Speaker
Dmitry Rudakov
(Center for Energy Research)
Description
An overview of recent Plasma-Material Interactions (PMI) research at DIII-D tokamak using the Divertor Material Evaluation Station (DiMES) is presented. The DiMES manipulator allows exposing material samples in the lower divertor of DIII-D under well-diagnosed ITER-relevant plasma conditions. Plasma parameters during the exposures are characterized by the extensive diagnostic suite including a number of spectroscopic diagnostics, Langmuir probes, IR imaging, and Divertor Thomson Scattering. Post-mortem measurements of net erosion/deposition on the samples are done by Ion Beam Analysis, and results are modelled by REDEP/WBC and ERO codes with plasma background parameters derived from OEDGE/DIVIMP modelling based on experimental inputs.
This presentation highlights the following key findings: (i) demonstration of strong reduction of net compared to gross erosion of molybdenum and tungsten by short-scale redeposition, in good agreement with REDEP/WBC modelling; (ii) demonstration of good survival of tungsten nano-structures (W-fuzz) under helium plasma exposures and reduction of gross erosion rate from the fuzz surface compared to solid W surface; (iii) studies of inter-ELM versus intra-ELM gross W erosion rates, showing that for attached divertor conditions inter-ELM erosion is dominant at the strike point, while further into the scrape-off-layer, intra-ELM erosion dominates; (iv) studies of active control of sheath conditions by external electric biasing, demonstrating suppression of Mo erosion with positive biasing, as predicted by ERO modelling; (v) formation of in-situ carbon coating by local methane injection leading to suppression of molybdenum erosion, in agreement with ERO modelling; (vi) results of dust remobilization tests from W substrate, showing that overheating of the dust particles by the plasma contact leads to enhanced adhesion to the substrate.
*Supported under US DOE DE-FG02-07ER54917aa, DE-AC05-06OR23100bb, DE‑AC05-00OR22725cc, DE-FC02-04ER54698ee, DE-AC52-07NA27344gg, DE-AC04-94AL85000hh, Collaborative Research Opportunities Grant from National Sciences and Engineering Research Council of Canadaff.
Co-authors
A. Briesemeister
(Oak Ridge National Laboratory, Oak Ridge, TN, United States)
A.G. McLean
(Lawrence Livermore National Laboratory, Livermore, CA, United States)
A.W. Leonard
(General Atomics, San Diego, CA, United States)
C. Chrobak
(General Atomics, San Diego, CA, United States)
C.J. Lasnier
(Lawrence Livermore National Laboratory, Livermore, CA, United States)
C.P.C. Wong
(General Atomics, San Diego, CA, United States)
D.M. Thomas
(General Atomics, San Diego, CA, United States)
DIII-D Team
(General Atomics, San Diego, CA, United States)
Dmitry Rudakov
(Center for Energy Research, University of California, San Diego, La Jolla, CA, United States)
E.A. Unterberg
(Oak Ridge National Laboratory, Oak Ridge, TN, United States)
H.Y. Guo
(General Atomics, San Diego, CA, United States)
I. Bykov
(Center for Energy Research, University of California, San Diego, La Jolla, CA, United States)
J.D. Elder
(Institute for Aerospace Studies, University of Toronto , Toronto, Canada)
J.G. Watkins
(Sandia National Laboratories, Albuquerque, NM, United States)
J.N. Brooks
(Purdue University, West Lafayette, IN, United States)
P.C. Stangeby
(Institute for Aerospace Studies, University of Toronto , Toronto, Canada)
R. Ding
(Oak Ridge Institute for Science and Education, Oak Ridge, TN, United States)
R.A. Moyer
(Center for Energy Research, University of California, San Diego, La Jolla, CA, United States)
R.E. Nygren
(Sandia National Laboratories, Albuquerque, NM, United States)
R.P. Doerner
(Center for Energy Research, University of California, San Diego, La Jolla, CA, United States)
T. Abrams
(Oak Ridge Institute for Science and Education, Oak Ridge, TN, United States)
W.R. Wampler
(Sandia National Laboratories, Albuquerque, NM, United States)
