Operational two-stage tapered gyro-TWT amplifier

A two-stage Ka-band gyro-TWT amplifier experiment operating in the TE/sub 10/ rectangular tapered waveguide with a 33 kV, 1.5 A beam has been operated successfully at the Naval Research Laboratory. The device incorporates precise axial tapering of both the magnetic field and the interaction circuit for broadband operation. The objective of this program is to demonstrate the stable wideband operation of a low voltage tapered gyro-TWT having high gain and good gain uniformity. By employing an electron beam with /spl alpha/ of near 0.7 at the entrance of the tapered waveguide circuit, stable operation is observed at full beam current. Small signal gain of 30 dB and saturated gain of 25 dB are observed over a wide (20%) instantaneous frequency range (32-39 GHz). Saturated efficiency of 16% has been obtained in good agreement with theory. The beam velocity spread on the tapered geometry can cause a sharp drop in gain when the electrons add up destructively in phase. The bandwidth of the two-stage tapered gyro-TWT amplifier can be extended by reducing the interaction length or beam voltage.<>