Numerical modelling of low pressure plasmas for industrial and biomedical applications

The development of plasma technologies requires a deep understanding of the plasma physics, for which numerical methods are essential. In this thesis, two plasma-based industrial challenges are addressed using specifically developed numerical methods.

The use of dual-frequency, low (LF<1 MHz) and higher frequency (HF>60 MHz), waveforms in capacitively coupled plasmas (CCPs) have important industrial applications. At HFs, inductive heating (IH) effects play an important role and, in view of current industrial needs, it is essential to understand these effects at the kinetic level. Therefore, a one-dimensional (1D) particle-in-cell model coupled to an IH model has been developed. This is a novel approach that enables 1D kinetic simulations of HF CCPs. The model was first used to simulate single HF CCPs, showing that IH couples most of its power to the bulk plasma-sheath interface. A further simulation shows a synergy between the HF and LF waveforms that enhances the inductive power coupling.

In the context of plasma sterilisation and materials processing, the control of vacuum ultraviolet (VUV) radiation is important. However, the understanding of the formation pathways of VUV photons remains limited and is restricted to a narrow range of operating parameters. In order to better understand radiation in plasma applications, a zero-dimensional global model (GM) and a self-consistent chemical-radiative reaction scheme for argon and oxygen have been developed and used to study VUV emission from oxygen atoms. The GM results have helped to identify the dominant reaction pathways leading to VUV emission, showing that it is dominated by the 130 nm resonance line. Furthermore, a parametric study over pressure (0.3-100 Pa), Ar/O2 mixture (0-20 %) and power deposition (100-2000 W) has been carried out, which concludes that oxygen VUV emission increases with power and oxygen fraction, with peak emission intensities found for pressures between 5-50 Pa.