Particle-in-cell simulations of the near-field of a lower hybrid grill

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dc.contributor Aalto-yliopisto fi
dc.contributor Aalto University en
dc.contributor.author Rantamäki, Karin
dc.date.accessioned 2012-02-10T09:27:25Z
dc.date.available 2012-02-10T09:27:25Z
dc.date.issued 2003-05-23
dc.identifier.isbn 951-38-6041-8
dc.identifier.issn 1455-0849
dc.identifier.uri https://aaltodoc.aalto.fi/handle/123456789/2200
dc.description.abstract Lower hybrid (LH) waves in the frequency range 1 to 10 GHz are used to heat and to drive current in a tokamak. A crucial issue for the future devices is the coupling of the wave power from the launching structure, the grill, to the plasma. A related problem is the formation of hot spots on the grill limiters and other components that are magnetically connected to the grill region. A probable explanation for these asymmetric heat loads is the parasitic absorption of the LH power. In parasitic absorption, the short-wavelength modes are absorbed by electrons within a very short distance in front of the grill. The cold edge electrons (Te ∼ 25 eV) may reach energies up to 2 keV through stochastic acceleration in the electric field in front of the lower hybrid grill. The particle-in-cell (PIC) technique is one of the most popular methods of kinetic simulations of plasmas. In PIC codes, a spatial grid is used to describe the field quantities, while the particles move in the continuous space. The field and particle motion are solved self-consistently. The advantage of the PIC codes is that they take into account the kinetic effects and the non-linearities of the problem. They also give the deposition profiles unlike pure test particle simulations. In this thesis, the use of PIC codes has been extended to a whole new branch of applications, the near-field of the LH grill. During the work, the grill model used in the electrostatic PIC code has been developed. The parasitic absorption and the generation of fast electrons in front of the waveguide mouth have been explored. The absorption and the heat load on the grill limiter increases with the edge density, the edge temperature and the launched power density. A weak indication of a power threshold was observed. The simulation results can explain experimental observations in Tore Supra. According to the simulations, the heat loads are not a problem in the next generation launchers used in ITER. en
dc.format.extent 74, [61]
dc.format.mimetype application/pdf
dc.language.iso en en
dc.publisher VTT Technical Research Centre of Finland en
dc.publisher VTT fi
dc.relation.ispartofseries VTT publications en
dc.relation.ispartofseries 493 en
dc.relation.haspart K. M. Rantamäki, T. J. H. Pättikangas, S. J. Karttunen, X. Litaudon and D. Moreau, Generation of hot spots by fast electrons in lower hybrid grills, Physics of Plasmas 5 (1998) pp. 2553-2559.
dc.relation.haspart K. M. Rantamäki, T. J. H. Pättikangas, S. J. Karttunen, X. Litaudon, D. Moreau, P. Bibet and A. Ekedahl, Particle-in-cell simulation of parasitic absorption of lower hybrid power in edge plasmas of tokamaks, Plasma Physics and Controlled Fusion 41 (1999) pp. 1125-1133.
dc.relation.haspart K. M. Rantamäki, T. J. H. Pättikangas, S. J. Karttunen, P. Bibet, X. Litaudon and D. Moreau, Estimation of heat loads on the wall structures in parasitic absorption of lower hybrid power, Nuclear Fusion 40 (2000) pp. 1477-1490.
dc.relation.haspart K. M. Rantamäki, Ph. Bibet, S. J. Karttunen, T. J. H. Pättikangas and X. Litaudon, Particle-in-Cell Simulations of the New Tore Supra LH Grill, in J. W. Connor, O. Sauter and E. Sindoni (Eds.) International School of Plasma Physics "Piero Caldirola", Theory of Fusion Plasmas, (Societa Italiana di Fisica, Bologna, Italy, 2000) pp. 463-468.
dc.relation.haspart K. M. Rantamäki, T. J. H. Pättikangas, S. J. Karttunen, K. M. Alm-Lytz, J. P. Verboncoeur and P. Mardahl, Electromagnetic Particle-in-Cell Simulations of a Lower Hybrid Grill, Plasma Physics and Controlled Fusion 44 (2002) pp. 1349-1362.
dc.subject.other Energy en
dc.subject.other Physics en
dc.title Particle-in-cell simulations of the near-field of a lower hybrid grill en
dc.type G5 Artikkeliväitöskirja fi
dc.description.version reviewed en
dc.contributor.department Department of Engineering Physics and Mathematics en
dc.contributor.department Teknillisen fysiikan ja matematiikan osasto fi
dc.subject.keyword plasma heating en
dc.subject.keyword microwaves en
dc.subject.keyword lower hybrid grill en
dc.subject.keyword lower hybrid waves en
dc.subject.keyword particle-in-cell simulation en
dc.subject.keyword parasitic absorption en
dc.subject.keyword wave coupling en
dc.subject.keyword thermonuclear devices en
dc.subject.keyword Tore Supra en
dc.subject.keyword tokmak en
dc.subject.keyword JET en
dc.subject.keyword current drive en
dc.subject.keyword nuclear fusion en
dc.identifier.urn urn:nbn:fi:tkk-001705
dc.type.dcmitype text en
dc.type.ontasot Väitöskirja (artikkeli) fi
dc.type.ontasot Doctoral dissertation (article-based) en


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