Controlling the surface potential of a dielectric target irradiated by an electron beam in medium vacuum

Abstract We show that in irradiation of a dielectric target by an electron beam in medium vacuum (several Pa), the target surface potential can be driven negative by overlapping the target surface with an auxiliary electrode with a central hole and applying a negative bias. The induced negative potential manifests itself in the formation of a narrow plasma column, generated by gas ionization by secondary electrons emitted from the dielectric surface. In this way, independent control of the potential of the dielectric surface during electron beam irradiation can be attained.