Plasma-facing components
JET provides invaluable expertise for the whole fusion community due to its unique capability to operate with the heavy radioactive hydrogen isotope. To find how and where tritium can be trapped inside JET and to determine the characteristics of erosion and deposition of the plasma facing components, investigations are carried out based on the analysis of tiles or flakes removed during shutdowns or on direct co-deposition monitoring (using e.g. quartz microbalances or rotating collectors). The results of these activities are also used in the modelling of the impurity transport inside the JET torus.
In many current tokamaks – including JET – Carbon Fibre Composite (CFC) tiles act as the plasma facing material. The fusion fuel, i.e. hydrogen isotopes, are co-deposited together with carbon, beryllium and other elements present in-vessel on these tiles. The co-deposits can fragment off to form flakes, which in JET fall into sub-divertor zones close to the water cooled louvres adjacent to the inner divertor. Flakes are collected via a remotely operated cyclone vacuum cleaner and analysed. They have an average diameter of 0.4 mm and are saturated with hydrogen isotopes. Optical spectroscopy reveals a layer structure coming from a sequential deposition process.
