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Title:  An Alpha LossCone Instability in the Central Cell of a Tandem Mirror Reactor 
Author(s):  Ho, Shu Kay 
Department / Program:  Nuclear Engineering 
Discipline:  Nuclear Engineering 
Degree Granting Institution:  University of Illinois at UrbanaChampaign 
Degree:  Ph.D. 
Genre:  Dissertation 
Subject(s):  Physics, Fluid and Plasma 
Abstract:  DT fusionborn alpha particles are mirrorconfined in the central cell of a tandem mirror reactor. The resulting anisotropic losscone distribution of the alpha particles in velocity space is capable of destabilizing low frequency plasma waves, thus affecting the energy balance in a tandem mirror plasma. The low frequency waves of a cold, cylindrical, sharpboundary, DT plasma are studied. Techniques have been developed to trace the wave propagation regions and search the wave eigenfrequencies. Three branches of waves are found, namely the Alfven, hybrid, and fast waves; but only the Alfven wave is destabilized by the alpha losscone instability. The modeling of the alpha distribution function for the linear and quasilinear instability calculations is done by a diffusionfront method and a numerical finite difference method, respectively. Their validity is established by comparing them with a converged 80term Legendre function expansion model of the alpha distribution. The growth rate of the instability is basically determined by the alpha number density, the losscone angle, and the polarization of the wave. These quantities are in turn mainly affected by the density and temperature of the plasma ions and electrons, the mirror ratio, and the plasma radius. A stability boundary in the nT plane is constructed to locate the stable and unstable regions. The instability is found to occur with moderate values of plasma density and temperature. A $1{1\over2}$D quasilinear diffusion code is developed to study the nonlinear evolution of the alpha distribution function due to enhanced diffusion in velocity space and radial position driven by the unstable Alfven wave. It is found that velocityspace diffusion pitchangle scattering of the resonant alphas into the losscone causes significant losses while radial diffusion driven leakage is negligible for a reactorsize plasma. For a typical tandem mirror reactor design (e.g. the MARS design), the added alpha density and energy losses due to the instability are 36% and 47%, respectively. As a result, the alpha plasma heating is greatly reduced that ignition in the central cell cannot not be achieved. For MARS, an additional heating power of about 200 MW is required to compensate for the alpha loss due to the instability. 
Issue Date:  1987 
Type:  Text 
Description:  225 p. Thesis (Ph.D.)University of Illinois at UrbanaChampaign, 1987. 
URI:  http://hdl.handle.net/2142/70908 
Other Identifier(s):  (UMI)AAI8721658 
Date Available in IDEALS:  20141216 
Date Deposited:  1987 
This item appears in the following Collection(s)

Dissertations and Theses  Nuclear, Plasma, and Radiological Engineering

Graduate Dissertations and Theses at Illinois
Graduate Theses and Dissertations at Illinois