SOLEDGE2D-EIRENE modelling for preparing WEST divertor operation G. Ciraolo, H. Bufferand, Ph. Ghendrih, J. • Bucalossi , Y. Marandet, J. Denis, N. Fedorczak, D. Galassi, J. Gunn, R. Leybros, B. Pégourié, E. Serre, P. Tamain 28th MAY 2015 | PAGE 1
Turning Tore Supra into WEST From Carbon limiter to W divertor Limiter configuration Divertor configuration Divertor coil Stabilizing plate WEST ITER/6 Divertor coil Stabilizing plate A major upgrade for investigating: H mode physics Tungsten environment Taking full benefit from Tore Supra assets Long pulse physics and operation Tungsten environment Carbon environment | PAGE 2
SOLEDGE2D-EIRENE 2D transport code developed in parallel to 3D turbulent code TOKAM3X Multi-species plasma solver coupled to EIRENE for neutrals Solves equations for densities, parallel velocities, temperatures and electric potential Drifts velocity are being implemented Example of SOLEDGE2D-EIRENE simulations for WEST geometry | PAGE 3
numerical modelling for preparing west divertor operation 1. WEST H mode plasmas : How to choose reasonable radial transport coefficients for SolEdge2D simulations? A standard procedure : setting these free parameters referring o to present experiments (example on an ASDEX H mode discharge) A possibly more predictive approach : Implementing a “turbulence” model in o SOLEDGE . 2. WEST long pulse requirements Modelling the plasma up to the wall in the divertor as well as in the main chamber region heat and particle flux (on divertor targets, baffle, limiter antenna...) o impurity sputtering/deposition o Neutral pressure | PAGE divertor and main chamber W sources o 4
setting cross field transport coefficients: the standard approach An example on ASDEX H mode discharge Based on a well documented deuterium H-mode plasma in AUG Carbon wall (sputtered radiator) / Sputtering yield adjusted to match experimental SOL radiated power Transport parameters from SOLEDGE2D-EIRENE [A. Chankin et al. , PPCF 48 simulation results in the (2006)] found to match OMP outboard mid plane experimental profiles | PAGE 5
Application to H-mode on ASDEX upgrade High recycling divertor solution Good agreement between simulation and experiment on target parameters | PAGE Objective: set transport parameters for WEST simulation 6
Application to H-mode on WEST Objective: high radiative H-mode plasma on WEST Same transport coefficients as in the AUG case Tungsten wall : C sputtering replaced by Nitrogen seeding Outboard Mid Plane Outer strike point Nitrogen puff | PAGE 7
To what extent these results are reliable and robust? Examples of radial profiles for transport coefficients « Quite large » set of possible combinations….. • Impact on heat and particle fluxes on divertor targets and • more generally on plasma behavior in the divertor region Can we find a way to obtain transport radial coefficient from a more « first principle » approach ? | PAGE 8
Taking inspiration from CFD community: Turbulence in mean flow equations Reynolds Averaged Navier-Stokes (RANS) approach: Averaging Reynolds tensor | PAGE 9
Estimation of eddy viscosity with a 2-equation model | PAGE 10
Why this simplified model is so interesting for us? Courtesy SimScale | PAGE 11
Coupling SOLEDGE2D with a turbulence model | PAGE 12
Test case for the model: MISTRAL base case on Tore Supra Comparison with experiment by J. Gunn et al., J. Nucl. Mat. 363-365 (2007)] evidence of transport enhancement on the LFS Ohmic plasmas. Plasma-wall contact point moved around the vessel HFS BOT LFS TOP
Preliminary results obtained with SOLEDGE coupled to the turbulence model HFS BOT LFS TOP The 4 configurations are simulated with SOLEDGE2D-EIRENE coupled with the turbulence model Spontaneous ballooned diffusion coefficients enhanced turbulence intensity in the outboard midplane (interchange instable side) | PAGE 14
Preliminary results obtained with SOLEDGE coupled to the turbulence model HFS BOT LFS TOP The 4 configurations are simulated with SOLEDGE2D-EIRENE coupled with the turbulence model Spontaneous ballooned diffusion coefficients enhanced turbulence intensity in the outboard midplane (interchange instable side) | PAGE 15
