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High resolution detection and excitation of resonant magnetic perturbations in a wall-stabilized tokamaka)
a)Paper JI2 5, Bull. Am. Phys. Soc. 56, 137 (2011).
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View: Figures


Image of FIG. 1.
FIG. 1.

Illustration of the new HBT-EP modular instrumented control shell. HBT-EPs control wall has 216 precisely located magnetic sensors, 120 modular feedback coils, for investigating MHD interactions between tokamak plasmas and surrounding structures.

Image of FIG. 2.
FIG. 2.

Contour plots of the perturbed magnetic field as a function of time during a period of saturated kink mode activity. (a) A poloidal array showing that the m = 3 and (b) toroidal array indicating that n = 1 is the dominant spatial mode structure of the field fluctuation.

Image of FIG. 3.
FIG. 3.

Biorthogonal decomposition spatial eigen modes for the fluctuations show in Fig. 2 indicating the multimode nature of naturally occurring kinks. (a1)-(a2) The m/n = 3/1 kink mode, (b1)-(b2) the m/n = 6/2 kink mode, and (c1)-(c2) a possible m/n = 9/3 kink component.

Image of FIG. 4.
FIG. 4.

Biorthogonal decomposition temporal mode (kink amplitude) behavior indicates that the m/n = 6/2 kink is not a nonlinear harmonic of the m/n = 3/1 kink given its independent temporal dynamics. (a) Contour plot of a poloidal sensor array. (b1 to b3) Spatial, temporal, and phase of m = 3 mode. (c1 to c3) Spatial, temporal, and phase of m = 6 mode.

Image of FIG. 5.
FIG. 5.

(a) Time evolution of the edge safety factor, (b) current in one of the control coils used to apply perturbed fields to the plasma, and (c) two magnetic sensors separated by 180° show clear measurement of n = 1 plasma response when the perturbation is applied to the plasma.

Image of FIG. 6.
FIG. 6.

Application of a resonant magnetic perturbation to a pre-existing saturated kink mode. (a) Contour plot showing magnetic field fluctuations from a poloidal array of sensors and (b) the time history of the applied radial saddle coil field.

Image of FIG. 7.
FIG. 7.

Kink plasma response measured as a function of the applied radial field strength normalized to the toroidal field on axis. Three distinct response regimes are observed. A linear regime at low applied fields, a region of saturated response, and if the applied field is large disruptions are induced in the plasma (shown shaded). Actual field amplitudes for disrupting plasmas are not shown.

Image of FIG. 8.
FIG. 8.

The same plasma ensemble data set shown in Figure 7, now sorted as a function of the time averaged edge safety during the period of application of the resonant field. (a) For edge safety factor between 2.7 and 2.85 a linear response is observed up to the disruptive limit. (b) For edge safety factor near the qa = 3 resonance kink response is observed to saturate.

Image of FIG. 9.
FIG. 9.

For an applied field in the linear response regime, the measured plasma response is observed to be a maximum when the qa = 3 resonance is external to the plasma edge indicative of a kink mode type response.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: High resolution detection and excitation of resonant magnetic perturbations in a wall-stabilized tokamaka)