New self-organization patterns observed in Cathode Boundary Layer Discharges in high purity xe gas

Abstract

Self-organized pattern formation has been observed previously in Cathode Boundary Layer Discharges (CBLD) in high purity xenon gas at pressures ranging from about 60 Torr to atmospheric pressure within a narrow range of discharge currents, which are in general adjusted directly from the DC power supply1. In this study, while retaining the same plasma reactor and gas purity, the electrical circuit was modified by connecting two 0–200 kΩ potentiometers in series with the 100 kΩ ballast resistor, to tune the discharge current on the microampere scale. A few new self-organized patterns were identified, which include: (1) a ring shape plasma pattern that was completely separated from boundary walls and (2) a series of elongated plasma segments arranged along a circle. Both patterns were most prominently observed at pressures ranging from 60 to 120 Torr. It is interesting to note that the transition to the ring shape plasma is unidirectional, while patterns can be transitioned to elongated plasma segments from distinctive plasma spots or vice versa. This observation is nicely described by COMSOL modeling results presented by P. Almeida and co-workers2. Detailed studies were also focused on the continuity of the transition from a homogeneous plasma to a diffuse mode of self-organized plasma patterns. The observation of these patterns may provide new insights into the self-organized pattern formation in CBLDs in xenon.