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The noise amplification mode in a plasma maser with inverse geometry was obtained experimentally for the first time. It is shown that the introduction of a microwave absorber transfers the maser operating mode from the oscillator to the amplifier. In both modes, the tuning of the radiation frequency has been shown when the plasma density changes. This work is a step in the implementation of a plasma relativistic noise amplifier with a short REB pulse.

A change in the operation mode of a plasma maser with a pulse duration of 40 ns from a noise amplifier to a feedback self-oscillator at a power level of up to 10 MW has been experimentally demonstrated for the first time. In the noise-amplifier mode, the radiation power is distributed almost uniformly in a frequency range from 3 to 9 GHz. In the self-oscillator mode, the emission spectrum contains characteristic frequencies of longitudinal oscillation modes of plasma—beam cavity.

Consideration is given to the research status and prospects for development of plasma relativistic microwave electronics as a basis for plasma masers. Possible applications are determined for plasma masers as high-power sources of microwave pulses. Design features of masers and their radiation characteristics are considered with a view to the type of device: self-oscillator, external signal amplifier, or noise amplifier.

Operated in the noise amplification regime, a plasma maser underwent a series of experiments. The pulse duration was 50 ns, the suppression of feedback was provided by microwave absorbers, transition from the noise amplification to a self-oscillation regime was demonstrated, and the maximum power of 10 MW with the efficiency of 3% was measured. For different plasma concentrations, the linear amplification rate was ranging from 0.1 to 0.2 cm−1. The frequency band of an emission pulse was 3–15 GHz, and the noise spectrum was stable during the pulse. The experiment provided the guidelines for further development, which are in the pulse duration reduction for abandoning the microwave absorber. The short-pulse plasma maser should be ∼35 cm long with the pulse duration

High frequency optimization of multigap IH-/CH-resonators requires solving the range of problems, particularly receiving high values of effective shunt impedance and realization of the uniform accelerating field distribution on its axes. H-mode resonators design contains flat vanes (pylons)to reach both of these goals. This article presents the results of electrodynamic modeling of CH- and IH-resonators in case of zero gap between the vanes and resonator end wall. The values of the optimized shunt impedances, Q-factor and field flatness for IH- and CH-designs are shown.