The interaction of atmospheric pressure plasmas with targets

Non-thermal atmospheric pressure plasmas are a focus of intense study in the recent years, due to their suitability and convenience for applications on sensitive substrates. In applications, those discharges come in contact with an array of targets, most notably with targets of varying conductivities. As these discharges are in a transient state, evolving quickly through time and space, sub-mm in characteristic size and characterized by a low ionization degree, the presence of any target affects them and the target properties determine the interaction.

This work focuses on the charging dynamics of targets while under plasma exposure. The model system consists of a plasma jet in a coaxial geometry where the inner electrode is powered and is also used as a gas inlet. The ground is placed on the outer side of a glass capillary. Sinusoidal AC at 30 kHz or pulsed voltage at 5 kHz is used to power the inner electrode. The typical power dissipated in the plasma is below 1 W. Helium is flown through the jet at rates between 500 SCCM and 1500 SCCM and allowed to expand in the room air at the exit of the glass capillary.