Fuel retention and carbon deposition on beryllium marker tiles from JET tokamak main chamber limiters investigated by ion beam analysis

Abstract

JET tokamak with the ITER-like wall is operated with arrays of castellated beryllium limiters in the main chamber. In several locations Be marker tiles were installed for erosion-deposition studies. The castellation sides and the plasma-facing surfaces (PFS) of Be marker tiles from three different locations of the JET main chamber, from the experimental campaigns 2011-12 (ILW-1) and 2013-14 (ILW-2), were analysed employing 2H and 3He micro-beams in order to determine carbon impurity deposition and deuterium retention. The deposited carbon and deuterium amount on the castellation sides (up to 1.5 mm deep into the groove) was assessed with respect to the ion/electron drift direction. Both the carbon and deuterium amount on the investigated castellation sides either stays constant or reduces with depth from the edge of the PFS. No systematic difference is observed in the carbon deposition or deuterium retention on the different castellation sides of each sample with respect to the ion/electron drift direction. Carbon and deuterium content is found to be lower on the PFS than on surfaces in the gaps of castellation for the majority of the samples. The carbon amount is, in general, higher than the deuterium one. No systematic correlation between the carbon and the deuterium amount has been observed.