Plasma shaping

Résumé

Magnetically confined fusion plasmas such as those generated in tokamaks and stellarators are characterized by a typical shape. Plasma shaping is the study of the plasma shape in such devices, and is particularly important for next step fusion devices such as ITER. This shape is conditioning partly the performance of the plasma. Tokamaks, in particular, are axisymmetric devices, and therefore one can completely define the shape of the plasma by its cross-section. History Early fusion reactor designs tended to have circular cross-sections simply because they were easy to design and understand. Generally, fusion machines using a toroidal layout, like the tokamak and most stellarators, arrange their magnetic fields so the ions and electrons in the plasma travel around the torus at high velocities. However, as the circumference of a path on the outside of the plasma area is longer than one on the inside, this caused several effects that disrupted the stability of the plasma. Du

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https://en.wikipedia.org/wiki/Plasma_shaping

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This course completes the knowledge in plasma physics that students have acquired in the previous two courses, with a discussion of different applications, in the fields of magnetic confinement and controlled fusion, astrophysical and space plasmas, and societal and industrial applications.

This course treats the main issues in operation and control of a tokamak. Control-oriented models are derived and controllers are designed using techniques from modern control theory. Operational limits are discussed as well as state-of-the-art research questions for future reactors.

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Determination of the Fast-Ion Phase-Space Coverage for the FILD Spatial Array of the ASDEX Upgrade Tokamak

Lorenzo Stipani

The fast-ion phase-space coverage of the ASDEX Upgrade Fast-Ion Loss Detectors (FILD) has been estimated and the results are presented here. To that end, a numerical tool has been developed to determine particle orbits that can be accepted by each detector in the machine, depending on their radial position, without colliding to the first wall. Two different plasma shapes have been analyzed and results show excellent phase-space coverage for mostly all the detectors, especially for those located at the midplane and below it. The methodology developed provides an excellent way to estimate the signal of these detectors depending on the plasma scenario and can be easily extended to other machines. Also, this study can be complemented with thermal analysis to consider the structural integrity of the detectors, allowing determining optimal operation parameters both from the signal and safety standpoints.

2019

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Characterisation of impurities in L and H modes created by divertor biasing and plasma triangularity in TdeV

2001

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Characterization of impurities in L- and H-modes created by divertor biasing and plasma triangularity in TdeV

A characterization of the H-mode in Tokamak de Varennes (TdeV) is presented, combining results obtained from spectroscopic measurements with observations of global plasma parameters. Controlled L- and H-modes are obtained by applying an external bias on the divertor plate and/or by varying the plasma triangularity using similar steady-state discharges with electron cyclotron resonance heating (ECRH). A qualitative study of the impurity emission asymmetries is presented and discussed by proposing a simple model which considers that the emissivity has radial and poloidal components. The poloidal velocities are small with no significant variations with respect to the plate biasing, EC power and plasma triangularity. Toroidal. rotation velocities show more consistent trends and have larger values in the H-modes with respect to the L-modes. No significant shear in the radial electric field is observed between the H- and L-modes. Differences in the electric field and in the E x B shear are observed for several discharges, but they are not consistent overall. A study on the impurity transport shows low diffusivity values in the plasma centre and high values in the edge during the H-mode. The energy confinement time decreases with the severity of the edge localized modes and, consequently, with the neutral fluxes. The presence of a toroidal torque which affects the particle transport inside the plasma plays an important role in the TdeV H-modes.

2001

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