Design And Simulation Research Of Optical Cavity In FEL-THz Source

Free Electron Laser Terahertz(FEL-THz) source is one of the best methods to realize the highpower THz source, which can not only produce high output power, but also obtain coherent and tunable wavelength to a large extent, can cover the whole THz frequency range,even higher.The optical cavity is one of the important modules in FEL, where the interaction between optical field and electron beam occurs and the development and evolution of FEL optical field happens. So, it's very necessary and important to design optical cavity well.On the basis of the research on FEL's basic principle, the sensitivity of FEL to the beam parameters and relative problems about the design of optical cavity are studied. According to the expected request of THz radiation, a set of beam parameters are designated by analyzing the sensitivity of FEL to the beam parameters, taking the practical technology level of the accelerator into account. In the condition that the beam parameters and wiggler parameters are given, the design and optimization of optical cavity is further investigated to produce the required THz radiation. The design of optical cavity configuration,the selection of the cavity mirror material, the computation of the optical cavity parameters and partial optimization are all included in this paper. Besides, the optical loss, output coupling, cavity detuning are also analyzed, and the improvement of optical cavity is put forward by analyzing the confinement to the optical beam in waverguide resonator,which is estimated approximately by calculating the transverse coupling factor between optical beam and electron beam.Meanwhile,the suppression of slippage in waveguide is also studied.In the end,the performance of THz radiation of the designed FEL-THz source is validated by FELO simulation.