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

The preliminary design of a voltage tunable far-infrared foe-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 MV/1A annular electron beam interacting with the TE(01) coaxial waveguide mode at approximately 1 THz (lambda = 300 mu m). 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.