Effects of DC substrate bias voltage on dust flux in the Large Helical Device

Abstract We measured the dependence of the collected flux of dust particles on the bias potential Δ ϕ with respect to ground in the Large Helical Device at the National Institute of Fusion Science. This is a first step toward developing a novel method for removing dust for fusion reactors based on applying a local bias potential. The collected dust particles were classified into two kinds: spherical carbon particles smaller than 300 nm and stainless-steel flakes smaller than 1 μm. For Δ ϕ = −70 to +70 V, the flux of spherical particles increased exponentially with increasing Δ ϕ . The flux of flakes increased when Δ ϕ was increased from −70 V to +30 V and it decreased at higher Δ ϕ . These results suggest that this method is useful for removing carbon and metal dust particles from the shadow area of fusion devices using appropriate control of the local bias potential.