W-Ojn-sT PPPL-2123 ' KOTlCt PORTIONS OF THIS REPORT ARE ILLEGIBLE, it fiaTblSirSproftuced trom 5he best available copy Is permit tho broadest passible avail ability.

LE, ttAs part of t.ie ISX surface physics program and the TFTR materials research program, ATJS graphite rail iimiters were installed in the ISX tokamak in order to compare them with the existing stainless steel liniters and to investigate any deleterious effects arising from operation at elevated temperatures of the graphite. To facilitate the latter experiment, heaters were installed in the graphite liniters since the power deposition on the limiter in ISX was expected to be considerably less than for TFTR. The graphite liniters also contained thermocouples to monitor the bulk temperature. Ho large systematic differences werr observed in the electron temperature profiles, electron density profile;-nor Zeff between successive runs with the stainless steel (SS) limiters and graphite (G) limiters. There was, however, a xonotonic decrease in Zeff for both cases from i-5.6 in the first run following the installation of the graphite limiters to ^ 2.8 after a two week period when the experiment was terminated due to a scheduled shutdown. Normal incidence UV spejtroscopic measurements of C, II, 0, and H radiation showed a factor of 3-k greater hydrogen light for the S3 case over the 5 case, but no systematic differences in the impurity light. Arc tracks were cbserved on the graphite limiters upor. removal and 3EM analysis was performed so that the amount of material removed could be estimated. In the hot graphite limiter experiment, the temperature of one of the graphite liniters was increased on successive shots. The hydrocarbons formed, as determined by residual gas analysis (RGA), increased monotonically with increasing limiter temperature, e.g. mass 16 (presumed to be CHj,) increased about a factor of two as the temperature was raised from 150°C to SQO°C. CO and COg were also found to increase only slightly. The carbon impurity light was also observed to increase by a factor of two as the limiter temperature was raised from 150°C to 500°C. Further experiments using graphite liraiters are indicatec. before their application in beam driven tokamaks.

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