Flux control of dust particles in a nanometer size range using dc bias voltage is discussed based on dust collection in a divertor simulator employed helicon hydrogen discharges. To discuss mechanisms of flux control, we have estimated etching rate of deposited dust particles due to hydrogen plasma irradiation and have measured current density toward the dc biased substrates. We have found the contribution of the etching can be negligible in a dc bias voltage V bias range between -50 and 70 V. Clear correlation between V bias dependence of current density and that of dust flux shows electrostatic force is one of important forces for controlling flux of dust particles.

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We have measured spatial profile of flux of dust particles generated due to interaction between H 2 plasmas and graphite target in a divertor simulator to study transport mechanism of dust particles. Dust particles were collected on c-Si substrates and observed with a scanning electron microscope. We have found nanostructure of 10 nm in size on the substrate surface. Dust fluxes of both spherical dust particles and flakes are maximum at a position between 80 and 140 mm from the center of the plasma column. The spatial profile of dust flux is determined by the balance between deposition of nanoparticles and their etching by H atoms.

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