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Abraham Bers. Decker, Joan, 1977- Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science. Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science 2006-08-25T18:58:20Z 2006-08-25T18:58:20Z 2005 2005 http://hdl.handle.net/1721.1/33937 67549860 Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005. Includes bibliographical references (p. 333-340). The steady-state confinement of tokamak plasmas in a fusion reactor requires non-inductively driven toroidal currents. Radio frequency waves in the electron cyclotron (EC) range of frequencies can drive localized currents and are thus particularly attractive for control of the current profile. In the high-[beta] regimes of spherical tokamaks (ST) such as NSTX and MAST, heating and current drive (CD) by conventional electron cyclotron waves is not possible. However, electron Bernstein waves (EBW) have been proposed as an alternative for CD in these overdense devices. Given the important role predicted for CD by EBWs in high-[beta] STs, a detailed study of EBWCD must be undertaken. In this thesis a systematic analysis of EBWCD is provided. In particular, the characteristics of EBWs, the physics of resonant wave-particle interaction, and the CD mechanisms are investigated in detail. The CD efficiency and the current deposition profile are calculated using the numerical code DKE, which solve the drift-kinetic equation. Two scenarios for EBWCD are identified. The first scenario consists of approaching a harmonic of the EC resonance from a lower B-field region and drives current in the plasma core using the Fisch-Boozer mechanism. (cont.) The other scenario consists of approaching a harmonic of the EC resonance from a higher B-field region and drives current off-axis on the outboard side using the Ohkawa mechanism. Both schemes drive current in the toroidal direction opposite to the parallel wave vector. The EBWCI) efficiency is found to be higher than ECCD efficiency because the EBW power is deposited in the tail of the electron distribution function. The results of this thesis confirm the important role of EBWs for driving currents in high-[beta] plasmas. The analytical and numerical tools developed as part of this thesis can be used to design, predict, and analyze future EBWCD experiments. Among these tools is the kinetic solver DKE, which can be used for electron current drive calculations in toroidal plasmas for different types of radio-frequency waves, such as lower hybrid and electron cyclotron waves. by Joan Decker. Ph.D. 340 p. 14541425 bytes 14556444 bytes application/pdf application/pdf eng Massachusetts Institute of Technology 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. http://dspace.mit.edu/handle/1721.1/7582 Electrical Engineering and Computer Science. Electron Bernstein wave current drive modeling in toroidal plasma confinement Thesis application/pdf Publication unknown unknown <Publication xmlns="https://www.openaire.eu/cerif-profile/1.1/" id="c32022b4-0d82-4dd0-a6f1-23675e177613"> <Type xmlns="https://www.openaire.eu/cerif-profile/vocab/COAR_Publication_Types">http://purl.org/coar/resource_type/c_1843</Type> <Language>eng</Language> <Title>Electron Bernstein wave current drive modeling in toroidal plasma confinement</Title> <PublishedIn> <Publication> </Publication> </PublishedIn> <PublicationDate>2005</PublicationDate> <Authors> <Author> <DisplayName>Decker, Joan, 1977-</DisplayName> <Affiliation> <OrgUnit> </OrgUnit> </Affiliation> </Author> </Authors> <Editors> </Editors> <Publishers> <Publisher> <DisplayName>Massachusetts Institute of Technology</DisplayName> <OrgUnit /> </Publisher> </Publishers> <License>http://dspace.mit.edu/handle/1721.1/7582</License> <Keyword>Electrical Engineering and Computer Science.</Keyword> <Abstract>The steady-state confinement of tokamak plasmas in a fusion reactor requires non-inductively driven toroidal currents. Radio frequency waves in the electron cyclotron (EC) range of frequencies can drive localized currents and are thus particularly attractive for control of the current profile. In the high-[beta] regimes of spherical tokamaks (ST) such as NSTX and MAST, heating and current drive (CD) by conventional electron cyclotron waves is not possible. However, electron Bernstein waves (EBW) have been proposed as an alternative for CD in these overdense devices. Given the important role predicted for CD by EBWs in high-[beta] STs, a detailed study of EBWCD must be undertaken. In this thesis a systematic analysis of EBWCD is provided. In particular, the characteristics of EBWs, the physics of resonant wave-particle interaction, and the CD mechanisms are investigated in detail. The CD efficiency and the current deposition profile are calculated using the numerical code DKE, which solve the drift-kinetic equation. Two scenarios for EBWCD are identified. The first scenario consists of approaching a harmonic of the EC resonance from a lower B-field region and drives current in the plasma core using the Fisch-Boozer mechanism.</Abstract> <Abstract>(cont.) The other scenario consists of approaching a harmonic of the EC resonance from a higher B-field region and drives current off-axis on the outboard side using the Ohkawa mechanism. Both schemes drive current in the toroidal direction opposite to the parallel wave vector. The EBWCI) efficiency is found to be higher than ECCD efficiency because the EBW power is deposited in the tail of the electron distribution function. The results of this thesis confirm the important role of EBWs for driving currents in high-[beta] plasmas. The analytical and numerical tools developed as part of this thesis can be used to design, predict, and analyze future EBWCD experiments. Among these tools is the kinetic solver DKE, which can be used for electron current drive calculations in toroidal plasmas for different types of radio-frequency waves, such as lower hybrid and electron cyclotron waves.</Abstract> <Access xmlns="http://purl.org/coar/access_right" > </Access> </Publication>