Dust particles in controlled fusion devices: morphology, observations in the plasma and influence on the plasma performance

The formation and release of particle agglomerates, i.e. debris and dusty o bjects, from plasma facing components and the impact of such materials on p lasma operation in controlled fusion devices lias been studied in the Extra p T2 reversed field pinch and the TEXTOR tokamak. Several plasma diagnostic techniques, camera observations and surface analysis methods were applied for in situ and ex situ investigation. The results are discussed in terms o f processes that are decisive for dust transfer: localized power deposition connected with wall locked modes causing emission of carbon granules, brit tle destruction of graphite and detachment of thick flaking co-deposited la yers. The consequences for large next step devices are also addressed.