Charging of micron-sized dust grains in a plasma has been investigated experimentally. Dust grains were dispersed into a fully ionized, steady-state, magnetized plasma column consisting of electrons and ${\mathrm{K}}^{+}$ ions, both at a temperature of ≅0.2 eV. Langmuir probe measurements were used to determine how the negative charge in the plasma is divided between free electrons and dust grains. By varying the ratio $\frac{d}{{\lambda }_D}$ between the intergrain spacing and the plasma Debye length, the predicted reduction in the grain charge for the case of "closely packed" grains $\frac{d}{{\lambda }_D}<1\mathrm{}$ has been demonstrated experimentally.

• Received 2 May 1994

DOI:https://doi.org/10.1103/PhysRevLett.73.3093