Resonant Magnetic Perturbation Field Research Articles

MARS-F modeling of post-disruption runaway beam loss by magnetohydrodynamic instabilities in DIII-D

A drift orbit model for relativistic test electrons has been incorporated into the MARS-F code (Liu et al 2000 Phys. Plasmas 7 3681), in order to study the runaway electron (RE) behavior in the presence of magneto-hydrodynamic perturbations computed by MARS-F. By implementing the model directly into the MARS-F curve-linear magnetic coordinates, maximal accuracy in representing the full field perturbation is preserved. The updated code is utilized to study the high current RE beam loss in a post-disruption DIII-D plasma, revealing that a fast growing, n = 1 (n is the toroidal mode number) resistive kink instability, at ∼100 Gauss level, can induce significant fraction of RE loss, largely by perturbing drift orbits of REs. A ∼1000 Gauss perturbation fully terminates the RE beam, as found in both experiment and modeling. The 3D field induced loss increases with the perturbation amplitude but decreases with the particle energy. The loss fraction is generally not sensitive to the initial particle pitch angle. The particle velocity change, due to electric field acceleration/deceleration, small pitch angle scattering, synchrotron radiation and Bremsstrahlung, further perturbs the RE trajectory but plays a minor role in prompt RE loss within microseconds time scale. Therefore, the dominant dependencies are simply the RE energy and instability strength. For comparison, a resonant magnetic perturbation field, generated by 4 kAt n = 3 even parity I-coil currents in DIII-D and with the plasma response field included, is found to induce almost no loss for the same RE beam.

Resonant effects on the loss of energetic trapped ions induced by low-n resonant magnetic perturbations

The fast ion dynamics and the associated loss channels under resonant magnetic perturbation (RMP) fields are investigated numerically with newly upgraded Monte-Carlo code ORBIT-RF. Special attention is paid to the effect of low-n () perturbations on the confinement of energetic trapped ions in an equilibrium from EAST experiments. Here, n donates the toroidal mode number. It is found that the dominant loss mechanism under n = 2 RMP is essentially different from that under n = 1 RMP. For n = 2 RMP, the enhanced losses are mainly due to the single resonance with . Here, and are, respectively, the precession and bounce frequencies. For n = 1 RMP, the losses are mainly due to orbital stochasticity near the trapped-passing boundary, which is mainly promoted by the nonlinear resonances. It is found that the loss fraction has a sine-like dependence on the phase difference between the upper and lower coil currents under both n = 1 and n = 2 RMPs, which suggests the possibility of active control of fast ion profile by designing the spectrum. The loss rate under n = 2 RMP shows a linear dependence on the perturbation amplitude, while the loss rate under n = 1 RMP shows a quadratic dependence. The results here highlight the importance of nonlinear resonances in fast ion confinement under RMP, in addition to that of linear resonances frequently emphasized before.

Effect of Resonant Magnetic Perturbation Field on Energetic Ion Behavior in the Large Helical Device

Effect of Resonant Magnetic Perturbation Field on Energetic Ion Behavior in the Large Helical Device

L–H transition trigger physics in ITER-similar plasmas with applied n = 3 magnetic perturbations

The L–H transition power threshold PLH is observed to increase with applied n = 3 resonant magnetic perturbations (RMP) in ITER-similar-shape plasmas with balanced neutral beam torque injection in DIII-D. The increase is most pronounced with added electron–cyclotron heating: PLH increases with decreasing edge plasma collisionality as PLH/PLH-08 ~ (ν*)−0.5, where PLH-08 is the 2008 ITPA multi-machine power threshold scaling. This result raises concerns for H-mode access at low edge collisionality in ITER, where RMP may have to be applied before the L–H transition to safely suppress the first edge-localized mode. Non-axisymmetric modifications with RMP include a simultaneous reduction of the radial electric field (Er) well depth and E × B shear. This can be attributed to increasing edge toroidal co-current rotation, and is consistent with substantially increased local long-wavelength turbulence (measured via beam emission spectroscopy). At high RMP perturbation strength the edge electric field Er reverses sign locally (becomes positive), with changes in dominant turbulence modes. Edge magnetic stochasticity provides an attractive explanation of the observed modifications, and the observed changes in toroidal rotation and Er are consistent with a simple fluid model describing radial electron current flow along stochastic fieldlines. The observed collisionality dependence of the L-mode edge electric field with applied RMP is also qualitatively consistent with this model. Reflectometry data indicate a significant reduction of the normalized L-mode radial density gradient a/Ln at high RMP field with simultaneous increase in radial particle flux and electron thermal flux from power balance analysis. We conjecture that the increase of PLH with RMP results from the combined effects of reduced E × B flow shear (increasing turbulent transport levels) and toroidal/poloidal flow modulation due to edge stochasticity. Initial experiments indicate that non-resonant n = 3 magnetic perturbations lead only to relatively small changes in Er, E × B shear and fluctuation characteristics, and have less impact on the L–H transition power threshold. This motivates further exploration of the RMP spectrum dependence of PLH for possible mitigation of the observed threshold increase.

