Secondary electron emission at anode, cathode, and floating plasma-facing surfaces

Abstract

The secondary electron emission coefficient is evaluated for electron impact on anode, cathode, and electrically floating plasma-facing surfaces. Two energy and angle distribution functions for electron impact on a plasma-facing surface are derived and different relations for the secondary electron emission coefficient which functionally depend on energy and angle are integrated over the distributions. One integration is in closed form and provides a parametric expression for the secondary electron emission coefficient of a plasma-facing surface. The other integrations are carried out numerically. Evaluation of the secondary electron emission coefficient for a variety of commonly-used plasma-facing materials shows that its value is near or above unity over a significant range of plasma temperatures.