Abstract
Earlier, the authors found a mechanism for the sequence of short relativistic electron bunches, which leads to resonant excitation of the wakefield, even if the repetition frequency of bunches differs from the plasma frequency. In this case, the synchronization of frequencies is restored due to defocusing of the bunches which get into the bad phases with respect to the plasma wave. However, in this case, the bunches are lost, which as a result of this do not participate in the excitation of the wakefield. In this paper, numerical simulation was used to study the dynamics of electron bunches and the excitation of the wakefield in a magnetized plasma by a long sequence of short bunches of relativistic electrons. When a magnetic field is used, the defocussed bunches return to the region of interaction with the field after a certain time. In this case, the electrons of the bunches, returning to the necessary phases of the field, participate in the excitation of the wakefield. Also, the use of a magnetic field leads to an increase of the frequency of the excited wave relative to the repetition frequency of bunches. The latter increases the time for maintaining the resonance and, consequently, leads to an increase of the amplitude of the excited wakefield.
Highlights
The authors found a mechanism for the sequence of short relativistic electron bunches, which leads to resonant excitation of the wakefield, even if the repetition frequency of bunches differs from the plasma frequency
It is shown that when the resonance is maintained, the amplitude of the wakefield increases in comparison with the case of the initial resonant conditions
The simulation results of the mechanism of maintaining the resonance of electron bunches with a wakefield using a magnetic field are presented in this paper
Summary
The authors found a mechanism for the sequence of short relativistic electron bunches, which leads to resonant excitation of the wakefield, even if the repetition frequency of bunches differs from the plasma frequency. In this case, the synchronization of frequencies is restored due to defocusing of the bunches which get into the bad phases with respect to the plasma wave. In an experiment in plasma, a dense electron bunch with the energy of 42 GeV excited the wakefield, and its tail accelerated to the energy 84 GeV (i.e., doubled the energy) at a distance of approximately 1 m [2], the electric field is Ez≈42 GeV/m. Because the dielectric accelerator is easier to operate, and the plasma provides larger fields, the dielectric and plasma accelerators are intensively investigated
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