Saturation operation of an 86 GHz free electron laser amplifier

Summary form only given, as follows. The advantages of the free electron laser amplifier using sheet (ribbon) electron beam and small period (9.6 mm) wiggler have been demonstrated with the successful saturation operation at 86 GHz frequency. The wiggler length was extended from 56 to 74 periods in order to approach saturation. In addition, the 2.8 mm by 4.0 cm amplifier waveguide was replaced by one with an interior cross-sectional dimensions of 3.2 mm by 4.0 cm so that the operating voltage and the effect of waveguide non-uniformity were reduced. The device has been broadly studied experimentally at various wiggler magnetic fields, beam currents, injected power levels, and beam voltages. A gain of 24 dB has been achieved with /spl sim/1 kW input power at 450 kV beam voltage, 17 A beam current, and 3.8 kG wiggler magnetic field. The gain at /spl sim/1 W input power level was measured to be over 30 dB.