A quantitative study of the carbon impurity production mechanisms from an inertial limiter in Tore Supra as determined by visible spectroscopy

In a steady-state tokamak, impurity production and transport from plasma facing components will have to be controlled. Recent results from several divertor tokamaks suggest the importance of chemical sputtering as an impurity production mechanism. However, since impurity production is minimized in high recycling divertor configurations, the quantitative characterization of impurity generation is more difficult than in the high heat flux environment of a limiter configuration. A quantitative study of the role of temperature dependent sputtering mechanisms on the outboard limiter in Tore Supra was performed. The methane flux proved to be significantly reduced above surface temperatures of 1,100 C and negligible above 1,300 C. The peak in the methane yield as a function of surface temperature is consistent with lab results. It was determined that chemical sputtering (early in the shot) had a small, to negligible, impact on the C{sup +} flux; while RES (late in the shot) had a strong impact on the C{sup +} flux. However, from the Z{sub eff} measurements, it was concluded that neither process contributed to the core carbon content