Remarkable advances in the emerging field of Ultrafast Electron Microscopy (UEM) have permitted atomic- resolution imaging and diffraction studies of dynamic processes with a temporal resolution measured in femtoseconds. However, limitations with femtosecond electron sources in brightness and pulse duration have prevented this technique from achieving its full potential. A higher performance electron gun would enhance UEM capabilities at leading research facilities, including those funded by the Department of Energy. This Phase I project will study the feasibility of producing a key technical component needed to improve the performance of laser-assisted field emission guns for UEM instruments. The limitations associated with field emitters used in current femtosecond electron sources will be addressed with the development of innovative advances to their design. Our field emitters are projected to exhibit narrower emission angles, better voltage characteristics, smaller and more perfect tip shapes, higher mechanical stability, better heat dissipation capabilities, and the unique capability to be completely regenerated to original emission specifications in situ after undergoing operational degradation from laser and ion impact damage. During Phase I research, a high-vacuum test chamber for field emission investigations will be constructed. The feasibility of the new field emitter design will be validated, and the emission characteristics of these cathodes measured. Practical means to incorporate this technology into standard electron microscopes will be studied. An electron microscopy facility involved in UEM research will be identified for collaboration during Phase II research, in which a complete femtosecond electron gun will be developed. Commercial Applications and Other
Benefits: In addition to its application in UEM, the technology being developed here should find productive use in more conventional forms of electron microscopy. Other scientific instrumentation that requires very bright electron sources will also benefit from the superior emission characteristics and durability of this novel field emission technology. This will increase the commercial potential of this project well beyond the specialized field of UEM. Although this proposal is responsive to DOE needs in electron microscopy, this research may also prove very valuable for other departmental interests such as high-energy electron accelerators and free electron lasers.
