Evaluation of charge-exchange neutral incident parameters onto plasma-facing materials in LHD with material probe method

Charge-exchange (CX) neutrals bombarding plasma-facing materials (PFMs) have large impacts not only on surface modifications of PFMs but also on plasma density control. To examine the effects of CX-neutrals on modifications of PFMs under specific plasma conditions, the controlled material probe experiments were performed in LHD. CX-neutrals incident parameters were evaluated quantitatively for each plasma condition from the viewpoint of microscopic damages. Microstructures of the samples exposed to LHD plasmas showed a significant dependence on the plasma density, working gas and sample temperature. These results are consistent with laboratory irradiation experiments and a modeling analysis. In addition, the suitability of this method as a CX-neutral monitor is discussed.