Investigation of asymmetric plasma blob dynamics

Abstract

The dynamics of asymmetric blobs is investigated in the Versatile Toroidal Facility (VTF) at MIT. Blobs are local regions of enhanced plasma density. Blobs are relevant to several areas of physics research, including fusion experiments. Understanding blob dynamics is important because blobs affect plasma confinement, a key issue for fusion experiments. The blobs in this experiment are created under varying magnetic and neutral gas density conditions. We explore several methods for creating these asymmetric blobs and offer theoretical predictions for some of the behavior. Four arrays of Langmuir probes are placed inside the toroidal chamber to measure plasma density. Data collected is shown to confirm the existence of a plasma blob and is analyzed to extract radial and toroidal information. Radial propagation is compared with a previous experiment that featured symmetric blobs. We find that the presence of a vertical magnetic field is a significant variable for radial speed. Toroidal motion is shown to be very fast relative to the radial propagation. This experiment serves as a useful reference for future research on asymmetric blobs.