Stability analysis of cold-emission cathodes with epoxy coating

In this paper, the current stability analysis was performed on the cold-emission cathode covered by a thin epoxy film. Non-destructive spectroscopic method, which is based on measuring current fluctuations, has been used to determine cathodes’ quality, which directly influents the stability of the emission current. Our investigations have been performed on tungsten cathodes with extra-sharp nanotip, operating under the HV (high-vacuum)conditions, usually in vacuums of 10-5 Pa order. All the cathodes used for this experiment have been prepared in our lab by improved electrochemical etching method, which is based on the presence of increased surface tension allowing reaching the geometrically precise shape of the cathodes’ tip. After the two phase etching method, the tip was cleared and covered by thin epoxy film, which prevents the tip to be destroyed by ion bombardment that is caused by ions attracted back on to the cathode surface. A comprehensive investigation was carried out to determine particular noise sources and to compare clean cathodes with the resin-coated one, in order to describe the influence of the oxide and dielectric epoxy layer on to the emission current stability. Spectra obtained, for various emission currents at different voltages, are described and explained. The results suggest that the resin-layer changes cathode performance and extends its durability