Nonlinear and stochastic interaction of waves with plasma.

Available from STL Prague, CZ / NTK - National Technical LibrarySIGLECZCzech Republi

Direct measurements of particle flux along gap sides in castellated plasma facing component in COMPASS

In this paper, we report results of a dedicated experiment that gives the plasma penetration profiles inside a gap of a tokamak castellated plasma-facing component. A specially designed probe that recreates a gap between two tiles has been built for the purpose of this study. It allows to measure ion saturation profiles along the 2 sides and at the bottom of the gap for both poloidal and toroidal orientations. The novelty of such experiment is the real time measurement of the plasma flux inside the gap during a tokamak D-shaped discharge compared to previous experimental studies which were mainly post-mortem. This experiment was performed in the COMPASS tokamak and results are compared with particle-in-cell simulations. The plasma deposition is found to be asymmetric in both orientations with a stronger effect in poloidal gaps. The Larmor radius of the incoming ions plays a role in the plasma penetration only in poloidal gaps but seems to have little impact in toroidal gaps. Profiles are qualitatively well reproduced by simulations. Ion current is recorded at the bottom of a toroidal gap under certain conditions

Tomographic reconstruction of tokamak edge turbulence from single visible camera data and automatic turbulence structure tracking

International audienceFollowing the lead of [Nguyen van Yen Nucl. Fus. 52 (2012) 013005 (11pp)], this article tackles the problem of tomographic inversion with one camera assuming a constant emissivity of light along the magnetic field lines. In this way, the 3D problem reduces to 2D by helical symmetry, allowing for the reconstruction of any poloidal plane in the field of view of the camera. It is shown in this article that the complexity of using a wavelet basis for the reconstruction, as presented by Nguyen van Yen, is not necessary. The method is also validated by confronting it to 3D numerical data coming from the TOKAM3X code, for which the emissivity is slowly varying along the field lines (up to 20 %), showing the robustness of the reconstruction. The technique is then applied to real camera data recorded during a D-shaped ohmic plasma shot realized in the COMPASS tokamak. The method is experimentally validated by comparing reconstructed data from camera and ion saturation currents measured by Langmuir probes in the divertor region. Finally, it is shown that automatic detection and tracking of structures visible in the reconstructed poloidal plane enables unique investigations of edge plasma physics and opens wide perspectives for this method

Oxidation of Inconel 625 superalloy upon treatment with oxygen or hydrogen plasma at high temperature

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