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Forward and Backward Modelling of Spectroscopic Diagnostics in Fusion Plasmas
Tomeš, Matěj ; Seidl, Jakub (advisor) ; De Bock, Maarten (referee) ; Den Hartog, Daniel J. (referee)
Title: Forward and Backward Modelling of Spectroscopic Diagnostics in Fusion Plasmas Author: Matěj Tomeš Department: Department of Surface and Plasma Science Supervisor: Mgr. Jakub Seidl, Ph.D., Institute of Plasma Physics of the Czech Academy of Sciences Abstract: The thesis primarily focuses on developing forward and backward models for fusion diagnostics. It encompasses the development and application of these models for Thomson scattering, the inference of neon concentrations in JET's divertor and for synchrotron radiation. In the first chapter, the forward model of Thomson scattering designed for Cherab is detailed. This includes the development of a laser module intended for a wide range of applications, primarily to facilitate Thomson scattering simulations. An application example is provided by a comprehensive model of the Thomson scattering diagnostic used at the COMPASS tokamak. The model of the diagnostic is combined with experimentally obtained electron profiles to assess its performance. The second half of the chapter focuses on the development of a backward model for Bayesian inference of temperature profiles from measured Thomson scattering data. The effectiveness of this model is compared to the conventional approach based on least square error optimization, revealing clear advantages of...
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RE beam generation in MGI disruptions on COMPASS.
Ficker, Ondřej ; Mlynář, Jan ; Macúšová, Eva ; Vlainić, M. ; Weinzettl, Vladimír ; Urban, Jakub ; Čeřovský, Jaroslav ; Farník, Michal ; Markovič, Tomáš ; Papřok, Richard ; Vondráček, Petr ; Imríšek, Martin ; Tomeš, Matěj ; Havlíček, Josef ; Varju, Jozef ; Varavin, Mykyta ; Bogár, Ondrej ; Havránek, Aleš ; Gospodarczyk, M. ; Rabinski, M. ; Jakubowski, M. ; Malinovski, K. ; Zebrowski, J. ; Plyusnin, V. ; Papp, G. ; Pánek, Radomír ; Hron, Martin
In the experiments with the massive gas injection (MGI) triggered disruptions in the COMPASS tokamak, post-disruptive runaway electron (RE) beams are generated occasionally. In this contribution, a relatively large set of discharges from the recent years is analysed in order to improve our understanding of the processes behind the beam generation. It seems that despite the low toroidal field applied in the discharges (typically 1.15 T) the magnetic perturbations may be small enough to allow the acceleration and confinement of the electrons. The influence of the different components and different sections of the frequency spectrum of the magnetic perturbations on the beam generation and RE beam current is examined. Fast visible camera images are also analysed. The relevance of COMPASS runaway electron experiments for large machines is discussed. Moreover, the potential of less common diagnostic tools (Cherenkov detector, vertical ECE, ...) to clarify the role of the pre-disruption fast electron population and the influence of prompt runaway electron losses in the current quench is discussed using the recent test measurements.
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