Simulation of the coherent THz radiation from a variable elliptically polarized undulator

A new type of coherent THz light source is building in SINAP. It will use the femto-second electron beam passing through a variable elliptically polarized undulator to produce the high bright THz radiation with various linear, elliptical or circular polarization. The paper describes the computation methods and the simulation results of the flux density, spectrum, polarization and coherence for this kind of radiation. For the electron beam with the energy 20 MeV, the emittance 1.5 πmm·mrad, the beam length 200fs and the electric charge 50 pC, the THz radiation with the horizontal linear polarization or the circular polarization of the maximum flux density of 2 x 109 photons/mm2/0.1%bw can be obtained at the distance 1m from the center of the undulator with 0.6m length