Study of carbon impurity generation by chemical sputtering in JT-60U

CD/CH-band intensities emitted from hydrocarbon molecules have been measured in the divertor region of JT-60U and the chemical sputtering yield of methane was estimated as a function of the surface temperature and the deuterium ion flux. The chemical sputtering yield increases with the surface temperature and decreases with increasing ion flux density in the L-mode plasmas. The B4C converted CFC tiles are installed in JT-60U and it is found that the chemical sputtering of B4C converted CFC tiles is suppressed in comparison to normal CFC tiles.