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 1 GA, 2 UCSD, 3 MPI-Griefswald, 4 Kharkov IPT, 5 LLNL, 6 SNL, Presented at NCSX Research Forum 2006 December 8 th, 2006

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

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 by NIMROD, M3D, JOREK – ELITE-3D??? will be required for efficient analysis of experimental stability threshold

Magnetic footprint structures predicted by TRIP3D/E3D have been observed on Xpt/IR-TV Xpt-TV ISP: filtered D  msTRIP3D ISP: field lines ms Asymmetric footprint observations can be used to validate the magnetic field model E3D ISP heat flux ms I-coil only

q 95 =3.55 Drift Effects? Detailed OSP footprint can be compared to strike point sweep of Langmuir probe array LPA: ms J sat at  =180 o Proper in-out asymmetry may require asymmetric D anom Drift effects? extra bump in private flux zone requires new explanation E3D: ms ISP at  =150 o and OSP at  =180 o

Paradox: the RMP primarily controls peeling-ballooning stability through particle transport! n decreases, not T

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

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

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

Detailed OSP footprint can be compared to strike point sweep of Langmuir probe array E3D heat flux simulation E3D heat flux qualitatively matches measured fluxes Quantitative agreement will require …? LPA J sat at  DIII-D =180 o ms q 95 =3.55 Due to drifts?

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

As RMP , predicted tangle structure grows & heats at 4650 ms BC’s: T e = 1.6 keV, T i = 2.6 keV at  n = 77% Te (eV): I-coil (kA): 0 (2D) 1 2 3

As RMP  predicted edge temperature cools at 4650 ms BC’s: T e = 1.6 keV, T i = 2.6 keV at  n = 77% Constant temperature BC’s Edge stochastic layer cools relative to pedestal –remains hot compared to SOL TeTe TiTi

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

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