Interplay of dust ordering and potential structures in magnetized low temperature plasmas

When micron-sized dust particles are introduced into a low-temperature plasma, they acquire a net negative charge and can self-organize into 2D crystalline structures with 6-fold symmetry under, a well known phenomenon in dusty plasma physics. Imposed ordering occurs when the particle arrangement aligns with the geometry of a conducting mesh placed above them in a strongly magnetized plasma. First observed in the Magnetized Dusty Plasma eXperiment (MDPX) [E. Thomas et al., Phys. Plasmas 22, 030701 (2015)], dust formed 4-fold symmetric structures matching a square-gridded mesh. We hypothesize that elongated electric potential structures from the mesh drive dust motion to mimic the mesh pattern. Imposed ordering varies with magnetic field, neutral pressure, and mesh geometry. Experiments covered a wide range of pressures and magnetic fields using two mesh types: a perforated sheet and an interwoven mesh. As magnetization increases and dust transitions from 6-fold self-ordering to 4-fold imposed ordering, motion becomes increasingly 3D and maps the potential. We quantify dust phases using particle tracking as a first step toward inferring potential structures. This work has potential relevance to multiple fields as the system can act as a macroscopic analog for phenomena such as phase transitions in crystal structures and pinning/depinning of particles on ordered substrates [C. Reichhardt & C. J. Olson Reichhardt, Rep. Prog. Phys. 80, 026501 (2017)].