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

JINR-IAP FEM oscillator with Bragg resonator

A FEM-oscillator with a reversed guide magnetic field and a Bragg resonator as a RF radiation source for collider applications was studied. The configuration with a step of the corrugation phase is proved to be advantageous. It possesses such features as a high efficiency, precise tunability of the operating frequency and a narrow spectral band. It is demonstrated experimentally that such an oscillator is capable of operating at frequencies of ~30 GHz in single-mode regime with the frequency tuning in interval up to 6%. Frequency and spectrum measurements have been performed with precision of ~0.1%

Generation of electromagnetic fields of extremely high intensity by coherent summation of Cherenkov superradiance pulses

We demonstrate both theoretically and experimentally the possibility of correlating the phase of a Cherenkov superradiance (SR) pulse to the sharp edge of a current pulse, when spontaneous emission of the electron bunch edge serves as the seed for SR processes. By division of the driving voltage pulse across several parallel channels equipped with independent cathodes we can synchronize several SR sources to arrange a two-dimensional array. In the experiments carried out, coherent summation of radiation from four independent 8-mm wavelength band SR generators with peak power 600 MW results in the interference maximum of the directional diagram with an intensity that is equivalent to radiation from a single source with a power of 10 GW

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]