A new atmospheric pressure plasma jet source with two plasma regions

We studied effects of electrodes gap and tip shape on the discharge characteristics of a syringe-type atmospheric pressure plasma jet source (APPJS). The APPJS has a powered electrode and a floating electrode instead of a ground electrode. As the input power increases, a plasma column is first created in front of the tip of the powered electrode and is extended to the floating electrode which is capacitively coupled with powered electrode. As the plasma column reached to the floating electrode, the power transfers through the plasma and thus, the voltage of the floating electrode becomes similar to powered electrode voltage. Above a certain threshold voltage, the jet plasma is generated at the tip of the floating electrode and is emitted along the gas flow. Under the condition that the gap between the powered electrode and floating electrode is narrow, the threshold voltage for the ignition of the jet plasma is critically affected by the shape of the floating electrode tip. In the wide gap condition, on the other hand, the threshold voltage depends on the gap distance.