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Impurity Transport in the Edge Transport Barrier of ASDEX Upgrade H-Mode Discharges

Impurity Transport in the Edge Transport Barrier of ASDEX Upgrade H-Mode Discharges. R. Dux, T. P ütterich, M.A. Janzer, R.M. McDermott and the ASDEX Upgrade Team. MPI für Plasmaphysik, EURATOM Assoziation, Garching bei München. Central tungsten density depends on….

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Impurity Transport in the Edge Transport Barrier of ASDEX Upgrade H-Mode Discharges

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  1. Impurity Transport in the Edge Transport Barrier of ASDEX Upgrade H-Mode Discharges R. Dux, T. Pütterich, M.A. Janzer, R.M. McDermott and the ASDEX Upgrade Team MPI für Plasmaphysik, EURATOM Assoziation, Garching bei München

  2. Central tungsten density depends on… R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 2

  3. Central tungsten density depends on… R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 3

  4. W- and C-density pedestal vs. ELM frequ. • Scan in D-puff rate changes ELM frequency • Lower ELM frequency leads to more nW inside pedestal • nC increases less strong with ΔtELM than nW • Need to know inter-ELM transport in ETB to understand effect of ELMs R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 4

  5. Overview • Measurements of the impurity transport in the ETBusing CXRS measurements – Z-dependent • Consequences for transport of W- 1D Transport/Erosion Model for W- results for AUGD and ITER • Summary R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 5

  6. Toroidal edge CXRS system at AUGD • spatial resolution: 3 mm • temporal resolution 1.9 ms R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 6

  7. STRAHL R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 7

  8. Scheme of Transport Evaluation Electron profiles, Geometry, Atomic Data Measured impurity profiles 1D-Transport Model STRAHL Fitting procedure input Vary A1,A2 compare R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 8

  9. Inputs for Modeling the Impurity Transport • Electron profiles and Edge-CXRS during type-I ELMy H-mode • Profiles are adjusted by a two-point model for power balance (i.e. Te =85eV at separatrix) • Analysis in inter-ELM phase Time [s] R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 9

  10. Model finds good match for impurity profiles • Profiles are well described, except 1ms after ELM (filaments, ELM-model) • Pedestal in C6+ is mainly due to pedestal in total C density • Separation of v and D possible due to: (1) modulation by ELM and (2) position of gradient R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 10

  11. Fitted values of v, D and v/D agree with neoclassical transport • D and v are separated, but with relative large uncertainties • v/D is determined well by the gradients and the pedestal height, i.e. pedestal peaking factor (In equilibrium, w/o sources) • Neoclassical transport (NEOART) is matched for v/D, (NEOART is equivalent to NCLASS) • Neocl. approximation valid for impurities; mostly PS, negligible banana, plateau contribution R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 11

  12. Neoclassical transport for He, C, Ne and Ar R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 12

  13. Neoclassical transport for He, C, Ne and Ar • Impurity scan gives stronger inward convection for higher charge • Implications: every impurity has a different gradient • W has even higher Z in ETB higher * and collisional diffusion coefficient stronger peaking R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 13

  14. Overview • Measurements of the impurity transport in the ETBusing CXRS measurements – Z-dependent • Consequences for transport of W- 1D Transport/Erosion Model for W- results for AUGD and ITER • Summary R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 14

  15. Model for Radial Transport of Tungsten during ELM cycle R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 15

  16. Modeled W profile evolution during ELM cycle R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 16

  17. Increase of prompt redeposition during ELM:immediate return to surface during first gyration R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 17

  18. Study dependence of confinement time of W R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 18

  19. Confinement time of W depends on ELM frequency and parallel loss time R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 19

  20. Code results for three AUG H-mode plasmas with f_ELM=50,100 and 200Hz R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 20

  21. ITER: much lower collisional transport due to higher temperature and B-field R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 21

  22. ITER: low W peaking in ETB for relevant ELM frequency range R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 22

  23. Summary • For type-I ELMy H-mode, inter-ELM impurity transport at the barrier is neoclassical • Absolute values of v and D agree • Neoclassical Z-scaling is observed • strong inward pinch • A multi-impurity transport/erosion code was developed combining the transport in the edge barrier and wall erosion including effects of ELMs • AUG: consistent description of including all experimental data • impurity peaking in ETB of ITER very weak for relevant ELMfrequencies R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 23

  24. Outboard limiters most important source • R-sweep modulates outboard W-source • Large divertor source does not play a role • cW reacts strongly to the limiter source R. Dux et. al., I-6 , PSI 2008, JNM 390-391, 858 R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 24

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