Design of a far-infrared CHI wiggler free-electron laser

The preliminary design of a voltage tunable far-infrared free-electron laser with a Coaxial Hybrid Iron (CHI) wiggler is presented. The CHI wiggler consists of a central rod and an outer ring of alternating ferromagnetic and non-ferromagnetic spacers. A period wiggler field is produced when the CHI structure is immersed in an axial magnetic field. The design under investigation makes use of a 1 MV1 A annular electron beam interacting with the TE01 coaxial waveguide mode at approximately 1 THz (λ = 300 μm). The nominal wiggler period is 0.5 cm and the inner and outer waveguide radii are 0.4 and 0.8 cm respectively. An axial guide field of 5–10 kG is used. The device performance is modeled with a slow-time-scale nonlinear code, and self-fields and axial velocity spread are included in the model. Simulation results show output powers above 2 kW at frequencies from 850 GHz to 1040 GHz can be achieved for voltages ranging from 0.93 to 1.07 MV.