Quasi-stationary Electron Beam Research Articles

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.

The amplification, compression, and self-induced transparency effects for the ultrashort electromagnetic pulses propagating along quasi-stationary electron beams

By analogy with the coherent interaction of short (on the scale of relaxation times) light pulses with inverted, i.e., active, and non-inverted, i.e., passive, two-level quantum systems, we study the possibility of the nonstationary amplification, self-induced transparency, and compression effects for the microwave electromagnetic pulses propagating along quasi-stationary electron beams. The considered analogy is not of only general physical, but also practical significance since a number of practically interesting transformation modes of ultrashort pulses, including the microwave superradiance pulses, can be implemented on its basis. The first experiments, in which the nonstationary amplification during the pulse—electron-beam interaction in a waveguide with dielectric insert was observed and pulses with subgigawatt peak powers at a carrier wavelength of 8 mm and uniquely short durations less than 100 ps were obtained, are described.

Amplification and Nonlinear Compression of Ultrashort Microwave Pulses by Quasi-Stationary Electron Beams: Theory and Experiment

The first experiments to observe amplification of ultrashort microwave superradiance (SR) pulses propagating along quasistationary electron beams were performed. For this purpose, an experimental set-up based on two high-current RADAN accelerators synchronized with an accuracy 100 – 300 ps was built. The first accelerator was used to drive the 37 GHz generator of superradiance pulses with a duration ∼300 ps based on relativistic back wave oscillator (BWO). The second accelerator with a current up to 1.2 kA and an electron energy of 300 keV was used to drive the amplification section in the form of a dielectric loaded waveguide. According to the theoretical analysis, amplification of electromagnetic pulses (minimum of 4 times in power) was accompanied by significant shortening of the SR pulse duration to less than 100 ps.

Effect of the nonlinear compression of ultrashort microwave pulses in the process of the amplification by quasistationary electron beams

An effect of the nonlinear compression of ultrashort microwave pulses has been observed in the process of the amplification of quasistationary electron beams. The Cherenkov mechanism of the interaction of a rectangular electron beam with a decelerated wave in a waveguide partially filled with an insulator is used. The experiment has been conducted on a setup consisting of two synchronized RADAN high-current accelerators. The first accelerator supplied a generator of 37-GHz superradiance pulses with a duration of about 300 ps. The second accelerator with a beam current of up to 1.2 kA and an electron energy of about 300 keV was used in an amplifying section. The theoretical analysis shows that the amplification of the electromagnetic pulses (at least by a factor of 4 in the power) is accompanied by a strong decrease in their duration (down to 100 ps).

A study of the propagation of a quasistationary relativistic electron beam in a dense gas. II. Experimental studies

Results obtained from experimental studies of the interaction between a quasistationary electron beam (300 keV, 20 A, 500 μsec, 0.3 cm) and a dense gas are presented. These investigations were carried out in air at atmospheric pressure and, for the purpose of modeling the propagation of a magnetostricted REB, at reduced pressure (3–300 torr). The rarefaction dynamics of a channel heated by the beam are studied and its maximum propagation distances in a dense gas are determined. The results obtained are compared with the theoretical model examined earlier.