Scrape-off layer plasma impurities and the choice of candidate materials for the fusion reactor first wall

Analysis of impurity flux measurements in the scrape-off regions of numerous tokamaks shows that, at existing near-wall plasma parameters, the contribution of impurity ions to the sputtering of surfaces located in the scrape-off layer is larger than that of hydrogenic ions. Nevertheless, this places only a weak constraint on the use of high-Z elements in the materials of the first-wall components of fusion reactors, if impurity transport and light-impurity ion content remain close to those in present-day devices.