Electron Temperature and Electron Density of Underwater Pulsed Discharge Plasma Produced by Solid-State Pulsed-Power Generator

Abstract

A pulsed discharge produced underwater has been an attractive method to treat waste water. For the optimization and realization of the water treatment system utilizing underwater pulsed discharge, modeling analysis could be one of the essential works. However, there is still no simulation work about the underwater pulsed discharge due to the lack of knowledge about its characteristic parameters such as electron temperature, electron density, and so on. In this paper, the temperature and the electron density in a pulsed discharge plasma produced underwater are measured and presented. A magnetic pulse compressor (MPC) was developed and used to create the electrical discharge in water. The developed MPC is all-solid state and is, therefore, a maintenance-free generator. To define the temperature and the electron density in an underwater pulsed discharge plasma, two kinds of spectroscopic measurements, called the line-pair method and Stark broadening, were carried out. According to the experimental results, the temperature and the electron density in the pulsed discharge plasma between point-plane electrodes immersed in water are determined to be 15 000 K and 10 18 /cm 3 , respectively.

Electrical Properties Associated with Discharge Developments in Water Subjected to Impulse Voltages

“…The time-lag 1 t for the streamer corona initiation after voltage application was sensitive to the magnitude of applied voltage, but it was insensitive to water resistivity. Both time-lags 1 t and 2 t were inversely proportional to the applied voltage. The time-lags 1 t tends to be shorter with increasing water resistivity, but the time-lags 2 t for higher water resistivities were longer than those for lower water resistivities at the same magnitude of applied voltage.…”

“…Both time-lags 1 t and 2 t were inversely proportional to the applied voltage. The time-lags 1 t tends to be shorter with increasing water resistivity, but the time-lags 2 t for higher water resistivities were longer than those for lower water resistivities at the same magnitude of applied voltage. The diverted result of the time parameter came from the variations of the conduction currents and the difference between the applied voltage and the peak voltage.…”

“…To analyze the ionization phenomena, the two time parameters are defined as shown in Fig. 7 (b): where the time-lag 1 t is the time to ionization threshold (preionization time) and the time-lag 2 t is the time to the second current peak (post-ionization time). Also, the preionization resistance 1 R is defined as the voltage divided by the current at the time of 1 t and the post-ionization resistance 2 R is calculated by the same method at time 2 t .…”

“…Fig. 8 shows the results of the time-lag to the ionization threshold 1 t and the time-lag to the second current peak 2 t as a function of peak voltage. The time-lag 1 t for the streamer corona initiation after voltage application was sensitive to the magnitude of applied voltage, but it was insensitive to water resistivity.…”

“…The characteristics of electrical discharges in water are widely used in a variety of industrial, medical and environmental applications, as well as energy storage, sewage treatment, switching and insulation in pulsed power systems, water purification, etc. [1]- [3]. Gas and solid discharge phenomena have been investigated in detail and their physical properties are relatively well known.…”