Experimental investigation of a broadband two-stage tapered gyro-TWT amplifier

A two-stage tapered gyro-TWT amplifier experiment operating in Ka-band is underway at the Naval Research Laboratory. 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. Nonlinear calculations for a two-stage tapered device operating at 33 kV, 1 A with a peak alpha of 0.9 and a 2% velocity spread indicate a saturated gain of 30 dB with an efficiency of approximately 30% and an instantaneous bandwidth of 15%. In contrast with single stage operation, the amplification band is observed to be very sensitive to the beam velocity spread. A two-stage tapered gyro-TWT has been assembled and is presently under test. Initial results on amplifier stability are presented.<>