The effect of gyration on the deposition of beryllium and deuterium at rough surface on the divertor tiles with ITER-like-wall in JET

• Published in: Nuclear materials and energy Vol. 19; pp. 155 - 160
• Main Authors: Zhou, Y., Bergsåker, H., Petersson, P., Possnert, G., Likonen, J.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.05.2019; Elsevier
• Subjects: Deuterium deposition; Divertor; JET; Micro-ion-beam; JET; Micro-ion-beam; Deuterium deposition; Divertor
• ISSN: 2352-1791; 2352-1791
• DOI: 10.1016/j.nme.2019.02.025

•IBA data suggested that surface D accumulated on the top stage of sample while Be stayed on the 10–20 μm stages from the top.•Gyro-motion of D could explain this accumulation on the top qualitative but overestimated the D amount in deeper stage.•IBA results for Be agreed with the simulation data on the stages located at ≈20 μm from the top.•Surface D accumulated on the region on which simulation overestimated Be amount. Experimental results from microbeam analyses on divertor tiles, through 2011-2012 and 2013-2014 operations in JET-ILW, showed that the deuterium retention and beryllium impurity deposition were non-uniform on the rough surface in micro meter scale. Frequently, Be and D were accumulated within pits, cracks and valleys in the range of ∼10 μm to ∼100 μm and selectively at side slopes within larger pits. In the deposited layers, it was also observed that cylindrical structures grow in a specific direction with respect to the magnetic field. In this work, a sample from the divertor in JET-ILW following 2013-2014 operation was analysed. The surface topography was measured with the focus stacking technique on photos from optical microscope and elemental distribution maps were obtained by micro-ion-beam analysis. In order to figure out the effect of ion gyro motion on Be and D deposition on the real divertor topography, a modelling of ion trajectories in plasma boundary was performed. Ion beam analysis data suggested that D accumulated on higher areas on the sample, while Be stayed on lower positions. The gyration of ions in edge plasma and corresponding impact positions on the sample surface could explain some IBA results qualitatively.