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GTC Status: Physics Capabilities & Recent Applications Y. Xiao for GTC team UC Irvine

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

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GTC Status: Physics Capabilities & Recent Applications Y. Xiao for GTC team UC Irvine

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  1. GTC Status: Physics Capabilities & Recent ApplicationsY. Xiao for GTC teamUC Irvine

  2. Global Gyrokinetic Toroidal Code (GTC) • Non-perturbative (full-f) & perturbative (df) 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 [Lin et al, Science, 1998] Lin, Holod, Zhang, Xiao, UCI Klasky, ORNL; Ethier, PPPL; Decyk, UCLA; et al

  3. GTC poloidal mesh Realistic temperature and density profiles from DIII-D shot #101391 [Candy and Waltz, PRL 2003] 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

  4. full-f ITG intensity Full-f capability df ITG intensity full-f zonal flows • Non-perturbative full-f and perturbative d-f models are implemented in the same version df zonal flows time

  5. 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

  6. 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

  7. Structure of GTC algorithm dne dfi&dge dA|| Dynamics due dA|| ZF dfes dfind Fields dA|| dui dni dne1 due1 dne Sources

  8. 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

  9. 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

  10. Numerical efficiency • Effective parallelization >105 cores • Global field-aligned mesh • Parallel PETSc solver • Advanced I/O system ADIOS

  11. 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]

  12. CTEM turbulent transport • 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 Xiao and Lin PRL 2009 Xiao et al, POP 2010

  13. 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

  14. 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 Holod & Lin, PoP 2008 Holod & Lin, PPCF 2010

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