Symmetries of 13C tracer deposition in EAST D and He plasmas investigated on the sub-mm to 100 mm scale by deuteron nuclear reaction analysis

Abstract

In continuation of an earlier study, this work focusses on deposit analysis in the mm region around the tracer injection hole of two 13CD4 injection experiments in EAST by using focussed 1.43 MeV deuteron ion beam analysis. This study adds ∼1500 data points to the former work on the same samples to assess more details on deposition patterns and symmetry and test the accuracy of former extrapolations.Mapping of the 13CD4 injection-hole vicinity using 0.2 mm lateral resolution yields compatible results as the former 1.8 mm resolution for the local co-deposit thickness. The new data reveal the deposition maximum to be 1 ± 0.2 mm away from the injection hole towards the ExB direction, resembling the triangular shape also seen on the larger scale. The analysis of 3 blocks along the magnetic field vector shows a dominant deposition along the surface area closest to the last closed flux surface. An edge with a factor ∼11 drop in deposit thickness within 2 mm spans here along the whole 150 mm tile size and along the axis of the magnetic field. The analysis using proton backscattering shows no He retention in the He plasma exposed co-deposits above the 1 % limit of detection.The total deposited 13C amount was underestimated by ∼5 % in the former study, a value not exceeding the measurement uncertainty. The combination of ∼0.2 mm spatial resolution around the injection-hole and at the deposit edge with ∼ 2 mm resolution but larger coverage outside these regions is found to provide a reasonable compromise of information quality and analysis effort.