Cyclotron resonance maser with a tapered magnetic field in the regime of "nonresonant" trapping of the electron beam.

A different version of the regime of electron trapping is proposed for electron microwave amplifiers. The use of this regime in a cyclotron resonance maser with a weakly relativistic electron beam can simultaneously provide efficiency as high as 50%, a very broad (tens of percent) frequency band, and very weak sensitivity to the spread in electron velocity.