Impurity transport modelling in edge plasmas of fusion devices with the Monte Carlo code ERO

The Monte Carlo code ERO simulates the three-dimensional transport of impurity particles in a background plasma using the test particle approximation. It treats the interaction of the plasma ions, atoms and of the impurities with the plasma facing components (PFC). ERO modelling for ITER estimates the lifetime of the inner target (erosion of 0.5 cm) to about 7000 shots with a shot length of 400s. The maximum allowed tritium retention due to eroded carbon not redeposited locally on the target plates would be already reached after 380-440 shots. Strike point sweeping might increase the target life time by a factor of about 4 while tritium retention seems not to be influenced. Apart from transient events especially material mixing effects of the elements foreseen for ITER as PFC (carbon, beryllium and tungsten) introduce uncertainties in the prediction. The injection of hydrocarbon (¹³CH₄) through spherical shaped limiters (one made of tungsten, one of graphite) in TEXTOR reveal that carbon has a reduced deposition efficiency on tungsten compared to graphite. This effect has not been taken into account until now in the modelling by the ERO code. The surface model of the code has therefore been substituted by a customized version of the Monte Carlo Code SDTrimSP which will help to clarify the effects of material mixing. A first successful test simulation shows that the depth distributed concentration of PFC influences sputtering yields.