Effects of Neutral-Beam Injection and Gas Puffing on Deuterium and Impurity Levels in the Scrapeoff Layer of ISX-B

摘要

Plasma-material interactions in the scrapeoff region of a tokamak have important effects on the overall performance of the machine. In order to prudently select the most-appropriate materials for walls, limiters, and armor plate, it is necessary to characterize the plasma that interacts with these surfaces and to understand what effect different modes of operation of the tokamak have on plasma characteristics. We have made a series of measurements on the ISX tokamak using deposition-probe techniques to identify and quantify the impurities (Z greater than or equal to 8) in the limiter shadow, and to determine the temporal behavior of both impurity and plasma particles in this region. These measurements have been made under a variety of tokamak operating conditions, including both ohmic and neutral-beam heated discharges. The results are interpreted in terms of edge conditions, impurity introduction, gas puffing, and the relative importance of wall and limiter contributions. (ERA citation 07:062393)