A 2.45 GHz Microwave-Excited Atmospheric Pressure Plasma Jet Source of Low Breakdown Power Threshold

Microwave coaxial resonators are widely used to generate atmospheric pressure plasma jets which have been applied in many fields such as biomedical treatment and material synthesis. A 2.45 GHz microwave-excited plasma jet source based on the coaxial resonator is designed to realize atmospheric pressure Ar plasma jet. It is found that the plasma does not disappear when we stop the gas flow keeping the microwave excitation unchanged after the plasma jet is generated. At this time, the air components including N
2
, O
2
and
$\boldsymbol{\mathrm{H}_{2}\mathrm{O}}$
will be used as new discharged gases. Active particles such as
$\boldsymbol{\mathrm{N}_{2}}$
, O, NO and OH will continue to collide with electrons to maintain a new ionized state as a plasma ball. On this basis, we propose a method of using Ar gas or He gas to assist other gases generating cold plasma jets. Finally we realize
$\mathbf{CO_{2}, N_{2}, O_{2}}$
plasma jets which are difficult to breakdown without providing high microwave power.