Power and bandwidth studies for W-band free-electron masers

Power and bandwidth studies for a high power W-band (≈94 GHz) FEM amplifier is presented for a helical wiggler/cylindrical waveguide configuration using 3D ARACHNE simulation code (H.P. Freund, T.M. Antonsen, Jr., Principles of Free-electron Lasers, 2nd edn., Chapman & Hall, London, 1996, Ch. 5). Using a 300 kV/20 A electron beam with a normalized emittance of 95 mm mrad, a 600 G wiggler field with a 0.88 cm period, and a strong guide field of 20 kG, efficiencies of greater than 8% are possible with a FWHM bandwidth of 4.5 GHz.