Pulsed power, used to produce underwater discharges, has been the subject of numerous studies to elucidate its mechanisms and applications. This paper reports on observation by a high-speed camera of the production and progress of streamer discharges created using a magnetic pulse compression pulsed power generator with maximum output energy of 40 Joules per shot in the medium of both tap and distilled water. Bubble production along streamers, bubble collapse, generation of shock waves, and extinction of bubbles was also observed by a high-speed camera.

The paper describes results of experimental studies to evaluate the effects of phase-change and/or density variation at the post-breakdown on the dielectric recovery characteristics of liquid and supercritical CO 2 . The study aims to explore the possibility of using supercritical CO 2 to develop high-repetition-rate pulsed-power switches. The experimental setup consisted of a sphere-to-sphere 10 mm radius electrodes configuration with 50 μm gap distance. Three phases of pressurized CO 2 ; subcritical liquid state (SLS), liquid with pressure higher than critical point (LHCP), and supercritical phase (SC), were used for the experiments. Experimental results revealed that SC CO 2 has a very short recovery time making it an appropriate fluid for MHz range highly-repetitive switches. Post-breakdown stage in SLS consisted of gas phase and liquid phase at the plasma channel between the electrodes, with the alternative expansion-contraction motion behavior of gas bubble determining dielectric recovery characteristics. Post-breakdown stages in SC were similar to those in LHCP, generating a low density region at the post-breakdown, where the state of density variation determined dielectric recovery characteristic. The low density region could be compressed by the surrounding medium, resulting in a considerably shorter recovery time.

This study details the effects of a streamer-like discharge under water on undesired micro-organisms in water such as algae. Algae are water organisms classified separately from plants. They are known to cause hazards to humans and the environment. Many face difficulties with the removal of algae. The present investigation shows algae treatment effects by pulse power discharges in water. Algae were treated by high voltage pulsed discharges using a copper pin electrode. Plasma discharge effects such as shock wave, hydroxyl radical, electric field and ultraviolet light on algae were investigated. The efficacy of the electric discharge phenomena in the inactivation of algae in water is shown.

This paper will describe the influence of mesh geometry on the homogeneity of discharges, power, and efficiency of ozone generation. Homogeneous discharges increase the efficiency of the generation of ozone. Geometry of mesh electrodes affects the power and type of discharges, concentration, and efficiency of the ozone generation. The analysis of selected results indicates the need for the use of mesh electrodes with a small cross section at least $0.1\times0.1$ mm ² mesh to obtain a homogeneous discharge. The mechanism by which the geometry of mesh electrodes on the homogeneity of discharge is illustrated in this paper. Homogeneous discharges increase the efficiency of the generation of ozone that reduces the cost of ozone production. The results of the experimental studies show an increase in the average efficiency of 60% of the ozone generation and a 20% reduction in the demand for power with the constant concentration of ozone, justifies the problem.

Many scientists are trying to increase the ozone production efficiency to improve the environment by increasing water and air quality. Important parameters, such as the dielectric constant, thickness, gap distance, and surface condition of an electrode, influence the efficiency of ozone production in a plasma reactor. This paper analyzed the results of experiments on the impact on the power generated in dielectric discharge that occur in a plasma reactor with mesh electrodes using two different dielectric materials. To carry out the experiment, a plasma reactor was constructed with the two mesh electrodes, the mesh having a 0.3 × 0.3 mm ² diameter, and either a glass dielectric with a thickness of 1.1 mm or a porous dielectric in the form of silica gel beads. The results were analyzed by comparing the power generated by the porous dielectric body versus the glass dielectric. The analysis concluded that the use of a porous dielectric demonstrated power increases up to 3.5 times more obtained for the glass dielectric. It was also noted that the discharge ignition voltage Vi and the supply voltage Vm of the porous dielectric were almost the same value, and the difference AV = 11%, while for the glass dielectric, AV = 60%. There were also differences in discharge characteristics, dielectric barrier discharge on streamer resistance, between the two dielectric materials.