation
GTC poloidal meshRealistic temperature and density profiles from DIII-D shot #101391 [Candy and Waltz, PRL 2003]
Full-f capability
• Non-perturbative full-f and perturbative -f models are implemented in the same version
time
full-f ITG intensity
f ITG intensity
full-f zonal flows
f zonal flows
Kinetic electrons
• Hybrid fluid-kinetic electron model is used
• In the lowest order of electron-to-ion mass ratio expansion electrons are adiabatic: fluid equations
• Higher-order kinetic correction is calculated by solving drift-kinetic equation
Electromagnetic capabilities• Only perpendicular perturbation of magnetic field
considered
• Parallel electric field expressed in terms of effective potential, obtained from electron density
• Continuity equation for adiabatic electron density, corrected by drift kinetic equation.
• Inverse Ampere’s law for electron current
• Time evolution for parallel vector potential
• Gyrokinetic Poisson equation for electrostatic potential
Structure of GTC algorithm
ne A||
ue
fige
neniuiA|| ne1 ue
1
indesA|| ZF
Dynamics
Sources
Fields
Equilibrium flows and neoclassical effects
• Equilibrium toroidal rotation is implemented
• Radial electric field satisfies radial force balance
• Neoclassical poloidal rotation satisfies parallel force balance
• Fokker-Planck collision operator conserving energy and momentum
Multiple ion species
• Fast ions treated the same way as thermal ion specie
• Energetic ion density and current non-perturbatively enter Poisson equation an Ampere’s law
Numerical efficiency
• Effective parallelization >105 cores• Global field-aligned mesh• Parallel PETSc solver• Advanced I/O system ADIOS
Recent GTC applications
• Electrostatic, kinetic electron applications– CTEM turbulent transport [Xiao et al, PRL2009; PoP2010]– Momentum transport [Holod & Lin, PoP2008; PPCF2010]– Energetic particle transport by microturbulence [W. Zhang et al,
PRL2008; PoP2010]– Turbulent transport in reversed magnetic shear plasmas [Deng &
Lin, PoP2009]– GAM physics [[H. Zhang et al,NF2009; PoP2010]
• Electromagnetic applications– Electromagnetic turbulence with kinetic electrons [Nishimura et
al, CiCP2009] – TAE [Nishimura, PoP2009; W. Zhang et al, in preparation]– RSAE [Deng et al, PoP2010, submitted]– BAE [H. Zhang et al, in preparation]
The CTEM turbulent transport studies reveal
• Transport scaling---Bohm to gyroBohm with system size increasing
• Turbulence properties---microscopic eddies mixed with mesoscale eddies
• Zonal flow---Zonal flow is important for the parameter applied
• Transport mechanism
electrons: track global profile of turbulent intensity; but contain a nondiffusive, ballistic component on mesoscale. The electron transport in CTEM is a 1D fluid process (radial) due to lack of parallel decorrelation and toroidal precession decorrelation and weak toroidal precession detuning
ions: diffusive, proportional to local EXB intensity. The ions decorrelate with turbulence in the parallel direction within one flux surface
CTEM turbulent transport
Xiao and Lin PRL 2009
Xiao et al, POP 2010
Experimental validation• Real radial temperature and density
profiles are loaded• Zonal flow solver is redesigned for the
general geometry• Heat conductivity uses the ITER
convention• The measured heat conductivity
(preliminary) is close to Candy-Waltz 2003 value
Tq
2
Toroidal momentum transport
• Simulations of toroidal angular momentum transport in ITG and CTEM turbulence
• Separation of momentum flux components. Non-diffusive momentum flux
• Intrinsic Prandtl number
Pr 0.2 0.7 (ITG)
Pr 0.5(CTEM)
Holod & Lin, PoP 2008
Holod & Lin, PPCF 2010