Packed bed dielectric barrier discharges (DBDs) are very promising for several applications including remediation of environmental pollutants and greenhouse gas conversion. In this work, we have investigated the space and time-resolved emission from a packed bed DBD operated in helium, to understand the plasma dynamics. We have chosen a simple planar DBD arrangement with a patterned dielectric, which mimics the spherical boundaries between the dielectric pellets and allows the optical access to the plasma. The results show that plasma is sustained in a packed bed DBD by three mechanisms: filamentary discharge in the void (between the center of dielectric structures and the opposite electrode), microdischarges at the contact points and surface ionization waves over the dielectric surface. It is observed that for most of the duration plasma is generated at the contact points between the dielectric structures.

The concentration of two species in a multi-dipole plasma was determined by measuring the ion acoustic wave group velocity and the electron temperature. The wave was launched from a grid immersed in the plasma and was detected by a Langmuir probe. Electron temperature was found separately from an $\mathrm{I–V}$ characteristic trace. The measurements were performed in helium/xenon and argon/xenon plasmas. Typical parameters of the plasma were $T_e\text{∼0.5–3\hspace{0.05em}}\mathrm{eV},$ density ${10}^{10} {\mathrm{cm}}^{\text{−3}},$ plasma potential of 3–5 V, and pressure range from 1 to 20 mTorr. The accuracy of the measurement was from 2% to 4% depending on the mass difference between the two species and how accurately the group velocity and electron temperature are measured.

A waveguide-based microwave plasma system was built using a resonant cavity and a quartz tube. 2.45 GHz 850 W magnetron was used to obtain helium discharge without an igniter. The temporal images of discharge were recorded on microsecond time scales using an intensified charge-coupled device camera. The excitation temperature was calculated as 3385 K using the helium lines, which were obtained from emission spectrum of the discharge. The gas temperature was measured as 1208 K by a thermocouple.

A new type of hybrid discharge is experimentally investigated in this work. A helicon source and an electron cyclotron resonance (ECR) source were combined to produce plasma. As a preliminary study of this type of plasma, the optical emission spectroscopy (OES) method was used to obtain values of electron temperature and density under a series of typical conditions. Generally, it was observed that the electron temperature decreases and the electron density increases as the pressure increased. When increasing the applied power at a certain pressure, the average electron density at certain positions in the discharge does not increase significantly possibly due to the high degree of neutral depletion. Electron temperature increased with power in the hybrid mode. Possible mechanisms of these preliminary observations are discussed.

Physical plasma is a quasi-neutral gaseous electronics that exhibit collective behavior. It has been known that it develops chaotic behavior of the type that leads to various instabilities. This is the main problem in confining physical plasma to achieve energy production for example. However, it is found that even a quiescent physical plasma system, which consists of a multi – dipole thermionic physical plasma source and a Langmuir electric probe as a diagnostic instrument, can reveal the system’s chaotic behavior at the physical plasma charge population collection level. By inspection, the classic Verhulst population curve was shown to resemble a typical physical plasma system Langmuir probe I - V (voltage – current) trace, thereby indicating such chaotic behavior. Further, an experiment was conducted by mixing of two ion species in the same physical plasma system which led to the occurrence of unstable modes, with their onset being sensitive to the percentage of density by pressure of each species, and the distance from the physical plasma vessel boundary region.