Gyrokinetic study of collisional resonant magnetic perturbation (RMP)-driven plasma density and heat transport in tokamak edge plasma using a magnetohydrodynamic screened RMP field

The total-f gyrokinetic particle-in-cell code XGC is applied to study various aspects of collisional transport in the tokamak edge pedestal in the presence of resonant magnetic perturbations (RMPs) calculated with M3D-C1. Simulations including the separatrix and scrape-off layer are exercised for a model DIII-D H-mode plasma. Neutral particle recycling is modeled by means of ionization and charge exchange with the plasma. A fully nonlinear Fokker–Planck collision operator is utilized to account for non-Maxwellian edge plasma. The study yields kinetic evidence that (i) neglecting the non-axisymmetric component of the RMP-generated electrostatic potential perturbation could yield a fictitiously high particle pump-out rate in the edge pedestal; that (ii) the experimental level of particle pump-out from the pedestal cannot be provided by collisional transport across Kolmogorov–Arnold–Moser surfaces except across the magnetic separatrix where stochastic magnetic field lines exist; that (iii) the H-mode type electron heat barrier is retained in the steep slope area under the M3D-C1 calculated RMPs; and that (iv) the stochastic electron heat-transport rate around the magnetic separatrix surface is much lower than the prediction by Rechester–Rosenbluth (1978 Phys. Rev. Lett. 40 38–41) and is qualitatively consistent with the experimentally observed rate. Detailed kinetic physics analysis on how the transport fluxes, electrostatic potential perturbation, and -well structure respond to onset of RMPs is also reported.

Formation of the non-axisymmetric helical current driven by a biased electrode in the scrape-off layer on J-TEXT

Resonant magnetic perturbations (RMPs), which change the magnetic topology, have been applied to control the edge-localized modes (ELMs) in many tokamak experiments. The non-axisymmetric helical currents induced by lower hybrid waves in the scrape-off layer (SOL) were observed to impact the magnetic topology profoundly and mitigated ELMs strongly in EAST (Liang et al 2013 Phys. Rev. Lett. 110 235002). In this paper, we present electrode biasing in the SOL as an alternative method to drive the non-axisymmetric helical currents in J-TEXT. A significant SOL current (e.g. ~150 A) was induced through the electrode with a biasing voltage of +200 V. The measured magnetic fields perturbed by the biasing current are consistent with those calculated from the helical currents flowing along the opened magnetic field lines in the SOL. This consistency reveals that the biased electrode induced non-axisymmetric helical currents in the SOL. The 3/1 component of the RMP field generated by the non-axisymmetric helical current can reach 13 Gauss kA−1 at the last closed flux surface. This indicates that the non-axisymmetric helical currents driven by biasing in the SOL might be an attractive new method for producing an RMP field and hence for controlling plasma instabilities such as ELMs.

Modeling 3D plasma boundary corrugation and tailoring toroidal torque profiles with resonant magnetic perturbation fields in ITER

