Behn, R.

Coster, D.

Gulejová, B.

Horacek, J.

Marki, J.

Pitts, R.A.

Wischmeier, M.

Infoscience - École polytechnique fédérale de Lausanne

Edge diagnostics in TCVTokamak à Configuration VariableTargetsLP : Langmuir probes=>  jsat, Te, ne at the targetsIR: fast Infrared thermographic camera=>perpendicular heat flux at outer targetUpstreamRCP: fast reciprocating Langmuir probe => Te, ne upstreamTS: edge Thomson scattering system=> Te, ne upstreamB. Gulejová a, R. A. Pitts a, R. Behn a, D. Coster b, J. Horacek a, J. Marki a, M. Wischmeier ba CRPP-EPFL, Association EURATOM-Confederation Suisse, CH-1015 Lausanne. Switzerland b Max-Planck Institut für Plasmaphysik, EURATOM-Association, Boltzmann Str.2, D-85748, Garching, GermanyTypical ELMing H- modeR=0.875 m, a=0.25 m, Bφ = 1.43 TAll-graphite machine Number of open diverted configurationsStandard operating mode with reversed toroidal field Bφ=> ion B x    B drift direction upwardsType III ELMing H-mode target dischargeSingle Null Low configuration Ip = 430 kA felm = 230 Hz ne = 6 x 1019 m-3κ95 = 1.65δ95 = 0.4 q95 = 2.5 n/nGW ~ 0.3Estored ~ 20kJPSOL = PΩ -PRAD = 275 kW# 26730neDαfelmSOLPS5 modelling of the ELMing H-mode on TCVScrape-Off Layer Plasma SimulationSuite of codes to simulate transport in edge plasma of tokamaksB2 - solves 2D multi-species fluid equations on a grid given from magnetic equilibrium EIRENE - kinetic transport code for neutrals based on Monte - Carlo algorithmSOLPS 5 = coupled EIRENE + B2.5TCV simulation mesh72 grid cells poloidallyalong separatrix24 grid cells radiallyMain inputs: magnetic equilibrium Psol = Pheat – Pradcoreupstream separatrix density neParameters: cross-field transport coefficients (D┴, χ ┴, v┴) systematically adjusteduntil agreement of simulation with experiment is achieved experimentally measuredInter-ELM simulation AnsatzCross-field radial transport in the main SOL-complex phenomenaSOL radial heat flux:SOL radial particle flux: nvdrdnD ⊥⊥⊥ +−=Γ))(5( ⊥⊥⊥⊥ ++−= nvdrdnDTdrdTnq χnrDeff ∇−=Γ ⊥⊥ ).( diffusion (D┴) + convection (v┴)Direct measurements of turbulent driven ExB radial fluxes using turbulent code ESEL predict very small values of D┴=> More appropriate approach would be ‘convective’(with D┴=D┴collisions and variation of v┴) However only the value of flux matters for the code and thus we can neglect convective term of equation for simplification and assume v┴=0Ansatz: D┴, χ┴- variationradially – transport barrier (TB)poloidally – no TB in divertor legsSOLPS vs experiment upstreamAssumption:Transport is specified differentlyin the main chamber SOL and divetror regionstanh fittanh fitpedestalpedestalseparatrixPedestal width (ne) = 0.0136 mPedestal height (ne)=3.6x 1019 m-3Pedestal width (Te)= 0.0102 mPedestal height (Te)= 179 eVRCP data multiplied by factor of 0.5to account for the overestimation due to Larmor radius effects increasing projescted area of the LP Foot of electron transport barrier(ETB) extends into SOL1 m2.s-1SOLCOREETBExcellent agreementei ⊥⊥ = χχSOLPS5 modelling of the ELMing H-mode on TCVSOLPS vs experiment at the targets∫ 0JEdge localized mode (ELM) - Coherently averaged ELMH-mode ? Edge MHD instabilities ?Periodic bursts of particles and energy into the SOL ELM leaves edge pedestal region in the form of a helical filamentary structurelocalised in the outboard midplane region of the poloidal cross-sectionW~200JDαEnergy expelled by Type III ELMs at TCV ~ 200 J  ELMs - too rapid  (frequency ~ 200 Hz) for comparison on an individual ELM basis Many similar events are coherently averaged inside the interval with reasonably periodic elmst[s]Dαpre-elm (inter-elm)    elm    post-elm phaseas a base scenario for simulation 1.step: Inter-ELM simulationAnalysis of LP data based on coherently averaged elm methodELM-time evolution of jsat at outer targetVoltage V=0 applied to Langmuir probesInner and outer target balance of  J0Thermoelectric currents flow from outer to inner (cold to hot) target[kA]outer targetouter targetinner targetJ0∫ 0J∫ 0Jinner targetnormalizedRef. R. A. Pitts et al., Nucl. Fusion 43 (2003) 1145(see Ref. )SOLPS D, χ in divertor legsSOLPSD, χ in divertor legsPerpendicular heat flux  Inner targetouter targetInner target outer targetjsat jsatTe Tene neSensitivity studyBallooning effectPrivate flux region vs. SOLjsat jsatjsatjsatouter targetInner targetBallooning coeff. Ballooning coeff.LP LPLPLP10.5 010.5 0Rescaling coeff. PRF/SOL Rescaling coeff. PRF/SOL0.610.615.7)( =SOLPSγ7)( =LPγ• Match is obtained only by “switching off”the transport barrier in divertor regions and increasing D, χ in divertor legs from 1? 6 m2.s-1 (cf. 1m2.s-1 in main chamber SOL). Increase of D, χ in inner leg doesn’t matter much • SOLPS models inner target well because it’s there probably dominated by geometry of TCVSimulation of ELMin progress…• Discrepancies at outer target might be explained by the fact that DRIFTS are not includedin simulations yet 

SOLPS5 modelling of the ELMing H-mode on TCV

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SOLPS5 modelling of the ELMing H-mode on TCV

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