Micro-analyses of dust particles generated in the JET tokamak with the ITER-like wall

Abstract

Dust generated in JET with the ITER-like wall (ILW) was collected from the divertor by vacuum cleaning and examined with ion and electron beam methods. From totally 1 g retrieved after the third ILW campaign (2015–2016) a number of specimens were prepared using sticky (adhesive) carbon tabs. The aim was to determine the distribution and amounts of constituents: from deuterium (D) to W with particular emphasis on the concentration ratio of D to other species. Two classes of particles containing deuterium were identified: (i) rich in Be and (ii) low-Z matrix without Be, that show large C concentrations with some O contribution and minor contributions from heavier elements. The D content in Be-based particles has been at the level not exceeding ≈2 at %, whereas in the C-rich particles, both in small (10–100 µm) and large conglomerates (>100 µm), the D contribution at the level of about 15 to 20 at % has been detected. W-rich particles are often accompanied by Ni, Cr and Fe and occasionally with Mo. The results clearly indicate that fuel retention in the ILW dust is predominantly associated with residual C, approximately 10–20 times greater retention was found in C-rich objects than in metal-based particles.