Beryllium accumulation at the inner divertor of JET

MkIIGB divertor tiles exposed in JET for the 1998–2001 and 1999–2001 campaigns have been used to assess the amount of beryllium and carbon deposited at the inner divertor wall. Total amount of Be at the inner divertor tiles was determined and integrated toroidally. Results were compared with data obtained with optical spectroscopy and good agreement was obtained. The amount of deposited C was computed from the amount of deposited Be assuming that the Be/C ratio arriving in the divertor is the same as the Be/C ratio in the main chamber. On the basis of this analysis we would expect there to be ∼0.4 kg of C deposited. This gives an average C deposition rate lower than during the MkIIA phase.