Characterization of ion polarization current stabilization (Tearing Mode) for IBS
2024 Research Campaign, Transient Control
Purpose of Experiment
Recent database analyses of DIII-D ITER baseline scenario discharges have revealed that the loss of differential rotation enabling transient MHD to trigger disruptive magnetic islands. Theoretically, rotation influences the governing equations of magnetic islands through the polarization current. Consequently, controlling the polarization current may offer a means to regulate plasma stability. This can be achieved in practice either by adjusting the island drift frequency, modifying the plasma rotation relative to the island, or by altering the density. This experiment aims to systematically measure the impact of plasma drift and density on magnetic island stability under well-controlled and reproducible plasma conditions.
Experimental Approach
Resonant magnetic perturbation (RMP) coils will be employed in low-density, L-mode plasma conditions to induce the growth of magnetic islands. Once the island width has reached saturation, the perturbation coil current will be reduced, allowing the magnetic island to decay to a new state determined by the lower perturbation current, while keeping it fixed in the laboratory frame to avoid undesirable complications that could arise if the island unlock and began to spin. The decay rate of the magnetic island will serve as a metric for evaluating stability. Through a series of repeated RMP perturbations, the influence of plasma rotation and density on island stability will be investigated while varying the net input torque and density.
See more details, including project leads, at U.S. Department of Energy, Office of Scientific and Technical Information (OSTI).