Transport code calculations concerning the plasma parameters in the scrape-off layer of poloidal limiter and the possible advantage of high Z wall materials in the cool plasma blanket approach

Abstract

The plasma parameters in the scrape-off layer (SoL) of a tokamak are calculated by introducing appropriate particle and energy loss terms into the six-regime version of Düchs code [1]. These terms take secondary electron emission from the limiter surface and a potential sheath in front of it into account. In the SoL we assume Bohm diffusion. Limiter materials with large secondary emission coefficients (SEC) (e.g. Mo) give lower potential steps ( U = 90 V) than low SEC materials (e.g. Be) which cause ( U = 250 V). The flux of the sputtered liner material and the resulting radiation losses can be decreased by neutral gas influx. When we use the same neutral gas influx and the same additional heating we find that radiation losses due to molybdenum are lower than those due to iron, although Mo is more toxic.