First lasing of the KAERI compact far-infrared free-electron laser driven by a magnetron-based microtron

The KAERI compact far-infrared (FIR) free-electron laser (FEL) has been operated successfully in the wavelength range of 97–150 μm. It is the first demonstration of FEL lasing by using a magnetron-based classical microtron. We developed a high precision undulator consisting of 80 periods, with each period being 25 mm. The field strength of the undulator can be changed from 4.5 to 6.8 kG with an amplitude deviation of only 0.05% in r.m.s value. The kinetic energy of the electron beam is 6.5 MeV. The average current and pulse duration of the electron beam macropulses are 45 mA and 5.5 μs, respectively. The measured power of the FEL with the electron beam parameters was more than 50 W for a FIR macropulse having a duration of 4 μs. The spectral width of the FEL was measured to be 0.5% of the central wavelength. The FEL system, aside from the racks for the controlling units, is compact enough to be located inside an area of 3×4 m2.