Emission Spectroscopy of Pulsed Power Microplasma for Atmospheric Pollution Control

Abstract

Pollution of the atmosphere from various sources, including factories and automobiles, is a serious problem worldwide and should be controlled and reduced. Nonthermal plasma is studied by various groups and has been applied for exhaust gas treatment and indoor air purification. Microplasma, which is atmospheric pressure nothermal plasma, has recently been studied by many researchers. Although nonthermal-plasma diagnosis by emission spectroscopy has been applied by many authors, the mechanisms are not sufficiently understood. In this paper, the diagnosis of the microplasma discharge in N 2 gas and N 2 /NO gas mixture are presented. An experimental Marx generator with MOSFET switches was used to generate pulsed output voltages of up to −1.8 kV. Emission spectra were observed by a spectrometer with intensified charge-coupled device camera and a photomultiplier tube. The formation of radicals was confirmed by NO-γ band, N 2 second positive band, and N + 2 first negative system. Time evolution of light emission that is measured by the photomultiplier tube showed differences between the NO-γ band and the N 2 second positive band. This condition is suggested to be the result of different light emission mechanisms; the N 2 second positive band is excited by direct electron impact, and the NO-γ band is excited by collisions of N 2 metastables.

Study of Sterilization and Disinfection in Room Air by Using Atmospheric Microplasma

“…This self made pulse power supply with MOSFET switches energized the electrodes and controlled the plasma emission and an ICCD camera by trigger signal [19,35]. It generates negative pulses up to -1.6 kV, rise time 80 ns and pulse width varied from 100 ns to 5 μs.…”

“…UV light emissions from microplasma were observed to confirm the effect of UV light on the bacteria sterilization process [19,35]. The emission spectra were measured by an intensified charge-coupled device (ICCD) camera (Ryoushi-giken, SMCP-ICCD 1024 HAM-NDS/UEmV), a spectrometer (Ryoushi-giken, VIS 351), and by a photomultiplier tube (Hamamatsu Photonics, R3896).…”

“…The combination of UV light emitted from 250 to 300 nm known as NO-γ band, and active species could have contributed to the sterilization process of bacteria in suspended air [35]. Figure 15 shows the photograhps of B. subtilis before and after sterilization by microplasma.…”

“…The shape of the B. subtilis was changed and torn to pieces after the microplasma treatment. During the microplasma treatment process, every bacteria was exposed to a high electric field and UV radiation while passing through the electrodes holes generating microplasma [35]. This could cause physical damage to the bacteria and affect their shape.…”

Study of Atmospheric Microplasma for Plasma-Life Science

“…It is not necessary a vacuum enclosure therefore it is small device. Our microplasma, which is generated between parallel plate electrodes, can treat a wider area than the plasma jet or corona discharge e. g. sterilization, odor removal, surface treatment [7][8][9]. Most of the plasma sterilization methods are using direct plasma method.…”