Preparation and characterization of marker graphite tiles for PWI research of HL-3

Abstract

In tokamaks, to understand the erosion and deposition pattern of plasma facing components (PFCs) is crucial for the study of plasma wall interaction (PWI). In this study, a set of dedicated marker graphite tiles consisting of substrate material same as the PFCs of HL-3 tokamak, an interlayer of 0.5 μm Tungsten (W) with width of 50 mm employed as marker, and a 5 μm thick with width of 30 mm carbon (C) marker layer on top, were designed and prepared for the PWI research. The magnetron sputtering technique was employed to make the marker layers including W and C layers. The scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDX) were used to study the surface morphology, elemental composition and layer structure characterization of marker graphite tiles. The Laser-induced breakdown spectroscopy (LIBS) was employed to perform elemental analysis along the depth direction of the C-W-C structure and W-C structure on the marker graphite tiles. Moreover, during the manufacturing process of marker graphite tiles, glass slides were used to be coated simultaneously with graphite and then measured by profilometer in order to evaluate the thickness of the coating. The cross-section of the marker graphite tiles measured by SEM revealed an average W interlayer thickness of 0.71 μm and an average C layer thickness of 4.75 μm. The LIBS results indicate that the thickness information of the C-W-C structure and the W-C structure is consistent with the findings from SEM analysis. The marker graphite tiles have been installed in HL-3 to perform the PWI studies including the C and W erosion, impurity deposition and material migration via surface element analysis and layer structure analysis of the marker graphite tiles in the next experimental campaign.