Collective processes in a microsecond relativistic electron beam: Basic rules and mechanisms

Collective processes taking place in the space charge of a microsecond relativistic electron beam with magnetic insulation are considered. The space-time characteristics of the low-frequency and high-frequency oscillations are found, and the effect of the magnetic compression of the beam near the cathode on these oscillations is studied. It is shown that the basic source of the low-frequency oscillations is the collective motion of the space charge, which takes place in crossed electric and magnetic fields near the cathode, while the primary reason for the high-frequency oscillations is two-stream instability in the beam. The possibility of suppressing both types of oscillations by compressing relativistic electron beams near the cathode is demonstrated. The effect of nonuniform magnetic fields, including their effect on the cathode plasma motion, is elucidated.     

Observation of shot noise suppression at optical wavelengths in a relativistic electron beam

Control of collective properties of relativistic particles is increasingly important in modern accelerators. In particular, shot noise affects accelerator performance by driving instabilities or by competing with coherent processes. We present experimental observations of shot noise suppression in a relativistic beam at the Linac Coherent Light Source. By adjusting the dispersive strength of a chicane, we observe a decrease in the optical transition radiation emitted from a downstream foil. We show agreement between the experimental results, theoretical models, and 3D particle simulations.     

On the injection of a cold relativistic electron beam into a cold plasma

In a one-dimensional model the initial phase of the injection of a relativistic electron beam into a plasma is studied, both analytically and computationally. We find that in a time of a few beam plasma periods the beam obtains a “temperature” which is much higher than expected from the analytic treatment.     

Features of relativistic electron beam-plasma interaction under high beam current

The specific features of the beam-plasma instability in waveguide under very high beam current are shown analytically. The differences (as compared to conventional case of beam-plasma instability under low beam current) are due to change of physical mechanisms of beam-plasma interaction.     

Collective atomic motion in an optical lattice formed inside a high finesse cavity

We report on collective nonlinear dynamics in an optical lattice formed inside a high finesse ring cavity in a so far unexplored regime, where the light shift per photon times the number of trapped atoms exceeds the cavity resonance linewidth. We observe bistability and self-induced squeezing oscillations resulting from the retroaction of the atoms upon the optical potential wells. We can well understand most of our observations within a simplified model assuming adiabaticity of the atomic motion. Nonadiabatic aspects of the atomic motion are reproduced by solving the complete system of coupled nonlinear equations of motion.     

箔-聚焦的强流电子束的平衡与稳定特性

通过箔 聚焦的电子束的包络方程研究了电子束的平衡与稳定特性,从而得到了能够传输的电子束的参数与箔之间距离和波导半径之间的关系。     

The dissipative instability of a relativistic electron beam

The theory of the wall instabilities of surface waves excited by an electron beam is developed. Their classification, linear, quasilinear and nonlinear theory is given. It is shown that dissipative instabilities convert practically all the energy lost by the beam into the heating of the lossy walls confining the beam.     

箔-聚焦的强流电子束的平衡与稳定特性

 通过箔 聚焦的电子束的包络方程研究了电子束的平衡与稳定特性，从而得到了能够传输的电子束的参数与箔之间距离和波导半径之间的关系。     

Anomalous scattering of a relativistic electron beam in a beam created plasma

Measurements of the velocity angular distribution of a relativistic electron beam (0.8 MV, 6 kA, 150 ns) after propagation through hydrogen gas are presented. At a pressure of 25 Pa scattering of the beam electrons into a preferential angular interval is observed. At 190 Pa anomalously large scattering is observed, up to an angular width of 90°, during about 30 ns.     

Angular velocity spread of relativistic electron beam generated by high current diode

Theoretical analysis and numerical simulations of the Relativistic Electron Beam (REB) generation in a high current diode immersed in an external magnetic field has been done. The calculations have confirmed that the generated beam is homogeneous and monoenergetic in a broad central region. In the case of cylindrical diode the mixing of electron trajectories has been observed only in a narrow periphery beam region. The angle between particle trajectories and external longitudinal magnetic field varies chaotically from 0° to –25°. This phenomenon suppresses the excitation of two stream instability excited by the REB in the plasma column.     

Passage of a high-current relativistic electron beam through matter

A solution is presented for the problem of passage of a high-current relativistic electron beam through matter in the stationary case with one-dimensional geometry. The system of equations describing the passage of the beam consists of the kinetic equation for fast electrons, which considers the effect of the electric field on the magnitude and direction of particle momentum, the equations for the field produced by the space charge generated by thermalized electrons, and relations connecting the conductivity of the medium to the radiation field. Higher-order perturbation theory is used for the solution. The solutions reveal that the distribution of expended energy, thermalized electrons, and other properties of the flow are highly dependent on the density of the incident flux and the conductivity of the medium. It will be shown that linear transfer theory may be applied to calculation of the passage of high-current beams through matter over a wide range of currents and conductivities, if the barrier thickness does not exceed one-half the path length, but cannot be used for calculation of passage through large-thickness barriers, i.e., with thickness comparable to the electron free path length.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 67–74, September, 1979.The author thanks A. N. Didenko and A. M. Kol'chuzhkin for their evaluation of the study.     

Collective acceleration of ions by relativistic electron rings

The collective acceleration of hydrogen and helium ions by relativistic electron rings has been successful, using a very fast ring compression, and has clearly been demonstrated by the inertia of the loaded rings and by nuclear track recording.     

Interaction of a relativistic electron beam with a spiral waveguide

The nonlinear period in the interaction of a relativistic electron beam (REB) with an electromagnetic wave in a spiral waveguide at the stage of saturation is investigated for a Cherenkov interaction mechanism. On the basis of the kinetic equation and laws of energy and momentum conservation, analytical relations are obtained, allowing the efficiency of excitation and amplification of the electromagnetic wave to be studied using REB in a retarding structure. The results of the analysis are in good agreement with the data of actual and numerical experiments.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 31–36, May, 1988.It remains to thank É. A. Perel'shtein, Yu. I. Aleksakhin, and their colleagues for discussion of the results.