Coherent emission and gain from a bunched electron beam

The radiation from a modulated electron beam, such as that produced in a radio-frequency accelerator, passing through a magnetic undulator is analyzed. The authors show that in a waveguide free electron laser (FEL), this may lead to an emission of a significant amount of coherent radiation in the far infrared to millimeter wave range. A simple and powerful method of calculating the spectral distribution of the radiated power is presented along with an analysis of the gain and the saturated power. The experimental results of spontaneous emission measurements on an RF driven FEL, are presented and compared to theoretical predictions.<
>