Influence of boronization on operation with high-Z plasma facing components in Alcator C-Mod

B. Lipschultz, Y. Lin, E.S. Marmar, S. Wukitch, I.H. Hutchinson, J. Irby, B. LaBombard, M.L. Reinke, J.L. Terry, D.G. Whyte, G. Wright

Research output: Contribution to journalArticlepeer-review


We report the results of operation of Alcator C-Mod with all high-Z molybdenum plasma facing component (PFC) surfaces. Without boron-coated PFCs energy confinement was poor (H ∼ 1) due to high core molybdenum (n/n ≤ 0.1%) and radiation. After applying boron coatings, n/n was reduced by a factor of 10-20 with H approaching 2. Results of between-discharge boronization, localized at various major radii, point towards important molybdenum source regions being small, outside the divertor, and due to RF-sheath-rectification. Boronization also has a significant effect on the plasma startup phase lowering Z, radiation, and lowering the runaway electron damage. The requirement of low-Z coatings over at least a fraction of the Mo PFCs in C-Mod for best performance together with the larger than expected D retention in Mo, give impetus for further high-Z PFC investigations to better predict the performance of un-coated tungsten surfaces in ITER and beyond.
Original languageEnglish
Pages (from-to)1110-1118
Number of pages9
JournalJournal of Nuclear Materials
Issue number1-3
Publication statusPublished - 15 Jun 2007

Cite this