Full-wave modeling of lower hybrid waves on Alcator C-Mod
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2012.
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| Format: | Thesis |
| Language: | eng |
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Massachusetts Institute of Technology
2013
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| Online Access: | http://hdl.handle.net/1721.1/76501 |
| _version_ | 1811082966993993728 |
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| author | Meneghini, Orso (Orso-Maria Cornelio) |
| author2 | Ronald R. Parker. |
| author_facet | Ronald R. Parker. Meneghini, Orso (Orso-Maria Cornelio) |
| author_sort | Meneghini, Orso (Orso-Maria Cornelio) |
| collection | MIT |
| description | Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2012. |
| first_indexed | 2024-09-23T12:15:48Z |
| format | Thesis |
| id | mit-1721.1/76501 |
| institution | Massachusetts Institute of Technology |
| language | eng |
| last_indexed | 2024-09-23T12:15:48Z |
| publishDate | 2013 |
| publisher | Massachusetts Institute of Technology |
| record_format | dspace |
| spelling | mit-1721.1/765012019-04-11T09:35:26Z Full-wave modeling of lower hybrid waves on Alcator C-Mod Meneghini, Orso (Orso-Maria Cornelio) Ronald R. Parker. Massachusetts Institute of Technology. Dept. of Nuclear Science and Engineering. Massachusetts Institute of Technology. Dept. of Nuclear Science and Engineering. Nuclear Science and Engineering. Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2012. Cataloged from PDF version of thesis. Includes bibliographical references (p. 225-237). This thesis focuses on several aspects of the Lower Hybrid (LH) wave physics, the common theme being the development of full-wave simulation codes based on Finite Element Methods (FEM) used in support of experiments carried out on the Alcator C-Mod tokamak. In particular, two non-linear problems have been adressed: high power antenna-plasma coupling and current drive (CD). In both cases, direct solution of the wave equation allowed testing the validity of approximations which were historically done and consider full-wave effects and realistic geometries. The first code, named POND, takes into account the interaction of high power LH waves and the plasma edge based on the non-linear ponderomotive force theory. Simulations found the effect of ponderomotive forces to be compatible with the density depletion which is measured in front of the antenna in presence of high power LH waves. The second code, named LHEAF, solves the problem of LH wave propagation in a hot non- Maxwellian plasma. The electron Landau damping (ELD) effect was expressed as a convolution integral along the magnetic field lines and the resultant integro-differential Helmholtz equation was solved iteratively. A 3D Fokker-Planck code and a synthetic Hard X-Ray (HXR) diagnostic modules are used to calculate the self-consistent electron distribution function and evaluate the resulting CD and bremsstrahlung radiation. LHEAF has been used to investigate the anomalous degradation of LHCD efficiency at high density. Results show that while a small fraction of the launched power can be absorbed in the SOL by collisions, it is a strong upshift in the nii spectrum that makes the overall LHCD efficiency low by allowing the waves to Landau damp near the edge. Wavelet analysis of the full-wave fields identified spectral broadening to occur after the waves reflect and propagate in the SOL. This work explains why on Alcator C-Mod the eikonal approximation is valid only in the low to moderate density regime, and why parasitic phenomena introduced in previous work can reproduce phenomenologically well the experimental results. by Orso Meneghini. Ph.D. 2013-01-23T19:45:22Z 2013-01-23T19:45:22Z 2012 2012 Thesis http://hdl.handle.net/1721.1/76501 823507517 eng 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 241 p. application/pdf Massachusetts Institute of Technology |
| spellingShingle | Nuclear Science and Engineering. Meneghini, Orso (Orso-Maria Cornelio) Full-wave modeling of lower hybrid waves on Alcator C-Mod |
| title | Full-wave modeling of lower hybrid waves on Alcator C-Mod |
| title_full | Full-wave modeling of lower hybrid waves on Alcator C-Mod |
| title_fullStr | Full-wave modeling of lower hybrid waves on Alcator C-Mod |
| title_full_unstemmed | Full-wave modeling of lower hybrid waves on Alcator C-Mod |
| title_short | Full-wave modeling of lower hybrid waves on Alcator C-Mod |
| title_sort | full wave modeling of lower hybrid waves on alcator c mod |
| topic | Nuclear Science and Engineering. |
| url | http://hdl.handle.net/1721.1/76501 |
| work_keys_str_mv | AT meneghiniorsoorsomariacornelio fullwavemodelingoflowerhybridwavesonalcatorcmod |