Chemical erosion of different carbon composites under ITER-relevant plasma conditions

We have studied the chemical erosion of different carbon composites in Pilot-PSI at ITER-relevant hydrogen plasma fluxes (similar to 10(24) m(-2) s(-1)) and low electron temperatures (T-e similar to 1 eV). Optical emission spectroscopy on the CH A-X band was used to characterize the chemical sputtering. Fine grain graphite (R 6650, SGL Carbon Group), ITER-reference carbon fiber composite material (SNECMA NB31 and NB41; Dunlop 3D), nano-and micro-crystalline diamond coatings on molybdenum and SiC (Silit (R) SKD Reaction-Bonded, Saint-Gobain Ceramics) were compared. The chemical sputtering was similar for the different composites under comparable plasma conditions, except for SiC, which produced a ten times lower rate. The CH emission was constant at electron temperatures T-e > 1 eV and ion fluxes ranging between 10(23) and 10(24) m(-2) s(-1), but decreased at lower temperatures. This decrease is possibly due to changes in the excitation of CH and not due to a change in the chemical erosion rate.