Structural Properties of Complex Plasmas in a Homogeneous dc Discharge

We report on the first three-dimensional (3D) complex plasma structure analysis for an experiment that was performed in an elongated discharge tube in the absence of striations. The low frequency discharge was established with 1 kHz alternating dc current through a cylindrical glass tube filled with neon at 30 Pa. The injected particle cloud consisted of monodisperse microparticles. A scanning laser sheet and a camera were used to determine the particle position in 3D. The observed cylindrical-shaped particle cloud showed an ordered structure with a distinct outer particle shell. The observations are in agreement with performed molecular dynamics simulations.