High current generation from field emission tip cathodes

Electron beams with current up to 1.2 A and current density over 10⁷ A/cm² have been generated from a pulsed, field emission tip cathode etched from commercial grade tungsten wire. Electron beams with current up to 0.8 A were also generated from a single molybdenum tip. The applied tip-anode voltage was up to 50 kV with pulse duration from 300 ns to 1.2 µs. Scanning electron micrographs indicate that tip radii varied between 100 nm to 1 µm. The background pressure in the system was below 3×10⁻⁹ Torr. Depending on the brightness, these types of electron beams could be suitable for channeling radiation X-ray lasers and might considerably decrease the operating wavelength of free-electron lasers at moderate beam energies.