Principle of electrical screening of a surface at high voltage by a nearly massless wire electrode at a slightly more negative voltage . Secondary electrons, which are emitted from the surface at potential —for example, by the interaction of cosmic muons or radiation by environmental radioactivity—will be reflected by the wire potential back to the wall, if the kinetic energy of the secondary electrons is not sufficient to pass the electrical potential barrier . If the wire electrode has a sufficiently small cross-section, the probability that unscreened secondary electrons emitted from the wires is small.
