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

A Monte-Carlo code called SURO has been developed to study the influence of surface roughness on the impurity deposition characteristic 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 3D 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 increases with surface roughness. Parameter studies with varying ¹²C and ¹³C fluxes were performed to gain insight into impurity deposition characteristic on the rough surface. Calculations of the exposure time needed for surface smoothing for TEXTOR and ITER were also carried out for different scenarios. (author)