The electron gun with field emission cathode is developed. The cathode was made of a bundle of carbon fibers. Specific properties of electron gun with bundles of carbon fibers are related to mechanical displacement of carbon fibers in the bundle. Specific types of emission current instability in connection with mechanical properties of cathode are described. The developed electron gun could be used to replace hot cathodes. Application of the gun for a light source and compact x-ray tube is considered. (C) 2003 American Vacuum Society.