Neutral iron generation with sawtooth oscillation in TEXTOR ICRF heated plasmas

The emission of neutral iron atoms from a metal target in the shadow of the limiter was investigated during ICRF heating of the TEXTOR plasma, using laser induced fluorescence. By collecting the data over many similar sawtooth periods, the sawtooth oscillation of the neutral iron density was found for the first time. The sawtooth oscillation of the neutral iron density occurring during additional heating was in reverse phase to the neutral oxygen flux from the main limiter, but in phase with the central electron temperature. On the other hand, another case which was in contrast to the above case was found. The incident ion on the metal surface was studied. (author)