Plasma response to 3D resonant magnetic perturbations (RMPs), applied for the purpose of controlling type-I edge localized modes (ELMs) in ITER with the baseline ELM control coils, is computed using a toroidal, resistive, full magneto-hydrodynamic model. Considered are five representative ITER plasmas, designed for different phases of the ITER exploration. The plasma response, measured by the plasma boundary corrugation, is found to be similar for the two DT scenarios at full plasma current (15 MA) and full toroidal field (5.3 T) but different fusion gain factors (Q = 5 versus Q = 10), indicating similar ELM control performance with the same RMP coil current configuration. The other plasma scenarios, with proportionally scaled down plasma current and toroidal field, can have different plasma boundary corrugation. The key plasma parameter affecting the response is the plasma toroidal flow near the pedestal region, which significantly varies depending on the transport model assumption for the toroidal momentum. Lower pedestal flow leads to a stronger edge peeling response from the plasma and thus probably a better ELM control. The optimal coil configuration for controlling type-I ELMs is similar for all four ITER plasmas with similar safety factor but different current levels, but is significantly different for the case at half plasma current (7.5 MA) and full field (5.3 T). On the other hand, for the purpose of controlling the radial profile of the plasma toroidal rotation in ITER using 3D fields, the relative amplitude of the toroidal torque density, between the plasma core and edge region, is optimized. Generally, a strong coupling between the core and edge torques is observed, largely due to the middle row ELM control coils. The best decoupling scheme of the core-edge torque distribution thus de-emphasizes the role of the middle row coils. Optimal coil current configurations are found for the ITER 15 MA/5.3 T Q = 10 plasma, that synergistically maximize the plasma edge-peeling response (indication for good ELM control) and the toroidal torque near the plasma edge (good for RMP field penetration through pedestal).

Overview of the recent experimental research on the J-TEXT tokamak

Recent J-TEXT research has highlighted the significance of the role that non-axisymmetric magnetic perturbations, so called three-dimensional (3D) magnetic perturbation (MP) fields, play in a fundamentally 2D concept, i.e. tokamaks. This paper presents the J-TEXT results achieved over the last two years, especially on the impacts of 3D MP fields on magnetohydrodynamic instabilities, plasma disruptions and plasma turbulence transport.On J-TEXT, the resonant MP (RMP) system, capable of providing either a static or a high frequency (up to 8 kHz) rotating RMP field, has been upgraded by adding a new set of 12 in-vessel saddle coils. The shattered pellet injection system was built in J-TEXT in the spring of 2018. The new capabilities advance J-TEXT to be at the forefront of international magnetic fusion facilities, allowing flexible study of 3D effects and disruption mitigation in a tokamak.The fast rotating RMP field has been successfully applied for avoidance of mode locking and the prevention of plasma disruption. A new control strategy, which applies pulsed RMP to the tearing mode only during the accelerating phase region, was proved by nonlinear numerical modelling to be efficient in accelerating mode rotation and even completely suppresses the mode. Remarkably, the rotating tearing mode was completely suppressed by the electrode biasing. The impacts of 3D magnetic topology on the turbulence has been investigated on J-TEXT. It is found that the fluctuations of electron density, electron temperature and plasma potential can be significantly modulated by the island structure, and a larger fluctuation level appears at the X-point of islands. The suppression of runaway electrons during disruptions is essential to the operation of ITER, and it has been reached by utilizing the 3D magnetic perturbations on J-TEXT. This may provide an alternative mechanism of runaway suppression for large-scale tokamaks and ITER.

Impact of a resonant magnetic perturbation field on impurity radiation, divertor footprint, and core plasma transport in attached and detached plasmas in the Large Helical Device

The effects of resonant magnetic perturbation (RMP) field on impurity radiation, divertor footprint distribution, and core plasma transport are investigated in the detachment discharges of the Large Helical Device (LHD). The RMP with m/n = 1/1 mode creates an edge magnetic island in the stochastic layer, which enhances the impurity emission from low charge states, C2+ and C3+, and then triggers a detachment transition. Emission from the higher charge states, C4+ and C5+, implies enhanced penetration of impurities during the detachment phase with RMP. The toroidal divertor particle flux distribution exhibits n = 1 mode structure in both the attached and detached phases, but with a large toroidal phase shift between the two phases. The distribution in the attached phase is well correlated with the magnetic footprint of field line connection length calculated by the vacuum approximation. During the detached phase, however, the phase shift is not well explained by the vacuum approximation, where a significant plasma response to the external RMP is observed. The energy confinement time becomes systematically shorter with RMP application due to the shrinkage of plasma volume caused by the edge magnetic island. On the other hand, the pressure profile during detachment with RMP is found to be more peaked than without RMP. The analysis using the core transport code TASK3D, considering the heating profiles of neutral beam injection, shows no significant transport degradation during detachment with RMP application, even with the enhanced radiation, reduced divertor flux, and possible impurity penetration.

