Numerical analysis of incident angle of heavy metal impurity to plasma facing components by IMPGYRO

The self-sputtering and reflection yields are important for a prediction of the tungsten impurity content penetrating into the main plasma in future fusion reactors. The self-sputtering and reflection yields greatly depend on the incident angle of impurities to plasma facing components. The IMPGYRO code is applied to the analysis of angle distribution of incident impurities, effects of the sheath on the incident angle and energy, and the resultant sputtering and reflection yield. The incident angle distribution is divided into several peaks by the sheath effect. Each peak corresponds to the peak for each charge state. In high temperature condition for the divertor plasma, the sputtering yield increases mainly due to the change of incident angle by the sheath. In low temperature condition, the effects of the sheath on the sputtering yield and the reflection yield are small because of low incident energy and large incident angle.