Contribution of H₂ plasma etching to radial profile of amount of dust particles in a divertor simulator

We have studied contribution of H2 plasma etching to radial profile of amount of dust particles generated due to interactions between H2 plasmas and graphite target in a divertor simulator. Dust fluxes of spherical particles and flakes are the maximum at the distance r 100 mm and 120 mm from the centre axis of the plasma column, respectively. From ion density and dust flux, we have deduced etched volume of deposited dust particles due to H2 plasma irradiation. Sum of the etched volume and measured volume of spherical dust particles is almost constant for r < 120 mm and decreases with increasing r for r > 120 mm, whereas that of flakes is the maximum at r 120 mm. H2 plasma etching significantly reduces size of dust particles for r smaller than 100 mm.