Development of a High-power Terahertz Free Electron Laser Using a Microtron accelerator and an Electro-magnetic Planar Undulator

A high-power terahetz FEL is under development at KAERI. We developed a compact microtron to accelerate electrons up to 5 MeV with the energy spread of about 0.4%. An electro-magnetic planar undulator was designed and fabricated to cover the FEL's lasing wavelength range of 350-650μm, The magnetic field strength in the gap of the undulator is changeable from 0.76 to 1.18 T by varying the coil current of the undulator from 1.4 to 2.4 kA. The undulator provides horizontal focusing force to keep the low energy electrons passing a specially-designed narrow waveguide.