CHARGING OF DUST GRAINS IN A PLASMA

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 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 dλD between the intergrain spacing and the plasma Debye length, the predicted reduction in the grain charge for the case of "closely packed" grains dλD<1 has been demonstrated experimentally. © 1994 The American Physical Society.