5.7 Conclusions

Magnesium oxide is a promising material for surface ionization. The negative ion yields for oxygen are 10% or more at energies above 100eV per atom and 3% or more for hydrogen. Because the expected particle fluxes are low surface charging does not seem to be a problem although the sensitivity to Lyman UV radiation would need further investigations. The large bandgap of MgO suggests a relatively low sensitivity to UV radiation. Other advantages of MgO are the low cost, easy handling and good surface quality (flatness) available commercially.