Propagation Dynamics Associated with Resonant Magnetic Perturbation Fields in High-Confinement Mode Plasmas inside the KSTAR Tokamak

The propagation dynamics of resonant magnetic perturbation fields in KSTAR $H$-mode plasmas with injection of small edge perturbations produced by a supersonic molecular beam injection is reported for the first time. The results show that the perturbation field first excites a plasma response on the $q=3$ magnetic surface and then propagates inward to the $q=2$ surface with a radially averaged propagation velocity of resonant magnetic perturbations field equal to $32.5\mathrm{m}/\mathrm{s}$. As a result, the perturbation field brakes the toroidal rotation on the $q=3$ surface first causing a momentum transport perturbation that propagates both inward and outward. A higher density fluctuation level is observed. The propagation velocity of the resonant magnetic perturbations field is larger than the radial propagation velocity of the perturbation in the toroidal rotation.

Figure 1

(a) $V_{\varphi }$ is modulated by small edge perturbations from the SMBI during the steady state RMP phase. (b) Spectrum of the Mirnov signal in arbitrary units. (c) Red curve is the current control signal of three RMP coils with $\sim 2.4\mathrm{kA}$ and the blue pulses are the SMBI control signal.

Figure 2

(a) Safety factor profile and (b) phase profile of the perturbed $V_{\varphi }$. Vertical double red lines and red bars represent the uncertainties of the safety factor profiles and the minimum phase locations, respectively. The dashed lines indicate the locations of the $q=3$ and $q=2$ rational surfaces separated by 13 cm.

Figure 3

(a) $\mathrm{\Delta }{V}_{\varphi }$ (in $\mathrm{km}/\mathrm{s}$) as a function of time following the application of the RMP field. (b) $V_{\varphi }$ profiles without and with RMP for shot 10 884 as shown using the black curve and the red curve, respectively. The $\mathrm{\Delta }{V}_{\varphi }$ is shown as blue dashed line. The inner small box represents the RMP time trace, and the black and red vertical lines in the small box indicate the time points of the $V_{\varphi }$ profiles obtained at 8.9 and 9.15 s, respectively.

Figure 4

(a) Coherence coefficient ($\gamma$) profiles and radial correlation length ($L_r$) without RMP during 9.0–9.006 s and (b) the same as in (a) but with RMP during 9.7–9.706 s. No SMBI pulses were injected during the time windows. The position of the pedestal top is at $\rho =0.9$, as shown by the red dotted line.