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Free-electron lasers (FELs) capable of operating in vibrational infrared (IR) (3 - 30 micrometer) regime have been developed at a small number of fixed sites around the world. However, there is a need for portable systems capable of operating in the 3 - 5 and 8 - 13 micrometer atmospheric windows for remote sensing applications. Wider use of FELs is inhibited by system size, cost, and the shielding requirements associated with the production of high current 15 - 45 MeV electron beams which are currently needed to lase in the infrared. The concept of an electromagnetic wiggler, in which the magnetostatic wiggler system of fixed transverse magnets is replaced by an intense counter-streaming microwave or optical radiation beam, has been of interest from the early work on FELs as a means of reducing the required electron beam energy. Although there has been little experimental progress to date due to the lack of high power wiggle radiation sources, the recent development of high power millimeter-wave gyrotrons has led to a re-evaluation of the feasibility of electromagnetic wigglers. We have published earlier studies of the possibility of IR FELs using low energy beams (3 - 5 MeV) using a gyrotron-powered millimeter-wave wiggler. Both waveguide cavity and open-mirror resonator (quasioptical) gyrotron (QOG) powered wigglers were considered. In this talk we present a new wiggler design, in which the millimeter-wave power generated by the QOG is coupled into a corrugated waveguide and compressed. This has the possibility of substantially increasing the single-pass FEL gain over previously published design concepts. Designs for proof-of- principle low voltage infrared FEL experiments based on both radio-frequency (rf) linear accelerator and electrostatic accelerator technology are presented together with point designs for portable systems covering the infrared windows in the atmosphere.
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