Abstract
We have started to develop a tungsten (W) field emission cathode for Cherenkov free electron laser (FEL) or Smith-Percell FEL. In this work, elementary properties of electron beam current from W tip have been investigated by numerical simulation and experiment using a system consisting of W tip, 1 st- and 2nd- gate, and anode. When there was no 2nd gate, the current increased up to-20μA with the absolute voltage of cathode according to the Fowler-Nordheim equation. The addition of 2nd gate decreased the current half to 5th lower than expected value from the simulation. However, it focused and enlarged the current of the electron beam in a certain voltage range of 2nd gate. These phenomena agreed qualitatively with those of the simulation. In further study, improved experiment will be made to get higher current and parallel smaller size of an electron beam.
