Spectroscopic investigation on confinement properties of spheromak
Abstract
The spheromak concept offers advantages over other magnetic confinement fusion devices due to is simple geometry. Unlike the tokamak there need be no material structure linking the plasma. Coupled with the possibility of Ohmic heating to ignition temperatures, the spheromak provides an attractive alternative. The most stable spheromak equilibrium is that of the force free or Taylor state where $\vec j$ $\times$ $\vec B$ = $\nabla$p $\sim$ 0 with the constraint of magnetic helicity conservation. Deviations in the current density profile from this idealized condition are often observed and, in many instances, a relaxation back to the Taylor state has been seen. Finite pressure gradients may also provide a source of free energy to drive instabilities. Since classical plasma confinement tends to produce such gradients, there may exist means by which to suppress the natural peaking of $n\sb e$, $T\sb e$, and j. The purpose of this work is to investigate these phenomena by conducting experiments which reveal some of the transport characteristics of the S $-$ 1 spheromak at the Princeton Plasma Physics Laboratory. By learning the effects of these phenomena, a description of physical mechanisms may be developed which will not only increase our understanding of transport phenomena in magnetic confinement devices but will possibly allow us to suggest means to suppress or control the features associated with poor confinement in spheromaks. Of particular interest are the anomalously small values of particle and energy confinement times observed in the experiment over those predicted by classical theory. In addition, ion temperatures well in excess of the classically predicted values due to electron-ion coupling are observed. The role of neutral particles is considered as it relates to both resistive decay and the removal of ion energy through charge exchange. The research herein is focused on the documentation and understanding of such phenomena.
Degree
Ph.D.
Advisors
Choi, Purdue University.
Subject Area
Nuclear physics
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.