SECONDARY-ELECTRON EMISSION AT ANODE, CATHODE, AND FLOATING PLASMA-FACING SURFACES

The secondary electron emission coefficient is evaluated for electron impact on anode, cathode, and electrically floating plasma-facing surf aces. 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 integratio n is in closed form and provides a parametric expression for the secon dary electron emission coefficient of a plasma-facing surface. The oth er integrations are carried out numerically. Evaluation of the seconda ry electron emission coefficient for a variety of commonly-used plasma -facing materials shows that its value is near or above unity over a s ignificant range of plasma temperatures. (C) 1996 American Institute o f Physics.