Search

The use of graphite for both first walls and limiters in fusion experiments has increased during recent years. However, graphite contains large amounts of gaseous contaminants that affect the plasma adversely. To study the vacuum characteristics of various candidate graphites and to evaluate conditioning techniques for these materials, we have built an outgassing facility, which is described in this paper. Induction heating is used to heat the sample to 2000 °C. This heating technique was chosen to avoid heating other components in the vacuum chamber. Since the walls are heated by radiation from the sample at the higher temperatures, they are kept at a constant elevated temperature of 100 °C by thermostatically controlled heaters throughout the experiment. The entire system is automated. Some results that compare POCO and pyrolytic graphites are shown.