Speaker
Dr
Rui Ding
(UsORAU)
Description
Significant advances have recently been made in the understanding of erosion and re-deposition of high-Z plasma facing components in a mixed materials environment, encouraging prospects on control of high-Z material erosion for future reactors. Dedicated DIII-D experiments coupled with modeling reveal that the net erosion rate of high-Z materials is strongly affected by carbon concentration in the plasma and the magnetic pre-sheath, and can be actively controlled with electrical biasing, as well as by local gas puffing. Thin film tungsten (W) and molybdenum (Mo) samples of different diameters were exposed under well-diagnosed divertor plasma conditions in DIII-D using the divertor materials evaluation system (DiMES) to measure the gross and net erosion rates by ion beam analysis. The net erosion rate of high-Z materials is significantly reduced due to the high local re-deposition ratio, which is mainly controlled by the electric field and plasma density within the magnetic pre-sheath. The modeling indicates that decreasing the sheath potential can suppress the net erosion. New experiments have demonstrated the strong correlation of erosion with external biasing voltage. High carbon impurity concentration in the background plasma is also found to reduce the net erosion rate of high-Z materials. Both DIII-D experiments and modeling show that local 13CH4 injection can create a carbon coating on the metal surface. The 13C deposition provides quantitative information on radial transport due to ExB drift and the cross field diffusion. Additionally, new experiments show that local deuterium gas injection upstream of the W sample not only reduced W net erosion rate by a factor of 2 but also increased the W re-deposition ratio significantly, mainly due to local plasma cooling. High-resolution measurements of the W erosion rate during and between ELM events near the outer strike point (OSP) demonstrate that peak W erosion during ELMs is shifted away from the OSP radius, dramatically broadening the erosion profile at the divertor target. These new findings have significant implications for the understanding and active control of W divertor target operation in ITER with its low-Z beryllium first wall.
Work supported in part by the US DOE under DE-AC05-06OR23100, DE-FG02-07ER54917, DE-AC04-94AL85000, DE-AC05-00OR22725, DE-FC02-04ER54698, and DE-AC52007NA27344.
| Country or International Organization | USA |
|---|---|
| Paper Number | MPT/1-2Rb |
Primary author
Dr
Rui Ding
(UsORAU)
Co-authors
Dr
Adam McLean
(Lawrence Livermore National Laboratory)
Dr
Alexis Briesemeister
(ORNL)
Dr
Andreas Kirschner
(Forschungszentrum Juelich GmbH)
Dr
Anthony W. Leonard
(USA)
Dr
Charles J. Lasnier
(Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550, USA)
Dr
Christopher P. Chrobak
(General Atomics, PO Box 85608, San Diego, CA 92186-5608, USA)
Mr
D. L. Rudakov
(University of California San Diego)
Dr
Daniel M. Thomas
(General Atomics, PO Box 85608, San Diego, CA 92186-5608, USA)
Dr
David Tskhakaya
(Fusion@ÖAW, Institute of Applied Physics, TU Wien, Wiedner Hauptstraße 8-10,1040 Vienna, Austria)
Dr
Ezekiel A. Unterberg
(Oak Ridge National Lab, Oak Ridge, Tennessee, US)
Prof.
Houyang Guo
(Institute of Plasma Physics, Chinese Academy of Sciences)
Dr
Huiqian Wang
(Oak Ridge Associated Universities, Oak Ridge, Tennessee, USA)
Dr
Igor Bykov
(University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0417, USA)
Dr
J. David Elder
(University of Toronto, Institute for Aerospace Studies, Toronto, M3H 5T6, Canada)
Dr
Jerome Guterl
(Oak Ridge Associated Universities, Oak Ridge, Tennessee, USA)
Dr
Jon G. Watkins
(Sandia National Laboratory, P.O. Box 5800, Albuquerque, NM 87185, USA)
Dr
Michael A. Makowski
(Lawrence Livermore National Laboratory)
Dr
Peter C. Stangeby
(University of Toronto, Institute for Aerospace Studies, Toronto, M3H 5T6, Canada)
Dr
Philip B. Snyder
(General Atomics, PO Box 85608, San Diego, CA 92186-5608, USA)
Dr
Sebastijan Brezinsek
(Forschungszentrum Jülich)
Dr
Tyler Abrams
(Oak Ridge Associated Universities, Oak Ridge, Tennessee, USA)
Dr
Vincent S. Chan
(General Atomics)
Dr
William R. Wampler
(Sandia National Laboratory, P.O. Box 5800, Albuquerque, NM 87185, USA)
