Numerical simulations of a waveguide FEL oscillator using hole coupling

We theoretically design a compact far-infrared FEL in Chinese Academy of Engineering Physics (CAEP). The 3D effects such as the diffraction, hole-coupling and misalignment, and transverse construction of optical field of CAEP FIR FEL are studied with an Integrated Numerical Experiment model in which transverse distribution is considered carefully. The results show that the optical transverse construction is good. The effects of misalignment such as the offset injection of electron beam and the tilts of the mirrors on the gain, optical power, output, construction of transverse modes are studied, and the limitations of various misalignments are given.