Photo Triggered Carbon Nanotube Field Emission Cathode for Free Electron Lasers

Busek Co. Inc (Busek) and Massachusetts Institute of Technology (MIT) propose to develop the design of a photon actuated, ultrafast carbon nanotube (CNT) field emission cathodes for high-power electron beam accelerator sources. The cathode will be based on massive arrays of Vertically Aligned Carbon Nano-Fibers (VA-CNFs) that are individually controlled by a vertical ungated field effect transistor (FET). These arrays would be activated using photons from a laser to achieve ultrafast current emission. The team will focus on designing a cathode based on massive arrays of VA-CNFs that is able to emit up to A/cm^2-level electron current, and on the design of a reflecting structure that concentrates photons from a common source on the surface of the VA-CNF tips. The proposed cathode will harness five important technologies that will enable current densities up to 10 A cm^-2, a total emission area of 25 mm^-2 or higher, and able to emit in 10 pico second level pulses: 1) Fabrication of uniform isolated VA-CNFs; 2) Individual ballasting of the field emitters using vertical FET; 3) Photon-enabled field emission for ultrafast cathode actuation; 4) High-pressure (>10^-3 torr) operation; and 5) Proximal electrostatic lenses to individually control the emission from each CNT tip.