Resistive versus ideal plasma response to RMP fields in DIII-D: roles of q95 and X-point geometry

Toroidal computation of the plasma response to the n = 2 (n is the toroidal mode number) resonant magnetic perturbation field, based on an H-mode plasma in DIII-D, is carried out for the purpose of investigating the role of the ideal versus resistive plasma response models while scanning the plasma safety factor (q) at the edge. Both response models, implemented in the MARS-F code (Liu et al 2000 Phys. Plasmas 7 3681), show significant amplification of the kink-peeling response in certain q-windows. A longstanding issue addressed in this work is the sensitivity of the q-window versus smoothing of the X-point geometry of the plasma separatrix. For this purpose, scan of the safety factor in 2D space (q95, qa) is carried out, where the q-value at 95% of the equilibrium poloidal flux, q95, is scanned by varying the total plasma current, whilst the edge safety factor qa is varied by gradually smoothing the X-point geometry at fixed total plasma current. Transition to the edge-peeling amplification domain is well described by simple analytic curves relating q95 and qa in the (q95, qa) space. These analytic curves not only help to quantify the sensitivity of the q95-window versus qa variation, but also establish the q95 window in the asymptotic limit of infinite qa (i.e. in the presence of true X-points). The ‘resonant’ q95 values (3.6, 4.05, 4.5) are found to roughly exhibit 1/n periodicity at infinite qa. Both ideal and resistive plasma response models, as well as the computed field at different pick-up locations, yield the same analytic curves describing transition to strong edge-peeling response. Detailed analysis of the computed plasma response and comparison with experiments are also performed.

Phase-detection-based feedback control for the power supply in tearing mode control system on J-TEXT

Tearing mode creates magnetic islands and easily causes a disruption in the tokamak. A new method to control the tearing mode has been proposed. The external resonant magnetic perturbation (RMP) coils are used to create modulated magnetic perturbation in certain magnetic island phase region. In the region of -0.5π to -π, RMP has an accelerating and stabilizing effects on tearing mode. To verify the mechanism, two variable frequency current-pulse power supplies have been developed, which have the maximum frequency of 8 kHz and the current of 3 kA. In this paper, the phase-detection-based and frequency feedback control are introduced. A fast island phase identification theory is used in the feedback control system to provide the magnetic island phase information in real time. It uses a poloidal array of Mirnov probes to identify the O-point of the magnetic island. There is a current amplitude feedback control to adjust the strength of RMP field. A bypass is used in the power supply to establish the output current quickly in initial period and protect the inverter. Finally, the feedback control system and the new power supplies have been used on the J-TEXT tokamak and two control methods are compared.

Magnetic field topology modeling under resonant magnetic perturbations on EAST

In order to understand the mechanism by which the resonant magnetic perturbation (RMP) mitigates or suppresses the edge-localized mode (ELM), the topological study of the edge magnetic field in ELM mitigation or suppression phase is a critical issue. To model the three-dimensional magnetic field topology superposed RMP on Experimental Advanced Superconducting Tokamak, a numerical model using the field line tracing method for both vacuum and ideal plasma response approximations is proposed. Using the numerical model, the topological change and the penetration depth of the stochastic field lines in the edge magnetic field are studied in an RMP experiment. Comparing profiles of minimum ρ on edge stochastic field lines and the particle flux pattern, the ideal plasma response changes the field line penetration depth while remaining similar profile relative to vacuum approximation. To mitigate and suppress ELM strongly, the deep penetration of RMP fields and topological changes of the edge magnetic field is a key from our modeling.

Impact of n = 1 field on the non-axisymmetric magnetic perturbations associated with the edge localized mode crashes in the ASDEX Upgrade tokamak

In the ASDEX Upgrade tokamak, the growth of non-axisymmetric magnetic perturbation (NAMP) associated with the ELM crash events has been observed, and both the poloidal and toroidal phases of NAMPs, measured by a set of Mirnov coils, were highly random. By applying an n = 1 magnetic perturbation (MP) field, the phases of NAMPs were locked to the phase of the total n = 1 resonant MP (RMP) field, which takes the plasma response to the MP field into account. This observation can be explained by the resonant electromagnetic J × B torque applied by the RMP field on a magnetic island formed due to the magnetic reconnection, which is predicted to occur during the ELM crashes by several numerical modelling results.

