Measurements of net erosion and redeposition of molybdenum in DIII-D

The net erosion of molybdenum by the divertor plasma in the DIII-D tokamak was determined from the reduction in thickness of a thin film test sample after a short exposure to well controlled plasma conditions. The spatial distribution of Mo deposited on adjacent carbon surfaces was also measured. Integration of the total quantity of Mo deposited within 2 cm of the source, gave only 19% of the amount lost from the film indicating that most of the Mo is transported to greater distances, in spite of the short path-length for ionization of Mo in the divertor plasma. These measurements provide benchmark data for comparisons between gross and net erosion and between measurements and simulations of erosion and deposition, which are discussed in companion papers at this conference. Erosion and deposition of carbon, and deuterium retention were also examined. (C) 2013 Published by Elsevier B. V.