Titanium carbide (TiC) coated carbon limiters, which suffered 1972 shots of tokamak discharge and 672 shots of stellarator discharge in JIPPT-II for about 3 months, are analyzed by AES and RBS. The stoichiometry and composition of a subsurface layer is found to be affected by the plasma exposure. In this region a large amount of oxygen and nitrogen are observed. These concentration profiles and the subsurface layer affected have systematic positional dependencies on the limiter, suggesting an inhomogeneous interaction between the plasma and limiter. The analysis of RBS data gave roughly 0.4 and 0.2 C and Ti atoms, respectively, being sputtered off for every impinging O atom.

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YSZ-based potentiometric gas sensors using a CeO2-added Au sensing electrode (Au(nCeO2)-dr, n: an additive amount of CeO2 (wt%)) were fabricated by a drop-coating (dr) method, and their sensing properties to toluene and methyl mercaptan were examined in the temperature range of 400 600°C. The magnitude of response ( E) to 50 ppm toluene increased by the addition of a small amount of CeO2, and the Au(8CeO2)-dr sensor showed the largest response among all the sensors with different amounts of CeO2. The Au(8CeO2)-dr sensor showed an almost linear relationship between the E and the logarithm of toluene concentration in the range of 20 100 ppm at 500°C. The balance between the catalytic activity and the electrocatalytic activity for toluene oxidation probably dominates the magnitude of the response. The Au(8CeO2)-dr sensor also showed rather high response to a low concentration of methyl mercaptan ( E: 17 mV, 0.1 ppm) at 500°C.