The Current–Voltage Characteristics of Atmospheric Pressure Plasma Jets With the Various Working Gases

The current-voltage characteristics of atmospheric pressure plasma jets with various working gases (He, Ne, Ar, N2, and air) are investigated. Systems of the plasma jets are composed of a syringe needle inserted into a glass tube and are operated by a sinusoidal high-voltage through a dc-ac inverter generating several tens of kilohertz. The various electrode structures with or without the ground electrode are analyzed by using an equivalent circuit model. For the biomedical applications concerning the discharge stability and the electric safety with a low plasma-current and a low voltage operation, the suitable structures of plasma jets for each gas are suggested. For the plasma jets of inert gases (He, Ne, and Ar), the discharge triggered by an external ground electrode seems to be suitable, because the low current of a plasma plume is adjusted readily with a low voltage of 1-2 kV. For the jets of N2 and air, the nozzle of a metal ground electrode at the end of a glass tube is suggested to reduce the operation voltage below 3 kV and to acquire a low plume-current of a few milliamperes exiting the metal nozzle.