Abstract
During typical operation of the DIII-D tokamak, physical and chemical sputtering
are the most important mechanisms for release of carbon at the divertor targets
[Nuclear Fusion 42 614 (2002)]. Modeling of C I spectral line profiles is discussed
as a technique for evaluating the relative contribution of each mechanism and is
applied to several types of DIII-D discharges. The line shapes are symmetric and
have shifts of about -0.03 � if they are produced solely from molecular
dissociation, but they exhibit distinct asymmetries and shifts approaching -0.20 �
if generated by physical sputtering. Modeled profiles must, in general, take
account of both mechanisms in order to match experimental data. An alternate
approach to distinguishing between the two processes, which relies on the
relative intensities of C I, CD, and C2 emissions, is examined in light of
conclusions drawn from the line-shape analysis.