Methyl radical chemical reactions on a tungsten surface

In this paper an interaction of the inner dome surfaces of the International Thermonuclear Experimental Reactor with a gas mixture containing hydrocarbon radicals has been modelled. To study the processes of transport and deposition of methyl radicals in a C x H y –H2–H (x=1−3, y=1−6) flow, a stream technique has been used. A radiofrequency inductive discharge initiated in methane at the inlet of a quartz tube was a source of methyl and hydrogen atoms. Methyl radicals were transported by a gas flow that passed through cylindrical tungsten inserts and were deposited on the tube wall, on silicon samples and on tungsten samples, forming polymer-like hydrogenated amorphous carbon films. It has been shown that at the tungsten insert temperature increases to 420 K, and carbon deposition rate decreased significantly. However, in the gaseous phase the secondary hydrocarbon species accumulated and condensed on the tungsten surface at a temperature lower than 340 K.