NDLI: Upgrade of the DIII-D vacuum vessel protection system

Content Provider	IEEE Xplore Digital Library
Author	Hollerbach, M.A. Lee, R.L. Smith, J.P. Taylor, P.L.
Copyright Year	1993
Description	Author affiliation: Gen. Atomics, San Diego, CA, USA (Hollerbach, M.A.; Lee, R.L.; Smith, J.P.; Taylor, P.L.)
Abstract	An upgrade of the General Atomics DIII-D tokamak armor protection system has been completed. The upgrade consisted of armoring the outer wall and the divertor gas baffle with monolithic graphite tiles and cleaning the existing floor, ceiling, and inner wall tiles to remove any deposited impurity layer from the tile surfaces. The new tiles replace the graphite tiles used as local armor for neutral beam shine through, three graphite poloidal back-up limiter bands, and miscellaneous Inconel protection tiles. The total number of tiles increased from 1636 to 3200 and corresponding vessel coverage from 40% to 90%. A new, graphite armored, toroidally continuous, gas baffle between the outer wall and the biased divertor ring was installed in order to accommodate the cryocondensation pump that was installed in parallel with the outer wall tiles. To eliminate a source of copper in the plasma, GRAFOIL gaskets replaced the copper felt metal gaskets previously used as a compliant heat transfer interface between the inertially cooled tiles and the vessel wall. GRAFOIL, an exfoliated, flexible graphite material from Union Carbide, Inc., was used between each tile and the vessel wall and also between each tile and its hold-down hardware. Testing was performed to determine the mechanical compliance, thermal conductance, and vacuum characteristics of the GRAFOIL material. To further decrease the quantity of high Z-materials exposed to the plasma, the 1636 existing graphite tiles were identified, removed, and grit blasted to eliminate a thin layer of deposited metals which included nickel, chromium, and molybdenum. Prior to any processing, a selected set of tiles was tested for radioactivity, including tritium contamination. The tiles were grit blasted in a negative-pressure blasting cabinet using 37 /spl mu/m boron carbide powder as the blast media and dry nitrogen as the propellant. A 30 to 50 /spl mu/m-thick layer was removed from the surfaces of each tile. The tiles were cleaned in an ultrasonic alcohol bath and vacuum baked to 1000/spl deg/C prior to reinstallation. The installation of the graphite armor and gas baffle and the grit blasting of the tiles was performed in August 1992 through January 1993. Initial operational experience with the new armor system is summarized.
Starting Page	1185
Ending Page	1188
File Size	706926
Page Count	4
File Format	PDF
ISBN	0780314123
DOI	10.1109/FUSION.1993.518534
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	1993-10-11
Publisher Place	USA
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Vacuum systems Protection Tiles Copper Plasma materials processing Gaskets Conducting materials Atomic layer deposition Tokamaks Cleaning
Content Type	Text
Resource Type	Article

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Upgrade of the DIII-D vacuum vessel protection system

Optimized baking of the DIII-D vessel

Upgrade of the DIII-D RF systems

Surface impurity removal from DIII-D graphite tiles by boron carbide grit blasting

Control system upgrade for the DIII-D neutral beamline

Long term retention of deuterium and tritium in Alcator C-Mod

An interior vessel viewing system for DIII-D

Reduction of carbon influx by minimizing tile heating in DIII-D

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Upgrade of the DIII-D vacuum vessel protection system

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