Measurements of carbon, deuterium and boron deposition in DIII-D

An experiment was recently conducted in DIII-D in which 13C methane (13CH4) was injected from the upper divertor plenum into 22 identical lower single null divertor L-mode plasmas. Twenty-nine graphite tiles were subsequently removed and analyzed to determine the spatial distribution of 13C deposited on the main chamber wall and divertor. 13C coverage was mapped by ion beam analysis using the 13C(3He, p)15N nuclear reaction. This technique also measures deuterium, boron and 12C content in the near-surface region of the tiles. The measurements show the 13C is deposited mainly at the inner divertor.