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Experiments are performed on polycrystalline MgO in order to investigate the internal effects of positive charging on the total electron emission yield (TEEY) under low incident electron fluence (a few to hundreds of fC mm−2) at 200 eV electron irradiation energy. It is experimentally shown that the Coulomb-attractive recombination of electrons undergoing emission with holes generated by the previously emitted electrons significantly affects the TEEY. Furthermore, quantitative analyses of experimental data are done to deduce the electron–hole recombination cross-section which is found to be of a few 10−11 cm−2.

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We report measurement of electron-emission yield (EEY) under the impact of electrons on materials of Hall-effect-thruster (HET) interest: BN, BN-SiO 2 , and Al 2 O 3 . The effects of the material aging (under electron irradiation) on the yield of BN and Al 2 O 3 are investigated. The EEY of BN grows with electron exposure, whereas that of Al 2 O 3 reduces. A simple analysis of our experimental results indicates that these variations are most likely because of surface and near surface composition changes caused by the electron beam. The representativeness of EEY measurements on ceramics that have not suffered from the specific environment of a HET (ion and electron bombardment) is discussed.