Conceptual design of the island divertor coils on the J-TEXT tokamak

A set of new resonant magnetic perturbation (RMP) coils is designed for the J-TEXT tokamak to form the island divertor (ID) configuration [F. Karger, Phys Lett A, 61 (1977) 385]. This design is aiming at investigating the effect of ID on the peak heat load reduction in a tokamak. The RMP field generated by these new coils can produce magnetic island in the plasma boundary. The field line of this magnetic island is opened by divertor targets, so as to form the island divertor configuration. Therefore, the edge island should be a vacuum island, which can be described by an analytical mode with assuming linear superposition of the plasma equilibrium field and the magnetic perturbation in a vacuum approximation. Numerical calculations have been carried out to calculate several parameters for the island divertor configuration such as the perturbed magnetic field generated by the coils, its spectrum, the field line tracing and the Poincaré plot. Conceptual design is based on the m/n = 4/1 magnetic island, which can be generated by either 16 out-vessel saddle coils or 8 in-vessel S-type modular coils. Here, m and n are the poloidal and toroidal mode numbers respectively. The ID configuration can be then established by the boundary 4/1 island intersecting with proper divertor targets.

Influence of resonant magnetic perturbations and induced islands on plasma rotations and turbulence properties in the J-TEXT tokamak

Dedicated experiments have been carried out at the J-TEXT tokamak for investigating plasma responses to the externally applied resonant magnetic perturbation (RMP) field with various RMP currents under four different toroidal phases. After its penetration, the dominant component of the RMP resonated at q = 2 surface and excited an m/n = 2/1 magnetic island, which rotated poloidally when changing the toroidal phase of the RMP. The experimental results show significant influence of the RMP on plasma toroidal and perpendicular rotations, density fluctuations and geodesic acoustic modes (GAMs) as well as nonlinear interaction of ambient turbulence. Whereas the plasma rotations do not show big difference at the RMP-induced island O- and X-point, the turbulence level is substantially lower at the island O-point due to reduced local temperature gradient. The GAM zonal flows outside the island area are profoundly affected by the RMP in various RMP phases. Moreover, it was found that under certain RMP currents the nonlinear coupling of ambient turbulence was considerably enhanced, no matter of at the island O- or X-point. The results suggest a possible controlling role of the RMP in regulating the nonlinear interplay of electrostatic turbulence.

Enhanced fast ion prompt loss due to resonant magnetic perturbations in KSTAR

We report a numerical study for the impact of resonant magnetic perturbation (RMP) on fast ion prompt loss in KSTAR using full orbit following simulation. Experimental observation in KSTAR indicates a sudden increase in RMP-induced fast ion prompt loss when the applied RMP field exceeds a threshold amplitude. Full orbit simulation with 3D perturbed equilibrium computed by the ideal plasma response reproduces the experimentally observed feature of RMP-induced prompt loss of fast ions and the existence of threshold RMP amplitude. Simulation with vacuum fields only shows a small increase in the fast ion loss that is insufficient to explain the observation. We show that the conservation of canonical angular momentum is broken due to the RMP during the fast ion transit, which is consistent with the enhanced fast ion loss above the threshold RMP amplitude. Phase space analysis suggests that trapped and intermediate pitch passing particles modified from initial high pitch passing ones are responsible for the threshold behavior of the fast ion loss in the simulation, while the phase space distribution of lost particles depends on the RMP field configuration.

Core plasma confinement during detachment transition with RMP application in LHD

The core plasma confinement during detachment phase is investigated in the discharges with application of resonant magnetic perturbation (RMP) field in LHD. The RMP application creates a remnant magnetic island in the edge stochastic layer, which largely changes the plasma parameter profiles including impurity radiation. The electron temperature and pressure profiles are flattened at the island, while the electron density is slightly peaked at the edge of the island. The estimated impurity radiation profile is enhanced and fixed around the magnetic island during the detached phase, where the discharge is stably sustained with controlled level of radiation. Without RMP, the radiation penetrates the confinement region, leading to radiation collapse. It is found that in the case of the RMP application the plasma stored energy increases discontinuously at the detachment transition. In spite of the reduced effective plasma volume caused by the edge magnetic island and by the enhanced radiation there, the central plasma pressure finally exceeds the case without RMP. This is caused by the pressure profile peaking at the central region in the case with RMP. These results indicate clear change of core plasma confinement during the detached phase with RMP.

