Noise Amplification by a Relativistic Electron Beam in a Double Coaxial Plasma–Metal Waveguide

Effective noise amplification is detected for the first time at the interaction of a relativistic electron beam with slow plasma waves in a coaxial plasma–metal waveguide. Unlike configurations of existing plasma masers, this configuration of the plasma–beam interaction region can be used for long operation in the pulsed-periodic mode with the hollow electron beam deposition on an easily cooled collector. In addition, the internal metal conductor at the ground potential increases the limiting vacuum current of the electron beam and the current at which the maximum transfer efficiency of the electron beam energy to the plasma wave is achieved. The electron beam with the energy of 250 keV, current of up to 1.5 kA, and duration of 2.5 ns has interacted with the plasma waves with the measured concentration of up to 3 × 10¹³ cm^–3. A radiation spectrum from 2 to 6 GHz with the power of up to 70 MW is recorded.