[en] Considered in the approximation of nonrelativistic hydrodynamics is the problem of the movement stability of an electron beam which completely fills a round waveguide, in a corrugated magnetic field, in relation to the excitation of potential waves in it. Lengths of excited waves are supposed to be small both as compared with the waveguide radius and in comparison with the period of the corrugating of a magnetic field. Some limitations imposed on the results of hydrodynamic consideration by the kinetic theory are discussed. It is shown that threshold values of the depths of the beam spatial modulation approach zero simultaneously with the Landau damping of a parametrically bonded wave. This circumstance makes practically important such regimes of parametric instability development at which the phase velocity of a wave is wide apart from the thermal velocity of beam particles

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[en] Considered is electrical field excitation by an electron bunch moving in a channel of the radius d in an unbounded isotropic medium with dielectric and magnetic permittivityes, the dispersion of which in the range of frequencies concerned being not essential. It is supposed, that the beam density is constant over the cross section, the change of the beam radius a < d can be neglected. It is shown that there is no longitudinal selffocusing of the bunch in such a channel. The calculated values of the electrical field in the channel are of interest from the viewpoint of ion acceleration

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[en] The numerical and laboratory experiments exploring the influence of the microwave fields in the region of the electron cyclotrone resonance (ECR) at the necks of the open magnetic bottle on the plasma trapping and holding were performed. The axial injection of plasma was used. The bottle center magnetic field was equal to 795 G at the bottle to neck ratio of 1.56. The bottle was filled in by hydrogen bunches. The bunch densities didn't exceed 6x10⁹ cm^-3. The ion and electron temperatures were 0.1 and 15 eV. The single and two combined ECR barrier bottles were used in experiments. In case of a single combined barrier the trapped ion plasma temperature was 38 eV. The charged particle lifetime was 20 μsec. In case of two combined barriers the charged particle lifetime is found to be larger than that for the single barrier case. The combined neck holds plasma well only provided the local ECR takes place. If so the microwave field pressure is negligible. The self-focusing condition implies that there is no microwave heating of the dminant fraction of electrons. When plasma is trapped the ion longitudinal motion energy is transformed into the thermal energy. The numerical experiments employing the tensor mass electron model have demonstrated that induction of the microwave resonance fields at necks eliminates the cone losses and results in establishment of the mean energies of particles if the self-focusing condition holds

[en] Theoretically investigated is the longitudinal multipole instability of bunches in ring proton accelerators. General formulae for the instability increments are obtained in the result of the dispersion relation solution. They are used during analyzing longitudinal bunch instabilities occurring due to finite conductivity of vacuum chamber walls and during beam interaction with a resonator. Landau damping has been taken into account in the instability analysis. Presented are diagrams for the regions of stability of multipole bunch oscillations and the formula for calculating permissible impedances of accelerator systems

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