Double sheaths in RF discharges

This paper analyzes the formation of double spacecharge sheaths, associated to the development of double ionization structures in radio frequency discharges. A simulation tool is used to generate space-time images of the ionization rate in hydrogen and in helium, obtained by inducing artificial modifications in the mobility of charged particles, with these gase

2D fluid approaches of DC magnetron discharge

A two dimensional (r,z) time-dependent fluid model was developed and used to describe a DC planar magnetron discharge with cylindrical symmetry. The transport description of the charged species uses the corresponding first three moments of Boltzmann equation: continuity, momentum transfer and mean energy transfer (the latter one only for electrons), coupled with Poisson equation. An original way is proposed to treat the transport equations. Electron and ion momentum transport equations are reduced to the classical drift-diffusion expression of the fluxes since the presence of the magnetic field is introduced as an additional part in the electron flux, while for ions an effective electric field was considered. Thus, both continuity and mean energy transfer equations are solved in a classical manner. Numerical simulations were performed considering Argon as buffer gas, with a neutral pressure varying between 5 and 30 mtorr, a gas temperature from 300 to 350 K and cathode voltages lying from -200 up to -600 V. Results obtained for densities of the charged particle, fluxes and plasma potential are in good agreement with previous works.Laboratoire de Physique des Gaz el des Plasmas (LPGP).Consiliul National al Cercetarii Stiintifice din Invatamantul Superior (CNCSIS) - A/1344/40213/2003

DC magnetron discharge fluid model using a new numerical scheme

Numerical modelling of an electrical discharge by fluid model can be accomplished through different procedures and approaches. A 2D time-dependent one was applied in order to describe a cylindrical symmetry Argon DC planar magnetron discharge. All transport equations, which means continuity and momentum transfer equations for electrons and ions and electron mean energy transport equation are solved in the same manner, using corrected classical drift-diffusion expressions for fluxes. For the validity of this last approach, the presence of magnetic field has been introduced as a correction in the electronic flux expression, while for ions an effective electric field has been considered. Plasma potential is given by Poisson equation

Two-dimensional fluid approach to the dc magnetron discharge

A two-dimensional (r, z) time-dependent fluid model was developed and used to describe a dc planar magnetron discharge with cylindrical symmetry. The transport description of the charged species uses the corresponding first three moments of the Boltzmann equation: continuity, momentum transfer and mean energy transfer (the last one only for electrons), coupled with the Poisson equation. An original method is proposed to treat the transport equations. Electron and ion momentum transport equations are reduced to the classical drift-diffusion expression for the fluxes since the presence of the magnetic field is introduced as an additional part in the electron flux, while for ions an effective electric field was considered. Thus, both continuity and mean energy transfer equations are solved in a classical manner. Numerical simulations were performed considering argon as a buffer gas, with a neutral pressure varying between 5 and 30 mTorr, for different voltages applied on the cathode. Results obtained for densities of the charged particle, fluxes and plasma potential are in good agreement with those obtained in previous studies.C Costin would like to thank the French Government for his PhD fellowship at Laboratoire de Physique des Gaz et des Plasmas. We are also grateful to Dr T Minea for very helpful discussions. This work was partly supported by CNCSIS Romania, grant A/1344/2003

Modelling the influence of frequency in a low pressure capacitively coupled hydrogen discharge

This paper investigates the dependence of plasma density and self-bias voltage with excitation frequency (13.56-40.68 MHz) using a two-dimensional (2D) fluid model in a low pressure (300 mTorr) radio frequency (RF) capacitively coupled hydrogen discharge. A comparison with experimental results reveals that the model predicts the correct trends of density and self-bias voltage variation with driving frequenc

Capacitively coupled hydrogen discharges : modeling vs. experiment

This paper presents a systematic characterization of hydrogen capacitively coupled very high frequency discharges, produced within a parallel plate cylindrical setup, by comparing numerical simulations to experimental measurements for various plasma parameters. A good quantitative agreement is found between calculation and experiment for the coupled electrical power and the plasma potential, at various frequencies, pressures and applied voltages. However, the model generally underestimates the electron density and the self-bias potential with respect to measured values. Model predictions for the absolute density of H(n=1) atoms are compared to first diagnostic results, obtained by two-photon absorption laser-induced fluorescence diagnostics at various pressures and frequencies.Fundação para a Ciência e a Tecnologia (FCT) - SFRH/BD/5012/200

Modelling and characterization of a low pressure capacitively coupled hydrogen discharge

This paper presents a systematic characterization of a pure hydrogen capacitively coupled radio frequency discharge, produced in a parallel plate cylindrical setup, comparing experimental measurements obtained for such discharge with numerical simulations. A good agreement is found between simulation results and experimental measurements for the discharge main electrical parameters. A comparison of H atom absolute density LIF measurements with simulation results will also be presented

Influence of vibrational kinetics in a low pressure capacitively coupled hydrogen discharge

In this paper we present the self consistent coupling of a 2D model of a parallel plate radio frequency discharge in pure hydrogen with a homogeneous chemical kinetics model including H2(X1Σg+,v=0..14) molecules and hydrogen atoms H(n=1-5). The model can estimate the ground state atomic hydrogen density and it was found that the vibrational kinetics changes the H3+ ion density and coupled power to the discharge about 40% when comparing with previous estimates using a simplified kinetics

Probing partonic structure in gamma* gamma -> pi pi near threshold

Hadron pair production gamma* gamma -> h hbar in the region where the c.m. energy is much smaller than the photon virtuality can be described in a factorized form, as the convolution of a partonic handbag diagram and generalized distribution amplitudes which are new non-perturbative functions describing the exclusive fragmentation of a quark-antiquark pair into two hadrons. Scaling behavior and a selection rule on photon helicity are signatures of this mechanism. The case where h is a pion is emphasized.Comment: 8 pages, 1 figure, LaTeX2