The growth of density fluctuations in a finite sized inhomogeneous plasma
Peterson, Robert Ross
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https://hdl.handle.net/2142/25574
Description
Title
The growth of density fluctuations in a finite sized inhomogeneous plasma
Author(s)
Peterson, Robert Ross
Issue Date
1979
Doctoral Committee Chair(s)
Adler, F.T.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
density fluctuation
finite sized inhomogeneous plasma
electromagnetic radiation absorption
laser-fusion physics
Language
en
Abstract
The details of the absorption of electromagnetic radiation in a
plasma are important to the physics of laser-fusion. We have studied the growth of density fluctuations in an inhomogeneous plasma because two mechanisms of absorption, anomalous absorption due to the growth of parametric instabilities and absorption by short wavelength density fluctuations, may be influenced by the growth of density fluctuations. An inhomogeneous bounded plasmas is modeled to represent a laser-fusion plasma; part of the plasma, which has been ablated from the main body of the plasma, is accounted
for by adjustment of the boundary conditions on the density fluctuations. A system of hydrodynamic wave equations has been developed to study the
growth of density fluctuations in an inhomogeneous bounded plasma. This formalism differs from established formalisms in that the spatial and temporal behaviors are separated by expanding the density fluctuations in eigenfunctions of the bounded inhomogeneous plasma. A variational technique has been developed to calculate these spatial eigenfunctions. Three separate approximations for the resulting temporal equations have been taken, which show that coupling between modes due to the beating of spatial eigenfunctions with the spatial profile of the incident electric field slows the growth of density fluctuations. Finally, the threshold electric field for the onset of instability is determined as a function of the size of the plasma, the wave-number of the density fluctuations and the density of the plasma.
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