Spatial dynamics of helium metastables in sheath or bulk dominated rf micro-plasma jets
نویسندگان
چکیده
Space resolved concentrations of helium He (S1) metastable atoms in an atmospheric pressure radio-frequency micro-plasma jet were measured using tunable diode laser absorption spectroscopy. The spatial profile of metastable atoms in the volume between the electrodes was deduced for various electrode gap distances. Density profiles reveal the sheath structure and reflect the plasma excitation distribution, as well as the dominance of the α-mode discharge. Gap width variations show the transition from a normal glow plasma to a pure sheath discharge. In order to analyse and verify the experimentally observed profiles of the metastable atoms, a two-dimensional simulation model was set up. Applying an appropriate He/N2/O2 chemistry model, the correlation between the metastable profiles and the underlying excitation mechanisms was obtained. (Some figures may appear in colour only in the online journal)
منابع مشابه
Electron energy dynamics in a RF discharge with trapezoidal driving voltage: comparison of experiment and particle-in-cell Monte Carlo collision simulation
We report on the properties of a special RF discharge characterized by a trapezoidal shape of the driving voltage pulse. This driving mode offers an advantage in comparison to the common sinusoidal voltage—in allowing the separation in time of effects which are connected with the time derivative of the driving voltage (displacement current, α-mechanism) from effects connected with the amplitude...
متن کاملTwo-dimensional laser collision-induced fluorescence measurements of plasma properties near an RF plasma cathode extraction aperture
A dense plasma structure was observed to form near the extraction aperture of a helium RF plasma cathode. Laser collision-induced fluorescence was used to generate two-dimensional spatial maps of the electron density and the effective electron temperature within the structure over a range of operating conditions. The aperture plasma reached densities nearly an order of magnitude higher than the...
متن کاملCoulomb Cluster in a Plasma under Cryogenic Environment
Coulomb cluster of dust particles in an RF helium plasma under cryogenic environment is observed experimentally. Background neutral temperature is controlled by cryogenic liquid such as liquid helium or liquid nitrogen. Dust dynamics in a sheath is studied. A dust injected into a sheath moves toward an equilibrium position where the sheath electric force balances with the gravitational force. D...
متن کاملThe effects of presheath dynamics on rf sheaths
A common approach to the study of rf sheaths is to separate the description of the sheaths from that of the bulk plasma. In order to solve the resulting set of equations, an appropriate boundary condition for the sheath model has to be specified at the sheath-plasma boundary. In the existing sheath models, this boundary condition is assumed to be stationary. In present paper, we investigate the...
متن کاملSheath Reversal During Transient Radio-Frequency Bias
Optical imaging is performed with temporal and spatial resolution in a capacitively coupled plasma. The region imaged is in front of an RF biased planar probe embedded in the center of the ground electrode of a standard Gaseous Electronics Conference (GEC) reference cell. Two main periods of interest stand out. The local sheath induced by the biasing and the main plasma bulk are affected. The f...
متن کامل