Preliminary results obtained with SOLEDGE2D-EIRENE coupled to the turbulence model Mach number contour plot obtained from simulations. Flow reversal observed at the top of the machine (probe in pink) HFS BOT LFS TOP The 4 configurations are simulated with SOLEDGE2D-EIRENE coupled with the turbulence model | PAGE 16
Comparison of Mach and density profiles (langmuir probes vs simulations) L a n g m u i r p r o b e s m i u Reasonable agreement for Mach number � flow reversal a l | PAGE t o i 17 n Difference in density: decay less pronounced in the simulation s
numerical modelling in support tO west divertor operation | PAGE 18
numerical modelling for preparing west divertor operation WEST long pulse requirements Access to plasma behavior all along the wall : heat and particle flux o impurity sputtering/deposition o o divertor and main chamber W sources | PAGE 19
28th MAY 2015 | PAGE 20
Coupling between species in soledge multifluid equations SolEdge-EIRENE adapted to simulate an arbitrary number of ions For every ion the following equations are solved: Mass balance ( ) ∇ ∂ n n = − + ⊥ α + ∇ ⋅ + = v D v α n n ( u b v ) S with α pinch α α α α n ∂ t α Momentum balance ( ) ( ) ∂ m n u ( ) + ∇ ⋅ + = − ∇ + + ∇ ⋅ ν ∇ + ν ∇ + + α α α nu m n u ( u b v ) n T q E m n u u b R S α α α α α α α α α α ⊥ ⊥ α α α α // // // // ∂ t Energy balance (also solved for electrons) ∂ 3 1 5 1 1 + 2 + ∇ ⋅ + + 2 + = + ∇ ⋅ ν ∇ 2 + χ ∇ n T m n u n T ( u b v ) m n u ( u b v ) q E u n u n T α α α α α α α α α α α α α α α α α ⊥ ⊥ α α ⊥ α // ∂ t 2 2 2 2 2 1 + ∇ ⋅ κ ∇ + ν ∇ − 2 T u h b α α α // // // 2 Coupling terms + + + E R u Q S α α α α α Atomic physics | PAGE
Coupling between species in soledge multifluid equations Coupling terms come from collisions between the different particles Example: effect of collisions in momentum balance § Thermal force: = ∇ + ∇ R T ( 1 ) ( 2 ) c T c T ∑ αβ αβ α αβ β // // = + T u R R R α αβ αβ § Friction force β ≠ α ( ) = − R u ( 3 ) c u u αβ αβ α β Impurities follow the plasma A closure for these terms has been derived by Braginskii (1965) only for a Drive impurity flows from cold flow toward the wall two species ion-electron plasma. to hot areas (contamination) (flushing) Expression for these terms have been inferred on heuristic basis from Braginskii’s work (Braams work for SOLPS - 1987) Ongoing work to express these terms from theoretical closure (Zhdanov, 24th NOVEMBRE 2014 | PAGE Rozhanski)
Checking the code – Are equation well implemented ? Equations checked with the Method of Manufactured Solutions (MMS): Check if the code solves the equation that it claims to solve Tests are run automatically when the code is modified non-regression tests C+ C2+ C3+ C4+ C5+ C6+ Atomic physics are being checked testing ionization- recombination equilibrium in a very simple domain geometry (no transport) Optimization effort to reduce computation time (G. Latu, C. Passeron) Ionization/recombination equilibrium for Carbon 24th NOVEMBRE 2014 | PAGE
SOLEDGE Validation on an ASDEX H-mode plasma Transport diffusivities have been determned by Chankin to match midplane experimental measurements with SOLPS results. Procedure: Use the same transport parameters and repeat the simulation with SOLEDGE – Attempt to use the same code settings (as far as possible) SOLEDGE grid 18 x 48 110 x 180 Full line with markers: SOLPS Dashed lines: SOLEDGE 29th September 2015 | PAGE 24
SOLEDGE Validation on an ASDEX H-mode plasma | PAGE 25
SOLEDGE Validation on an ASDEX H-mode plasma | PAGE 26
SOLEDGE Validation on an ASDEX H-mode plasma Target profiles comparison: heat flux | PAGE 27
SOLEDGE Validation on an ASDEX H-mode plasma Target profiles comparison: probe data | PAGE SOLPS results: 2.7MW with drifts 28
SOLEDGE Validation on an ASDEX H-mode plasma | PAGE 29
WEST minimizes risks for ITER divertor construction and operation Divertor: a crucial component for power exhaust ITER divertor heat loads specs: Steady state: 10 MW/m2 Slow transients: 20 MW/m2 ELMs - disruptions WEST: risk minimization in support to ITER divertor strategy | PAGE 30
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