Effect of magnetic islands on the local plasma behavior in a tokamak experiment

Experiments provide simultaneous, local measurements of the pressure and ion velocity perturbations from rotating m/n=2/1 magnetic islands using Mach probes in a tokamak. Measurements were made both inside and around the islands. Pressure perturbations followed the magnetic island motion for both naturally rotating and actively controlled islands. The toroidal ion velocity profile was sharply peaked near the center of the 2/1 magnetic island, and the magnitude of this peak was ∼30% of the magnetic island velocity. Active rotation control experiments also successfully changed the ion fluid velocity. The acceleration of the ion fluid was ∼20% of that experienced by the magnetic islands. Understanding the effect of magnetic islands on the pressure and ion velocity profiles is crucial for both fundamental plasma studies and the development of more efficient tokamak using advanced tokamak concepts