Transient impurity events in JET with the new ITER-like wall

Transient impurity events leading to an unexpected increase in radiated power have been studied in JET from the installation of the ITER-like wall. A total of 1800 events over 2800 plasma discharges have been detected. None have led to permanent changes in the plasma conditions. Of all the events 60% show traces of W and 25% of either Ni, Fe or Cr from either Inconel or steel structures. They occur mainly in diverted magnetic configuration, independently of strike-point position. The effect of disruptions on dust redistribution has been investigated using the Thomson scattering diagnostic and correlated with transient impurity event occurrence. The number of dust events detected increases with disruption force and, in comparison to the full-C wall, the amount of dust mobilized is found to be about an order of magnitude lower. Their time evolution correlates well with that of the transient impurity events. (paper)