The growth of density fluctuations in a finite sized inhomogeneous plasma

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.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Year dc:date

2011

Author dc:creator

• Peterson, Robert Ross

Contributors dc:contributor

• Adler, F.T.

• density fluctuation
• finite sized inhomogeneous plasma
• electromagnetic radiation absorption
• laser-fusion physics

Statement dc:rights

• 1979 Robert Ross Peterson

Language dc:language

en

Identifier

360803

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/25574