Transport of and deposition from hydrocarbon radicals in a flow tube downstream from a CH4 RF discharge

Increased recombination of CH3 radicals on stainless steel

“…As a source of radicals, a radio-frequency (RF) inductive discharge was used in flows of methane or methane/hydrogen mixtures (CH 4 pressure $30 Pa at gas flow of 6.9 sccm, hydrogen flow changed from 0 to 70 sccm) at the tube inlet. The discharge was limited by a stainless steel (SS) grid [4,5]. In the downstream region behind the grid (afterglow zone, Fig.…”

“…Polymer-like carbon films were deposited on the tube wall at 300 K. The Ôstream techniqueÕ allows to measure the transport length L and diffusion coefficient D and to calculate the surface loss probability b of deposited species if the carbon deposition rate decreases along the tube as exp (Àx/L) [4]. To do this, Si samples (10 · 5 · 0.3 mm) were located along the whole tube length.…”

“…The H atom concentration ($5 · 10 11 cm À3 ) near the grid was determined in CH 4 discharge erosion experiments with hard a-C:H films (W. Jacob, Garching, Germany) located at different distances from the grid at 650 K [4]. We assume that the erosion coefficient of such films is equal to 0.02 at.C/at.H [10].…”

“…It can be seen that the slope of the deposition curve changes in the zone within the insert. In stream technique [4] this means that the radical surface loss probability b increased 3 times up to b = 1.3 · 10 À3 (see Table 1). In the subsequent experiments the b coefficient decreased with the increase of the thickness of the carbon deposits inside the insert.…”

Laboratory Experiments on Modeling of Transfer and Deposition of Hydrocarbons in Tokamak Main Chamber Areas Shadowed From Plasma

“…Средняя линейная ско-рость потока составляла 120 см/с. Разряд был огра-ничен стальной сеткой с размером ячейки в не-сколько десятых мм [13,14]. За сеткой, в направле-нии газового потока, выделенная часть трубы с ней-тральной смесью протяжённостью 15 см могла на-греваться передвижной цилиндрической печью до 1000 К. Если при определённых условиях (темпе-ратура, состав газовой смеси) углеводородные плёнки покрывали стенки трубы, то имело место ) опре-делялась методом РСМА по интенсивности излучения линии углерода СК  с энергией гамма-кванта 282 эВ.…”