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Characterization of low-frequency electric potential oscillations near the edge of a plasma confined by a levitated magnetic dipole

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dc.contributor.advisor Jay Kesner and Darren T. Garnier. en_US
dc.contributor.author Bergmann, Ryan M en_US
dc.contributor.other Massachusetts Institute of Technology. Dept. of Nuclear Science and Engineering. en_US
dc.date.accessioned 2010-03-25T15:19:29Z
dc.date.available 2010-03-25T15:19:29Z
dc.date.copyright 2009 en_US
dc.date.issued 2009 en_US
dc.identifier.uri http://hdl.handle.net/1721.1/53240
dc.description Thesis (S.M. and S.B.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2009. en_US
dc.description Cataloged from PDF version of thesis. en_US
dc.description Includes bibliographical references (p. 95-96). en_US
dc.description.abstract A vertically adjustable electrostatic probe array was made to observe the previously seen low-frequency angular oscillations in LDX and identify if they are related to computationally expected convective cells. The array rests one meter from the centerline and measures edge fluctuations at field lines near the separatrix. It spans ninety degrees and has 24 probes mounted on it for total probe tip separation of 6.8cm. Bispectral analysis of the fluctuations show that that an inverse cascade of energy is present at times in LDX. The cascade transfers energy from small spatial scale structures to large scale structures. The wavenumber spectrum is xc k-1.4 to cx k-25 at high wavenumbers, which encompasses the inverse energy cascade regime of c k-5/3. The plasma also has a linear dispersion relation which gives a phase velocity of 2-16 k. This phase velocity is inversely correlated with neutral gas pressure in the vessel. The velocity also has a local maximum at 5 pTorr which is the pressure that produces maximum plasma density. The radial E x B drift velocities are observed to have a mean near zero, which indicates a closed structure like a convective cell. The instantaneous radial drift velocities are on the order of the ion sound speed, which is 35 km/s. en_US
dc.description.statementofresponsibility by Ryan M. Bergmann. en_US
dc.format.extent xi, 96 p. en_US
dc.language.iso eng en_US
dc.publisher Massachusetts Institute of Technology en_US
dc.rights M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission. en_US
dc.rights.uri http://dspace.mit.edu/handle/1721.1/7582 en_US
dc.subject Nuclear Science and Engineering. en_US
dc.title Characterization of low-frequency electric potential oscillations near the edge of a plasma confined by a levitated magnetic dipole en_US
dc.type Thesis en_US
dc.description.degree S.M.and S.B. en_US
dc.contributor.department Massachusetts Institute of Technology. Dept. of Nuclear Science and Engineering. en_US
dc.identifier.oclc 535773556 en_US


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