engleski

Ion micro-beam analyses of dust particles and co- deposits from JET with ITER-like wall

Plasma-surface interaction processes in devices for controlled thermonuclear fusion cause erosion of plasma-facing components (PFC). A certain part of material eroded from the walls is converted into dust. Plasma dynamics in a tokamak includes transport of dust down toward the divertor. Its formation in present-day machines does not pose operation issues, because quantities are small, especially in the presence of metal walls. However, in International Thermonuclear Experimental Reactor (ITER), which is under construction in France, generation of large quantities of loose particles could create serious problems. Therefore, studies of metal dust generation, composition, size and morphology of particles in the Joint European Torus (JET) tokamak with the ITER-like wall (ILW), is a topic of vital interest to next-step fusion devices because of safety issues in plasma operation. In this presentation we report about simultaneous use of Nuclear Reaction Analysis (NRA) and Particle-Induced X-ray Emission (PIXE) with focused 4 MeV 3He micro-beam to study composition of dust particles related to the JET tokamak operation with the ITER-Like Wall, with the focus on ‘beryllium rich particles’ and their main constituents like beryllium, deuterium and heavier metals like Cr, Fe Ni, Mo, W. Dust sampled after the second ILW campaign (2013-2014) using a sticky carbon pad from the divertor was studied. The particles found are composed of a mix of co-deposited species up to 100 x 120 µm in size with the thickness of 30-40 µm. The main constituents are: deuterium from the fusion fuel, beryllium and tungsten originating from the main plasma-facing components, nickel and chromium from Inconel grills of antennas for auxiliary plasma heating. Elemental concentrations of major and minor elements have been estimated by quantitative iterative NRA-PIXE analysis. NRA- PIXE data acquisition and analytical procedures are presented and main results elaborated.

fusion ; JET ; dust ; NRA ; PIXE ; IBA

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