Flux dependence of carbon chemical erosion by deuterium ions

Roth, J.*; Preuss, R.*; Bohmeyer, W.*; Brezinsek, S.*; Cambe, A.*; Casarotto, E.*; Doerner, R.*; Gauthier, E.*; Federici, G.*; Higashijima, Satoru; Hogan, J.*; Kallenbach, A.*; Kirschner, A.*; Kubo, Hirotaka; Layet, J. M.*; Nakano, Tomohide; Philipps, V.*; Pospieszczyk, A.*; Pugno, R.*; Ruggiri, R.*; Schweer, B.*; Sergienko, G.*; Stamp, M.*

Chemical erosion of carbon has been studied in ion beam experiments, and the yield values are available as a function of ion energy and surface temperature. ITER divertor condition, however, cannot be simulated by ion beam. For extrapolating to ITER, the erosion must be investigated in plasma simulators and in SOL or divertors of present fusion devices. In the past, erosion values were reported, but the values showed a wide scatter as a function of ion flux, . Therefore, a joint attempt was made through the EU Task Force on Plasma-Wall Interaction and the International Tokamak Physics Activity (ITPA) to clarify the flux dependence. For each data point the local plasma conditions were normalized to impact energy of 30 eV, the data were selected for a surface temperature close to the maximum yield or to room temperature, and the diagnostic was calibrated in-situ. Through this procedure, the previous large scatter could be drastically reduced. A fit using Bayesian probability analysis was performed yielding a decrease of the erosion yield with at high ion fluxes.