Simulation and experimental study on tungsten field emission cathode

We have been developing a tungsten field emission cathode for a Cherenkov F EL or Smith-Purcell FEL. The properties of the electron beam from a tungste n tip have been investigated using numerical simulation and some experiment s. Although the 2nd gate reduced the emission current due to a decrease of the effective field at the tungsten tip, it focused and enlarged the electr on beam current in a certain potential range of the 2nd gate depending on t he cathode voltage and the distance between 1st and 2nd gates. The electron beam diameter was reduced to similar to 2 mm on the fluorescent screen at the anode. (C) 1999 Elsevier Science B.V. All rights reserved.