STABLE HIGH-POWER TE(01) GYRO-TWT AMPLIFIERS

The stability of high power gyro TWT amplifiers operating in the low-l oss TE(01) mode of cylindrical waveguide has been studied. Linear theo ry has been used to determine the threshold start-oscillation beam cur rent for absolute instability in the operating mode and the critical s ection lengths for the dominant gyro-BWO interactions occurring at var ious cyclotron harmonics in other waveguide modes. The performance of the amplifier was evaluated with a nonlinear, self-consistent slow-tim escale simulation code. Utilizing interaction sections whose lengths a re less than the threshold start-oscillation length and are separated by attenuating severs for isolation, two stable three-section devices have been designed which are predicted to yield: (1) a peak output pow er of 230 kW at 35 GHz with an efficiency of 23%, a saturated gain of 46 dB and a constant drive bandwidth of 6% for a 100 kV, 10 A electron beam with an alpha = v(perpendicular to)/v(z), = 1.0 and an axial vel ocity spread Delta v(z)/v(z) = 5% and (2) 105 kW at 94 GHz with 21% ef ficiency, 45 dB saturated gain and 5% constant-drive bandwidth for a s imilar 5 A electron beam. In addition, the design of the 0 dB input/ou tput couplers and the MIG electron gun are given. Due to the low loss of the TE(01)(circle) mode, both of these amplifiers can be operated c ontinuously.