Optical and electrical characterization of an atmospheric pressure microplasma jet with a capillary electrode

A microplasma jet with a capillary electrode working at atmospheric pressure is developed to create nonthermal plasma. This jet can be operated at an excitation frequency either in several tens of kilohertz ac range (or pulsed voltage with a repetition rate of kilohertz range) or in radio-frequency range. The working gas, helium or argon, and the additive gas, oxygen, are fed into the plasma jet. The discharge has been characterized by optical emission spectroscopy. The electrical property of the discharge has been studied by means of voltage and current probes. The dynamic nature of the plume is investigated by using intensified charged coupled device camera. The electron temperature is estimated from the modified Boltzmann plot method utilizing the Ar 4p -> 4s transitions. The plume temperature is determined by using the fitting the fine structure of the emission bands of OH molecules and by utilizing the line shape of the transition. They are compared with the results obtained by optical fiber thermometer. The characteristics of plasma jet are studied by employing different excitation mode and by adjusting the gas flow rates, the applied voltage, and the amount of additive O-2 flow. The characteristic differences between the Ar plasma jet and the He plasma jet are compared. The effects of the additive O-2 gas are investigated. The plasma bullet velocity is found to increase with the applied voltage but to decrease with the duty cycle. Also the preliminary results of microplasma effects on the human breast cancer cells are presented. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3330507]