PARTICLE INDUCED ELECTRON-EMISSION

Particle induced electron emission from the wall of a plasma device alters the sheath potential and plasma transport in the scrape-off layer. Incident electrons eject electrons from a solid by a kinetic process. The ejected electrons cannot be distinguished from the reflected electrons and so the total yield is the sum of the two processes. Heavy particles eject electrons by the kinetic mechanism; when the projectile is ionized or excited, there may also be a contribution from potential ejection processes. Available data on electron ejection and electron reflection are reviewed, the most reliable data selected and, where appropriate, formulas are proposed that represent the functional dependence of the yield on the impact energy and impact angle.