Investigations of the spatio-temporal build-up of atomic oxygen inside the micro-scaled atmospheric pressure plasma jet

Abstract.

The ascent of atomic oxygen densities created inside the micro-scaled atmospheric pressure plasma jet has been investigated spatially resolved under parameter variations such as applied power, gas mixture and gas velocity using two-photon absorption laser induced fluorescence spectroscopy. Along the discharge channel an increase of the atomic oxygen density within the plasma is observed. The density shows an exponentially asymptotic convergence into an equilibrium close to the effluent. In the post-discharge effluent an exponential spatial decrease can be found. Typical ascent distances of a few hundreds of μm decrease with the applied power and increase with gas velocity and oxygen admixture. The maximum atomic oxygen density increases with applied power and admixed molecular oxygen up to more than 10¹⁶ cm^-3. An increase of the maximum atomic oxygen density with increasing gas velocity has been found. Optical emission spectroscopy measurements indicate a strong increase of the nitrogen emission at low gas flow rates along the channel.