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The main results of theoretical and experimental researches concerning the physical processes in a dielectric wakefield accelerator based on the accelerating wakefield excitation in a dielectric structure with the use of a long sequence of electron bunches are presented. The enhancement of the excited wakefield amplitude is achieved owing to the coherent summation of wakefields generated by separate bunches. The bunches are accelerated in the total wakefield by arbitrarily dividing the bunch sequence into the exciting and accelerated parts, by using the appropriate frequency detuning of the bunch repetition frequency with respect to the frequency of the excited principal transverse mode. The influence of plasma in the transit channel on the amplitude of excited wakefields and the focusing of driving and accelerated bunches is analyzed. K e y w o r d s: plasma-dielectric structure, electron bunch sequence, wakefield excitation, bunch acceleration, plasma frequency.

The paper presents some results of experimental studies of the excitation of wake fields and the acceleration of electrons in waveguide-dielectric structures (DS) upon injection of a sequence of electron bunches into them. Exper-iments have shown an increase in the amplitude of the wake wave and the acceleration of a small fraction of elec-trons when the wavelength of the excited field is equal to the doubled bunch length. A simple physical model of the observed phenomenon is given. Also, the paper proposes a method for accelerating a part of each electron bunch in the steady-state mode of the resonator dielectric structure. Some of the electrons are “cut out” by the collimator and enter the accelerating phase of the previously excited wake wave. The wave is displaced due to the difference in the distances traveled by the wave and the accelerated part of the electrons.