New results of the phase-coherent harmonic-multiplying inverted gyrotwystron

Summary form only given, as follows. A highly overmoded, Ka-band, phase-coherent, harmonic-multiplying, inverted, gyrotwystron (phigtron) experiment is described. The phigtron was composed of the following parts: a fundamental gyro-TWT as prebunching input section; a short buncher cavity (1.5/spl lambda/); and, a long output cavity (12/spl lambda/), with both cavities operating at the second harmonic of the electron cyclotron frequency. Phase locking, amplification and mode selection have been studied and compared with performance in a previous one-cavity phigtron. Enhanced amplifier efficiency of 25% and improved frequency response characteristics are obtained with the new two-cavity version, further demonstrating that the phigtron has the potential of becoming a high average power, millimeter wave generator with good efficiency, high gain, compact driver, and medium bandwidth for radar and other advanced applications.