Physics and considerations on millimetre-wave free electron lasers with low energy electron beams

In the frame of the development of a millimetre-wave source for industrial applications, the European Network on Microwave Applications of Industrial Free Electron Laser aims at producing a working design of a broadband, compact and low-cost millimetre-wave source (10-100 GHz) of sufficient power (more than 1 kW, CW or average) so as to be able to aid industrial manufacturing. For the sake of compactness, low electron beam energies (of about 100 keV) and currents of a few A at most, are required. In order to select the best candidates a study has been performed on the principles and physics of low energy electron beam millimetre-wave sources. Although the gyrotron is a well established and highly efficient millimetre-wave source, we are considering alternative sources such as the Cherenkov FEL, Smith-Purcell based FELs, and undulator based FELs for more cost-effective and technological simpler devices in the kW power range.