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Experiments have demonstrated high-power amplification (100 MW class) from a traveling wave amplifier driven by a modulated electron beam. The modulated electron beam is generated by applying a modulated voltage pulse from a nonlinear transmission line (NLTL) to the cathode of the electron gun. The system showed that over the designed operating range of the disk-on-rod (DoR) TWT amplifier (1.2–1.4 GHz), the peak frequency of the amplifier output tracked the peak frequency of the NLTL to within ±2%; however, the output was not phase stable. Measured RF energy gain for this frequency regime ranged from 1.5 at 1.2 GHz up to 5.0 at 1.4 GHz). [ABSTRACT FROM AUTHOR]

The harmonic recirculating planar magnetron (HRPM) is a frequency-agile, multispectral HPM source. The HRPM implements an $L$ -band oscillator (LBO) and an $S$ -band oscillator (SBO) near 1 and 2 GHz, respectively. The novel coaxial-all-cavity-extraction (CACE) method was implemented to extract power from the SBO. The two oscillators demonstrated harmonic frequency locking, where the SBO frequency locked to the LBO second harmonic frequency. The two oscillators are concluded to operate as a damped, driven, harmonic oscillator system. In the locked state, the LBO acts as the driving oscillator, the SBO acts as the driven oscillator, and the coupling mechanism between the two oscillators is the harmonic content in the electron spokes as they propagate directly from the LBO to the adjacent SBO. The two primary variables studied in this system are the LBO harmonic frequency and the SBO quality factor, $Q$. In isolated SBO experiments, the dominant operating state of the magnetron was the $5\pi $ /6 mode. However, when operated in tandem with the LBO, the SBO was forced to operate in the $\pi $ -mode. Output powers in HRPM experiments generated SBO powers of 9.5 ± 1.4 MW at high $Q$ , 19 ± 6 MW at moderate $Q$ , and 28 ± 9 MW at low $Q$. Output powers in the isolated SBO configuration were not significantly different from the HRPM. By experimentally manipulating the hub drift direction and altering the evolution of harmonic content received by the SBO, the locked state was significantly diminished, suggesting that the beam spokes play a crucial role. [ABSTRACT FROM AUTHOR]

Calibrated microwave power and phase measurements are presented for the first recirculating planar magnetron prototype consisting of two coupled six-cavity 1-GHz planar cavity arrays. The results are presented for a solid cathode and two mode-control cathodes (MCCs) with aluminum or velvet electron emitters. The measurements were conducted using a prototype coaxial microwave power extraction scheme. The experimental operating parameters included: pulsed cathode voltages between −250 and −300 kV, voltage pulselengths of 200–600 \mu \texts , axial magnetic fields of 0.1–0.32 T, and entrance currents of 1–10 kA. The results showed improved oscillator frequency locking for the MCCs and increases in power and efficiency using the velvet electron emitter. [ABSTRACT FROM PUBLISHER]

Microwave oscillation has been measured for the first time in a 12-cavity axial-magnetic-field recirculating planar magnetron, designed to operate in \pi mode at 1 GHz. The device operates with a -300-kV pulsed cathode voltage and a 0.2-T axial magnetic field, and oscillates at transverse currents exceeding 1 kA when driven by an electron beam pulselength between 0.5 and 1 \mu\s. Microwave pulses were measured at frequencies between 0.97–1 GHz and achieved several hundred nanoseconds in length. Mode competition was observed between the \pi and 5 \pi/6 modes. [ABSTRACT FROM PUBLISHER]