The first operation of a two-stage tapered gyrotron traveling wave amplifier employing two tapered waveguide circuits and tapered magnetic fields is reported. Small-signal gain of 30 dB and saturated gain of 25 dB over a 20% bandwidth at an efficiency of 16% have been observed using a 33 kV, 1.5 A electron beam. Comparison with supporting theory is satisfactory.

• Received 29 August 1994

DOI:https://doi.org/10.1103/PhysRevLett.74.2399