A systematic investigation on the plasma response to the externally applied resonant magnetic perturbation (RMP) field, for the purpose of controlling edge localized modes (ELMs), is carried out for an EU DEMO reference plasma. Particular emphasis is on the role of kinetic effects associated with both thermal particles and fusion-born alphas. The single fluid, resistive model predicts a large peak amplification of the n=1 (n is the toroidal mode number) plasma response for the target equilibrium, which is found to be close to the Troyon no-wall limit. More advanced response model, including kinetic resonances between the RMP perturbation and drift motions of thermal and energetic particles, on the other hand finds strong suppression of the n=1 field amplification. A major role is played by the precessional drift resonance of fusion-born alphas. A strong parallel sound wave damping (SWD) model is found to well reproduce the full kinetic response results for the DEMO plasma, in terms of both the resonant field response amplitude and the plasma displacement. Finally, both fluid and kinetic models produce similar response for the n=2 and 3 RMP fields for the considered DEMO plasma, whilst kinetic effects again become important for the n=4 RMP due to proximity of the reference plasma to the no-wall limit for the n=4 ideal kink instability.

It is well known that large-scale type-I edge localized modes (ELMs) may pose serious risks to machine components in future large fusion devices. The resonant magnetic perturbation (RMP), generated by magnetic coils external to the plasma, can either suppress or mitigate ELMs, as has been shown in recent experiments on several present-day fusion devices. Understanding ELM control with RMP may involve various physics. This work focuses on understanding of the roles of three key physical quantities:the edge safety factor, the RMP coil current and the particle drift kinetic effects from thermal and fusion-born α-particles. Full toroidal computations are performed using the MARS-F/K codes. It shows that both of the plasma response based figures of merit-one is the pitch resonant radial field component near the plasma edge and the other is the plasma displacement near the X-point of the separatrix-consistently yield the same periodic amplification as <i>q</i>₉₅ varies. The number of peaks <i>y</i> is positively correlated with the toroidal number <i>n</i>, i.e., <i>y</i>≈<i>n</i>△<i>q</i>₉₅ with △<i>q</i>₉₅=3.5. The peak window in <i>q</i>₉₅ occurs when a new resonant surface passes through a specific region of the plasma edge. Two-dimensional parameter scans, for the edge safety factor and the coil phasing between the upper and lower rows of coils, yield a linear dependence between the optimal/worst current phase difference and <i>q</i>₉₅, which can be well fitted by a simple analytic model. The optimal value of coil current amplitude is sensitive to <i>n</i>. Compared with the same current amplitude assumed for the two/three rows of coils, the optimal current amplitude can increase the ξ_X but does not alter the prediction of the relative toroidal phase difference. More advanced response model, including kinetic resonances between the RMP perturbation and drift motions of thermal particles and fusion-born alphas, shows that the modification of kinetic effects should be considered in order to better describe the plasma response to RMP fields in high-<i>β</i> plasmas. The fluid response model with a strong parallel sound wave damping (<i>κ</i>_||=1.5) can well predict the plasma response for the DEMO-like equilibria. For low β plasma, the kinetic response is consistent with the fluid response, independent of the presence or absence of a strong parallel sound wave damping.