Screening of resonant magnetic perturbation fields by poloidally varying toroidal plasma rotation

The angular frequency of the subsonic equilibrium toroidal flow in a tokamak plasma is often assumed constant at magnetic flux surfaces, i.e., the rotation frequency does not vary along the poloidal angle of the flux surface. However, there are several cases where this symmetry is broken. An interesting situation is a recently observed complex flow pattern induced by magnetic field line ergodization, in the presence of the tri-dimensional (3-D) resonant magnetic perturbation (RMP) [Schmitz et al., Nucl. Fusion 56, 066008 (2016)]. A new flow model including poloidally varying rotation frequencies has been implemented in the full resistive linear MHD code MARS-F [Liu et al., Phys. Plasmas 7, 3681 (2000)], allowing poloidal variation of the angular frequency of the equilibrium toroidal rotation in a generic toroidal geometry. The effect of this asymmetric flow, on top of a poloidally symmetric toroidal flow, on the plasma response to RMP fields is numerically investigated. It is found that a poloidally varying toroidal flow component enhances the favourable average curvature induced plasma screening of the applied 3-D field, for low toroidal flow velocities. At faster flow, when the resistive-inertial response becomes important, the asymmetric toroidal flow reduces the plasma screening. The largest effect is found to come from the m = 1 component of the poloidal asymmetry in the toroidal rotation frequency.

Toroidal plasma response based ELM control coil design for EU DEMO

Magnetic coil design study is carried out, for the purpose of mitigating or suppressing the edge localized modes (ELMs) in a EU DEMO reference scenario. The coil design, including both the coil geometry and the coil current requirement, is based on criteria derived from the linear, full toroidal plasma response computed by the MARS-F code (Liu et al 2000 Phys. Plasma 7 3681). With a single midplane row of coils, a coil size covering about 30°–50° poloidal angle of the torus is found to be optimal for ELM control using the n > 2 resonant magnetic perturbation (RMP) field (n is the toroidal mode number). For off-midplane coils, the coils’ poloidal location, as well as the relative toroidal phase (coil phasing) between the upper and lower rows of coils, also sensitively affects the ELM control according to the specified criteria. Assuming that the optimal coil phasing can always be straightforwardly implemented, following a simple analytic model derived from toroidal computations, it is better to place the two off-midplane rows of coils near the midplane, in order to maximize the resonant field amplitude and to have larger effects on ELMs. With the same coil current, the ex-vessel coils can be made as effective as the in-vessel coils, at the expense of increasing the ex-vessel coils’ size. This is however possible only for low-n (n = 1–3) RMP fields. With these low-n fields, and assuming 300 kAt maximal coil current, the computed plasma displacement near the X-point can meet the 10 mm level, which we use as the conservative indicator for achieving ELM mitigation in EU DEMO. The risk of partial control coil failure in EU DEMO is also assessed based on toroidal modeling, indicating that the large n = 1 sideband due to coil failure may need to be corrected, if the nominal n > 1 coil configurations are used for ELM control in EU DEMO.

Extreme Ultraviolet Spectroscopy Applied to Study RMP Effects on Core Impurity Concentration in EAST

A space-resolved extreme ultraviolet (EUV) spectrometer has been used to observe the spatial distribution and temporal behavior of core impurity emissions at the experimental advanced superconducting tokamak (EAST), evaluating the effects of resonant magnetic perturbations (RMPs) on impurity concentration. The vertical profiles of impurity emissions from the 0 ≤ Z ≤ 450 mm range results in spectra in the wavelength range of 30 A $\le \lambda \le 500\,{\mathring {\mathrm {A}}}$ . Line emissions of impurity carbon, lithium, and iron were observed for C VI (33.7 A, 2p–1s), Li III (135 A, 2p–1s), and Fe XXIII (132.9 A, 1s22s2p–1s22s2), respectively, whereas the unresolved transition array (UTA) of tungsten in the wavelength range of $\lambda = 48$ to 70 A is monitored to study tungsten behavior with RMP. It is clearly observed that the intensities of C VI, Li III, Fe XXIII, and W-UTA emissions are reduced by the application of RMP fields, during stages of edge-localized modes (ELMs). In addition, the reduction in Fe and W emissions with $n = 1$ and 2 (n: toroidal mode number) RMP is more significant than that of carbon and lithium emissions, i.e., ~50% to 70% for Fe XXIII and W-UTA, and ~30% for C VI and Li III. Considering that the changes in $n_{e}$ and $T_{e}$ cannot account for the impurity emissions mitigation, the EUV measurements may indicate that RMP can significantly and selectively decrease the impurity accumulation in the core region with slight effects on the main plasma. Spatial distributions of impurity emissions are also measured for different impurity species using the EUV spectrometer, confirming the space-resolved diagnostic’s feasibility to study RMP effects on core impurity concentration.