Speaker
Richard E. Nygren
(Sandia National Laboratories)
Description
Power exhaust is perhaps foremost among the issues for ITER and post-ITER devices, as well as for existing large confinement devices as they increase power. A related concern is the alignment of plasma facing components to avoid protruding (leading) edges that would intercept field lines and incur very high loads and high erosion. This concern prompted the transient melt experiment in JET, followed by additional ITER-coordinated W (tungsten) leading edge experiments first in DIII-D and then in EAST.
Alignment is a concern also in the DIII-D Metal Tile Experiment planned in the 2016 campaign. The focus, on high-Z impurity transport in the plasma edge, is part of a broader long range goal to develop and test advanced divertor configurations and validate reactor-relevant materials. Each tile in two toroidal rings of divertor tiles, one on the shelf, another ring on the floor, will have a W-coated TZM (molybdenum alloy) insert spanning its toroidal width. The TZM inserts are 50 mm wide radially, 9.5 mm thick, bolted from the back into wide slots in newly made carbon tiles. Adequate thermal management includes well aligned tiles (specifications plus experience with installation); filleted leading edges; and thermal modeling showing acceptable temperatures and stresses for representative heat loads for L and H mode plasmas and with ELMs.
The team considered several approaches (fish-scale, roof top, chamfer, fillet) to minimize power to any leading edges. Thermal modeling of a flat insert/tile with a 2-mm fillet gave Tmax on the insert surface of 745°C at the end of a 3.5 s shot for an insert 0.3 mm above its neighbor, strike point with 6.5 MW/m22 peak toward the inside of the insert, and 2.5° angle of incidence. ELMs (10X power for 2 ms) brought a very small area on the leading edge to ~1500°C.
This work is supported by the U.S. DOE under DE-AC04-94AL8500011 and DE-FC02-04ER5469833, DE-FG02-07ER5491744, DE-AC05-00OR2272555
Co-authors
Chris J. Murphy
(General Atomics, P.O. Box 85608, San Diego, California 92186-5608, United States)
Dmitry L. Rudakov
(University of California, San Diego, La Jolla, California 92093-0417, United States)
Jon G. Watkins
(Sandia National Laboratories, Albuquerque, New Mexico 87185, United States)
Peter C. Stangeby
(University of Toronto Institute for Aerospace Studies, Toronto, M3H 5T6, Canada)
Richard E. Nygren
(Sandia National Laboratories, Albuquerque, New Mexico 87185, United States)
Zeke A. Unterberg
(Oak Ridge National Laboratory, Oak Ridge, TN 37830, United States)
