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NTM control by ECCD on ASDEX Upgrade

NTM control by ECCD on ASDEX Upgrade. S. Günter, F. Leuterer, A. Manini, M. Maraschek, H. Zohm, ASDEX Upgrade Team Max-Planck-Institut f ür Plasmaphysik Garching, Germany. Influence of ECCD deposition width on stabilization efficiency - direct NTM stabilization - ST control

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NTM control by ECCD on ASDEX Upgrade

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  1. NTM control by ECCD on ASDEX Upgrade S. Günter, F. Leuterer, A. Manini, M. Maraschek, H. Zohm, ASDEX Upgrade Team Max-Planck-Institut für Plasmaphysik Garching, Germany • Influence of ECCD deposition width on stabilization efficiency • - direct NTM stabilization • - ST control • - early deposition (before NTM onset) • modulated vs. non-modulated CD (in progress) • Upgrade of ECCD system on AUGD

  2. What is the optimum launch angle? so far 15° launch angle used • Optimisation problem (both IECCD and d increase with toroidal launch angle) • modelling predicts optimum angle to be smaller than previously used angle

  3. Narrow deposition width is beneficial for NTM stabilization Increased efficiency of ECCD for very narrow deposition width >> full NTM stabilization at lower ECCD power

  4. (3,2) NTM control at high bN with narrow deposition width

  5. Increased efficiency also for (2,1) NTMs

  6. NTM avoidance by early ECCD? Early ECCD close to (3,2) surface delays NTM onset (only for large deposition width >> total current counts)

  7. NTM avoidance by ST control ST avoidance by: off-axis co-ECCD on-axis ctr ECCD (fishbone triggers NTM) Mück, Goodman, Sauter 2003

  8. NTM avoidance by ST control Again less total current required for more localized current drive (Manini et al., EPS 2005)

  9. NTM avoidance by early ST control About same efficiency for wide and narrow ECCD although different total current Heating effect for counter ECCD stronger for wide deposition

  10. DC/AC stabilization efficiency AC DC  >> 1/c Modulated versus Non-Modulated CD • First experiments on ASDEX Upgrade did not show any difference • in stabilization efficiency between AC and DC current drive • Reason: - Current driven at X-point is not effective as flux surface • averaged current density is small • - Modulation expected to be more effective for small islands On schedule for next week, sorry!

  11. Upgrade plans for the ECRH system one delivered

  12. Summary • Smaller deposition width beneficial for NTM stabilization • - both for (3,2) and (2,1) • small deposition (smaller current!) also ok for ST tailoring • modulated vs. non-modulated ECCD (w < wECCD) are on the way

  13. MHD control by ECCD on ASDEX Upgrade

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