Filamentation Morphology in Capacitively Coupled Highly Magnetized Plasmas

Due to the small charge-to-mass ratio of dust particles, it is often necessary to use large magnetic fields of B ≥ 1 T, in order to observe the influence of magnetic forces in laboratory dusty plasmas. However, when experiments are performed at high magnetic fields in capacitively coupled, radio frequency discharges, the background plasma is often observed to form filamentary structures between the electrodes that are aligned to the external magnetic field which disrupt the uniformity of the plasma and adversely impact our dust experiments. Experiments performed in the Magnetized Dusty Plasma Experiment (MDPX) device have identified and characterized these filamentary structures. This presentation discusses the morphology of several distinct filamentary modes that are formed in low temperature plasmas with different neutral gases. There is strong evidence that each spatial mode has a threshold condition that is dependent on the ion Hall parameter – which is a function of magnetic field, neutral pressure, and ion mass. The criteria for the formation of the filaments are shown to be consistent with predictions of numerical simulations.