Alexander Wollny

Spatially resolved simulation of a radio-frequency driven micro-atmospheric pressure plasma jet and its effluent

Radio-frequency driven plasma jets are frequently employed as efficient plasma sources for surface modification and other processes at atmospheric pressure. The radio-frequency driven micro-atmospheric pressure plasma jet (μAPPJ) is a particular variant of that concept whose geometry allows direct optical access. In this work, the characteristics of the μAPPJ operated with a helium–oxygen mixture and its interaction with a helium environment are studied by numerical simulation. The density and temperature of the electrons, as well as the concentration of all reactive species are studied both in the jet itself and in its effluent. It is found that the effluent is essentially free of charge carriers but contains a substantial amount of activated oxygen (O, O3 and O2(1Δ)).The simulation results are verified by comparison with experimental data.

Ionization wave propagation on a micro cavity plasma array

The simulation was performed using the computer modeling platform nonPDPSIM, described in detail in Refs. 10–12 and briefly discussed here. Poisson’s equation for the electrostatic potential is self-consistently coupled with driftdiffusion equations for the transport of charged species and the surface charge balance equation. The set of equations is simultaneously integrated in time using an implicit Newton iteration technique. This integration step is followed by an implicit update of the electron temperature by solving the electron energy equation. To capture the non-Maxwellian behavior of the electrons, the electron transport coefficients and rate coefficients are obtained by solving the zerodimensional Boltzmann’s equation for the electron energy distribution. A Monte Carlo simulation is used to track the trajectories of sheath accelerated secondary electrons. The transport of photons is treated by means of a Green’s function propagator. The discharge is sustained in argon at atmospheric pressure. The species in the model are electrons, Ar(3s), Ar(4s), Ar(4p), Ar þ ,A r �, and Ar þ . The photon transport we tracked in the model is dimer radiation from Ar � .I n

Ignition of a Microcavity Plasma Array

Microcavity plasma arrays are regular arrays of inverse pyramidal cavities created on positively doped silicon wafers. Each cavity acts as a microscopic dielectric barrier discharge. It has an opening of 50 μm × 50 μm and a depth of 45 μm. The separation of the cavities is 50 μm. Operated at atmospheric pressure in argon and excited with a 100-kHz RF voltage, each cavity develops a localized microplasma. Experiments show a strong interaction of the individual cavities, leading, for example, to the propagation of ionization waves along the array surface. This paper studies the ignition of a microcavity plasma array by means of a numerical simulation. The propagation of an ionization wave is observed. Its propagation speed matches experimental findings.

Custom tailored ion energy distribution functions online for everybody

Summary form only given. Plasma processes, particularly plasma etching and plasma deposition processes are crucial for a large variety of industrial manufacturing processes. For these processes the knowledge of the ion energy distribution function plays a key role. Measurements of the ion energy distribution function (IEDF) are at least challenging and often impossible in industrial processes. An alternative to measurements of the IEDF are simulations.

Numerical simulation of a coaxial microplasma jet at atmospheric pressure

Summary form only given. Microplasmas at or around atmospheric pressure gained rising attention recently. Their technological benefits and application-oriented flexibility allows microplasmas to explore new fields of plasma technology, e.g. biomedical applications. One particular type of microplasma sources that shows a variety of interesting physics and applications is the so called cold microplasma jet.

Numerical study of the electron dynamics in radio-frequency plasmas at atmospheric pressure

The dynamics of electrons plays an important role for the behavior of radio-frequency driven discharges, particularly at high pressures. The electron dynamics itself is highly driven by the dynamics of the plasma boundary sheath. In this work we study a radio-frequency driven atmospheric pressure plasma jet which is frequently employed as an efficient plasma sources for surface modification. We concentrate on secondary electron effects and excitation mechanisms in Helium/Oxygen mixtures by means of self-consistent plasma simulations.

Dynamics of micro cavity plasma arrays: Simulation of ionization wave propagation

Summary form only given. The microcavity plasma array has been developed by J.G. Eden and co-workers as an efficient light source. This device consists of a silicon wafer with a matrix of inverse pyramidal cavities of the size of a few ten micro meters. The structure is covered by dielectrics. A nickel grid embedded inside the dielectrics acts as counter electrode. The discharge is driven by a triangular voltage at a frequency of 10-100 kHz in argon at atmospheric pressure. For the naked eye the array emits a bright glow that appears homogeneous over a very large area. However, spatially and temporally resolved emission spectroscopy performed by V. Schulz-von der Gathen and co-workers reveals that this impression is misleading. The discharge as a hole shows strong interactions between neighboring micro discharges. In this contribution we investigate the fundamental phenomenon behind the plasma-plasma interaction by numerical simulations.

Spatially resolved simulation of an radio-frequency driven atmospheric pressure plasma jet in ambient air

Radio frequency driven plasma jets are frequently employed as efficient plasma sources for surface modification and other processes at atmospheric pressure, e.g. in the increasing field of biomedical applications. The radio-frequency driven micro-scaled atmospheric pressure plasma jet (μAPPJ) is a particular variant of that concept. In this work, the characteristics of a μAPPJ operated with a helium-oxygen mixture and its interaction with ambient air are studied by spatially resolved numerical simulation. The density and temperature of the electrons, as well as the concentration of all relevant species are studied in both the discharge itself and its effluent.

A first look into plasma-plasma interaction at atmospheric pressure via numerical simulation

The micro plasma array developed by J.G. Eden and co-workers consists of a matrix of hollow cathode discharges of the size of a few ten micro meters. A silicon substrate with inverse pyramidal cavities is used as one electrode. The second electrode, separated by a dielectrica, covers the space between cavities. The whole structure is covered with a second dielectric layer. The discharges are driven by a sinusoidal voltage at a frequency of 10-100kHz in atmospheric pressure Argon. Experiments performed by Schulz-von der Gathen and co-workers show strong interactions between the the micro discharges2. The fundamental phenomenon is still unclear. This contribution is intended to show a first look into the modeling and simulation of micro plasma array and the plasma-plasma interaction.

Numerical simulation of an rf driven micro-plasmajet at atmospheric pressure

Summary form only given. An increasing number of different microplasma sources were developed over the last years. These sources differ in the underlying application, hence different types of geometry and discharge configuration, DC or RF discharges and the used chemistry exist. The variety of applications contains - among others - the wide field of surface modifications, light sources, steriliztation and display panels.