Photo Enhanced Nano-Forest Cathode Guns

Improved electron beam gun technologies are needed to replace the present inefficient guns that are currently used in numerous linear accelerator applications. Improvements to the cathodes, which are frequently the root of the gun problem, offer the best potential to make significant advancements. New cathodes must be robust and satisfy demanding specifications with respect to current density, emittance, lifetime, reproducibility, and survivability in harsh environments. This project will develop a Photo Enhanced Nano-Forest Gun to satisfy the demanding electron source requirements. The novel cathode concept is based on the premise that coherent light from a laser resonantly couples energy into a cathode that is composed of an array of nano-pins (a nano-forest), thereby creating several effects that enable the efficient generation of large current densities with a minimal amount of input energy. The resonantly coupled light promises to significantly enhance local electric fields and preferentially elevate the temperature at the tips of the pins; thus resulting in the ¿Thermofield¿ emission of a reproducible, high-current-density electron beam. In Phase I: (1) prototype nano-forest cathodes will be designed and fabricated from gold nanowires and carbon nanotubes, some of which may be treated with low work function coatings; (2) performance metrics will be determined via a series of experiments; (3) a conceptual design for the Photo Enhanced Nano-Forest Gun will be developed; and (4) an experimental plan will be prepared. Commercial Applications and other Benefits as described by the awardee: The Photo Enhanced Nano-Forest Gun should benefit many current and future linear accelerators at home and abroad, as they could be deployed in numerous applications, such as RF guns and Klystrons. Moreover, the nano-forest cathodes are potentially one of the best hopes for achieving a quantum leap in DoD directed energy applications, because they could be used as the repetition rate electron-beam sources required by such high power microwave generators as magnetically insulated line oscillators, relativistic magnetrons, railtrons, and ubitrons.