The Design and Use of Tungsten Coated TZM Molybdenum Tile Inserts in the DIII-D Tokamak Divertor

Conference · Tue Aug 01 00:00:00 EDT 2017

DOI:https://doi.org/10.1080/15361055.2017.1347456· OSTI ID:1414708

Holtrop, Kurt ^[1]; Buchenauer, Dean ^[2]; Chrobak, C P. ^[1]; Murphy, Christopher ^[1]; Nygren, R. E. ^[2]; Unterberg, Ezekial  ^[3]; Zach, Mike  ^[3]

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1. General Atomics, San Diego
2. Sandia National Laboratories (SNL)
3. ORNL

Future tokamak devices are envisioned to utilize a high-Z metal divertor with tungsten as theleading candidate. However, tokamak experiments with tungsten divertors have seen significantdetrimental effects on plasma performance. The DIII-D tokamak presently has carbon as theplasma facing surface but to study the effect of tungsten on the plasma and its migration aroundthe vessel, two toroidal rows of carbon tiles in the divertor region were modified with high-Zmetal inserts, composed of a molybdenum alloy (TZM) coated with tungsten. A dedicated twoweek experimental campaign was run with the high-Z metal inserts. One row was coated withtungsten containing naturally occurring levels of isotopes. The second row was coated withtungsten where the isotope 182W was enhanced from the natural level of 26% up to greater than90%. The different isotopic concentrations enabled the experiment to differentiate between thetwo different sources of metal migration from the divertor. Various coating methods wereexplored for the deposition of the tungsten coating, including chemical vapor deposition,electroplating, vacuum plasma spray, and electron beam physical vapor deposition. The coatingswere tested to see if they were robust enough to act as a divertor target for the experiment. Testsincluded cyclic thermal heating using a high power laser and high-fluence deuterium plasmabombardment. The issues associate with the design of the inserts (tile installation, thermal stress,arcing, leading edges, surface preparation, etc.), are reviewed. The results of the tests used toselect the coating method and preliminary experimental observations are presented.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 1414708
• Resource Relation: Journal Volume: 72; Journal Issue: 4; Conference: TOFE 2016 - Philadelphia, Pennsylvania, United States of America - 8/21/2016 12:00:00 AM-
• Country of Publication: United States
• Language: English