Kinetic theory of instability in the interaction of an electron beam and plasma with an arbitrary anisotropic electron velocity distribution function

Based on the kinetic approach, this work investigates the stability of the system consisting of a fast electron beam and a dense plasma at an arbitrary (anisotropic) electron velocity distribution function. It is shown that during the interaction of a fast electron beam with a cold plasma, both the conditions for losing stability and the increment do not depend on the form of the electron distribution function (EDF) of a plasma and are determined only by the ratio of the electron beam energy to the mean energy in a plasma. With an increase in the mean electron energy in the plasma, it becomes necessary to take into account the moments of the EDF following for energy moment. It was found that the plasma anisotropy has a significant effect on both the stability loss conditions and the increment. The physical reason for this effect is the shift in the plasma frequency due to the Doppler effect caused by the plasma anisotropy in the coordinate system moving along with the beam. Other findings include a region of anomalous dispersion of the electron beam - plasma system and regions of negative group velocity of perturbations in such system. Physical interpretations are proposed for all the observed effects.

Электрофизические и диэлектрические свойства поликристаллов железо-иттриевого феррита-граната, полученных по технологии радиационно-термического спекания

In this paper the electrical and dielectric properties of polycrystalline yttrium iron garnet, obtained by the radiation-thermal sintering technology in a fast electron beam were investigated. Spectra of complex dielectric constant, dielectric loss tangent and conductivity were measured in the frequency range 25 – 1∙106 Hz. For comparison, DC resistance measurements were also performed. The temperature dependences of the above parameters were measured at frequencies of 1 kHz, 100 kHz in the range 25 - 300 °C. It is shown, that conduction activations energy, permittivity, loss tangent and resistance vary significantly from sintering temperature in the range of 1300 to 1450 °C. It is found that with an increase in the sintering temperature to 1450 °C, dielectric properties are the same as samples made by the traditional ceramic technology.

The weakened Weibel instability of collimated fast electron beam in nanotube array

The Weibel instability of the collimated MeV fast electron beams in a nanotube array target is researched in this work. It is found that the filamentation of the fast electrons is significantly suppressed. When fast electrons propagate the nanotube array, a strong magnetic field is created near the surface of tubes to obstruct the transverse movement of the fast electrons and bend them into the inner vacuum spaces between the successive tubes. In consequence, the positive feedback loop between the magnetic field perturbation and the electrons density perturbation is broken and the Weibel instability is thus weakened. Furthermore, the calculated results by a hybrid particle-in-cell code have also proven this weakening effect on the Weibel instability. Because of the high-energy density delivered by the MeV electrons, these results indicate some significant applications in the high-energy physics, such as radiography, fast-electron beam focusing, and perhaps fast ignition.

Features of crystal structure and phase composition of the anisotropic hexagonal ferrites bafe12o19 and bafe9,5al2,5o19, obtained by radiation-thermal sintering

The method of radiation-thermal sintering (RTS) in the fast electron beam by accelerator ILU-6 obtained samples of barium hexaferrite BaFe12O19 and substituted barium hexaferrite BaFe9,5Al2,5O19 (with additions of Ni, Ti, Mn). The research synthesized samples was carried out by X-ray structural analysis and X-ray phase analysis. It is found that both compounds besides the main phase samples (BaFe12O19 and BaFe9,5Al2,5O19, respectively), is also present phase BaFe2O4. With increasing sintering temperature from 1100°C to 1300°C phase barium monoferrite intensity decreases or disappears completely, and at a temperature of 1400°C this phase is fixed again (its intensity continues to increase). The possibility of practical use of the results.