15 research outputs found
Raman micro-spectroscopy as a tool to measure the absorption coefficient and the erosion rate of hydrogenated amorphous carbon films heat-treated under hydrogen bombardment
We present a fast and simple way to determine the erosion rate and absorption
coefficient of hydrogenated amorphous carbon films exposed to a hydrogen atomic
source based on ex-situ Raman micro-spectroscopy. Results are compared to
ellipsometry measurement. The method is applied to films eroded at different
temperatures. A maximum of the erosion rate is found at ~ 450 {\degree}C in
agreement with previous results. This technique is suitable for future
quantitative studies on the erosion of thin carbonaceous films, especially of
interest for plasma wall interactions occurring in thermonuclear fusion
devices
Raman study of CFC tiles extracted from the toroidal pump limiter of Tore Supra
International audienceThe structure of six tiles extracted from the erosion and deposition zones (thin and thick deposition) of the Tore Supra toroidal pump limiter (TPL) have been analysed in the framework of the DITS campaign using micro-Raman spectroscopy. This post-mortem analysis gives information on both carbon structure and D content. We have found that the carbon structure is most often similar to that of plasma-deposited hard amorphous carbon layers. The role of the surface temperature during the discharge in the D content is investigated: in all locations where the temperature does not reach more than 500°C the D content seems to be roughly uniform with D/D+C ≈ 20%
Plasma growth processes inside gaps of the castellated limiter of the Tore Supra tokamak
We performed electron microscopy analysis of carbon tiles dismantled from the toroidal limiter of the Tore Supra tokamak. The tile top surfaces are either eroded, or covered with deposits, depending on ion flux. On the contrary, the tile gap surfaces are covered with deposits whatever the region of the limiter. We analyzed both the topography and the microstructure of gap deposits. Deposits are tip-shaped and deposition is significant only down to ~1 mm, due to the limited penetration of ions. The direction of tips results from the combination of the ion speed along the magnetic lines and the drift associated to the local electric fields. The microstructure of deposits reveals the presence of graphitic species, such as onion-like nanoparticles, and our results therefore show that deposition results from local plasma chemistry similar to what is observed for cold plasmas
Post-mortem analyses of the Tore Supra toroidal limiter: experimental evidence of ion transport in a magnetized sheath
Abstract The topography of tiles dismantled from the main plasma-facing component of Tore Supra has been analyzed by scanning electron microscopy. Erosion zones show striation corresponding to a surface ripple. Deposition zones show well-oriented deposits with tip shapes. We show that these features are footprints of ion flow at the component surface. They are in good agreement with what is expected by modeling of ion trajectories in the case of grazing incidence in a strongly magnetized sheath