Development of a Be reaction mechanism for plasma modelling

Beryllium (Be), a soft alkaline earth metal, is used by the fusion community as a first wall material and within mixed-breeder blankets. During operation, Be is spread throughout the reactor and deposits on plasma-facing surfaces, including optical components. These Be coated surfaces readily oxidise forming BeO, degrading the optical properties and leading to Be and O being present in the plasmas formed near these surfaces. In this paper we present an Ar/O (Formula presented) (Formula presented) /Be reaction mechanism for use in low-temperature plasma modelling, derived from calculated excitation, ionisation and momentum cross-sections for Be. Due to the similar properties of Be and aluminium (Al), Al is often used as a proxy in experiments; we compare plasma properties for Be containing plasmas with a well characterised Ar/O (Formula presented) (Formula presented) /Al reaction mechanism. The two mechanisms produce similar plasma densities but dissimilar rates of diffusion, highlighting the limitations of using Al as a proxy. This work underlines that correct modelling of gas flow throughout the reactor is important in reliably predicting the re-deposition of eroded material such as BeO.