Carbon nanotubes as electron source in an x-ray tube

Field emitters comprised of aligned carbon nanotubes are shown to be promis ing as a primary electron source in an x-ray tube working in a nonultrahigh vacuum ambience. At a pressure of 2x10(-7) Torr, the nanotube emitters con tinue to emit electrons for more than 1 h, and yield better resolved x-ray images than do thermionic emitters, independently of whether the sample is biological or nonbiological. The near-uniformity in energy distribution of electrons emitted from carbon nanotubes might be related to the improved im age quality in the field-emission mode. (C) 2001 American Institute of Phys ics.