Published June 9, 2020 | Version v1
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Theoretical analysis and full-wave simulations combined in the development of the synthetic Doppler reflectometry diagnostics for tokamaks

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Description

Plasma turbulence is nowadays believed to be responsible for the anomalous transport and consequently the degradation of discharge conditions in magnetic confined fusion devices, such as tokamaks. Since a good energy confinement time is crucial for achieving a positive energy yield, understanding and control of turbulent processes is currently one of the major goals of the Magnetic Confinement Fusion research. To study the plasma turbulence, experimental tools that are able to provide information about its characteristics are necessary. Such tools include microwave diagnostics and, in particular, Doppler reflectometry and radial correlation Doppler reflectometry. While these non-invasive diagnostics benefit from the simplicity of the setup, there are a number of unresolved issues when it comes to the interpretation of the experimental data. Issues such are small-angle scattering and plasma curvature effects limit the range of applicability of the simple interpretation of the measurements, while nonlinear scattering effects make it inapplicable altogether. These problems make it necessary to validate the interpretation of experimental data. Thus, the primary goal of this thesis was to create a synthetic Doppler reflectometry and radial correlation Doppler reflectometry diagnostic for the interpretation of the FT-2 tokamak experimental results. This goal is achieved by applying full-wave IPF-FD3D code to the results of gyrokinetic plasma modelling with ELMFIRE code to obtain the synthetic signals, which are then benchmarked with experimental measurements. The synthetic diagnostic is also used for a more general study of the possibility of nonlinear effects influencing the experimental measurements. Finally, the secondary goal of this thesis was to perform an analytical research of plasma curvature effects, nonlinear scattering and a novel technique for turbulence structures' characterization. The first principles analytical study was performed by considering the Helmholtz equation and obtaining an analytical expression for the experimental signals. The results for the latter two topics were numerically validated with the partial use of specially developed linear numerical model and the full-wave IPF-FD3D code.(author)

Abstract (French)

La turbulence du plasma est consideree aujourd'hui comme le mecanisme responsable du transport anormal induisant la degradation du confinement de l'energie des plasmas de fusion confines magnetiquement, tels que les tokamaks. Le temps de confinement de l'energie est un parametre crucial pour atteindre un rendement energetique positif. La maitrise de ce parametre passe la comprehension et le controle de la turbulence du plasma. Ces themes de recherche correspondent actuellement aux principaux objectifs de la recherche sur la fusion par confinement magnetique. Pour realiser l'etude de la turbulence plasma, des outils experimentaux capables de fournir ses caracteristiques sont necessaires. Ces outils comprennent les diagnostics par micro-ondes et, en particulier, la reflectometrie Doppler et la reflectometrie de correlation radiale Doppler. Bien que ces diagnostics non invasifs beneficient d'une configuration simple, il existe un certain nombre de problemes non resolus associes a l'interpretation des donnees experimentales. Des problemes tels que la diffusion aux petits angles et les effets de courbure du plasma limitent le champ d'application d'une interpretation simple des mesures. La prise en compte des effets de diffusion non lineaire rende l'interpretation standard inapplicable. Ces problemes necessitent de valider l'interpretation des donnees experimentales. Ainsi, l'objectif principal de cette these etait de creer un diagnostic de reflectometrie Doppler synthetique et de reflectometrie de correlation radiale Doppler pour l'interpretation des resultats experimentaux du tokamak FT-2. Cet objectif fut atteint en appliquant le code full-wave IPFFD3D aux resultats d'une modelisation gyrocinetique du plasma turbulent avec le code ELMFIRE pour obtenir les signaux synthetiques. Ces derniers sont ensuite compares avec des mesures experimentales. Le diagnostic synthetique est egalement utilise pour une etude plus generale de la contribution des effets non lineaires lors des mesures experimentales. Un objectif secondaire de cette these correspondait a une recherche analytique sur les effets de courbure du plasma et de la diffusion non lineaire puis sur une nouvelle technique pour la caracterisation des structures turbulentes. L'etude analytique basee sur les premiers principes a ete realisee en considerant l'equation de Helmholtz et en obtenant une expression analytique pour les signaux experimentaux. Les resultats pour ces deux derniers sujets ont ete valides numeriquement avec l'utilisation partielle d'un modele numerique lineaire specialement developpe pour ce type d'etudes et du code IPF-FD3D. (auteur)

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Additional details

Additional titles

Original title (English)
Etudes Theoriques et de simulations dediees a la conception et l'application, pour les tokamaks, de diagnostiques synthetiques de reflectometrie Doppler

Publishing Information

Imprint Pagination
112 p.
Report number
FRNC-TH--12080

INIS

Country of Publication
France
Country of Input or Organization
France
INIS RN
52103227
Subject category
S70: PLASMA PHYSICS AND FUSION TECHNOLOGY;
Resource subtype / Literary indicator
Thesis
Descriptors DEI
PLASMA DIAGNOSTICS; PLASMA SIMULATION; REFLECTIVITY; TOKAMAK DEVICES; TURBULENCE
Descriptors DEC
CLOSED PLASMA DEVICES; OPTICAL PROPERTIES; PHYSICAL PROPERTIES; SIMULATION; SURFACE PROPERTIES; THERMONUCLEAR DEVICES

Optional Information

Notes
78 refs.; Available from the INIS Liaison Officer for France, see the INIS website for current contact and E-mail addresses