A NEW FEL CONCEPT DRIVEN BY A VACUUM MICROFIELD EMITTER

In order to reduce the scale and construction cost of free election la sers, it is necessary to investigate various new ideas with respect to electron beam generation, acceleration and radiation mechanisms. In t his paper, a microscale free electron laser is proposed which is drive n by a very small diameter (less than a few mum) electron beam. The mi croscopic electron beam can be generated with a needle cathode, for an example, a Spindt cathode. By injecting the microscopic electron beam into a microdielectric channel, we generate radiations of several mum wavelength by Cherenkov emission, Smith-Purcell emission and so on. I n the design of a microfield emitter FEL (MFE FEL). It is shown that a 2 mm long dielectric pipe with an electron beam of diameter 1 mum and with a current of 50 muA gives a one pass gain of 50% for a 10 mum wa velength radiation.