INTERPRETATION OF EDGE TRANSPORT IN DIII-D

1. INTERPRETATION OF EDGE TRANSPORT IN DIII-D W. M. Stacey, J-P. Floyd, M-H. Sayer, T. M. WilksGeorgia Tech R. J. Groebner and T. E. Evans General Atomics TTF2013, Santa Rosa, CA April, 2013

2. BACKGROUND THEORY • Radial and toroidal ion momentum equations constrain the main ion “j” pressure gradient. Heat conduction constrains ion & electron T gradients. where “k” is impurity ion, can be interpreted from experiment and • This constraint implies a pinch-diffusion relation • These quantities can be measured, providing new insights into the physics of the edge pedestal.

3. NET OUTWARD ION FLUX IS DIFFERENCE BETWEEN LARGE INWARD PINCH AND LARGE OUTWARD DIFFUSIVE CONTRIBUTIONS

4. ELECTRO-MAGNETIC FORCES MORE IMPORTANT THAN RECYCLING NEUTRALS IN DETERMINING EDGE PEDESTAL PRESSURE PROFILERecycling neutrals effect pressure profile through the ionization source term in continuity equation which determines Vrj. Electromagnetic and other forces effect pressure profile through Vpinch.

6. CHANGE IN IOL INTRINSIC ROTATION AT L-H TRANSITION REDUCES VφREPRESENTED AS CHANGE IN MOMENTUM TRANSFER FREQUENCY

7. ION ORBIT LOSS CORRECTIONS CHANGE INTERPRETTED χ AT L-H

8. MATCHING H-MODE & RMP DISCHARGESDENSITY PUMP-OUT MAY BE DUE MORE TO REDUCTION IN INWARD PINCH THAN TO AN INCREASE IN DIFFUSION COEFFICIENT FOR RMP RELATIVE TO H-MODE

9. DENSITY TRANSPORT BETWEEN ELMS Following an ELM, the diffusion coefficient and the outward pinch both increase in the flattop ρ<0.92, increasing the particle flux from the core into the edge pedestal to rebuild the pedestal.

10. CONCLUSIONS • There is a fundamental linkage between momentum and particle transport. • The fundamental transport coefficients are the toroidal and poloidal momentum transfer frequencies and the thermal diffusivities. • Net radial particle flux is the difference between a large outward diffusive term and a large inward pinch. • Electromagnetic pinch dominates neutral ionization in determination of edge pressure gradient. • Large increase in inward particle pinch at L-H transition. • At L-H, toroidal rotation increases in core but decreases in edge, due to decrease in ion-orbit-loss intrinsic rotation. • Ion-orbit-loss of thermalized ions provides much of the particle and energy transport out of the edge pedestal and produces intrinsic co-rotation in the edge. • Density pumpout with RMP due more to reduction in inward pinch than to increase in diffusion coefficient. • Following an ELM, the diffusion coefficient and the outward pinch both increase in the flattop ρ<0.92, increasing the particle flux from the core into the edge pedestal to rebuild the pedestal.

11. References • “Toroidal phasing of resonant magnetic perturbation effect on edge transport in the DIII-D tokamak”, Phys. Plasmas 20 ( 2013). • “Interpretation of changes in diffusive and non-diffusive transport in the edge plasma during pedestal buildup following a low-high transition in DIII-D”, Phys. Plasmas 20, 012509 (2013). • “Interpretation of diffusive and non-diffusive transport in tokamak edge pedestal measurements”, Fusion Sci.&Techn. 63, 34 (2013). • “Intrinsic rotation produced by ion orbit loss and X-loss”, Phys. Plasmas 19, 112503 (2012). • “Non-diffusive transport in the tokamak edge plasma”, Nucl. Fusion 52, 114020 (2012). • “The effect of ion orbit loss and X-loss on the interpretation of ion energy and particle transport in the DIII-D edge plasma”, Phys. Plasmas 18, 102504 (2011). • “Evolution of the H-mode edge pedestal between ELMs”, Nucl. Fusion 51, 063024 (2011). • “The role of radial particle pinches in ELM suppression by resonant magnetic perturbations”, Nucl. Fusion 51, 013007 (2011). • “Force balance and ion particle transport differences in high and low confinement tokamak edge pedestals”, Phys. Plasmas 17, 112512 (2010).