Examining how a 2/1 magnetic island responds to variations in differential rotation at DIII-D

Magnetic islands driven by Neoclassical Tearing Modes (NTMs) are a leading cause of disruptions in tokamaks. Differential rotation between the island and the surrounding plasma is theorized to drive a stabilizing current via ambipolar drifts, which suppresses island growth. To directly test this effect, we used DIII-D’s RMP coils to reproducibly generate slowly rotating 2/1 islands while a sweep in torque was performed to vary the differential rotation. This controlled approach enables repeatable studies with spatial resolution not achievable using naturally occurring NTMs. Superior resolution allows more precise probing of the island-plasma boundary. Using magnetic probes, Electron Cyclotron Emission, Thomson Scattering, Beam Emission Spectroscopy, and Charge Exchange Recombination diagnostics, we examine how temperature, density, turbulence, and rotation profiles across the island respond to differential rotation, and assess the island dynamics in comparison with theoretical predictions and drift-kinetic models of current stabilization.

Work supported by the U.S. DOE under contract Award DE-FC02-04ER54698