Measurement of Negatively Charged Dust by Using an Electric Probe in Large RF Helium Plasmas

We investigated charged dust and its effect on RF plasma by using a planar electric probe in a large-scale device. In background plasmas, the particle density is 10⁸ to 10⁹ cm⁻³ and the electron temperature is 2 to 4 eV. When dust is contained in plasma, it is negatively charged by electrons attached to the dust. The charged dust density and the charge were calculated by comparing dusty helium plasma to pure helium plasma. Depending on the increase in the amount of dust, the charged dust density increases with the decrease in the charge due to depletion of the electrons in the background plasma. The results show that the charge changes the interactions between the dust and particles in the background plasma.