E. Vainonen-Ahlgren

Distribution of Hydrogen Isotopes, Carbon and Beryllium on In-Vessel Surfaces in the Various JET Divertors

JET has operated with divertors of differing geometries since 1994. Impurities accumulated in the inner leg of all the divertors, and operation of the first (Mk I) divertor with beryllium tiles demonstrated that most are eroded from the main chamber walls and swept along the scrape-off layer to the inner divertor. Carbon deposited at the inner divertor is then locally transported to shadowed regions such as the inner louvres, where, for example, most of the tritium was trapped during the deuterium-tritium experiment (DTE1). Factors affecting these transport processes (e.g. temperature) are important for ITER, but are not well understood.

Fuel Retention in the Gas Box Divertor of JET

Components of the JET Mk-II Gas Box divertor have been analysed ex-situ after 18 months of operation with that divertor structure. The aim was to give an account on the distribution of the retained fuel along the poloidal cross-section of the divertor and, in particular, in the septum. Inside the gas box thick hydrogenated deposits were formed only on surfaces located in the near-plasma region from the inner divertor side whereas very little deposition was detected deep inside the gas box, i.e. on the support and divider plates.