On the amplitude of dust-density waves in inhomogeneous dusty plasmas

Density waves in a cloud of submicron dust particles confined in an rf plasma are examined with respect to their amplitude. The plasma shows a strong inhomogeneity in its densities and the dust particle charge. An ion density gradient appears due to ambipolar diffusion and leads to a dust charge gradient provided by charge depletion. Using dust-density wave frequency and wave number as a diagnostic for the plasma parameters, it is found that the wave amplitude increases or decreases as the wave travels into regions with decreasing or increasing particle charge. The experimental amplitude profile is similar to the theoretical curve predicted by a formula from Singh and Rao [Phys. Plasmas 6, 3157-3162 (1999)]. Published by AIP Publishing.