Analysis of Rotating Collectors from the Private Region of JET with Carbon Wall and Metallic ITER-Like Wall
Rotating collectors are used in JET to provide time-resolved measurements of erosion and redeposition of vessel materials. The silicon collecting disks rotate behind an aperture, driven by pulsing of the toroidal magnetic field, with the deposits analysed ex-situ by Nuclear Reaction Analysis. The angular dependence of deposition is mapped to discharge number using the B-field history, allowing the influence of different plasma configurations and parameters to be investigated. A simple geometrical model using sputtering and reflection from the strike point has qualitatively reproduced the deposition found on collectors located under the central divertor tile and facing towards the inner strike point. The beryllium deposition on the ITER- like wall (ILW) collector showed an order of magnitude reduction in deposition compared to carbon deposition on the carbon wall collector. This reduced deposition is attributed to low long range divertor transport due to low chemical sputtering and codeposition of beryllium relative to carbon.