Numerical study of optical-cavity misalignment effects for a far-infrared FEL

A far-infrared FEL will be newly installed in the IR FEL Research Center at the Science University of Tokyo (FEL-SUT) in 2002. In this study, optical cavity misalignment effects for the far-infrared FEL are researched by using the simulation code that has been developed at Kawasaki Heavy Industries, Ltd. Results show not only cavity losses but also the gain reduction by the tilt and the offset of the mirror and the offset of the electron beam. The required alignment accuracy is also obtained in this study.