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Numerical Modeling of RMP ELM Suppression with Incomplete I-coil set in DIII-D

Author: Dmitri M. Orlov
Requested Type: Poster Only
Submitted: 2015-02-06 14:07:39

Co-authors: R.A.Moyer, UCSD; T.E.Evans, N.M.Ferraro, C.Paz-Soldan, A.D.Turnbull, GA; S.Lazerson, N.Logan, PPPL; F.Turco, Columbia U.; A.Wingen, ORNL

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University of California San Diego
9500 Gilman Drive
La Jolla, California   92093-0
USA

Abstract Text:
In this work we present results of the numerical modeling performed in order to understand the effect of the toroidal mode spectrum due to external edge-resonant magnetic perturbations (RMPs) on the RMP edge localized mode (ELM) suppression. In recent experiments on DIII-D addressing urgent ITER needs we have demonstrated that toroidally-monochromatic spectral content of the edge RMPs is not a necessary condition for suppression of ELMs. Robust ELM suppression has been reproducibly obtained on DIII-D during experiments in which various non-axisymmetric coil loops were turned off pseudo-randomly. It was shown that RMP ELM suppression could be achieved with as few as 5 out of 12 I-coils on DIII-D at similar coil.
Variations in the applied perturbation spectrum are analyzed with a number of codes. SURFMN results show that the n=3 dominant toroidal mode number perturbation fields decrease by approximately 50% as the coils are removed, while the Vacuum Island Overlap Width design criterion for the ITER ELM coils is satisfied. The results of M3D-C1 modeling confirm the increasing contribution from other toroidal harmonics as the perturbation spectrum changes, in particular showing increase in n=2 sidebands in 7 and 5 coils cases.
Simulations with ideal perturbed equilibrium code IPEC, and linear resistive MHD stability code MARS were done using I-coil and C-coil model to investigate the plasma response to the changes in the n=1 error-field correction and n=3 I-coils RMP fields. IPEC suggests that n=2 SVD coupling to dominant mode increases as the n=3 part decreases, possibly explaining the reasons for ELM suppression with reduced set of I-coils.

*Supported by the US DOE under DE-FG02-05ER54809 & DE-FC02-04ER54698.

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