Simulation and design of the CAEP far-infrared FEL

A far-infrared free-electron laser oscillator with a wavelength of 100 μm, which is driven by a L-band RF accelerator and has a linear planar wiggler, has been built in China Academy of Engineering Physics (CAEP) and is now ready to undergo the first lasing experiments. The simulation and design of the CAEP FIR FEL has been made with the help of our 3D FEL code. The results show that the energy spread and emittance of the electron beam must be <1% and 1.5π mm mrad, respectively. It is also found that the total loss of the optical cavity is about 30% due to the loss on the wall of the beam duct, which must be reduced or overcome by larger gain.