Self-amplification of coherent spontaneous emission in a cherenkov free-electron maser

Ultrashort pulses of microwave radiation have been produced in a dielectric-lined Cherenkov free-electron maser (FEM) amplifier. An intense initial seed pulse, due to coherent spontaneous emission (CSE), arises at the leading edge of the electron pulse. There is evidence to show that 3-4 cycle spikes are produced through the amplification of these seed pulses. A strong dependence of the start-up power on the rise time of the electron pulse has been found. The experimental results are verified by a theoretical analysis. Our study shows that amplification in a FEM amplifier is always initiated by CSE arising from the edge of the electron pulse when the rise time is comparable to the electromagnetic wave period

Summation of emission from superradiant sources as a way to obtain extreme power density microwaves

A theoretical model that covers both spontaneous and stimulated Cherenkov emission from an extended electron bunch has been developed. The initiation is described of the generation of superradiant pulses [1-3] by emission from the leading edge of the electron bunch. In combination with the proven experimentally picosecond stability of explosive emission from a cold cathode [4], it provides the possibility for strong correlation of phase of the SR pulses with respect to the leading edge of the electron pulse [5]

Generation, amplification, and nonlinear self-compression of powerful superradiance pulses

Superradiance (SR) of electron bunches can be considered an effective method of production of ultrashort electromagnetic pulses. Different types of SR associated with different mechanisms (cyclotron, Cherenkov, and bremsstrahlung) of stimulated emission are observed experimentally in the millimeter and centimeter wavelength bands. Progress in this research has enabled a new type of generator to be created capable of generating unique short (under 200-300 ps) electromagnetic pulses at super high peak powers exceeding 1 GW in the millimeter and 3 GW in the centimeter waveband. Some new methods for further increasing of the SR pulse peak power along with the promotion of such sources to higher frequency bands are discussed. These new methods include phase synchronization of several SR pulse generators, the amplification of an SR pulse during its propagation along a quasi-stationary electron beam and nonlinear compression in the process of induced self-transparency

Experimental plasma maser as a broadband noise amplifier. II. Short pulse

This paper presents an experimental plasma maser driven by a 2-ns long, high-current electron beam with a typical particles energy of 270 ± 10 keV, a pulsed power of 450 ± 30 MW, and a total energy of 0.85 ± 0.03 J. Tunable plasma characteristics define variations in the spectral maxima of excited high-power microwaves in the range from 3 to 25 GHz. The short beam current pulse has provided the device operation in the mode of a noise amplification with the energy efficiency of 26% ± 3%, mean microwave power over the beam current pulse of 117 ± 10 MW, and an instant (peak) power of up to 430 ± 30 MW. © 2021 Author(s)