EFFECTS OF BEAM VELOCITY SPREAD ON 2-STAGE TAPERED GYRO-TWT AMPLIFIER

The recent successful operation of a two-stage K-a-band gyro-TWT ampli fier at the Naval Research Laboratory has demonstrated its viability a s a source of broadband high-power millimeter waves, However, it has b een observed experimentally that sharp gain reductions occur at certai n frequencies, In this paper, an analytical theory is presented which describes the effect of electron beam quality on the device's instanta neous bandwidth, It is shown that these observed gain dips are due to electron phase-mixing, resulting from finite beam velocity spreads, in the frequency-dependent sever, In addition, the theory demonstrates t hat the velocity-spread induced dips can be shifted or reduced by adju sting the magnetic field profile, circuit length, and beam axial veloc ity, consistent with experimental observations.