Wall Forum 2022

Helium diffusion, clustering and bubble nucleation and growth is modelled using the finite element method. The existing model from Faney et al. (Model Simul Mater Sci Eng 22:065010, 2018; Nucl Fusion 55:013014, 2015) is implemented with FEniCS and simplified in order to greatly reduce the number of equations. A parametric study is performed to investigate the influence of exposure conditions on helium inventory, bubbles density and size. Temperature is varied from 120 K to 1200 K and the implanted flux of 100 eV He is varied from 1017 m−2 s−1 to 5 × 1021 m−2 s−1. Bubble mean size increases as a power law of time whereas the bubble density reaches a maximum. The maximum He content in bubbles was approximately 4 × 108 He at 5 × 1021 m−2 s−1. After 1 h of exposure, the helium inventory varies from 5 × 1016 m−2 at low flux and high temperature to 1025 m−2 at high flux and low temperature. The bubbles inventory varies from 5 × 1012 bubbles m−2 to 2 × 1019 bubbles m−2. Comparison with experimental measurements is performed. The bubble density simulated by the model is in quantitative agreement with experiments. [mehr]

The assessment of transport phenomena as well as fuel retention plays a major role in the operation of a fusion device. That is why the instruments and methods designed for in situ measurements of erosion-deposition phenomena or fuel retention will play a leading role. LIBS (Laser-Induced Breakdown Spectroscopy) measurements is one of the investigation technique with a large perspectives in this respect. In order to assure a correct assessment of the investigated regions, these investigation instruments should be calibrated using reference samples with composition as close as possible with the real tiles exposed to fusion plasma.In this talk we report the results obtained in production of W based coatings with gas inclusions (D, He etc). The production of the coatings was performed by using an equipment provided with 2 magnetrons. The magnetrons can be energized independently by using DC or HiPIMS (High Power Impulse Magnetron Sputtering) power supplies. This fact allows a higher control of the deposition rates, and consequently of the stoichiometry of the deposited compound when 2 different target materials are used. The magnetrons are mounted in the deposition chamber in such a way that the substrate holder is situated in confocal position.The chemical composition (elemental depth profile) of the coatings was performed by using Glow Discharge Optical Emission Spectrometry (GDOES). Thermal Desorption Spectrometry (TDS) measurements were also performed in order to evaluate the gas content (D, He, Ar) released from the coatings. [mehr]