A two-stage, phase-coherent, harmonic-multiplying, inverted gyrotwystron

Theory, design, and stable operation of a novel, high-power millimeter wave source, the phase-coherent harmonic-multiplying inverted gyrotwystron (phigtron), are presented. It is a two-stage hybrid gyrodevice which comprises an input waveguide section for fundamental gyro-TWT interaction to prebunch the beam, a radiation-free drift section to rapidly develop the harmonic components in the beam current by ballistic bunching, and a RF energy-extraction output cavity with a number of well selected axial modes resonating at the second harmonic of the input frequency. A large value of the gain-bandwidth product is achieved by using an input section composed of a traveling wave interaction circuit and a long extended interaction structure for the output section. Stable operation of the phigtron may be due in part to operating the input section at half the output frequency and in a relatively low order mode, and in part to employing a mode selective circuit as an input coupler and at each interaction stage to suppress competing modes. In chapter 1, motivation and general description of the phigtron are introduced. The physical mechanism and general formulation for the two-stage phigtron is presented in chapter 2. The engineering design and experimental setup are discussed in chapter 3.; Chapter 4 presents the experimental results of the phigtron and simulations. Experiments demonstrated that the phigtron can be operated either as a phase-locked oscillator or a frequency-doubling amplifier. In the case of phase-locked oscillator with the {dollar}TEsb{lcub}02{rcub}{dollar} mode in the input section and {dollar}TEsb{lcub}03{rcub}{dollar} mode in the output cavity, widest bandwidth operation at 34.6 GHz gives 8 MHz bandwidth, 110 kW output power, 30 dB gain and 30% efficiency. A highly overmoded, high gain, broadband, stable amplification was observed with the {dollar}TEsb{lcub}22{rcub}{dollar} mode in the input section and the {dollar}TEsb{lcub}42{rcub}{dollar} mode in the output cavity; bandwidth was 1.3% with saturated gain of 33 dB around 31.8 GHz. The measured gain-bandwidth performance represents a significant advance in the state of the art for millimeter wave gyrotron amplifiers operating in such high order modes. Also, the phigtron operating in the {dollar}TEsb{lcub}42{rcub}{dollar} output mode has the highest order output mode of any gyro-amplifiers to date.; As pointed out in chapter 5, the theoretical and experimental studies conducted in this dissertation work has supported the realization of the phigtron concept. The phigtron shows promise for operating as a highly overmoded, high gain, broadband, low magnetic field, high power millimeter wave amplifier with possible application to millimeter wave radar and communications systems.