Author: Ihor Holod
Requested Type: Pre-Selected Invited
Submitted: 2016-02-15 12:49:29
Co-authors: Z. Lin, S. Taimourzadeh, R. Nazikian, A. Wingen
University of California Irvine
Irvine, CA 92697
Strong pressure and current gradients in H-mode plasma pedestal can destabilize dangerous edge localized modes (ELM) leading to pedestal collapse and destruction of plasma facing materials. One possibility to control drastic ELM activity is applying resonant magnetic perturbations (RMP). Due to extreme complexity of the processes involved, the detailed mechanism of RMP effect is not completely clear. EML mitigation is typically accompanied by increased of short wavelength turbulent transport and particle fluxes, which points on the key role of microinstabilities.
In this work we address specifically the effect of RMP-modified magnetic equilibrium on intermediate-n ballooning stability and microturbulence in DIII-D pedestal. To separate other effect, such as rotation generation, and transport due to magnetic field stochasticity, we fix the background profiles and exclude magnetic islands, i.e. assume non-axisymmetric closed flux surface magnetic geometry. To examine the effect of RMP we construct a set of magnetic equilibriums with various strength of RMP perturbation. We have observed the increase of kinetic-ballooning mode growth rate when RMP is applied, however this change is only detectable for artificially amplified RMP strength. The direct effect of RMP magnetic geometry perturbation on zonal flow generation and turbulent transport is found to be insignificant.
Work is supported by General Atomics subcontract 4500055243, U.S. DOE theory grant DE-SC0010416 and DE-SC0013804, and by General Atomics collaboration agreement under DOE grant DE-FG03-94ER54271