EVALUATION OF SIC COATED CARBON LIMITERS IN THE TCA TOKAMAK
Carbon limiters coated with 100-150 mum of silicon carbide (SiC) have been placed in the TCA Tokamak in an attempt to reduce impurity generation during both ohmic and Alfven wave heating. The results are compared with those with bare carbon limiters operated under similar conditions. The SiC coated limiters were conditioned by 150 hours of Taylor discharge cleaning. During both ohmic and Alfven wave heating, the radiation profile is strongly hollow, with no measurable radiated power on axis. The light impurity line emission intensities are reduced by factors of 3-10 for C, N and O, while the intensity of the silicon line emission naturally increased. During Alfven wave heating, the density of metallic impurities is less than with bare carbon limiters. Z-eff dropped from 4.2 to 2.4, and the loop voltage fell from 1.5 to 1 V. The relative drop in plasma resistivity and radiated power is largest at high electron density (5 x 10**13cm**-3). The plasma operational range is similar to that obtained using bare carbon limiters. In conclusion, the SiC coated limiters have led to significant improvements in plasma performance due to impurity reduction.
Bibliographic Reference: WRITE TO CONFEDERATION SUISSE, CENTRE DE RECHERCHES EN PHYSIQUE DES PLASMAS, ECOLE POLYTECHNIQUE FEDERALE DE LAUSANNE, 21, AVENUE DES BAINS, CH-1007 LAUSANNE (SWITZERLAND), MENTIONING REPORT: LRP 255
Record Number: 1989124033700 / Last updated on: 1987-01-01
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