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DIII-D 3D edge physics capabilities: modeling, experiments and physics validation

DIII-D 3D edge physics capabilities: modeling, experiments and physics validation. Presented by T.E. Evans 1 I. Joseph 2 , R.A. Moyer 2 , M.J. Schaffer 1 , A. Runov 3 , R. Schneider 3 , S.V. Kasilov 4 , M.E. Fenstermacher 5 , M. Groth 5 , J.W. Watkins 6

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DIII-D 3D edge physics capabilities: modeling, experiments and physics validation

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  1. DIII-D 3D edge physics capabilities: modeling, experiments and physics validation Presented by T.E. Evans1 I. Joseph2, R.A. Moyer2, M.J. Schaffer1, A. Runov3, R. Schneider3, S.V. Kasilov4, M.E. Fenstermacher5, M. Groth5, J.W. Watkins6 1GA, 2UCSD, 3MPI-Griefswald, 4Kharkov IPT, 5LLNL, 6SNL, Presented at NCSX Research Forum 2006 December 8th, 2006

  2. DIII-D has generated capability in 3D edge physics modeling & interest in validation of physical models • DIII-D’s most successful ELM suppression techniques rely on the essential 3D physics of non-axisymmetric perturbations • RMP H-mode: externally induced resonant fields • QH-mode: internally generated, nonlinearly saturated EHO hypothesis • 3D equilibrium reconstructions are critical to validating underlying physics mechanisms • DIII-D plasmas can be used to benchmark 3D equilibrium codes • VMEC, V3FIT, PIES, EFIT + ideal DCON response, … • Field line tracing used to explore field structure: TRIP3D (GA) • Braginskii 2-fluid codes used for equilibrium transport • E3D (MPI-Greifswald) thermal transport in stochastic fields • EMC3-EIRENE (FZ-Jülich) currently used by TEXTOR collaborators • MHD: NIMROD, M3D, JOREK

  3. Key physics issues for DIII-D are clearly important for NCSX • Can we validate the physics of resonant magnetic field penetration? • MHD modeling by NIMROD, M3D, JOREK codes can be used to assess physics of forced reconnection at finite toroidal flow • Extended MHD models can test various neoclassical predictions for viscosity • Parallel kinetic closures can extend validity to lower collisionality • ELM peeling-ballooning stability needs to be reassessed in 3D equilibria • Experimental results from DIII-D and JET seem to indicate that the Type-I ELM threshold can be continuously tuned by applying external perturbations • MHD modeling byNIMROD, M3D, JOREK • ELITE-3D??? will be required for efficient analysis of experimental stability threshold

  4. Magnetic footprint structures predicted by TRIP3D/E3D have been observed on Xpt/IR-TV TRIP3D ISP: field lines 123301 2170 ms Xpt-TV ISP: filtered D123301 2170 ms • Asymmetric footprint observations can be used to validate themagnetic fieldmodel E3D ISP heat flux 122342 4650 ms I-coil only

  5. q95=3.55 Detailed OSP footprint can be compared to strike point sweep of Langmuir probe array • Proper in-out asymmetry may require asymmetric Danom • Drift effects? extra bump in private flux zone requires new explanation Drift Effects? LPA: 125912 3200-3800 ms Jsat at =180o E3D: 122342 4650 ms ISP at=150o and OSP at=180o

  6. Paradox: the RMP primarily controls peeling-ballooning stability through particle transport! n decreases, notT

  7. Resolution? pedestal toroidal rotation and Er change promptly when RMP is applied at q95 resonance • H-mode pedestal v spins up and Er well narrows.

  8. Summary • Experience gained at DIII-D in 3D edge physics may be valuable for NCSX • Validation of 3D edge models • Equilibrium reconstruction • Field line integration and mapping • Fluid transport (heat, particle and momentum) • Resonant field screening (flow and pressure) • Divertor footprints • MHD stability (peeling-ballooning, forced reconnection, etc.) • Availability of experimental data in high power discharges • Developing 3D diagnostic capabilities • Developing 3D boundary control systems and technology

  9. N = 3 perturbations induce edge stochastic layer which destroys axisymmetric flux surfaces • Color = # toroidal transits for escape (red=201 max, black<10) • Caveat: no plasma response in this model

  10. q95=3.55 Due to drifts? Detailed OSP footprint can be compared to strike point sweep of Langmuir probe array LPA Jsat at DIII-D=180o 125912 3200-3800 ms E3D heat flux simulation • E3D heat flux qualitatively matches measured fluxes • Quantitative agreement will require …?

  11. E3D simulations show that the tangle also efficiently guides heat flux to the divertor targets • Private flux region still exists due to short divertor connection length • The field lines cannot sample the lower branches of the tangle

  12. As RMP , predicted tangle structure grows & heats 122342 at 4650 ms BC’s: Te= 1.6 keV, Ti= 2.6 keV at n = 77% I-coil (kA): 0 (2D) 1 2 3 Te (eV): 50 100 150 200

  13. As RMP  predicted edge temperature cools122342 at 4650 ms BC’s: Te= 1.6 keV, Ti= 2.6 keV at n = 77% Ti Te • Constant temperature BC’s • Edge stochastic layer cools relative to pedestal • remains hot compared to SOL

  14. Escaping field lines are trapped by the invariant manifolds which exit theX-point • The outline of the field line escape pattern traces out the surfaces of the invariant manifold • The homoclinic tangle encodes the structure of chaos 123301 3000ms Color = field line length red<2km blue<200m Backward Escape Upper “Stable” manifold Forward escape Upper “Unstable” manifold

  15. The tangle forms non-axisymmetric magnetic footprints which have been experimentally observed 123300: filtered CIII Xpt-TV • Te reflects a superposition of both upper invariant manifolds • Multiple magnetic footprint stripes observed during I-coil operation 123301: filtered D Xpt-TV

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