Optical Diagnostics of Micro Discharge Jets

Abstract

Micro plasmas operated at ambient pressure with dimensions of the confining geometry in the order of a few ten micrometers to a millimeter are actually in the focus of interest due to the broad regime of applicability they offer and due to a similarly broad range of open physical questions. Here we present optical measurements within the discharge core and the effluent region of an especially developed micro discharge jet. To get an understanding of the complex system of this discharge it is important to analyse transport phenomena of energy and particles within both parts of the discharge by various highly sophisticated diagnostics. As a consequence of the limited access and the dimensions of the micro discharge most of these diagnostics are optical. Here we present diagnostics applied to determine spatially resolved absolute atomic oxygen densities as the most reactive constituent of the effluent, density maps of ozone as final reaction product of the gas chemical chain induced by the discharge and phase resolved optical emission spectroscopy yielding insight into the excitation dynamics of the discharge.

Cold atmospheric pressure plasma jet interactions with plasmid DNA

“…In this study, plasmid DNA in solution was exposed to the effluent of a rf atmospheric pressure plasma jet, 11,12 and simultaneously, the absolute density of ground state atomic oxygen in the jet was measured. The plasma is ignited between two parallel stainless steel electrodes confined between two quartz windows.…”

“…Under all conditions, the plasma operates in a low-density alpha-mode where a stable, homogeneous glow discharge is sustained between the two electrodes. 11,12 An effluent is emitted from the plasma bulk into ambient air and the investigations presented are performed a distance of 2 mm from the end of the electrodes ͑see Ref. 16͒.…”

“…The maximum gas temperature measured inside the plasma core using rotational bands of nitrogen is 75°C, while in the effluent applied to the DNA, it is 40°C. 12 The interactions at the plasma liquid interface are complex with a large variety of relevant species and a broad range of densities and particle fluxes. The discharge configuration is such that the electric field direction is perpendicular to the gas flow and plasma channel exit nozzle.…”

“…14 Measurements have shown ground state atomic oxygen, and ozone densities penetrate with relatively high densities as far as 100 mm from the nozzle of the plasma channel. 11,12 In fact, synergistic processes involving two or more of the above species are likely mechanisms for DNA damage.…”

“…13 Neutral species, reactive particles in particular, and UV radiation dominate its characteristics. 11,12 Reactive oxygen species and reactive nitrogen species, e.g., O, O 3 , O 2 ͑a 1 ⌬ g ͒, OH, N, N 2 , and NO, are particularly known for their aggressive influence on biomolecules. 14 Measurements have shown ground state atomic oxygen, and ozone densities penetrate with relatively high densities as far as 100 mm from the nozzle of the plasma channel.…”