Modelling of local carbon deposition on a rough test limiter exposed to the edge plasma of TEXTOR

A Monte-Carlo code called SURO was developed to study the influence of surface roughness on the impurity deposition characteristics in fusion experiments. SURO uses the test particle approach to describe the impact of background plasma and the deposition of impurity particles on a sinusoidal surface. The local impact angle and dynamic change of surface roughness as well as surface concentrations of different species due to erosion and deposition are taken into account. Coupled with the three-dimensional Monte-Carlo code ERO, SURO was used to study the impact of surface roughness on ¹³C deposition in ¹³CH₄ injection experiments in TEXTOR. The simulations showed that the amount of net deposited ¹³C species increased with surface roughness. Parameter studies with varying ¹²C and ¹³C fluxes were performed to gain insights into impurity deposition characteristics on the rough surface. Calculations of the exposure time needed for surface smoothing for TEXTOR and ITER were also carried out for different scenarios.