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An Experimental and Theoretical Investigation of a Finite Beta Modified Drift Wave


Fredrickson, Eric Donald (1985) An Experimental and Theoretical Investigation of a Finite Beta Modified Drift Wave. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/fdcx-m289.


The saturated slate of a low frequency coherent, m=2, global mode has been studied in the Encore tokamak using probe techniques. The mode is found to have large fluctuations in density, electron temperature, space potential and magnetic field. The equilibrium plasma characteristics were also determined with probe measurements. Magnetic probes were used to determine the radial profile of the poloidal magnetic field, from which the rotational transform and current density profiles could be deduced. A Langmuir probe was used to measure radial profiles of the density, electron temperature and space potential.

By comparing the experimental measurements with the predictions of a computer code. the mode was identified as a finite βτ modified drift wave. The code is based on a linear, two-fluid theory of the coupling of drift and shear-Alfven modes. Of the two shear-Alfven solutions and the drift branch solution, it was found that the drift wave solution best fit the observed frequency of the mode and the relative amplitudes of the density, space potential and magnetic fluctuations. The identification of the mode as a finite βτ modified drift wave means that the mode is more closely related to the higher frequency, turbulent fluctuations observed on larger machines. rather than the lower frequency, coherent Mirnov oscillations.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Applied Physics
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Applied Physics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Bellan, Paul Murray
Thesis Committee:
  • Bellan, Paul Murray (chair)
  • Gould, Roy Walter
  • Corngold, Noel Robert
  • Liepmann, Hans Wolfgang
  • Moffet, Alan Theodore
Defense Date:30 July 1984
Funding AgencyGrant Number
Department of Energy (DOE)DE-FG03-84ER53173
Record Number:CaltechTHESIS:12112018-111733645
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:11306
Deposited By: Benjamin Perez
Deposited On:11 Dec 2018 19:56
Last Modified:16 Apr 2021 23:07

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