Broadband dielectric constant measurements in the frequency range between 40 Hz and 50 GHz of pure water, tap water, and sodium chloride aqueous solutions with different DC conductivities up to 5 S/m were conducted. The measurements were done using an impedance analyzer for the frequency range 40 Hz to 110 MHz and a vector network analyzer for 10 MHz to 50 GHz. The results show that the dielectric constant decreases with the increase in DC conductivity and is dependent on the frequency. The dielectric relaxation of water with a constant dielectric loss peak was also observed. The frequency dependence of the conductivity is also large.

The characteristics of volume-averaged plasma density on axial propagation for atmospheric argon (Ar) plasma bullets are experimentally investigated. The non-thermal plasma bullets are ejected through a glass tube into the surrounding ambient air. Taking into consideration the time and space profile of the plasma movement, the plasma propagation is measured using a Rogowski coil. The plasma density is evaluated from the propagation velocity and the current magnitude. The plasma density profiles are presented as functions of the applied voltage and the length of growth. The plasma density is in the order of 1016 m−3 and the propagation velocity is in the order of 105 m s−1. These values are similar to those of weakly ionized non-thermal plasma jets.

An atmospheric pressure plasma jet was used for the surface modification of fused silica glasses. The length of an atmospheric pressure argon plasma jet generated at an applied voltage of 10 kV, at a frequency of 9 kHz and at an argon gas flow rate of 10 L/min was approximately 3 cm. The wettability of the glass surface was improved by the irradiation of the argon plasma jet. The contact angle of a water drop on the glass surface after the argon plasma jet irradiation for 10 s decreased from 70 to 7 degree, indicated that the glass surface after the irradiation became super-hydrophilic. The super-hydrophilicity changed to ordinary hydrophilicity after one hour and the hydrophilicity was kept three weeks on the glass surface. From the results of XPS measurements, the super-hydrophilicity with irradiation was attributed to the removal of carbon atoms (organic compounds) adsorbed on the glass surface.

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