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The effects of resonant magnetic perturbations(RMPs)on the behavior of high Z-number impurities in the core of tokamak plasmas have been studied using1D and3D impurity transport codes.Spatial distributions and temporal evolutions of impurities observed by extreme ultraviolet(EUV)spectrometry at the Experimental Advanced Superconducting Tokamak(EAST)serve as the basis for the transport numerical simulations.Line radiation emissions of impurities(e.g.carbon,lithium,iron and tungsten)were monitored to study the impurity response to RMPs.All impurity intensities are observed to decline by the application of RMP fields,during stages of mitigation or suppressed edge localized modes(ELMs)instabilities during high performance mode(H-mode)operation.
The～50％to70％reductions in Fe and W emissions with n=1(n:toroidal mode number)RMPs are more significant than those of low-Z carbon and lithium emissions(～30％).Small changes in stored energy,ne and Te do not account for the impurity emissions mitigation,so the measurements indicate that RMPs significantly and selectively decrease the impurity accumulation in the core region with minimal impact on plasma confinement.A purely inertial particle pump-out process is ruled out,and the targeted effect on the most detrimental(higher-Z)impurities highlights a promising advantage of RMPs use for impurity control,owed to transport effects from changes in the magnetic topology.
The transport coefficients of impurity ions are calculated with the STRAHL1D impurity transport code,based on measured Fe-ⅩⅩⅢprofiles.It is found that DFe increases from1.0-2.0m2s-1to1.5-3.0m2s-1from the boundary of the core region outward(p＞0.50)after the onset of RMPs.Meanwhile,vFe shows a decrease in the outward direction in the core.The DFe and vFe variations combined lead to reduced Fe profiles.The diffusion shows anomalous values toward the edge,expression of the increased stochasticity produced tjere by the RMPs breaking of toroidal symmetry and the introduction of3D fields.The increase in diffusivity is not entirely localized at the edge and also allows the exhaust of high-Z core impurities.
The3D edge impurity transport code EMC3-EIRENE is applied for the first time in an RMP case at EAST to study impurity transport.A toroidal phase dependence is found in the distribution of impurities as a result of the RMP coils toroidal asymmetry showing typically anomalous transport phenomena such as blobs and filaments of impurity concentration.The exhaust of C-Ⅵtoward the scrape-off layer(SOL)and the overall suppression of W are observed in the cases with RMPs,confirming the feasibility of using the method for active impurity control in fusion plasmas.
The～50％to70％reductions in Fe and W emissions with n=1(n:toroidal mode number)RMPs are more significant than those of low-Z carbon and lithium emissions(～30％).Small changes in stored energy,ne and Te do not account for the impurity emissions mitigation,so the measurements indicate that RMPs significantly and selectively decrease the impurity accumulation in the core region with minimal impact on plasma confinement.A purely inertial particle pump-out process is ruled out,and the targeted effect on the most detrimental(higher-Z)impurities highlights a promising advantage of RMPs use for impurity control,owed to transport effects from changes in the magnetic topology.
The transport coefficients of impurity ions are calculated with the STRAHL1D impurity transport code,based on measured Fe-ⅩⅩⅢprofiles.It is found that DFe increases from1.0-2.0m2s-1to1.5-3.0m2s-1from the boundary of the core region outward(p＞0.50)after the onset of RMPs.Meanwhile,vFe shows a decrease in the outward direction in the core.The DFe and vFe variations combined lead to reduced Fe profiles.The diffusion shows anomalous values toward the edge,expression of the increased stochasticity produced tjere by the RMPs breaking of toroidal symmetry and the introduction of3D fields.The increase in diffusivity is not entirely localized at the edge and also allows the exhaust of high-Z core impurities.
The3D edge impurity transport code EMC3-EIRENE is applied for the first time in an RMP case at EAST to study impurity transport.A toroidal phase dependence is found in the distribution of impurities as a result of the RMP coils toroidal asymmetry showing typically anomalous transport phenomena such as blobs and filaments of impurity concentration.The exhaust of C-Ⅵtoward the scrape-off layer(SOL)and the overall suppression of W are observed in the cases with RMPs,confirming the feasibility of using the method for active impurity control in fusion plasmas.