Electron-induced secondary electron emission coefficient of lithium, tungsten and stainless steel surfaces exposed to low-pressure plasmas

The secondary electron emission (SEE) coefficient by electron impact of Li, W and stainless steel (SS) surfaces exposed to a glow discharge is evaluated and analyzed in the energy range of Ee < 200 eV. While the values of the SEE coefficient for SS and W show a small increase with respect to their vacuum value, an enhancement of this parameter up to a factor of 6 has been deduced for clean Li surfaces. Experiments with different plasma gas discharges (He, Ar and H2) are undertaken in order to address the possible mechanisms related to such enhancement. No major effect of the bombarding ion mass or incident electron flux is observed. The implications of these findings on the use of Li as a plasma-facing component in fusion devices are addressed.