RF Gun with High-Current-Density Field Emission Cathode

75748-Cathodes have a dominant influence on the quality of the electron beams produced from laser photo-cathodes in radio frequency (rf) guns used as injectors in many electron accelerators. Similar limitations are also suffered by thermionic cathodes in diode guns used in high-power rf amplifiers for accelerator applications. These limitations could be surmounted by a field-emission cold cathode capable of high current density. This project will combine the high-current-density field emission from an array of carbon nanotubes with secondary electron channel multiplication in a ceramic facing structure, to produce a cold cathode of exceptional promise for rf guns and diode guns. The cathode will be installed and tested in an existing S-band 2-1/2 cell rf gun. With emission control and modulation, and with current density in the range of 1 kA/cm2, this cathode could provide performance and long-life not enjoyed by other currently-available cathodes. In Phase I, electrodynamic and space-charge flow simulations will be conducted to specify the cathode configuration as well as the range of emission current density from the field-emission cold cathode. Design and preliminary tests will be conducted prior to the fabrication of the gun during Phase II. Commercial Applications and Other Benefits as described by the awardee: Replacing thermionic cathodes and laser photocathodes in rf guns and diode guns by a cold cathode with high-current-density and long lifetime could improve device performance and lower costs. Applications in a range of commercial and military vacuum electronics devices could be anticipated.