Heat flow through a plasma sheath in the presence of secondary electron emission from plasma‐wall interaction

Abstract

The formation of a plasma sheath in front of a negative wall emitting secondary electron is studied by a one‐dimensional fluid model. The model takes into account the effect of the ion temperature. With the secondary electron emission (SEE) coefficient obtained by integrating over the Maxwellian electron velocity distribution for various materials such as Be, C, Mo, and W, it is found that the wall potential depends strongly on the ion temperature and the wall material. Before the occurrence of the space‐charge‐limited (SCL) emission, the wall potential decreases with increasing ion temperature. The variation of the sheath potential caused by SEE affects the sheath energy transmission and impurity sputtering yield. If SEE is below SCL emission, the energy transmission coefficient always varies with the wall materials as a result of the effect of SEE, and it increases as the ion temperature is increased. By comparison of with and without SEE, it is found that sputtering yields have pronounced differences for low ion temperatures but are almost the same for high ion temperatures.