Laboratory Studies of Avalanche Transport in Magnetized Plasmas

University Of California-Los Angeles, Los Angeles CA

Investigators

Abstract

The goal of this project is to improve our understanding of avalanches in a plasma, a cloud of ionized gas, that is permeated by a magnetic field. Avalanches are sudden events that cause major changes over an extended region of a physical system. Although the concept is commonly associated with catastrophic "snow avalanches", the general phenomenon occurs widely in both natural and artificial systems. A typical driver and source of energy for an avalanche is a sharp change in one of the parameters that describes the underlying system. This project is a synergistic experimental and theoretical study of avalanches triggered by a steep slope in plasma temperature and density across a magnetic field. This is a situation widely encountered in natural plasmas, such as in magnetic field structures on the Sun and around the Earth, and has to be accounted for in any design of a magnetic fusion device. The project will involve a graduate student who will gain a unique perspective on modern experimental techniques and will also participate in theoretical and numerical modeling work. To date, the majority of experimental information about avalanche transport in a magnetized plasma has been obtained in devices designed for fusion studies. However, due to the complexity of these devices, it has proven difficult to unravel the underlying physical mechanisms of the process. This project aims to significantly expand the experimental knowledge base by exploring the behavior of a well-defined plasma configuration that exhibits repeatable, controllable avalanche events. The data obtained in the experiments will provide quantitative information about the role of self-organized criticality dynamics, the formation and evolution of streamers, the effect of flows and flow shear, and the manifestation of nonlocal transport of both temperature and density. These topics are at the frontier of plasma science and are the subject of numerous ongoing theoretical and computational studies.