Saburo Satoh

Development of measurement equipment of half life of ozone

Abstract In the present research, a new measurement method and the mechanism of half-lifetime τ (h) of ozone decay is proposed. Ozone is generated by such electric discharge as a silent or surface discharge and has a strong oxidation power and is widely used for air or water purification. But to determine the dosage of ozone, it is necessary to know the half-lifetime of ozone decay τ in air and/or water [1] . Ozone decay is found to change in a logarithmic way. Through the measurements of the ozone concentration x (g/m3) with time t, the half-lifetime of ozone decay, τ, is estimated [2] .

Modification of hydroxyapatite crystallization using CO2 laser

To remineralize the dentine surface viz. improve the micro-hardness and acid-resistance of the surface of teeth IR laser application was concerned in this study. Experimental aims are concentrating to investigate changes of hydroxyapatite crystal structure before and after laser irradiation with characteristic absorption wavelength region around 10.6 μ m. As a preliminary study for FEL application in biological field, the results we have got with the 10.6 μ m irradiation demonstrate that the capability of FEL of precisely deliver energy over a wide band of IR wavelength, offering control over surface modification, made it an attractive tool for further ameliorating of hydroxyapatite crystallization.

Characteristics of a plasma production and a laser‐induced discharge by a CO2 laser on DC electric field

The experiments of a laser‐induced discharge were carried out with a CO2 laser radiation in the atmospheric ambient gases under a DC electric field applied. In these experiments, both of the laser‐induced discharge and the plasma production by the CO2 laser were suppressed with an increasing DC electric field strength. Although the laser‐produced plasma was generated between the electrodes without DC electric field, both the probability of induced‐discharge and plasma production decreased with the applied voltage across the electrodes. In this paper, the mechanisms of the phenomena for the suppression of the plasma production under applying the electric field between electrodes were discussed. It was found that the attachment processes of electrons most likely played an important role in this phenomena.

Biological Application of Barrier Discharge in Water

Discharges in liquid media can generate high electrical field, ultraviolet rays, as well as various chemically active species which can be utilized for sterilization and decompositions of toxin and bacteria in water. In order to obtain continuous and stable discharge in water, barrier discharge was produced. The electrical and optical characteristics of the barrier discharge in water are discussed. The mechanism and possible application of barrier discharge in water are also prospected

Evaluation of weakly ionized plasma channel by accumulation effect of charged particles for laser-triggered lightning

Density of charged particles produced by KrF excimer laser with high repetition rate of kHz order has been measured. The accumulation effect of charged particles was confirmed in the case of the repetition rate above 1 kHz of a laser. The density of charged particles increased exponentially and it was calculated that the plasma density must be increased one or two orders for the laser-triggered lightning, which required laser repetition rate of 3.5 kHz or 6 kHz, respectively.

Weakly ionized plasma channel by accumulation effect of charged particles using high repetition rate excimer laser

This paper describes accumulation effect of charged particles using high repetition rate KrF excimer laser for the laser-triggered lightning technique. The accumulation effect was investigated by the measurement of charged particle density varying the repetition rate of the laser. The process and effect of the accumulation of charged particles were confirmed in the case of laser repetition rate of 1 kHz.