EROSION OF SI-DOPED AND TI-DOPED GRAPHITES DUE TO DEUTERIUM IRRADIATION

During irradiation of carbon materials with hydrogen ions hydrocarbon molecules are formed resulting in an enhancement of the erosion yield. At temperatures around 800K hydrocarbon molecules are released in a t hermal activated process, while at low temperatures and low ion energi es physical sputtering of lightly bound hydrocarbon radicals enhances the erosion yield. Doping of carbon materials with B, Si and Ti result s in a reduction of its chemical reactivity with hydrogen ions. While B reduces drastically the thermal activated process it does not alter the sputtering of hydrocarbons at low energies. For isotropic graphite s doped with 10 at% Si(LS10) and 10 at% Ti(LT10) it is shown that pref erential erosion of carbon leads to enrichment of the dopant at the su rface. The thermal activated hydrocarbon emission is reduced already a t low ion fluences for LS10 and LT10, while the low energy process is only reduced after high fluence irradiation and carbon surface depleti on in the case of Ti doping. Depending on the microstructure of the ma terial a very pronounced surface topography develops. Carbidic grains protect the underlying carbon material from erosion until a columnar s tructure evolves. Due to the high threshold for physical sputtering of Ti the total erosion yield for LT10 shows the predicted threshold beh aviour for physical sputtering.