WP 3: modelling studies

The objectives of work package 3 on modelling studies include : modelling of the effect of molecular gases on the electrical parameters, emitted spectra and ion concentrations, including a  collision-radiative for Ar + H₂, Ar + O₂ and/or Ar + N₂ discharges coupled to experimental verification. Modelling of crater shapes of pulsed discharges, including a physical model for the ignition of the plasma and thermal effects of the sputter gas or sample to understand the crater shape dependent on gas flow, pressure and electrical parameters.

Situation at mid-term:

At the University of Antwerp a modelling network for Ar/H2 glow discharges was developed earlier for the so-called VG9000 glow discharge cell, to study the effect of small admixtures of hydrogen to an argon glow discharge. This modelling network was adapted to the Grimm-type source most commonly used in GD-OES instruments. In the next stage, a new modelling network was developed for an Ar/N2 glow discharge in the Grimm-type configuration.

Aranka Derzsi in RISSP developed a hybrid fluid-Monte Carlo model for the self-consistent description of the analytical glow discharge on the level of elementary processes. The model includes the description of all important plasma species, in particular those that are responsible for cathode sputtering, such as Ar and Cu ions and fast atoms. The model can be used to calculate sputtering yields at different positions of the cathode therefore can predict crater shapes. The model has been extended to handle gas heating and non-uniform gas temperature in the source and proved that the gas temperature has a major effect on the crater profile.