Back-Gate Field Emission-Based Cathode RF Electron Gun

High current electron sources are required in numerous applications of interest to the DOE; however, current RF guns based upon thermionic cathodes and photocathodes have serious limitations. While thermionic cathodes have high average electron currents, they suffer from degraded beam quality when used in RF guns; this degradation in beam quality is due to the fact that the electron emission cannot be gated to a particular fraction of the RF period, because of the continuous electron emission. The photocathode is a very high current source, but the laser used to drive it cannot produce a pulse at every RF period; thus, the average power is lower than that for thermionic cathodes. In this project, field emission cathodes, which emit electrons in the presence of high electric fields, will be explored an alternative technology to solve the problems associated with thermionic cathodes and photocathodes. Above the threshold for emission, the current increases rapidly with increasing electric field and will emit electrons at every RF period. Commercial Applications and other Benefits as described by the awardee Field emission cathodes, or so called cold cathodes, consume less power during operation and as a result would be desirable for use in displays for portable devices. They also can be used in various analytical instruments such as mass spectrometers and vacuum gages. The DOD has long sought cold cathodes for high power microwave tubes, the primary long range communication technology for the Navy. For the DOE the electron gun can be used for free electron lasers, abatement of gases from the burning of fossil fuels, compact high precision welding systems, and sources of THz radiation and compact microscopes.