Ka-band Harmonic Gyrotron Traveling Wave Tube Study Of High-frequency Structure

Because of gyro-TWT miniaturization and cost of the potential, a new type device-frequency multiplying gyro-TWT is gradually becoming the new direction, this device is both a frequency multiplier and amplifier.First, the paper analyzes amplification mechanism of frequency multiplying gyro-TWT, and then study the problem of self-excited oscillation of frequency multiplier gyro-TWT. The details are as follows:1. Amplification mechanism of frequency multiplying gyro-TWT is analyzed profoundly. According to the nonlinear self-consistent equation of gyro-TWT, the nature of electron beam interaction with high-frequency field of frequency multiplying gyro-TWT is studied. At the same time, electron density of the pre- cluster in frequency multiplying gyro-TWT is calculated. The results show that pre-Cluster electron density is related to horizontal and vertical velocity ratio of electron beam, electron cyclotron radius, guiding center radius, amplitude of high-frequency field. When rc=0.43*rw1 is satisfied, not only the second component of pre-clustering electron density is largest, but also energy exchange of electron beam and high-frequency field can more fully in the second waveguide stage.2. The linear theory of frequency multiplying gyro-TWT is analyzed in the paper. By studying self-excited oscillation of frequency multiplying gyro-TWT in the first interaction stage and second interaction stage, we gained conditions of absolute instability and backward wave oscillation was suppressed in theory.When beam voltage =70 kV, perpendicular to-parallel velocity ratio =1.2, and waveguide radial rw1=10.71mm, guiding center radial position =0.43*rw1, magnetic field B0=O.65T, conductivity=1300s/m. In the first interaction stage ,start-oscillation current of absolute instability I=18A, starting oscillation length of TE11(1),TE21(1),TE02(2)backward wave oscillation modes are13.4cm,9.2cm,12.7cm,respectively. In the second interaction stage, self-excited oscillation of TE02(2) and TE03(2) absolute instability modes is not motivated at all, and conductivity=300s/m, starting oscillation length of TE11(1),TE21(1) backward wave oscillation modes are 12.5cm,10.2cm, respectively. 3. self-consistent nonlinear equations of gyro-TWT are given in the form of a complex, finally, equations is simplified by a series calculate.