High Power Millimeter Wave Backward Wave Device Research

Backward-wave Oscillator (BWO) is one of the highest power microwave devices, is also the highest power and the highest efficiency millimeter wave microwave devices based on superradiance mechanism.The dissertation mainly involves three parts. In the part 1, consisting of chap.2, the nonlinear theory of relativistic backward wave oscillator (RBWO) is developed. In the part 2, consisting of chap.3 and chap.4, the normal stimulated radiation millimeter wave BWO is investigated. In the part 3, consisting of chap.5, the two millimeter backward wave oscillators based on superradiance mechanism are simulated.In the dissertation, the electric field and magnetic field in the area interacting between the electron beam and the electromagnetic field under a series of hypothesis is listed, the self-consistent nonlinear formulas of the RBWO are derived, the simulation procedure is edited on the MATLAB 6.1 and the curve of the slowly varying magnitude of the backward-wave versus the normalized length is calculated to test and verify the nonlinear formula of the BWO.In the part 2, using the 2.5D, relativistic, fully electromagnetic, PIC code KARAT, the millimeter wave BWO based on normal stimulated radiation is simulated, the results of the optimum design is followings: Employing an annular electron beam with pulse voltage 170kV, current 800A, pulse width 4ns, the millimeter wave output with output power ²5MW, frequency ³9GHz, pulse width ³ns, efficiency ²1% and mode TM₀₁ is obtained. The normalized output power versus the radius of the electron beam and guiding magnetic field are presented. The experiment is carried out to verify the simulation results, the experiment results is followings: Utilizing an annular electron beam with voltage ¹75kV, current ⁷85A, the outer radius of the cathode 2.25mm, the distance between the cathode and the anode 3.5mm, the millimeter wave with power ¹8MW, pulse width ³ns, efficiency ¹2.9% and radiation mode TE₁₁ is obtained, the experiment under the repetition rate 10Hz is also done. There is a good agreement between the numerical simulations and the experiment measurements.In the last part, the optimum designs of two millimeter wave BWO based on superradience mechanism are listed. The optimum design results of BWO (D/λ = 1) isfollowings, exploiting the electron beam with voltage ²00kV, current ⁸00A, pulseduration 1.2ns, the rising time ⁰.1ns, the trailing time —0.1ns, the guiding magnetic filed ³.7T, the millimeter wave with power ^<sup>75MW, pulse width ^<sup>35Ops, frequency ^<sup> 36.5GHz, power efficiency ⁴7% and the radiation mode TMoi is reached., The normalized output power versus guiding magnetic field, the radius of the electron beam, the thickness of the electron beam, the pulse width of the current, the rise time of the diode voltage, the current and the voltage are listed. The over-mode millimeter wave BWO (&/. = 2.65) with/ Areflection net based on superradiance mechanism is presented, simulated and designed, the designed results is following, exploiting the electron beam with voltage ^<sup>240kV, current ^<sup> 3kA, pulse duration 1.3ns, the rising time ⁰.25ns, the trailing time ⁰.2ns, the guiding magnetic filed ⁴.7T, the millimeter wave with power ⁷50MW, pulse width ²00ps, frequency —36.5GHz and power efficiency 104.2% is reached.. The working character of the BWO is developed, the normalized output power versus the rise time of the diode voltage is explain briefly.